Merge pull request #9649 from Snektron/address-space

Address Spaces

doc/docgen.zig

@@ -901,6 +901,7 @@ fn tokenizeAndPrintRaw(
         switch (token.tag) {
             .eof => break,
 
+            .keyword_addrspace,
             .keyword_align,
             .keyword_and,
             .keyword_asm,

lib/std/builtin.zig

@@ -166,6 +166,15 @@ pub const CallingConvention = enum {
     SysV,
 };
 
+/// This data structure is used by the Zig language code generation and
+/// therefore must be kept in sync with the compiler implementation.
+pub const AddressSpace = enum {
+    generic,
+    gs,
+    fs,
+    ss,
+};
+
 /// This data structure is used by the Zig language code generation and
 /// therefore must be kept in sync with the compiler implementation.
 pub const SourceLocation = struct {
@@ -226,6 +235,7 @@ pub const TypeInfo = union(enum) {
         is_const: bool,
         is_volatile: bool,
         alignment: comptime_int,
+        address_space: AddressSpace,
         child: type,
         is_allowzero: bool,
 

lib/std/mem.zig

@@ -2472,6 +2472,7 @@ fn CopyPtrAttrs(comptime source: type, comptime size: std.builtin.TypeInfo.Point
             .is_volatile = info.is_volatile,
             .is_allowzero = info.is_allowzero,
             .alignment = info.alignment,
+            .address_space = info.address_space,
             .child = child,
             .sentinel = null,
         },
@@ -2960,6 +2961,7 @@ fn AlignedSlice(comptime AttributeSource: type, comptime new_alignment: u29) typ
             .is_volatile = info.is_volatile,
             .is_allowzero = info.is_allowzero,
             .alignment = new_alignment,
+            .address_space = info.address_space,
             .child = info.child,
             .sentinel = null,
         },

lib/std/meta.zig

@@ -235,6 +235,7 @@ pub fn Sentinel(comptime T: type, comptime sentinel_val: Elem(T)) type {
                         .is_const = info.is_const,
                         .is_volatile = info.is_volatile,
                         .alignment = info.alignment,
+                        .address_space = info.address_space,
                         .child = @Type(.{
                             .Array = .{
                                 .len = array_info.len,
@@ -254,6 +255,7 @@ pub fn Sentinel(comptime T: type, comptime sentinel_val: Elem(T)) type {
                     .is_const = info.is_const,
                     .is_volatile = info.is_volatile,
                     .alignment = info.alignment,
+                    .address_space = info.address_space,
                     .child = info.child,
                     .is_allowzero = info.is_allowzero,
                     .sentinel = sentinel_val,
@@ -271,6 +273,7 @@ pub fn Sentinel(comptime T: type, comptime sentinel_val: Elem(T)) type {
                                 .is_const = ptr_info.is_const,
                                 .is_volatile = ptr_info.is_volatile,
                                 .alignment = ptr_info.alignment,
+                                .address_space = ptr_info.address_space,
                                 .child = ptr_info.child,
                                 .is_allowzero = ptr_info.is_allowzero,
                                 .sentinel = sentinel_val,

lib/std/zig/Ast.zig

@@ -262,6 +262,9 @@ pub fn renderError(tree: Tree, parse_error: Error, stream: anytype) !void {
                 token_tags[parse_error.token].symbol(),
             });
         },
+        .extra_addrspace_qualifier => {
+            return stream.writeAll("extra addrspace qualifier");
+        },
         .extra_align_qualifier => {
             return stream.writeAll("extra align qualifier");
         },
@@ -1021,7 +1024,7 @@ pub fn lastToken(tree: Tree, node: Node.Index) TokenIndex {
         },
         .fn_proto_one => {
             const extra = tree.extraData(datas[n].lhs, Node.FnProtoOne);
-            // linksection, callconv, align can appear in any order, so we
+            // addrspace, linksection, callconv, align can appear in any order, so we
             // find the last one here.
             var max_node: Node.Index = datas[n].rhs;
             var max_start = token_starts[main_tokens[max_node]];
@@ -1034,6 +1037,14 @@ pub fn lastToken(tree: Tree, node: Node.Index) TokenIndex {
                     max_offset = 1; // for the rparen
                 }
             }
+            if (extra.addrspace_expr != 0) {
+                const start = token_starts[main_tokens[extra.addrspace_expr]];
+                if (start > max_start) {
+                    max_node = extra.addrspace_expr;
+                    max_start = start;
+                    max_offset = 1; // for the rparen
+                }
+            }
             if (extra.section_expr != 0) {
                 const start = token_starts[main_tokens[extra.section_expr]];
                 if (start > max_start) {
@@ -1055,7 +1066,7 @@ pub fn lastToken(tree: Tree, node: Node.Index) TokenIndex {
         },
         .fn_proto => {
             const extra = tree.extraData(datas[n].lhs, Node.FnProto);
-            // linksection, callconv, align can appear in any order, so we
+            // addrspace, linksection, callconv, align can appear in any order, so we
             // find the last one here.
             var max_node: Node.Index = datas[n].rhs;
             var max_start = token_starts[main_tokens[max_node]];
@@ -1068,6 +1079,14 @@ pub fn lastToken(tree: Tree, node: Node.Index) TokenIndex {
                     max_offset = 1; // for the rparen
                 }
             }
+            if (extra.addrspace_expr != 0) {
+                const start = token_starts[main_tokens[extra.addrspace_expr]];
+                if (start > max_start) {
+                    max_node = extra.addrspace_expr;
+                    max_start = start;
+                    max_offset = 1; // for the rparen
+                }
+            }
             if (extra.section_expr != 0) {
                 const start = token_starts[main_tokens[extra.section_expr]];
                 if (start > max_start) {
@@ -1138,6 +1157,7 @@ pub fn globalVarDecl(tree: Tree, node: Node.Index) full.VarDecl {
     return tree.fullVarDecl(.{
         .type_node = extra.type_node,
         .align_node = extra.align_node,
+        .addrspace_node = extra.addrspace_node,
         .section_node = extra.section_node,
         .init_node = data.rhs,
         .mut_token = tree.nodes.items(.main_token)[node],
@@ -1151,6 +1171,7 @@ pub fn localVarDecl(tree: Tree, node: Node.Index) full.VarDecl {
     return tree.fullVarDecl(.{
         .type_node = extra.type_node,
         .align_node = extra.align_node,
+        .addrspace_node = 0,
         .section_node = 0,
         .init_node = data.rhs,
         .mut_token = tree.nodes.items(.main_token)[node],
@@ -1163,6 +1184,7 @@ pub fn simpleVarDecl(tree: Tree, node: Node.Index) full.VarDecl {
     return tree.fullVarDecl(.{
         .type_node = data.lhs,
         .align_node = 0,
+        .addrspace_node = 0,
         .section_node = 0,
         .init_node = data.rhs,
         .mut_token = tree.nodes.items(.main_token)[node],
@@ -1175,6 +1197,7 @@ pub fn alignedVarDecl(tree: Tree, node: Node.Index) full.VarDecl {
     return tree.fullVarDecl(.{
         .type_node = 0,
         .align_node = data.lhs,
+        .addrspace_node = 0,
         .section_node = 0,
         .init_node = data.rhs,
         .mut_token = tree.nodes.items(.main_token)[node],
@@ -1249,6 +1272,7 @@ pub fn fnProtoSimple(tree: Tree, buffer: *[1]Node.Index, node: Node.Index) full.
         .return_type = data.rhs,
         .params = params,
         .align_expr = 0,
+        .addrspace_expr = 0,
         .section_expr = 0,
         .callconv_expr = 0,
     });
@@ -1265,6 +1289,7 @@ pub fn fnProtoMulti(tree: Tree, node: Node.Index) full.FnProto {
         .return_type = data.rhs,
         .params = params,
         .align_expr = 0,
+        .addrspace_expr = 0,
         .section_expr = 0,
         .callconv_expr = 0,
     });
@@ -1282,6 +1307,7 @@ pub fn fnProtoOne(tree: Tree, buffer: *[1]Node.Index, node: Node.Index) full.FnP
         .return_type = data.rhs,
         .params = params,
         .align_expr = extra.align_expr,
+        .addrspace_expr = extra.addrspace_expr,
         .section_expr = extra.section_expr,
         .callconv_expr = extra.callconv_expr,
     });
@@ -1298,6 +1324,7 @@ pub fn fnProto(tree: Tree, node: Node.Index) full.FnProto {
         .return_type = data.rhs,
         .params = params,
         .align_expr = extra.align_expr,
+        .addrspace_expr = extra.addrspace_expr,
         .section_expr = extra.section_expr,
         .callconv_expr = extra.callconv_expr,
     });
@@ -1453,6 +1480,7 @@ pub fn ptrTypeAligned(tree: Tree, node: Node.Index) full.PtrType {
     return tree.fullPtrType(.{
         .main_token = tree.nodes.items(.main_token)[node],
         .align_node = data.lhs,
+        .addrspace_node = 0,
         .sentinel = 0,
         .bit_range_start = 0,
         .bit_range_end = 0,
@@ -1466,6 +1494,7 @@ pub fn ptrTypeSentinel(tree: Tree, node: Node.Index) full.PtrType {
     return tree.fullPtrType(.{
         .main_token = tree.nodes.items(.main_token)[node],
         .align_node = 0,
+        .addrspace_node = 0,
         .sentinel = data.lhs,
         .bit_range_start = 0,
         .bit_range_end = 0,
@@ -1480,6 +1509,7 @@ pub fn ptrType(tree: Tree, node: Node.Index) full.PtrType {
     return tree.fullPtrType(.{
         .main_token = tree.nodes.items(.main_token)[node],
         .align_node = extra.align_node,
+        .addrspace_node = extra.addrspace_node,
         .sentinel = extra.sentinel,
         .bit_range_start = 0,
         .bit_range_end = 0,
@@ -1494,6 +1524,7 @@ pub fn ptrTypeBitRange(tree: Tree, node: Node.Index) full.PtrType {
     return tree.fullPtrType(.{
         .main_token = tree.nodes.items(.main_token)[node],
         .align_node = extra.align_node,
+        .addrspace_node = extra.addrspace_node,
         .sentinel = extra.sentinel,
         .bit_range_start = extra.bit_range_start,
         .bit_range_end = extra.bit_range_end,
@@ -2063,6 +2094,7 @@ pub const full = struct {
             mut_token: TokenIndex,
             type_node: Node.Index,
             align_node: Node.Index,
+            addrspace_node: Node.Index,
             section_node: Node.Index,
             init_node: Node.Index,
         };
@@ -2130,6 +2162,7 @@ pub const full = struct {
             return_type: Node.Index,
             params: []const Node.Index,
             align_expr: Node.Index,
+            addrspace_expr: Node.Index,
             section_expr: Node.Index,
             callconv_expr: Node.Index,
         };
@@ -2288,6 +2321,7 @@ pub const full = struct {
         pub const Components = struct {
             main_token: TokenIndex,
             align_node: Node.Index,
+            addrspace_node: Node.Index,
             sentinel: Node.Index,
             bit_range_start: Node.Index,
             bit_range_end: Node.Index,
@@ -2397,6 +2431,7 @@ pub const Error = struct {
         expected_var_decl_or_fn,
         expected_loop_payload,
         expected_container,
+        extra_addrspace_qualifier,
         extra_align_qualifier,
         extra_allowzero_qualifier,
         extra_const_qualifier,
@@ -2723,13 +2758,13 @@ pub const Node = struct {
         /// main_token is the `fn` keyword.
         /// extern function declarations use this tag.
         fn_proto_multi,
-        /// `fn(a: b) rhs linksection(e) callconv(f)`. `FnProtoOne[lhs]`.
+        /// `fn(a: b) rhs addrspace(e) linksection(f) callconv(g)`. `FnProtoOne[lhs]`.
         /// zero or one parameters.
         /// anytype and ... parameters are omitted from the AST tree.
         /// main_token is the `fn` keyword.
         /// extern function declarations use this tag.
         fn_proto_one,
-        /// `fn(a: b, c: d) rhs linksection(e) callconv(f)`. `FnProto[lhs]`.
+        /// `fn(a: b, c: d) rhs addrspace(e) linksection(f) callconv(g)`. `FnProto[lhs]`.
         /// anytype and ... parameters are omitted from the AST tree.
         /// main_token is the `fn` keyword.
         /// extern function declarations use this tag.
@@ -2893,11 +2928,13 @@ pub const Node = struct {
     pub const PtrType = struct {
         sentinel: Index,
         align_node: Index,
+        addrspace_node: Index,
     };
 
     pub const PtrTypeBitRange = struct {
         sentinel: Index,
         align_node: Index,
+        addrspace_node: Index,
         bit_range_start: Index,
         bit_range_end: Index,
     };
@@ -2920,8 +2957,13 @@ pub const Node = struct {
     };
 
     pub const GlobalVarDecl = struct {
+        /// Populated if there is an explicit type ascription.
         type_node: Index,
+        /// Populated if align(A) is present.
         align_node: Index,
+        /// Populated if addrspace(A) is present.
+        addrspace_node: Index,
+        /// Populated if linksection(A) is present.
         section_node: Index,
     };
 
@@ -2953,6 +2995,8 @@ pub const Node = struct {
         param: Index,
         /// Populated if align(A) is present.
         align_expr: Index,
+        /// Populated if addrspace(A) is present.
+        addrspace_expr: Index,
         /// Populated if linksection(A) is present.
         section_expr: Index,
         /// Populated if callconv(A) is present.
@@ -2964,6 +3008,8 @@ pub const Node = struct {
         params_end: Index,
         /// Populated if align(A) is present.
         align_expr: Index,
+        /// Populated if addrspace(A) is present.
+        addrspace_expr: Index,
         /// Populated if linksection(A) is present.
         section_expr: Index,
         /// Populated if callconv(A) is present.

lib/std/zig/c_translation.zig

@@ -325,6 +325,7 @@ pub fn FlexibleArrayType(comptime SelfType: type, ElementType: type) type {
                 .is_const = ptr.is_const,
                 .is_volatile = ptr.is_volatile,
                 .alignment = @alignOf(ElementType),
+                .address_space = .generic,
                 .child = ElementType,
                 .is_allowzero = true,
                 .sentinel = null,

lib/std/zig/parse.zig

@@ -629,7 +629,7 @@ const Parser = struct {
         };
     }
 
-    /// FnProto <- KEYWORD_fn IDENTIFIER? LPAREN ParamDeclList RPAREN ByteAlign? LinkSection? CallConv? EXCLAMATIONMARK? TypeExpr
+    /// FnProto <- KEYWORD_fn IDENTIFIER? LPAREN ParamDeclList RPAREN ByteAlign? AddrSpace? LinkSection? CallConv? EXCLAMATIONMARK? TypeExpr
     fn parseFnProto(p: *Parser) !Node.Index {
         const fn_token = p.eatToken(.keyword_fn) orelse return null_node;
 
@@ -639,6 +639,7 @@ const Parser = struct {
         _ = p.eatToken(.identifier);
         const params = try p.parseParamDeclList();
         const align_expr = try p.parseByteAlign();
+        const addrspace_expr = try p.parseAddrSpace();
         const section_expr = try p.parseLinkSection();
         const callconv_expr = try p.parseCallconv();
         _ = p.eatToken(.bang);
@@ -650,7 +651,7 @@ const Parser = struct {
             try p.warn(.expected_return_type);
         }
 
-        if (align_expr == 0 and section_expr == 0 and callconv_expr == 0) {
+        if (align_expr == 0 and section_expr == 0 and callconv_expr == 0 and addrspace_expr == 0) {
             switch (params) {
                 .zero_or_one => |param| return p.setNode(fn_proto_index, .{
                     .tag = .fn_proto_simple,
@@ -683,6 +684,7 @@ const Parser = struct {
                     .lhs = try p.addExtra(Node.FnProtoOne{
                         .param = param,
                         .align_expr = align_expr,
+                        .addrspace_expr = addrspace_expr,
                         .section_expr = section_expr,
                         .callconv_expr = callconv_expr,
                     }),
@@ -698,6 +700,7 @@ const Parser = struct {
                             .params_start = span.start,
                             .params_end = span.end,
                             .align_expr = align_expr,
+                            .addrspace_expr = addrspace_expr,
                             .section_expr = section_expr,
                             .callconv_expr = callconv_expr,
                         }),
@@ -708,7 +711,7 @@ const Parser = struct {
         }
     }
 
-    /// VarDecl <- (KEYWORD_const / KEYWORD_var) IDENTIFIER (COLON TypeExpr)? ByteAlign? LinkSection? (EQUAL Expr)? SEMICOLON
+    /// VarDecl <- (KEYWORD_const / KEYWORD_var) IDENTIFIER (COLON TypeExpr)? ByteAlign? AddrSpace? LinkSection? (EQUAL Expr)? SEMICOLON
     fn parseVarDecl(p: *Parser) !Node.Index {
         const mut_token = p.eatToken(.keyword_const) orelse
             p.eatToken(.keyword_var) orelse
@@ -717,9 +720,10 @@ const Parser = struct {
         _ = try p.expectToken(.identifier);
         const type_node: Node.Index = if (p.eatToken(.colon) == null) 0 else try p.expectTypeExpr();
         const align_node = try p.parseByteAlign();
+        const addrspace_node = try p.parseAddrSpace();
         const section_node = try p.parseLinkSection();
         const init_node: Node.Index = if (p.eatToken(.equal) == null) 0 else try p.expectExpr();
-        if (section_node == 0) {
+        if (section_node == 0 and addrspace_node == 0) {
             if (align_node == 0) {
                 return p.addNode(.{
                     .tag = .simple_var_decl,
@@ -759,6 +763,7 @@ const Parser = struct {
                     .lhs = try p.addExtra(Node.GlobalVarDecl{
                         .type_node = type_node,
                         .align_node = align_node,
+                        .addrspace_node = addrspace_node,
                         .section_node = section_node,
                     }),
                     .rhs = init_node,
@@ -1440,8 +1445,8 @@ const Parser = struct {
     /// PrefixTypeOp
     ///     <- QUESTIONMARK
     ///      / KEYWORD_anyframe MINUSRARROW
-    ///      / SliceTypeStart (ByteAlign / KEYWORD_const / KEYWORD_volatile / KEYWORD_allowzero)*
+    ///      / SliceTypeStart (ByteAlign / AddrSpace / KEYWORD_const / KEYWORD_volatile / KEYWORD_allowzero)*
-    ///      / PtrTypeStart (KEYWORD_align LPAREN Expr (COLON INTEGER COLON INTEGER)? RPAREN / KEYWORD_const / KEYWORD_volatile / KEYWORD_allowzero)*
+    ///      / PtrTypeStart (AddrSpace / KEYWORD_align LPAREN Expr (COLON INTEGER COLON INTEGER)? RPAREN / KEYWORD_const / KEYWORD_volatile / KEYWORD_allowzero)*
     ///      / ArrayTypeStart
     /// SliceTypeStart <- LBRACKET (COLON Expr)? RBRACKET
     /// PtrTypeStart
@@ -1474,16 +1479,7 @@ const Parser = struct {
                 const asterisk = p.nextToken();
                 const mods = try p.parsePtrModifiers();
                 const elem_type = try p.expectTypeExpr();
-                if (mods.bit_range_start == 0) {
+                if (mods.bit_range_start != 0) {
-                    return p.addNode(.{
-                        .tag = .ptr_type_aligned,
-                        .main_token = asterisk,
-                        .data = .{
-                            .lhs = mods.align_node,
-                            .rhs = elem_type,
-                        },
-                    });
-                } else {
                     return p.addNode(.{
                         .tag = .ptr_type_bit_range,
                         .main_token = asterisk,
@@ -1491,12 +1487,35 @@ const Parser = struct {
                             .lhs = try p.addExtra(Node.PtrTypeBitRange{
                                 .sentinel = 0,
                                 .align_node = mods.align_node,
+                                .addrspace_node = mods.addrspace_node,
                                 .bit_range_start = mods.bit_range_start,
                                 .bit_range_end = mods.bit_range_end,
                             }),
                             .rhs = elem_type,
                         },
                     });
+                } else if (mods.addrspace_node != 0) {
+                    return p.addNode(.{
+                        .tag = .ptr_type,
+                        .main_token = asterisk,
+                        .data = .{
+                            .lhs = try p.addExtra(Node.PtrType{
+                                .sentinel = 0,
+                                .align_node = mods.align_node,
+                                .addrspace_node = mods.addrspace_node,
+                            }),
+                            .rhs = elem_type,
+                        },
+                    });
+                } else {
+                    return p.addNode(.{
+                        .tag = .ptr_type_aligned,
+                        .main_token = asterisk,
+                        .data = .{
+                            .lhs = mods.align_node,
+                            .rhs = elem_type,
+                        },
+                    });
                 }
             },
             .asterisk_asterisk => {
@@ -1504,16 +1523,7 @@ const Parser = struct {
                 const mods = try p.parsePtrModifiers();
                 const elem_type = try p.expectTypeExpr();
                 const inner: Node.Index = inner: {
-                    if (mods.bit_range_start == 0) {
+                    if (mods.bit_range_start != 0) {
-                        break :inner try p.addNode(.{
-                            .tag = .ptr_type_aligned,
-                            .main_token = asterisk,
-                            .data = .{
-                                .lhs = mods.align_node,
-                                .rhs = elem_type,
-                            },
-                        });
-                    } else {
                         break :inner try p.addNode(.{
                             .tag = .ptr_type_bit_range,
                             .main_token = asterisk,
@@ -1521,12 +1531,35 @@ const Parser = struct {
                                 .lhs = try p.addExtra(Node.PtrTypeBitRange{
                                     .sentinel = 0,
                                     .align_node = mods.align_node,
+                                    .addrspace_node = mods.addrspace_node,
                                     .bit_range_start = mods.bit_range_start,
                                     .bit_range_end = mods.bit_range_end,
                                 }),
                                 .rhs = elem_type,
                             },
                         });
+                    } else if (mods.addrspace_node != 0) {
+                        break :inner try p.addNode(.{
+                            .tag = .ptr_type,
+                            .main_token = asterisk,
+                            .data = .{
+                                .lhs = try p.addExtra(Node.PtrType{
+                                    .sentinel = 0,
+                                    .align_node = mods.align_node,
+                                    .addrspace_node = mods.addrspace_node,
+                                }),
+                                .rhs = elem_type,
+                            },
+                        });
+                    } else {
+                        break :inner try p.addNode(.{
+                            .tag = .ptr_type_aligned,
+                            .main_token = asterisk,
+                            .data = .{
+                                .lhs = mods.align_node,
+                                .rhs = elem_type,
+                            },
+                        });
                     }
                 };
                 return p.addNode(.{
@@ -1560,7 +1593,7 @@ const Parser = struct {
                     const mods = try p.parsePtrModifiers();
                     const elem_type = try p.expectTypeExpr();
                     if (mods.bit_range_start == 0) {
-                        if (sentinel == 0) {
+                        if (sentinel == 0 and mods.addrspace_node == 0) {
                             return p.addNode(.{
                                 .tag = .ptr_type_aligned,
                                 .main_token = asterisk,
@@ -1569,7 +1602,7 @@ const Parser = struct {
                                     .rhs = elem_type,
                                 },
                             });
-                        } else if (mods.align_node == 0) {
+                        } else if (mods.align_node == 0 and mods.addrspace_node == 0) {
                             return p.addNode(.{
                                 .tag = .ptr_type_sentinel,
                                 .main_token = asterisk,
@@ -1586,6 +1619,7 @@ const Parser = struct {
                                     .lhs = try p.addExtra(Node.PtrType{
                                         .sentinel = sentinel,
                                         .align_node = mods.align_node,
+                                        .addrspace_node = mods.addrspace_node,
                                     }),
                                     .rhs = elem_type,
                                 },
@@ -1599,6 +1633,7 @@ const Parser = struct {
                                 .lhs = try p.addExtra(Node.PtrTypeBitRange{
                                     .sentinel = sentinel,
                                     .align_node = mods.align_node,
+                                    .addrspace_node = mods.addrspace_node,
                                     .bit_range_start = mods.bit_range_start,
                                     .bit_range_end = mods.bit_range_end,
                                 }),
@@ -1624,7 +1659,7 @@ const Parser = struct {
                                 .token = p.nodes.items(.main_token)[mods.bit_range_start],
                             });
                         }
-                        if (sentinel == 0) {
+                        if (sentinel == 0 and mods.addrspace_node == 0) {
                             return p.addNode(.{
                                 .tag = .ptr_type_aligned,
                                 .main_token = lbracket,
@@ -1633,7 +1668,7 @@ const Parser = struct {
                                     .rhs = elem_type,
                                 },
                             });
-                        } else if (mods.align_node == 0) {
+                        } else if (mods.align_node == 0 and mods.addrspace_node == 0) {
                             return p.addNode(.{
                                 .tag = .ptr_type_sentinel,
                                 .main_token = lbracket,
@@ -1650,6 +1685,7 @@ const Parser = struct {
                                     .lhs = try p.addExtra(Node.PtrType{
                                         .sentinel = sentinel,
                                         .align_node = mods.align_node,
+                                        .addrspace_node = mods.addrspace_node,
                                     }),
                                     .rhs = elem_type,
                                 },
@@ -1661,6 +1697,7 @@ const Parser = struct {
                             .keyword_const,
                             .keyword_volatile,
                             .keyword_allowzero,
+                            .keyword_addrspace,
                             => return p.fail(.ptr_mod_on_array_child_type),
                             else => {},
                         }
@@ -2879,6 +2916,15 @@ const Parser = struct {
         return expr_node;
     }
 
+    /// AddrSpace <- KEYWORD_addrspace LPAREN Expr RPAREN
+    fn parseAddrSpace(p: *Parser) !Node.Index {
+        _ = p.eatToken(.keyword_addrspace) orelse return null_node;
+        _ = try p.expectToken(.l_paren);
+        const expr_node = try p.expectExpr();
+        _ = try p.expectToken(.r_paren);
+        return expr_node;
+    }
+
     /// ParamDecl
     ///     <- (KEYWORD_noalias / KEYWORD_comptime)? (IDENTIFIER COLON)? ParamType
     ///     / DOT3
@@ -3011,6 +3057,7 @@ const Parser = struct {
 
     const PtrModifiers = struct {
         align_node: Node.Index,
+        addrspace_node: Node.Index,
         bit_range_start: Node.Index,
         bit_range_end: Node.Index,
     };
@@ -3018,12 +3065,14 @@ const Parser = struct {
     fn parsePtrModifiers(p: *Parser) !PtrModifiers {
         var result: PtrModifiers = .{
             .align_node = 0,
+            .addrspace_node = 0,
             .bit_range_start = 0,
             .bit_range_end = 0,
         };
         var saw_const = false;
         var saw_volatile = false;
         var saw_allowzero = false;
+        var saw_addrspace = false;
         while (true) {
             switch (p.token_tags[p.tok_i]) {
                 .keyword_align => {
@@ -3063,6 +3112,12 @@ const Parser = struct {
                     p.tok_i += 1;
                     saw_allowzero = true;
                 },
+                .keyword_addrspace => {
+                    if (saw_addrspace) {
+                        try p.warn(.extra_addrspace_qualifier);
+                    }
+                    result.addrspace_node = try p.parseAddrSpace();
+                },
                 else => return result,
             }
         }

lib/std/zig/parser_test.zig

@@ -404,6 +404,10 @@ test "zig fmt: trailing comma in fn parameter list" {
         \\pub fn f(
         \\    a: i32,
         \\    b: i32,
+        \\) addrspace(.generic) i32 {}
+        \\pub fn f(
+        \\    a: i32,
+        \\    b: i32,
         \\) linksection(".text") i32 {}
         \\pub fn f(
         \\    a: i32,
@@ -553,8 +557,8 @@ test "zig fmt: sentinel-terminated slice type" {
 test "zig fmt: pointer-to-one with modifiers" {
     try testCanonical(
         \\const x: *u32 = undefined;
-        \\const y: *allowzero align(8) const volatile u32 = undefined;
+        \\const y: *allowzero align(8) addrspace(.generic) const volatile u32 = undefined;
-        \\const z: *allowzero align(8:4:2) const volatile u32 = undefined;
+        \\const z: *allowzero align(8:4:2) addrspace(.generic) const volatile u32 = undefined;
         \\
     );
 }
@@ -562,8 +566,8 @@ test "zig fmt: pointer-to-one with modifiers" {
 test "zig fmt: pointer-to-many with modifiers" {
     try testCanonical(
         \\const x: [*]u32 = undefined;
-        \\const y: [*]allowzero align(8) const volatile u32 = undefined;
+        \\const y: [*]allowzero align(8) addrspace(.generic) const volatile u32 = undefined;
-        \\const z: [*]allowzero align(8:4:2) const volatile u32 = undefined;
+        \\const z: [*]allowzero align(8:4:2) addrspace(.generic) const volatile u32 = undefined;
         \\
     );
 }
@@ -571,8 +575,8 @@ test "zig fmt: pointer-to-many with modifiers" {
 test "zig fmt: sentinel pointer with modifiers" {
     try testCanonical(
         \\const x: [*:42]u32 = undefined;
-        \\const y: [*:42]allowzero align(8) const volatile u32 = undefined;
+        \\const y: [*:42]allowzero align(8) addrspace(.generic) const volatile u32 = undefined;
-        \\const y: [*:42]allowzero align(8:4:2) const volatile u32 = undefined;
+        \\const y: [*:42]allowzero align(8:4:2) addrspace(.generic) const volatile u32 = undefined;
         \\
     );
 }
@@ -580,8 +584,8 @@ test "zig fmt: sentinel pointer with modifiers" {
 test "zig fmt: c pointer with modifiers" {
     try testCanonical(
         \\const x: [*c]u32 = undefined;
-        \\const y: [*c]allowzero align(8) const volatile u32 = undefined;
+        \\const y: [*c]allowzero align(8) addrspace(.generic) const volatile u32 = undefined;
-        \\const z: [*c]allowzero align(8:4:2) const volatile u32 = undefined;
+        \\const z: [*c]allowzero align(8:4:2) addrspace(.generic) const volatile u32 = undefined;
         \\
     );
 }
@@ -589,7 +593,7 @@ test "zig fmt: c pointer with modifiers" {
 test "zig fmt: slice with modifiers" {
     try testCanonical(
         \\const x: []u32 = undefined;
-        \\const y: []allowzero align(8) const volatile u32 = undefined;
+        \\const y: []allowzero align(8) addrspace(.generic) const volatile u32 = undefined;
         \\
     );
 }
@@ -597,7 +601,7 @@ test "zig fmt: slice with modifiers" {
 test "zig fmt: sentinel slice with modifiers" {
     try testCanonical(
         \\const x: [:42]u32 = undefined;
-        \\const y: [:42]allowzero align(8) const volatile u32 = undefined;
+        \\const y: [:42]allowzero align(8) addrspace(.generic) const volatile u32 = undefined;
         \\
     );
 }
@@ -1129,6 +1133,16 @@ test "zig fmt: linksection" {
     );
 }
 
+test "zig fmt: addrspace" {
+    try testCanonical(
+        \\export var python_length: u64 align(1) addrspace(.generic);
+        \\export var python_color: Color addrspace(.generic) = .green;
+        \\export var python_legs: u0 align(8) addrspace(.generic) linksection(".python") = 0;
+        \\export fn python_hiss() align(8) addrspace(.generic) linksection(".python") void;
+        \\
+    );
+}
+
 test "zig fmt: correctly space struct fields with doc comments" {
     try testTransform(
         \\pub const S = struct {

lib/std/zig/render.zig

@@ -797,6 +797,14 @@ fn renderPtrType(
         }
     }
 
+    if (ptr_type.ast.addrspace_node != 0) {
+        const addrspace_first = tree.firstToken(ptr_type.ast.addrspace_node);
+        try renderToken(ais, tree, addrspace_first - 2, .none); // addrspace
+        try renderToken(ais, tree, addrspace_first - 1, .none); // lparen
+        try renderExpression(gpa, ais, tree, ptr_type.ast.addrspace_node, .none);
+        try renderToken(ais, tree, tree.lastToken(ptr_type.ast.addrspace_node) + 1, .space); // rparen
+    }
+
     if (ptr_type.const_token) |const_token| {
         try renderToken(ais, tree, const_token, .space);
     }
@@ -921,6 +929,7 @@ fn renderVarDecl(gpa: *Allocator, ais: *Ais, tree: Ast, var_decl: Ast.full.VarDe
 
     const name_space = if (var_decl.ast.type_node == 0 and
         (var_decl.ast.align_node != 0 or
+        var_decl.ast.addrspace_node != 0 or
         var_decl.ast.section_node != 0 or
         var_decl.ast.init_node != 0))
         Space.space
@@ -930,8 +939,8 @@ fn renderVarDecl(gpa: *Allocator, ais: *Ais, tree: Ast, var_decl: Ast.full.VarDe
 
     if (var_decl.ast.type_node != 0) {
         try renderToken(ais, tree, var_decl.ast.mut_token + 2, Space.space); // :
-        if (var_decl.ast.align_node != 0 or var_decl.ast.section_node != 0 or
+        if (var_decl.ast.align_node != 0 or var_decl.ast.addrspace_node != 0 or
-            var_decl.ast.init_node != 0)
+            var_decl.ast.section_node != 0 or var_decl.ast.init_node != 0)
         {
             try renderExpression(gpa, ais, tree, var_decl.ast.type_node, .space);
         } else {
@@ -948,6 +957,23 @@ fn renderVarDecl(gpa: *Allocator, ais: *Ais, tree: Ast, var_decl: Ast.full.VarDe
         try renderToken(ais, tree, align_kw, Space.none); // align
         try renderToken(ais, tree, lparen, Space.none); // (
         try renderExpression(gpa, ais, tree, var_decl.ast.align_node, Space.none);
+        if (var_decl.ast.addrspace_node != 0 or var_decl.ast.section_node != 0 or
+            var_decl.ast.init_node != 0)
+        {
+            try renderToken(ais, tree, rparen, .space); // )
+        } else {
+            try renderToken(ais, tree, rparen, .none); // )
+            return renderToken(ais, tree, rparen + 1, Space.newline); // ;
+        }
+    }
+
+    if (var_decl.ast.addrspace_node != 0) {
+        const lparen = tree.firstToken(var_decl.ast.addrspace_node) - 1;
+        const addrspace_kw = lparen - 1;
+        const rparen = tree.lastToken(var_decl.ast.addrspace_node) + 1;
+        try renderToken(ais, tree, addrspace_kw, Space.none); // addrspace
+        try renderToken(ais, tree, lparen, Space.none); // (
+        try renderExpression(gpa, ais, tree, var_decl.ast.addrspace_node, Space.none);
         if (var_decl.ast.section_node != 0 or var_decl.ast.init_node != 0) {
             try renderToken(ais, tree, rparen, .space); // )
         } else {
@@ -1267,6 +1293,14 @@ fn renderFnProto(gpa: *Allocator, ais: *Ais, tree: Ast, fn_proto: Ast.full.FnPro
                 smallest_start = start;
             }
         }
+        if (fn_proto.ast.addrspace_expr != 0) {
+            const tok = tree.firstToken(fn_proto.ast.addrspace_expr) - 3;
+            const start = token_starts[tok];
+            if (start < smallest_start) {
+                rparen = tok;
+                smallest_start = start;
+            }
+        }
         if (fn_proto.ast.section_expr != 0) {
             const tok = tree.firstToken(fn_proto.ast.section_expr) - 3;
             const start = token_starts[tok];
@@ -1407,6 +1441,16 @@ fn renderFnProto(gpa: *Allocator, ais: *Ais, tree: Ast, fn_proto: Ast.full.FnPro
         try renderToken(ais, tree, align_rparen, .space); // )
     }
 
+    if (fn_proto.ast.addrspace_expr != 0) {
+        const align_lparen = tree.firstToken(fn_proto.ast.addrspace_expr) - 1;
+        const align_rparen = tree.lastToken(fn_proto.ast.addrspace_expr) + 1;
+
+        try renderToken(ais, tree, align_lparen - 1, .none); // addrspace
+        try renderToken(ais, tree, align_lparen, .none); // (
+        try renderExpression(gpa, ais, tree, fn_proto.ast.addrspace_expr, .none);
+        try renderToken(ais, tree, align_rparen, .space); // )
+    }
+
     if (fn_proto.ast.section_expr != 0) {
         const section_lparen = tree.firstToken(fn_proto.ast.section_expr) - 1;
         const section_rparen = tree.lastToken(fn_proto.ast.section_expr) + 1;

lib/std/zig/tokenizer.zig

@@ -11,6 +11,7 @@ pub const Token = struct {
     };
 
     pub const keywords = std.ComptimeStringMap(Tag, .{
+        .{ "addrspace", .keyword_addrspace },
         .{ "align", .keyword_align },
         .{ "allowzero", .keyword_allowzero },
         .{ "and", .keyword_and },
@@ -132,6 +133,7 @@ pub const Token = struct {
         float_literal,
         doc_comment,
         container_doc_comment,
+        keyword_addrspace,
         keyword_align,
         keyword_allowzero,
         keyword_and,
@@ -251,6 +253,7 @@ pub const Token = struct {
                 .angle_bracket_angle_bracket_right => ">>",
                 .angle_bracket_angle_bracket_right_equal => ">>=",
                 .tilde => "~",
+                .keyword_addrspace => "addrspace",
                 .keyword_align => "align",
                 .keyword_allowzero => "allowzero",
                 .keyword_and => "and",

src/AstGen.zig

@@ -1116,6 +1116,11 @@ fn fnProtoExpr(
     const align_inst: Zir.Inst.Ref = if (fn_proto.ast.align_expr == 0) .none else inst: {
         break :inst try expr(gz, scope, align_rl, fn_proto.ast.align_expr);
     };
+
+    if (fn_proto.ast.addrspace_expr != 0) {
+        return astgen.failNode(fn_proto.ast.addrspace_expr, "addrspace not allowed on function prototypes", .{});
+    }
+
     if (fn_proto.ast.section_expr != 0) {
         return astgen.failNode(fn_proto.ast.section_expr, "linksection not allowed on function prototypes", .{});
     }
@@ -2371,6 +2376,7 @@ fn varDecl(
     const gpa = astgen.gpa;
     const tree = astgen.tree;
     const token_tags = tree.tokens.items(.tag);
+    const main_tokens = tree.nodes.items(.main_token);
 
     const name_token = var_decl.ast.mut_token + 1;
     const ident_name_raw = tree.tokenSlice(name_token);
@@ -2385,6 +2391,14 @@ fn varDecl(
         return astgen.failNode(node, "variables must be initialized", .{});
     }
 
+    if (var_decl.ast.addrspace_node != 0) {
+        return astgen.failTok(main_tokens[var_decl.ast.addrspace_node], "cannot set address space of local variable '{s}'", .{ident_name_raw});
+    }
+
+    if (var_decl.ast.section_node != 0) {
+        return astgen.failTok(main_tokens[var_decl.ast.section_node], "cannot set section of local variable '{s}'", .{ident_name_raw});
+    }
+
     const align_inst: Zir.Inst.Ref = if (var_decl.ast.align_node != 0)
         try expr(gz, scope, align_rl, var_decl.ast.align_node)
     else
@@ -2714,6 +2728,7 @@ fn ptrType(
     const elem_type = try typeExpr(gz, scope, ptr_info.ast.child_type);
 
     const simple = ptr_info.ast.align_node == 0 and
+        ptr_info.ast.addrspace_node == 0 and
         ptr_info.ast.sentinel == 0 and
         ptr_info.ast.bit_range_start == 0;
 
@@ -2732,6 +2747,7 @@ fn ptrType(
 
     var sentinel_ref: Zir.Inst.Ref = .none;
     var align_ref: Zir.Inst.Ref = .none;
+    var addrspace_ref: Zir.Inst.Ref = .none;
     var bit_start_ref: Zir.Inst.Ref = .none;
     var bit_end_ref: Zir.Inst.Ref = .none;
     var trailing_count: u32 = 0;
@@ -2744,6 +2760,10 @@ fn ptrType(
         align_ref = try expr(gz, scope, align_rl, ptr_info.ast.align_node);
         trailing_count += 1;
     }
+    if (ptr_info.ast.addrspace_node != 0) {
+        addrspace_ref = try expr(gz, scope, .{ .ty = .address_space_type }, ptr_info.ast.addrspace_node);
+        trailing_count += 1;
+    }
     if (ptr_info.ast.bit_range_start != 0) {
         assert(ptr_info.ast.bit_range_end != 0);
         bit_start_ref = try expr(gz, scope, .none, ptr_info.ast.bit_range_start);
@@ -2764,6 +2784,9 @@ fn ptrType(
     if (align_ref != .none) {
         gz.astgen.extra.appendAssumeCapacity(@enumToInt(align_ref));
     }
+    if (addrspace_ref != .none) {
+        gz.astgen.extra.appendAssumeCapacity(@enumToInt(addrspace_ref));
+    }
     if (bit_start_ref != .none) {
         gz.astgen.extra.appendAssumeCapacity(@enumToInt(bit_start_ref));
         gz.astgen.extra.appendAssumeCapacity(@enumToInt(bit_end_ref));
@@ -2779,6 +2802,7 @@ fn ptrType(
                 .is_volatile = ptr_info.volatile_token != null,
                 .has_sentinel = sentinel_ref != .none,
                 .has_align = align_ref != .none,
+                .has_addrspace = addrspace_ref != .none,
                 .has_bit_range = bit_start_ref != .none,
             },
             .size = ptr_info.size,
@@ -2847,7 +2871,7 @@ const WipDecls = struct {
         is_pub: bool,
         is_export: bool,
         has_align: bool,
-        has_section: bool,
+        has_section_or_addrspace: bool,
     ) Allocator.Error!void {
         if (wip_decls.decl_index % fields_per_u32 == 0 and wip_decls.decl_index != 0) {
             try wip_decls.bit_bag.append(gpa, wip_decls.cur_bit_bag);
@@ -2857,7 +2881,7 @@ const WipDecls = struct {
             (@as(u32, @boolToInt(is_pub)) << 28) |
             (@as(u32, @boolToInt(is_export)) << 29) |
             (@as(u32, @boolToInt(has_align)) << 30) |
-            (@as(u32, @boolToInt(has_section)) << 31);
+            (@as(u32, @boolToInt(has_section_or_addrspace)) << 31);
         wip_decls.decl_index += 1;
     }
 
@@ -2922,7 +2946,8 @@ fn fnDecl(
         const maybe_inline_token = fn_proto.extern_export_inline_token orelse break :blk false;
         break :blk token_tags[maybe_inline_token] == .keyword_inline;
     };
-    try wip_decls.next(gpa, is_pub, is_export, fn_proto.ast.align_expr != 0, fn_proto.ast.section_expr != 0);
+    const has_section_or_addrspace = fn_proto.ast.section_expr != 0 or fn_proto.ast.addrspace_expr != 0;
+    try wip_decls.next(gpa, is_pub, is_export, fn_proto.ast.align_expr != 0, has_section_or_addrspace);
 
     var params_scope = &fn_gz.base;
     const is_var_args = is_var_args: {
@@ -3011,6 +3036,9 @@ fn fnDecl(
     const align_inst: Zir.Inst.Ref = if (fn_proto.ast.align_expr == 0) .none else inst: {
         break :inst try expr(&decl_gz, params_scope, align_rl, fn_proto.ast.align_expr);
     };
+    const addrspace_inst: Zir.Inst.Ref = if (fn_proto.ast.addrspace_expr == 0) .none else inst: {
+        break :inst try expr(&decl_gz, params_scope, .{ .ty = .address_space_type }, fn_proto.ast.addrspace_expr);
+    };
     const section_inst: Zir.Inst.Ref = if (fn_proto.ast.section_expr == 0) .none else inst: {
         break :inst try comptimeExpr(&decl_gz, params_scope, .{ .ty = .const_slice_u8_type }, fn_proto.ast.section_expr);
     };
@@ -3112,7 +3140,7 @@ fn fnDecl(
     _ = try decl_gz.addBreak(.break_inline, block_inst, func_inst);
     try decl_gz.setBlockBody(block_inst);
 
-    try wip_decls.payload.ensureUnusedCapacity(gpa, 9);
+    try wip_decls.payload.ensureUnusedCapacity(gpa, 10);
     {
         const contents_hash = std.zig.hashSrc(tree.getNodeSource(decl_node));
         const casted = @bitCast([4]u32, contents_hash);
@@ -3127,8 +3155,10 @@ fn fnDecl(
     if (align_inst != .none) {
         wip_decls.payload.appendAssumeCapacity(@enumToInt(align_inst));
     }
-    if (section_inst != .none) {
+
+    if (has_section_or_addrspace) {
         wip_decls.payload.appendAssumeCapacity(@enumToInt(section_inst));
+        wip_decls.payload.appendAssumeCapacity(@enumToInt(addrspace_inst));
     }
 }
 
@@ -3175,10 +3205,14 @@ fn globalVarDecl(
     const align_inst: Zir.Inst.Ref = if (var_decl.ast.align_node == 0) .none else inst: {
         break :inst try expr(&block_scope, &block_scope.base, align_rl, var_decl.ast.align_node);
     };
+    const addrspace_inst: Zir.Inst.Ref = if (var_decl.ast.addrspace_node == 0) .none else inst: {
+        break :inst try expr(&block_scope, &block_scope.base, .{ .ty = .address_space_type }, var_decl.ast.addrspace_node);
+    };
     const section_inst: Zir.Inst.Ref = if (var_decl.ast.section_node == 0) .none else inst: {
         break :inst try comptimeExpr(&block_scope, &block_scope.base, .{ .ty = .const_slice_u8_type }, var_decl.ast.section_node);
     };
-    try wip_decls.next(gpa, is_pub, is_export, align_inst != .none, section_inst != .none);
+    const has_section_or_addrspace = section_inst != .none or addrspace_inst != .none;
+    try wip_decls.next(gpa, is_pub, is_export, align_inst != .none, has_section_or_addrspace);
 
     const is_threadlocal = if (var_decl.threadlocal_token) |tok| blk: {
         if (!is_mutable) {
@@ -3256,7 +3290,7 @@ fn globalVarDecl(
     _ = try block_scope.addBreak(.break_inline, block_inst, var_inst);
     try block_scope.setBlockBody(block_inst);
 
-    try wip_decls.payload.ensureUnusedCapacity(gpa, 9);
+    try wip_decls.payload.ensureUnusedCapacity(gpa, 10);
     {
         const contents_hash = std.zig.hashSrc(tree.getNodeSource(node));
         const casted = @bitCast([4]u32, contents_hash);
@@ -3271,8 +3305,9 @@ fn globalVarDecl(
     if (align_inst != .none) {
         wip_decls.payload.appendAssumeCapacity(@enumToInt(align_inst));
     }
-    if (section_inst != .none) {
+    if (has_section_or_addrspace) {
         wip_decls.payload.appendAssumeCapacity(@enumToInt(section_inst));
+        wip_decls.payload.appendAssumeCapacity(@enumToInt(addrspace_inst));
     }
 }
 

src/Module.zig

@@ -288,6 +288,8 @@ pub const Decl = struct {
     align_val: Value,
     /// Populated when `has_tv`.
     linksection_val: Value,
+    /// Populated when `has_tv`.
+    @"addrspace": std.builtin.AddressSpace,
     /// The memory for ty, val, align_val, linksection_val.
     /// If this is `null` then there is no memory management needed.
     value_arena: ?*std.heap.ArenaAllocator.State = null,
@@ -351,7 +353,7 @@ pub const Decl = struct {
         /// to require re-analysis.
         outdated,
     },
-    /// Whether `typed_value`, `align_val`, and `linksection_val` are populated.
+    /// Whether `typed_value`, `align_val`, `linksection_val` and `addrspace` are populated.
     has_tv: bool,
     /// If `true` it means the `Decl` is the resource owner of the type/value associated
     /// with it. That means when `Decl` is destroyed, the cleanup code should additionally
@@ -366,8 +368,8 @@ pub const Decl = struct {
     is_exported: bool,
     /// Whether the ZIR code provides an align instruction.
     has_align: bool,
-    /// Whether the ZIR code provides a linksection instruction.
+    /// Whether the ZIR code provides a linksection and address space instruction.
-    has_linksection: bool,
+    has_linksection_or_addrspace: bool,
     /// Flag used by garbage collection to mark and sweep.
     /// Decls which correspond to an AST node always have this field set to `true`.
     /// Anonymous Decls are initialized with this field set to `false` and then it
@@ -489,14 +491,22 @@ pub const Decl = struct {
         if (!decl.has_align) return .none;
         assert(decl.zir_decl_index != 0);
         const zir = decl.namespace.file_scope.zir;
-        return @intToEnum(Zir.Inst.Ref, zir.extra[decl.zir_decl_index + 6]);
+        return @intToEnum(Zir.Inst.Ref, zir.extra[decl.zir_decl_index + 7]);
     }
 
     pub fn zirLinksectionRef(decl: Decl) Zir.Inst.Ref {
-        if (!decl.has_linksection) return .none;
+        if (!decl.has_linksection_or_addrspace) return .none;
         assert(decl.zir_decl_index != 0);
         const zir = decl.namespace.file_scope.zir;
-        const extra_index = decl.zir_decl_index + 6 + @boolToInt(decl.has_align);
+        const extra_index = decl.zir_decl_index + 7 + @boolToInt(decl.has_align);
+        return @intToEnum(Zir.Inst.Ref, zir.extra[extra_index]);
+    }
+
+    pub fn zirAddrspaceRef(decl: Decl) Zir.Inst.Ref {
+        if (!decl.has_linksection_or_addrspace) return .none;
+        assert(decl.zir_decl_index != 0);
+        const zir = decl.namespace.file_scope.zir;
+        const extra_index = decl.zir_decl_index + 7 + @boolToInt(decl.has_align) + 1;
         return @intToEnum(Zir.Inst.Ref, zir.extra[extra_index]);
     }
 
@@ -3072,7 +3082,7 @@ pub fn semaFile(mod: *Module, file: *Scope.File) SemaError!void {
     new_decl.is_pub = true;
     new_decl.is_exported = false;
     new_decl.has_align = false;
-    new_decl.has_linksection = false;
+    new_decl.has_linksection_or_addrspace = false;
     new_decl.ty = struct_ty;
     new_decl.val = struct_val;
     new_decl.has_tv = true;
@@ -3202,6 +3212,24 @@ fn semaDecl(mod: *Module, decl: *Decl) !bool {
         if (linksection_ref == .none) break :blk Value.initTag(.null_value);
         break :blk (try sema.resolveInstConst(&block_scope, src, linksection_ref)).val;
     };
+    const address_space = blk: {
+        const addrspace_ctx: Sema.AddressSpaceContext = switch (decl_tv.val.tag()) {
+            .function, .extern_fn => .function,
+            .variable => .variable,
+            else => .constant,
+        };
+
+        break :blk switch (decl.zirAddrspaceRef()) {
+            .none => switch (addrspace_ctx) {
+                .function => target_util.defaultAddressSpace(sema.mod.getTarget(), .function),
+                .variable => target_util.defaultAddressSpace(sema.mod.getTarget(), .global_mutable),
+                .constant => target_util.defaultAddressSpace(sema.mod.getTarget(), .global_constant),
+                else => unreachable,
+            },
+            else => |addrspace_ref| try sema.analyzeAddrspace(&block_scope, src, addrspace_ref, addrspace_ctx),
+        };
+    };
+
     // Note this resolves the type of the Decl, not the value; if this Decl
     // is a struct, for example, this resolves `type` (which needs no resolution),
     // not the struct itself.
@@ -3258,6 +3286,7 @@ fn semaDecl(mod: *Module, decl: *Decl) !bool {
             decl.val = try decl_tv.val.copy(&decl_arena.allocator);
             decl.align_val = try align_val.copy(&decl_arena.allocator);
             decl.linksection_val = try linksection_val.copy(&decl_arena.allocator);
+            decl.@"addrspace" = address_space;
             decl.has_tv = true;
             decl.owns_tv = owns_tv;
             decl_arena_state.* = decl_arena.state;
@@ -3319,6 +3348,7 @@ fn semaDecl(mod: *Module, decl: *Decl) !bool {
     decl.val = try decl_tv.val.copy(&decl_arena.allocator);
     decl.align_val = try align_val.copy(&decl_arena.allocator);
     decl.linksection_val = try linksection_val.copy(&decl_arena.allocator);
+    decl.@"addrspace" = address_space;
     decl.has_tv = true;
     decl_arena_state.* = decl_arena.state;
     decl.value_arena = decl_arena_state;
@@ -3526,8 +3556,8 @@ pub fn scanNamespace(
 
         const decl_sub_index = extra_index;
         extra_index += 7; // src_hash(4) + line(1) + name(1) + value(1)
-        extra_index += @truncate(u1, flags >> 2);
+        extra_index += @truncate(u1, flags >> 2); // Align
-        extra_index += @truncate(u1, flags >> 3);
+        extra_index += @as(u2, @truncate(u1, flags >> 3)) * 2; // Link section or address space, consists of 2 Refs
 
         try scanDecl(&scan_decl_iter, decl_sub_index, flags);
     }
@@ -3553,10 +3583,10 @@ fn scanDecl(iter: *ScanDeclIter, decl_sub_index: usize, flags: u4) SemaError!voi
     const zir = namespace.file_scope.zir;
 
     // zig fmt: off
-    const is_pub          = (flags & 0b0001) != 0;
+    const is_pub                       = (flags & 0b0001) != 0;
-    const export_bit      = (flags & 0b0010) != 0;
+    const export_bit                   = (flags & 0b0010) != 0;
-    const has_align       = (flags & 0b0100) != 0;
+    const has_align                    = (flags & 0b0100) != 0;
-    const has_linksection = (flags & 0b1000) != 0;
+    const has_linksection_or_addrspace = (flags & 0b1000) != 0;
     // zig fmt: on
 
     const line = iter.parent_decl.relativeToLine(zir.extra[decl_sub_index + 4]);
@@ -3639,7 +3669,7 @@ fn scanDecl(iter: *ScanDeclIter, decl_sub_index: usize, flags: u4) SemaError!voi
         new_decl.is_exported = is_exported;
         new_decl.is_usingnamespace = is_usingnamespace;
         new_decl.has_align = has_align;
-        new_decl.has_linksection = has_linksection;
+        new_decl.has_linksection_or_addrspace = has_linksection_or_addrspace;
         new_decl.zir_decl_index = @intCast(u32, decl_sub_index);
         new_decl.alive = true; // This Decl corresponds to an AST node and therefore always alive.
         return;
@@ -3656,7 +3686,7 @@ fn scanDecl(iter: *ScanDeclIter, decl_sub_index: usize, flags: u4) SemaError!voi
     decl.is_exported = is_exported;
     decl.is_usingnamespace = is_usingnamespace;
     decl.has_align = has_align;
-    decl.has_linksection = has_linksection;
+    decl.has_linksection_or_addrspace = has_linksection_or_addrspace;
     decl.zir_decl_index = @intCast(u32, decl_sub_index);
     if (decl.getFunction()) |_| {
         switch (mod.comp.bin_file.tag) {
@@ -4028,6 +4058,7 @@ pub fn allocateNewDecl(mod: *Module, namespace: *Scope.Namespace, src_node: Ast.
         .val = undefined,
         .align_val = undefined,
         .linksection_val = undefined,
+        .@"addrspace" = undefined,
         .analysis = .unreferenced,
         .deletion_flag = false,
         .zir_decl_index = 0,
@@ -4052,7 +4083,7 @@ pub fn allocateNewDecl(mod: *Module, namespace: *Scope.Namespace, src_node: Ast.
         .generation = 0,
         .is_pub = false,
         .is_exported = false,
-        .has_linksection = false,
+        .has_linksection_or_addrspace = false,
         .has_align = false,
         .alive = false,
         .is_usingnamespace = false,
@@ -4185,6 +4216,9 @@ pub fn createAnonymousDeclFromDeclNamed(
     new_decl.src_line = owner_decl.src_line;
     new_decl.ty = typed_value.ty;
     new_decl.val = typed_value.val;
+    new_decl.align_val = Value.initTag(.null_value);
+    new_decl.linksection_val = Value.initTag(.null_value);
+    new_decl.@"addrspace" = .generic; // default global addrspace
     new_decl.has_tv = true;
     new_decl.analysis = .complete;
     new_decl.generation = mod.generation;
@@ -4330,10 +4364,59 @@ pub fn simplePtrType(
     elem_ty: Type,
     mutable: bool,
     size: std.builtin.TypeInfo.Pointer.Size,
+    @"addrspace": std.builtin.AddressSpace,
 ) Allocator.Error!Type {
+    return ptrType(
+        arena,
+        elem_ty,
+        null,
+        0,
+        @"addrspace",
+        0,
+        0,
+        mutable,
+        false,
+        false,
+        size,
+    );
+}
+
+pub fn ptrType(
+    arena: *Allocator,
+    elem_ty: Type,
+    sentinel: ?Value,
+    @"align": u32,
+    @"addrspace": std.builtin.AddressSpace,
+    bit_offset: u16,
+    host_size: u16,
+    mutable: bool,
+    @"allowzero": bool,
+    @"volatile": bool,
+    size: std.builtin.TypeInfo.Pointer.Size,
+) Allocator.Error!Type {
+    assert(host_size == 0 or bit_offset < host_size * 8);
+
+    if (sentinel != null or @"align" != 0 or @"addrspace" != .generic or
+        bit_offset != 0 or host_size != 0 or @"allowzero" or @"volatile")
+    {
+        return Type.Tag.pointer.create(arena, .{
+            .pointee_type = elem_ty,
+            .sentinel = sentinel,
+            .@"align" = @"align",
+            .@"addrspace" = @"addrspace",
+            .bit_offset = bit_offset,
+            .host_size = host_size,
+            .@"allowzero" = @"allowzero",
+            .mutable = mutable,
+            .@"volatile" = @"volatile",
+            .size = size,
+        });
+    }
+
     if (!mutable and size == .Slice and elem_ty.eql(Type.initTag(.u8))) {
         return Type.initTag(.const_slice_u8);
     }
+
     // TODO stage1 type inference bug
     const T = Type.Tag;
 
@@ -4352,34 +4435,6 @@ pub fn simplePtrType(
     return Type.initPayload(&type_payload.base);
 }
 
-pub fn ptrType(
-    arena: *Allocator,
-    elem_ty: Type,
-    sentinel: ?Value,
-    @"align": u32,
-    bit_offset: u16,
-    host_size: u16,
-    mutable: bool,
-    @"allowzero": bool,
-    @"volatile": bool,
-    size: std.builtin.TypeInfo.Pointer.Size,
-) Allocator.Error!Type {
-    assert(host_size == 0 or bit_offset < host_size * 8);
-
-    // TODO check if type can be represented by simplePtrType
-    return Type.Tag.pointer.create(arena, .{
-        .pointee_type = elem_ty,
-        .sentinel = sentinel,
-        .@"align" = @"align",
-        .bit_offset = bit_offset,
-        .host_size = host_size,
-        .@"allowzero" = @"allowzero",
-        .mutable = mutable,
-        .@"volatile" = @"volatile",
-        .size = size,
-    });
-}
-
 pub fn optionalType(arena: *Allocator, child_type: Type) Allocator.Error!Type {
     switch (child_type.tag()) {
         .single_const_pointer => return Type.Tag.optional_single_const_pointer.create(
@@ -4709,7 +4764,7 @@ pub fn populateTestFunctions(mod: *Module) !void {
     const builtin_file = (mod.importPkg(builtin_pkg) catch unreachable).file;
     const builtin_namespace = builtin_file.root_decl.?.namespace;
     const decl = builtin_namespace.decls.get("test_functions").?;
-    var buf: Type.Payload.ElemType = undefined;
+    var buf: Type.SlicePtrFieldTypeBuffer = undefined;
     const tmp_test_fn_ty = decl.ty.slicePtrFieldType(&buf).elemType();
 
     const array_decl = d: {

src/Sema.zig

@@ -1373,7 +1373,13 @@ fn zirRetPtr(
         return sema.analyzeComptimeAlloc(block, sema.fn_ret_ty);
     }
 
-    const ptr_type = try Module.simplePtrType(sema.arena, sema.fn_ret_ty, true, .One);
+    const ptr_type = try Module.simplePtrType(
+        sema.arena,
+        sema.fn_ret_ty,
+        true,
+        .One,
+        target_util.defaultAddressSpace(sema.mod.getTarget(), .local),
+    );
     return block.addTy(.alloc, ptr_type);
 }
 
@@ -1521,7 +1527,13 @@ fn zirAlloc(sema: *Sema, block: *Scope.Block, inst: Zir.Inst.Index) CompileError
     const ty_src: LazySrcLoc = .{ .node_offset_var_decl_ty = inst_data.src_node };
     const var_decl_src = inst_data.src();
     const var_type = try sema.resolveType(block, ty_src, inst_data.operand);
-    const ptr_type = try Module.simplePtrType(sema.arena, var_type, true, .One);
+    const ptr_type = try Module.simplePtrType(
+        sema.arena,
+        var_type,
+        true,
+        .One,
+        target_util.defaultAddressSpace(sema.mod.getTarget(), .local),
+    );
     try sema.requireRuntimeBlock(block, var_decl_src);
     return block.addTy(.alloc, ptr_type);
 }
@@ -1538,7 +1550,13 @@ fn zirAllocMut(sema: *Sema, block: *Scope.Block, inst: Zir.Inst.Index) CompileEr
         return sema.analyzeComptimeAlloc(block, var_type);
     }
     try sema.validateVarType(block, ty_src, var_type);
-    const ptr_type = try Module.simplePtrType(sema.arena, var_type, true, .One);
+    const ptr_type = try Module.simplePtrType(
+        sema.arena,
+        var_type,
+        true,
+        .One,
+        target_util.defaultAddressSpace(sema.mod.getTarget(), .local),
+    );
     try sema.requireRuntimeBlock(block, var_decl_src);
     return block.addTy(.alloc, ptr_type);
 }
@@ -1598,7 +1616,13 @@ fn zirResolveInferredAlloc(sema: *Sema, block: *Scope.Block, inst: Zir.Inst.Inde
         try sema.mod.declareDeclDependency(sema.owner_decl, decl);
 
         const final_elem_ty = try decl.ty.copy(sema.arena);
-        const final_ptr_ty = try Module.simplePtrType(sema.arena, final_elem_ty, true, .One);
+        const final_ptr_ty = try Module.simplePtrType(
+            sema.arena,
+            final_elem_ty,
+            true,
+            .One,
+            target_util.defaultAddressSpace(sema.mod.getTarget(), .local),
+        );
         const final_ptr_ty_inst = try sema.addType(final_ptr_ty);
         sema.air_instructions.items(.data)[ptr_inst].ty_pl.ty = final_ptr_ty_inst;
 
@@ -1620,7 +1644,13 @@ fn zirResolveInferredAlloc(sema: *Sema, block: *Scope.Block, inst: Zir.Inst.Inde
             try sema.validateVarType(block, ty_src, final_elem_ty);
         }
         // Change it to a normal alloc.
-        const final_ptr_ty = try Module.simplePtrType(sema.arena, final_elem_ty, true, .One);
+        const final_ptr_ty = try Module.simplePtrType(
+            sema.arena,
+            final_elem_ty,
+            true,
+            .One,
+            target_util.defaultAddressSpace(sema.mod.getTarget(), .local),
+        );
         sema.air_instructions.set(ptr_inst, .{
             .tag = .alloc,
             .data = .{ .ty = final_ptr_ty },
@@ -1774,7 +1804,14 @@ fn zirStoreToBlockPtr(sema: *Sema, block: *Scope.Block, inst: Zir.Inst.Index) Co
     }
     const ptr = sema.resolveInst(bin_inst.lhs);
     const value = sema.resolveInst(bin_inst.rhs);
-    const ptr_ty = try Module.simplePtrType(sema.arena, sema.typeOf(value), true, .One);
+    const ptr_ty = try Module.simplePtrType(
+        sema.arena,
+        sema.typeOf(value),
+        true,
+        .One,
+        // TODO figure out which address space is appropriate here
+        target_util.defaultAddressSpace(sema.mod.getTarget(), .local),
+    );
     // TODO detect when this store should be done at compile-time. For example,
     // if expressions should force it when the condition is compile-time known.
     const src: LazySrcLoc = .unneeded;
@@ -1821,7 +1858,14 @@ fn zirStoreToInferredPtr(sema: *Sema, block: *Scope.Block, inst: Zir.Inst.Index)
         // for the inferred allocation.
         try inferred_alloc.data.stored_inst_list.append(sema.arena, operand);
         // Create a runtime bitcast instruction with exactly the type the pointer wants.
-        const ptr_ty = try Module.simplePtrType(sema.arena, operand_ty, true, .One);
+        const ptr_ty = try Module.simplePtrType(
+            sema.arena,
+            operand_ty,
+            true,
+            .One,
+            // TODO figure out which address space is appropriate here
+            target_util.defaultAddressSpace(sema.mod.getTarget(), .local),
+        );
         const bitcasted_ptr = try block.addTyOp(.bitcast, ptr_ty, ptr);
         return sema.storePtr(block, src, bitcasted_ptr, operand);
     }
@@ -3004,7 +3048,7 @@ fn analyzeCall(
             new_decl.is_pub = module_fn.owner_decl.is_pub;
             new_decl.is_exported = module_fn.owner_decl.is_exported;
             new_decl.has_align = module_fn.owner_decl.has_align;
-            new_decl.has_linksection = module_fn.owner_decl.has_linksection;
+            new_decl.has_linksection_or_addrspace = module_fn.owner_decl.has_linksection_or_addrspace;
             new_decl.zir_decl_index = module_fn.owner_decl.zir_decl_index;
             new_decl.alive = true; // This Decl is called at runtime.
             new_decl.has_tv = true;
@@ -3658,7 +3702,13 @@ fn zirOptionalPayloadPtr(
     }
 
     const child_type = try opt_type.optionalChildAlloc(sema.arena);
-    const child_pointer = try Module.simplePtrType(sema.arena, child_type, !optional_ptr_ty.isConstPtr(), .One);
+    const child_pointer = try Module.simplePtrType(
+        sema.arena,
+        child_type,
+        !optional_ptr_ty.isConstPtr(),
+        .One,
+        optional_ptr_ty.ptrAddressSpace(),
+    );
 
     if (try sema.resolveDefinedValue(block, src, optional_ptr)) |pointer_val| {
         if (try pointer_val.pointerDeref(sema.arena)) |val| {
@@ -3773,7 +3823,13 @@ fn zirErrUnionPayloadPtr(
         return sema.mod.fail(&block.base, src, "expected error union type, found {}", .{operand_ty.elemType()});
 
     const payload_ty = operand_ty.elemType().errorUnionPayload();
-    const operand_pointer_ty = try Module.simplePtrType(sema.arena, payload_ty, !operand_ty.isConstPtr(), .One);
+    const operand_pointer_ty = try Module.simplePtrType(
+        sema.arena,
+        payload_ty,
+        !operand_ty.isConstPtr(),
+        .One,
+        operand_ty.ptrAddressSpace(),
+    );
 
     if (try sema.resolveDefinedValue(block, src, operand)) |pointer_val| {
         if (try pointer_val.pointerDeref(sema.arena)) |val| {
@@ -6879,6 +6935,7 @@ fn zirPtrTypeSimple(sema: *Sema, block: *Scope.Block, inst: Zir.Inst.Index) Comp
         elem_type,
         null,
         0,
+        .generic,
         0,
         0,
         inst_data.is_mutable,
@@ -6911,6 +6968,12 @@ fn zirPtrType(sema: *Sema, block: *Scope.Block, inst: Zir.Inst.Index) CompileErr
         break :blk try sema.resolveAlreadyCoercedInt(block, .unneeded, ref, u32);
     } else 0;
 
+    const address_space = if (inst_data.flags.has_addrspace) blk: {
+        const ref = @intToEnum(Zir.Inst.Ref, sema.code.extra[extra_i]);
+        extra_i += 1;
+        break :blk try sema.analyzeAddrspace(block, .unneeded, ref, .pointer);
+    } else .generic;
+
     const bit_start = if (inst_data.flags.has_bit_range) blk: {
         const ref = @intToEnum(Zir.Inst.Ref, sema.code.extra[extra_i]);
         extra_i += 1;
@@ -6933,6 +6996,7 @@ fn zirPtrType(sema: *Sema, block: *Scope.Block, inst: Zir.Inst.Index) CompileErr
         elem_type,
         sentinel,
         abi_align,
+        address_space,
         bit_start,
         bit_end,
         inst_data.flags.is_mutable,
@@ -8339,7 +8403,13 @@ fn panicWithMsg(
     const panic_fn = try sema.getBuiltin(block, src, "panic");
     const unresolved_stack_trace_ty = try sema.getBuiltinType(block, src, "StackTrace");
     const stack_trace_ty = try sema.resolveTypeFields(block, src, unresolved_stack_trace_ty);
-    const ptr_stack_trace_ty = try Module.simplePtrType(arena, stack_trace_ty, true, .One);
+    const ptr_stack_trace_ty = try Module.simplePtrType(
+        arena,
+        stack_trace_ty,
+        true,
+        .One,
+        target_util.defaultAddressSpace(sema.mod.getTarget(), .global_constant), // TODO might need a place that is more dynamic
+    );
     const null_stack_trace = try sema.addConstant(
         try Module.optionalType(arena, ptr_stack_trace_ty),
         Value.initTag(.null_value),
@@ -8423,7 +8493,7 @@ fn fieldVal(
         .Pointer => switch (object_ty.ptrSize()) {
             .Slice => {
                 if (mem.eql(u8, field_name, "ptr")) {
-                    const buf = try arena.create(Type.Payload.ElemType);
+                    const buf = try arena.create(Type.SlicePtrFieldTypeBuffer);
                     const result_ty = object_ty.slicePtrFieldType(buf);
                     if (try sema.resolveMaybeUndefVal(block, object_src, object)) |val| {
                         if (val.isUndef()) return sema.addConstUndef(result_ty);
@@ -8457,21 +8527,32 @@ fn fieldVal(
                 }
             },
             .One => {
-                const elem_ty = object_ty.elemType();
+                const ptr_child = object_ty.elemType();
-                if (elem_ty.zigTypeTag() == .Array) {
+                switch (ptr_child.zigTypeTag()) {
-                    if (mem.eql(u8, field_name, "len")) {
+                    .Array => {
-                        return sema.addConstant(
+                        if (mem.eql(u8, field_name, "len")) {
-                            Type.initTag(.comptime_int),
+                            return sema.addConstant(
-                            try Value.Tag.int_u64.create(arena, elem_ty.arrayLen()),
+                                Type.initTag(.comptime_int),
-                        );
+                                try Value.Tag.int_u64.create(arena, ptr_child.arrayLen()),
-                    } else {
+                            );
-                        return mod.fail(
+                        } else {
-                            &block.base,
+                            return mod.fail(
-                            field_name_src,
+                                &block.base,
-                            "no member named '{s}' in '{}'",
+                                field_name_src,
-                            .{ field_name, object_ty },
+                                "no member named '{s}' in '{}'",
-                        );
+                                .{ field_name, object_ty },
-                    }
+                            );
+                        }
+                    },
+                    .Struct => {
+                        const struct_ptr_deref = try sema.analyzeLoad(block, src, object, object_src);
+                        return sema.unionFieldVal(block, src, struct_ptr_deref, field_name, field_name_src, ptr_child);
+                    },
+                    .Union => {
+                        const union_ptr_deref = try sema.analyzeLoad(block, src, object, object_src);
+                        return sema.unionFieldVal(block, src, union_ptr_deref, field_name, field_name_src, ptr_child);
+                    },
+                    else => {},
                 }
             },
             .Many, .C => {},
@@ -8595,9 +8676,8 @@ fn fieldPtr(
                 );
             }
         },
-        .Pointer => {
+        .Pointer => switch (object_ty.ptrSize()) {
-            const ptr_child = object_ty.elemType();
+            .Slice => {
-            if (ptr_child.isSlice()) {
                 // Here for the ptr and len fields what we need to do is the situation
                 // when a temporary has its address taken, e.g. `&a[c..d].len`.
                 // This value may be known at compile-time or runtime. In the former
@@ -8627,26 +8707,39 @@ fn fieldPtr(
                         .{ field_name, object_ty },
                     );
                 }
-            } else switch (ptr_child.zigTypeTag()) {
+            },
-                .Array => {
+            .One => {
-                    if (mem.eql(u8, field_name, "len")) {
+                const ptr_child = object_ty.elemType();
-                        var anon_decl = try block.startAnonDecl();
+                switch (ptr_child.zigTypeTag()) {
-                        defer anon_decl.deinit();
+                    .Array => {
-                        return sema.analyzeDeclRef(try anon_decl.finish(
+                        if (mem.eql(u8, field_name, "len")) {
-                            Type.initTag(.comptime_int),
+                            var anon_decl = try block.startAnonDecl();
-                            try Value.Tag.int_u64.create(anon_decl.arena(), ptr_child.arrayLen()),
+                            defer anon_decl.deinit();
-                        ));
+                            return sema.analyzeDeclRef(try anon_decl.finish(
-                    } else {
+                                Type.initTag(.comptime_int),
-                        return mod.fail(
+                                try Value.Tag.int_u64.create(anon_decl.arena(), ptr_child.arrayLen()),
-                            &block.base,
+                            ));
-                            field_name_src,
+                        } else {
-                            "no member named '{s}' in '{}'",
+                            return mod.fail(
-                            .{ field_name, object_ty },
+                                &block.base,
-                        );
+                                field_name_src,
-                    }
+                                "no member named '{s}' in '{}'",
-                },
+                                .{ field_name, object_ty },
-                else => {},
+                            );
-            }
+                        }
+                    },
+                    .Struct => {
+                        const struct_ptr_deref = try sema.analyzeLoad(block, src, object_ptr, object_ptr_src);
+                        return sema.structFieldPtr(block, src, struct_ptr_deref, field_name, field_name_src, ptr_child);
+                    },
+                    .Union => {
+                        const union_ptr_deref = try sema.analyzeLoad(block, src, object_ptr, object_ptr_src);
+                        return sema.unionFieldPtr(block, src, union_ptr_deref, field_name, field_name_src, ptr_child);
+                    },
+                    else => {},
+                }
+            },
+            .Many, .C => {},
         },
         .Type => {
             _ = try sema.resolveConstValue(block, object_ptr_src, object_ptr);
@@ -8788,13 +8881,20 @@ fn structFieldPtr(
     const arena = sema.arena;
     assert(unresolved_struct_ty.zigTypeTag() == .Struct);
 
+    const struct_ptr_ty = sema.typeOf(struct_ptr);
     const struct_ty = try sema.resolveTypeFields(block, src, unresolved_struct_ty);
     const struct_obj = struct_ty.castTag(.@"struct").?.data;
 
     const field_index = struct_obj.fields.getIndex(field_name) orelse
         return sema.failWithBadFieldAccess(block, struct_obj, field_name_src, field_name);
     const field = struct_obj.fields.values()[field_index];
-    const ptr_field_ty = try Module.simplePtrType(arena, field.ty, true, .One);
+    const ptr_field_ty = try Module.simplePtrType(
+        arena,
+        field.ty,
+        struct_ptr_ty.ptrIsMutable(),
+        .One,
+        struct_ptr_ty.ptrAddressSpace(),
+    );
 
     if (try sema.resolveDefinedValue(block, src, struct_ptr)) |struct_ptr_val| {
         return sema.addConstant(
@@ -8885,6 +8985,7 @@ fn unionFieldPtr(
     const arena = sema.arena;
     assert(unresolved_union_ty.zigTypeTag() == .Union);
 
+    const union_ptr_ty = sema.typeOf(union_ptr);
     const union_ty = try sema.resolveTypeFields(block, src, unresolved_union_ty);
     const union_obj = union_ty.cast(Type.Payload.Union).?.data;
 
@@ -8892,7 +8993,13 @@ fn unionFieldPtr(
         return sema.failWithBadUnionFieldAccess(block, union_obj, field_name_src, field_name);
 
     const field = union_obj.fields.values()[field_index];
-    const ptr_field_ty = try Module.simplePtrType(arena, field.ty, true, .One);
+    const ptr_field_ty = try Module.simplePtrType(
+        arena,
+        field.ty,
+        union_ptr_ty.ptrIsMutable(),
+        .One,
+        union_ptr_ty.ptrAddressSpace(),
+    );
 
     if (try sema.resolveDefinedValue(block, src, union_ptr)) |union_ptr_val| {
         // TODO detect inactive union field and emit compile error
@@ -9068,10 +9175,13 @@ fn elemPtrArray(
 ) CompileError!Air.Inst.Ref {
     const array_ptr_ty = sema.typeOf(array_ptr);
     const pointee_type = array_ptr_ty.elemType().elemType();
-    const result_ty = if (array_ptr_ty.ptrIsMutable())
+    const result_ty = try Module.simplePtrType(
-        try Type.Tag.single_mut_pointer.create(sema.arena, pointee_type)
+        sema.arena,
-    else
+        pointee_type,
-        try Type.Tag.single_const_pointer.create(sema.arena, pointee_type);
+        array_ptr_ty.ptrIsMutable(),
+        .One,
+        array_ptr_ty.ptrAddressSpace(),
+    );
 
     if (try sema.resolveDefinedValue(block, src, array_ptr)) |array_ptr_val| {
         if (try sema.resolveDefinedValue(block, elem_index_src, elem_index)) |index_val| {
@@ -9162,6 +9272,7 @@ fn coerce(
                 const dest_is_mut = !dest_type.isConstPtr();
                 if (inst_ty.isConstPtr() and dest_is_mut) break :src_array_ptr;
                 if (inst_ty.isVolatilePtr() and !dest_type.isVolatilePtr()) break :src_array_ptr;
+                if (inst_ty.ptrAddressSpace() != dest_type.ptrAddressSpace()) break :src_array_ptr;
 
                 const dst_elem_type = dest_type.elemType();
                 switch (coerceInMemoryAllowed(dst_elem_type, array_elem_type, dest_is_mut)) {
@@ -9297,6 +9408,10 @@ fn coerceInMemoryAllowed(dest_type: Type, src_type: Type, dest_is_mut: bool) InM
             return child;
         }
 
+        if (dest_info.@"addrspace" != src_info.@"addrspace") {
+            return .no_match;
+        }
+
         const ok_sent = dest_info.sentinel == null or src_info.size == .C or
             (src_info.sentinel != null and
             dest_info.sentinel.?.eql(src_info.sentinel.?, dest_info.pointee_type));
@@ -9590,11 +9705,11 @@ fn analyzeDeclRef(sema: *Sema, decl: *Decl) CompileError!Air.Inst.Ref {
     const decl_tv = try decl.typedValue();
     if (decl_tv.val.castTag(.variable)) |payload| {
         const variable = payload.data;
-        const ty = try Module.simplePtrType(sema.arena, decl_tv.ty, variable.is_mutable, .One);
+        const ty = try Module.simplePtrType(sema.arena, decl_tv.ty, variable.is_mutable, .One, decl.@"addrspace");
         return sema.addConstant(ty, try Value.Tag.decl_ref.create(sema.arena, decl));
     }
     return sema.addConstant(
-        try Module.simplePtrType(sema.arena, decl_tv.ty, false, .One),
+        try Module.simplePtrType(sema.arena, decl_tv.ty, false, .One, decl.@"addrspace"),
         try Value.Tag.decl_ref.create(sema.arena, decl),
     );
 }
@@ -9617,8 +9732,9 @@ fn analyzeRef(
     }
 
     try sema.requireRuntimeBlock(block, src);
-    const ptr_type = try Module.simplePtrType(sema.arena, operand_ty, false, .One);
+    const address_space = target_util.defaultAddressSpace(sema.mod.getTarget(), .local);
-    const mut_ptr_type = try Module.simplePtrType(sema.arena, operand_ty, true, .One);
+    const ptr_type = try Module.simplePtrType(sema.arena, operand_ty, false, .One, address_space);
+    const mut_ptr_type = try Module.simplePtrType(sema.arena, operand_ty, true, .One, address_space);
     const alloc = try block.addTy(.alloc, mut_ptr_type);
     try sema.storePtr(block, src, alloc, operand);
 
@@ -9779,6 +9895,7 @@ fn analyzeSlice(
         return_elem_type,
         if (end_opt == .none) slice_sentinel else null,
         0, // TODO alignment
+        if (ptr_child.zigTypeTag() == .Pointer) ptr_child.ptrAddressSpace() else .generic,
         0,
         0,
         !ptr_child.isConstPtr(),
@@ -10286,6 +10403,7 @@ fn resolveTypeFields(sema: *Sema, block: *Scope.Block, src: LazySrcLoc, ty: Type
         .atomic_order => return sema.resolveBuiltinTypeFields(block, src, "AtomicOrder"),
         .atomic_rmw_op => return sema.resolveBuiltinTypeFields(block, src, "AtomicRmwOp"),
         .calling_convention => return sema.resolveBuiltinTypeFields(block, src, "CallingConvention"),
+        .address_space => return sema.resolveBuiltinTypeFields(block, src, "AddressSpace"),
         .float_mode => return sema.resolveBuiltinTypeFields(block, src, "FloatMode"),
         .reduce_op => return sema.resolveBuiltinTypeFields(block, src, "ReduceOp"),
         .call_options => return sema.resolveBuiltinTypeFields(block, src, "CallOptions"),
@@ -10680,6 +10798,7 @@ fn typeHasOnePossibleValue(
         .atomic_order,
         .atomic_rmw_op,
         .calling_convention,
+        .address_space,
         .float_mode,
         .reduce_op,
         .call_options,
@@ -10865,6 +10984,7 @@ pub fn addType(sema: *Sema, ty: Type) !Air.Inst.Ref {
         .atomic_order => return .atomic_order_type,
         .atomic_rmw_op => return .atomic_rmw_op_type,
         .calling_convention => return .calling_convention_type,
+        .address_space => return .address_space_type,
         .float_mode => return .float_mode_type,
         .reduce_op => return .reduce_op_type,
         .call_options => return .call_options_type,
@@ -10960,7 +11080,13 @@ fn analyzeComptimeAlloc(
     block: *Scope.Block,
     var_type: Type,
 ) CompileError!Air.Inst.Ref {
-    const ptr_type = try Module.simplePtrType(sema.arena, var_type, true, .One);
+    const ptr_type = try Module.simplePtrType(
+        sema.arena,
+        var_type,
+        true,
+        .One,
+        target_util.defaultAddressSpace(sema.mod.getTarget(), .global_constant),
+    );
 
     var anon_decl = try block.startAnonDecl();
     defer anon_decl.deinit();
@@ -10976,3 +11102,58 @@ fn analyzeComptimeAlloc(
         .decl = decl,
     }));
 }
+
+/// The places where a user can specify an address space attribute
+pub const AddressSpaceContext = enum {
+    /// A function is specificed to be placed in a certain address space.
+    function,
+
+    /// A (global) variable is specified to be placed in a certain address space.
+    /// In contrast to .constant, these values (and thus the address space they will be
+    /// placed in) are required to be mutable.
+    variable,
+
+    /// A (global) constant value is specified to be placed in a certain address space.
+    /// In contrast to .variable, values placed in this address space are not required to be mutable.
+    constant,
+
+    /// A pointer is ascripted to point into a certian address space.
+    pointer,
+};
+
+pub fn analyzeAddrspace(
+    sema: *Sema,
+    block: *Scope.Block,
+    src: LazySrcLoc,
+    zir_ref: Zir.Inst.Ref,
+    ctx: AddressSpaceContext,
+) !std.builtin.AddressSpace {
+    const addrspace_tv = try sema.resolveInstConst(block, src, zir_ref);
+    const address_space = addrspace_tv.val.toEnum(std.builtin.AddressSpace);
+    const target = sema.mod.getTarget();
+    const arch = target.cpu.arch;
+
+    const supported = switch (address_space) {
+        .generic => true,
+        .gs, .fs, .ss => (arch == .i386 or arch == .x86_64) and ctx == .pointer,
+    };
+
+    if (!supported) {
+        // TODO error messages could be made more elaborate here
+        const entity = switch (ctx) {
+            .function => "functions",
+            .variable => "mutable values",
+            .constant => "constant values",
+            .pointer => "pointers",
+        };
+
+        return sema.mod.fail(
+            &block.base,
+            src,
+            "{s} with address space '{s}' are not supported on {s}",
+            .{ entity, @tagName(address_space), arch.genericName() },
+        );
+    }
+
+    return address_space;
+}

src/Zir.zig

@@ -443,10 +443,10 @@ pub const Inst = struct {
         /// this instruction; a following 'ret' instruction will do the diversion.
         /// Uses the `str_tok` union field.
         ret_err_value_code,
-        /// Create a pointer type that does not have a sentinel, alignment, or bit range specified.
+        /// Create a pointer type that does not have a sentinel, alignment, address space, or bit range specified.
         /// Uses the `ptr_type_simple` union field.
         ptr_type_simple,
-        /// Create a pointer type which can have a sentinel, alignment, and/or bit range.
+        /// Create a pointer type which can have a sentinel, alignment, address space, and/or bit range.
         /// Uses the `ptr_type` union field.
         ptr_type,
         /// Slice operation `lhs[rhs..]`. No sentinel and no end offset.
@@ -1672,6 +1672,7 @@ pub const Inst = struct {
         atomic_order_type,
         atomic_rmw_op_type,
         calling_convention_type,
+        address_space_type,
         float_mode_type,
         reduce_op_type,
         call_options_type,
@@ -1928,6 +1929,10 @@ pub const Inst = struct {
                 .ty = Type.initTag(.type),
                 .val = Value.initTag(.calling_convention_type),
             },
+            .address_space_type = .{
+                .ty = Type.initTag(.type),
+                .val = Value.initTag(.address_space_type),
+            },
             .float_mode_type = .{
                 .ty = Type.initTag(.type),
                 .val = Value.initTag(.float_mode_type),
@@ -2129,8 +2134,9 @@ pub const Inst = struct {
                 is_volatile: bool,
                 has_sentinel: bool,
                 has_align: bool,
+                has_addrspace: bool,
                 has_bit_range: bool,
-                _: u2 = undefined,
+                _: u1 = undefined,
             },
             size: std.builtin.TypeInfo.Pointer.Size,
             /// Index into extra. See `PtrType`.
@@ -2360,12 +2366,13 @@ pub const Inst = struct {
         else_body_len: u32,
     };
 
-    /// Stored in extra. Depending on the flags in Data, there will be up to 4
+    /// Stored in extra. Depending on the flags in Data, there will be up to 5
     /// trailing Ref fields:
     /// 0. sentinel: Ref // if `has_sentinel` flag is set
     /// 1. align: Ref // if `has_align` flag is set
-    /// 2. bit_start: Ref // if `has_bit_range` flag is set
+    /// 2. address_space: Ref // if `has_addrspace` flag is set
-    /// 3. bit_end: Ref // if `has_bit_range` flag is set
+    /// 3. bit_start: Ref // if `has_bit_range` flag is set
+    /// 4. bit_end: Ref // if `has_bit_range` flag is set
     pub const PtrType = struct {
         elem_type: Ref,
     };
@@ -2483,7 +2490,7 @@ pub const Inst = struct {
     ///      0b000X: whether corresponding decl is pub
     ///      0b00X0: whether corresponding decl is exported
     ///      0b0X00: whether corresponding decl has an align expression
-    ///      0bX000: whether corresponding decl has a linksection expression
+    ///      0bX000: whether corresponding decl has a linksection or an address space expression
     /// 5. decl: { // for every decls_len
     ///        src_hash: [4]u32, // hash of source bytes
     ///        line: u32, // line number of decl, relative to parent
@@ -2495,7 +2502,10 @@ pub const Inst = struct {
     ///          this is a test decl, and the name starts at `name+1`.
     ///        value: Index,
     ///        align: Ref, // if corresponding bit is set
-    ///        link_section: Ref, // if corresponding bit is set
+    ///        link_section_or_address_space: { // if corresponding bit is set.
+    ///            link_section: Ref,
+    ///            address_space: Ref,
+    ///        }
     ///    }
     /// 6. inst: Index // for every body_len
     /// 7. flags: u32 // for every 8 fields
@@ -2547,7 +2557,7 @@ pub const Inst = struct {
     ///      0b000X: whether corresponding decl is pub
     ///      0b00X0: whether corresponding decl is exported
     ///      0b0X00: whether corresponding decl has an align expression
-    ///      0bX000: whether corresponding decl has a linksection expression
+    ///      0bX000: whether corresponding decl has a linksection or an address space expression
     /// 6. decl: { // for every decls_len
     ///        src_hash: [4]u32, // hash of source bytes
     ///        line: u32, // line number of decl, relative to parent
@@ -2559,7 +2569,10 @@ pub const Inst = struct {
     ///          this is a test decl, and the name starts at `name+1`.
     ///        value: Index,
     ///        align: Ref, // if corresponding bit is set
-    ///        link_section: Ref, // if corresponding bit is set
+    ///        link_section_or_address_space: { // if corresponding bit is set.
+    ///            link_section: Ref,
+    ///            address_space: Ref,
+    ///        }
     ///    }
     /// 7. inst: Index // for every body_len
     /// 8. has_bits: u32 // for every 32 fields
@@ -2592,7 +2605,7 @@ pub const Inst = struct {
     ///      0b000X: whether corresponding decl is pub
     ///      0b00X0: whether corresponding decl is exported
     ///      0b0X00: whether corresponding decl has an align expression
-    ///      0bX000: whether corresponding decl has a linksection expression
+    ///      0bX000: whether corresponding decl has a linksection or an address space expression
     /// 6. decl: { // for every decls_len
     ///        src_hash: [4]u32, // hash of source bytes
     ///        line: u32, // line number of decl, relative to parent
@@ -2604,7 +2617,10 @@ pub const Inst = struct {
     ///          this is a test decl, and the name starts at `name+1`.
     ///        value: Index,
     ///        align: Ref, // if corresponding bit is set
-    ///        link_section: Ref, // if corresponding bit is set
+    ///        link_section_or_address_space: { // if corresponding bit is set.
+    ///            link_section: Ref,
+    ///            address_space: Ref,
+    ///        }
     ///    }
     /// 7. inst: Index // for every body_len
     /// 8. has_bits: u32 // for every 8 fields
@@ -2641,7 +2657,7 @@ pub const Inst = struct {
     ///      0b000X: whether corresponding decl is pub
     ///      0b00X0: whether corresponding decl is exported
     ///      0b0X00: whether corresponding decl has an align expression
-    ///      0bX000: whether corresponding decl has a linksection expression
+    ///      0bX000: whether corresponding decl has a linksection or an address space expression
     /// 1. decl: { // for every decls_len
     ///        src_hash: [4]u32, // hash of source bytes
     ///        line: u32, // line number of decl, relative to parent
@@ -2653,7 +2669,10 @@ pub const Inst = struct {
     ///          this is a test decl, and the name starts at `name+1`.
     ///        value: Index,
     ///        align: Ref, // if corresponding bit is set
-    ///        link_section: Ref, // if corresponding bit is set
+    ///        link_section_or_address_space: { // if corresponding bit is set.
+    ///            link_section: Ref,
+    ///            address_space: Ref,
+    ///        }
     ///    }
     pub const OpaqueDecl = struct {
         decls_len: u32,

src/codegen.zig

@@ -4895,7 +4895,7 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
             switch (typed_value.ty.zigTypeTag()) {
                 .Pointer => switch (typed_value.ty.ptrSize()) {
                     .Slice => {
-                        var buf: Type.Payload.ElemType = undefined;
+                        var buf: Type.SlicePtrFieldTypeBuffer = undefined;
                         const ptr_type = typed_value.ty.slicePtrFieldType(&buf);
                         const ptr_mcv = try self.genTypedValue(.{ .ty = ptr_type, .val = typed_value.val });
                         const slice_len = typed_value.val.sliceLen();

src/codegen/c.zig

@@ -251,7 +251,7 @@ pub const DeclGen = struct {
                     try writer.writeByte('(');
                     try dg.renderType(writer, t);
                     try writer.writeAll("){");
-                    var buf: Type.Payload.ElemType = undefined;
+                    var buf: Type.SlicePtrFieldTypeBuffer = undefined;
                     try dg.renderValue(writer, t.slicePtrFieldType(&buf), val);
                     try writer.writeAll(", ");
                     try writer.print("{d}", .{val.sliceLen()});

src/codegen/llvm.zig

@@ -558,7 +558,8 @@ pub const DeclGen = struct {
             llvm_params_len,
             .False,
         );
-        const llvm_fn = self.llvmModule().addFunction(decl.name, fn_type);
+        const llvm_addrspace = self.llvmAddressSpace(decl.@"addrspace");
+        const llvm_fn = self.llvmModule().addFunctionInAddressSpace(decl.name, fn_type, llvm_addrspace);
 
         const is_extern = decl.val.tag() == .extern_fn;
         if (!is_extern) {
@@ -580,7 +581,24 @@ pub const DeclGen = struct {
         if (llvm_module.getNamedGlobal(decl.name)) |val| return val;
         // TODO: remove this redundant `llvmType`, it is also called in `genTypedValue`.
         const llvm_type = try self.llvmType(decl.ty);
-        return llvm_module.addGlobal(llvm_type, decl.name);
+        const llvm_addrspace = self.llvmAddressSpace(decl.@"addrspace");
+        return llvm_module.addGlobalInAddressSpace(llvm_type, decl.name, llvm_addrspace);
+    }
+
+    fn llvmAddressSpace(self: DeclGen, address_space: std.builtin.AddressSpace) c_uint {
+        const target = self.module.getTarget();
+        return switch (target.cpu.arch) {
+            .i386, .x86_64 => switch (address_space) {
+                .generic => llvm.address_space.default,
+                .gs => llvm.address_space.x86.gs,
+                .fs => llvm.address_space.x86.fs,
+                .ss => llvm.address_space.x86.ss,
+            },
+            else => switch (address_space) {
+                .generic => llvm.address_space.default,
+                else => unreachable,
+            },
+        };
     }
 
     fn llvmType(self: *DeclGen, t: Type) error{ OutOfMemory, CodegenFail }!*const llvm.Type {
@@ -609,7 +627,7 @@ pub const DeclGen = struct {
             .Bool => return self.context.intType(1),
             .Pointer => {
                 if (t.isSlice()) {
-                    var buf: Type.Payload.ElemType = undefined;
+                    var buf: Type.SlicePtrFieldTypeBuffer = undefined;
                     const ptr_type = t.slicePtrFieldType(&buf);
 
                     const fields: [2]*const llvm.Type = .{
@@ -619,7 +637,8 @@ pub const DeclGen = struct {
                     return self.context.structType(&fields, fields.len, .False);
                 } else {
                     const elem_type = try self.llvmType(t.elemType());
-                    return elem_type.pointerType(0);
+                    const llvm_addrspace = self.llvmAddressSpace(t.ptrAddressSpace());
+                    return elem_type.pointerType(llvm_addrspace);
                 }
             },
             .Array => {
@@ -685,7 +704,9 @@ pub const DeclGen = struct {
                     @intCast(c_uint, llvm_params.len),
                     llvm.Bool.fromBool(is_var_args),
                 );
-                return llvm_fn_ty.pointerType(0);
+                // TODO make .Fn not both a pointer type and a prototype
+                const llvm_addrspace = self.llvmAddressSpace(.generic);
+                return llvm_fn_ty.pointerType(llvm_addrspace);
             },
             .ComptimeInt => unreachable,
             .ComptimeFloat => unreachable,
@@ -753,7 +774,7 @@ pub const DeclGen = struct {
             .Pointer => switch (tv.val.tag()) {
                 .decl_ref => {
                     if (tv.ty.isSlice()) {
-                        var buf: Type.Payload.ElemType = undefined;
+                        var buf: Type.SlicePtrFieldTypeBuffer = undefined;
                         const ptr_ty = tv.ty.slicePtrFieldType(&buf);
                         var slice_len: Value.Payload.U64 = .{
                             .base = .{ .tag = .int_u64 },
@@ -783,12 +804,13 @@ pub const DeclGen = struct {
                     decl.alive = true;
                     const val = try self.resolveGlobalDecl(decl);
                     const llvm_var_type = try self.llvmType(tv.ty);
-                    const llvm_type = llvm_var_type.pointerType(0);
+                    const llvm_addrspace = self.llvmAddressSpace(decl.@"addrspace");
+                    const llvm_type = llvm_var_type.pointerType(llvm_addrspace);
                     return val.constBitCast(llvm_type);
                 },
                 .slice => {
                     const slice = tv.val.castTag(.slice).?.data;
-                    var buf: Type.Payload.ElemType = undefined;
+                    var buf: Type.SlicePtrFieldTypeBuffer = undefined;
                     const fields: [2]*const llvm.Value = .{
                         try self.genTypedValue(.{
                             .ty = tv.ty.slicePtrFieldType(&buf),

src/codegen/llvm/bindings.zig

@@ -197,6 +197,9 @@ pub const Module = opaque {
     pub const addFunction = LLVMAddFunction;
     extern fn LLVMAddFunction(*const Module, Name: [*:0]const u8, FunctionTy: *const Type) *const Value;
 
+    pub const addFunctionInAddressSpace = ZigLLVMAddFunctionInAddressSpace;
+    extern fn ZigLLVMAddFunctionInAddressSpace(*const Module, Name: [*:0]const u8, FunctionTy: *const Type, AddressSpace: c_uint) *const Value;
+
     pub const getNamedFunction = LLVMGetNamedFunction;
     extern fn LLVMGetNamedFunction(*const Module, Name: [*:0]const u8) ?*const Value;
 
@@ -209,6 +212,9 @@ pub const Module = opaque {
     pub const addGlobal = LLVMAddGlobal;
     extern fn LLVMAddGlobal(M: *const Module, Ty: *const Type, Name: [*:0]const u8) *const Value;
 
+    pub const addGlobalInAddressSpace = LLVMAddGlobalInAddressSpace;
+    extern fn LLVMAddGlobalInAddressSpace(M: *const Module, Ty: *const Type, Name: [*:0]const u8, AddressSpace: c_uint) *const Value;
+
     pub const getNamedGlobal = LLVMGetNamedGlobal;
     extern fn LLVMGetNamedGlobal(M: *const Module, Name: [*:0]const u8) ?*const Value;
 
@@ -1005,3 +1011,65 @@ pub const TypeKind = enum(c_int) {
     BFloat,
     X86_AMX,
 };
+
+pub const address_space = struct {
+    pub const default: c_uint = 0;
+
+    // See llvm/lib/Target/X86/X86.h
+    pub const x86_64 = x86;
+    pub const x86 = struct {
+        pub const gs: c_uint = 256;
+        pub const fs: c_uint = 257;
+        pub const ss: c_uint = 258;
+
+        pub const ptr32_sptr: c_uint = 270;
+        pub const ptr32_uptr: c_uint = 271;
+        pub const ptr64: c_uint = 272;
+    };
+
+    // See llvm/lib/Target/AVR/AVR.h
+    pub const avr = struct {
+        pub const data_memory: c_uint = 0;
+        pub const program_memory: c_uint = 1;
+    };
+
+    // See llvm/lib/Target/NVPTX/NVPTX.h
+    pub const nvptx = struct {
+        pub const generic: c_uint = 0;
+        pub const global: c_uint = 1;
+        pub const constant: c_uint = 2;
+        pub const shared: c_uint = 3;
+        pub const param: c_uint = 4;
+        pub const local: c_uint = 5;
+    };
+
+    // See llvm/lib/Target/AMDGPU/AMDGPU.h
+    pub const amdgpu = struct {
+        pub const flat: c_uint = 0;
+        pub const global: c_uint = 1;
+        pub const region: c_uint = 2;
+        pub const local: c_uint = 3;
+        pub const constant: c_uint = 4;
+        pub const private: c_uint = 5;
+        pub const constant_32bit: c_uint = 6;
+        pub const buffer_fat_pointer: c_uint = 7;
+        pub const param_d: c_uint = 6;
+        pub const param_i: c_uint = 7;
+        pub const constant_buffer_0: c_uint = 8;
+        pub const constant_buffer_1: c_uint = 9;
+        pub const constant_buffer_2: c_uint = 10;
+        pub const constant_buffer_3: c_uint = 11;
+        pub const constant_buffer_4: c_uint = 12;
+        pub const constant_buffer_5: c_uint = 13;
+        pub const constant_buffer_6: c_uint = 14;
+        pub const constant_buffer_7: c_uint = 15;
+        pub const constant_buffer_8: c_uint = 16;
+        pub const constant_buffer_9: c_uint = 17;
+        pub const constant_buffer_10: c_uint = 18;
+        pub const constant_buffer_11: c_uint = 19;
+        pub const constant_buffer_12: c_uint = 20;
+        pub const constant_buffer_13: c_uint = 21;
+        pub const constant_buffer_14: c_uint = 22;
+        pub const constant_buffer_15: c_uint = 23;
+    };
+};

src/print_zir.zig

@@ -1147,7 +1147,7 @@ const Writer = struct {
             cur_bit_bag >>= 1;
             const has_align = @truncate(u1, cur_bit_bag) != 0;
             cur_bit_bag >>= 1;
-            const has_section = @truncate(u1, cur_bit_bag) != 0;
+            const has_section_or_addrspace = @truncate(u1, cur_bit_bag) != 0;
             cur_bit_bag >>= 1;
 
             const sub_index = extra_index;
@@ -1165,7 +1165,12 @@ const Writer = struct {
                 extra_index += 1;
                 break :inst inst;
             };
-            const section_inst: Zir.Inst.Ref = if (!has_section) .none else inst: {
+            const section_inst: Zir.Inst.Ref = if (!has_section_or_addrspace) .none else inst: {
+                const inst = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+                extra_index += 1;
+                break :inst inst;
+            };
+            const addrspace_inst: Zir.Inst.Ref = if (!has_section_or_addrspace) .none else inst: {
                 const inst = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
                 extra_index += 1;
                 break :inst inst;
@@ -1196,6 +1201,11 @@ const Writer = struct {
                     try self.writeInstRef(stream, align_inst);
                     try stream.writeAll(")");
                 }
+                if (addrspace_inst != .none) {
+                    try stream.writeAll(" addrspace(");
+                    try self.writeInstRef(stream, addrspace_inst);
+                    try stream.writeAll(")");
+                }
                 if (section_inst != .none) {
                     try stream.writeAll(" linksection(");
                     try self.writeInstRef(stream, section_inst);

src/stage1/all_types.hpp

@@ -86,6 +86,14 @@ enum CallingConvention {
     CallingConventionSysV
 };
 
+// Stage 1 supports only the generic address space
+enum AddressSpace {
+    AddressSpaceGeneric,
+    AddressSpaceGS,
+    AddressSpaceFS,
+    AddressSpaceSS,
+};
+
 // This one corresponds to the builtin.zig enum.
 enum BuiltinPtrSize {
     BuiltinPtrSizeOne,

src/stage1/analyze.cpp

@@ -1019,6 +1019,16 @@ bool calling_convention_allows_zig_types(CallingConvention cc) {
     zig_unreachable();
 }
 
+const char *address_space_name(AddressSpace as) {
+    switch (as) {
+        case AddressSpaceGeneric: return "generic";
+        case AddressSpaceGS: return "gs";
+        case AddressSpaceFS: return "fs";
+        case AddressSpaceSS: return "ss";
+    }
+    zig_unreachable();
+}
+
 ZigType *get_stack_trace_type(CodeGen *g) {
     if (g->stack_trace_type == nullptr) {
         g->stack_trace_type = get_builtin_type(g, "StackTrace");

src/stage1/analyze.hpp

@@ -242,6 +242,8 @@ Error get_primitive_type(CodeGen *g, Buf *name, ZigType **result);
 bool calling_convention_allows_zig_types(CallingConvention cc);
 const char *calling_convention_name(CallingConvention cc);
 
+const char *address_space_name(AddressSpace as);
+
 Error ATTRIBUTE_MUST_USE file_fetch(CodeGen *g, Buf *resolved_path, Buf *contents);
 
 void walk_function_params(CodeGen *g, ZigType *fn_type, FnWalk *fn_walk);

src/stage1/ir.cpp

@@ -16124,7 +16124,7 @@ static Stage1AirInst *ir_analyze_instruction_optional_unwrap_ptr(IrAnalyze *ira,
 
 static Stage1AirInst *ir_analyze_instruction_ctz(IrAnalyze *ira, Stage1ZirInstCtz *instruction) {
     Error err;
-    
+
     ZigType *int_type = ir_resolve_int_type(ira, instruction->type->child);
     if (type_is_invalid(int_type))
         return ira->codegen->invalid_inst_gen;
@@ -16166,7 +16166,7 @@ static Stage1AirInst *ir_analyze_instruction_ctz(IrAnalyze *ira, Stage1ZirInstCt
             return ira->codegen->invalid_inst_gen;
         if (val->special == ConstValSpecialUndef)
             return ir_const_undef(ira, instruction->base.scope, instruction->base.source_node, ira->codegen->builtin_types.entry_num_lit_int);
-        
+
         if (is_vector) {
             ZigType *smallest_vec_type = get_vector_type(ira->codegen, vector_len, smallest_type);
             Stage1AirInst *result = ir_const(ira, instruction->base.scope, instruction->base.source_node, smallest_vec_type);
@@ -16200,7 +16200,7 @@ static Stage1AirInst *ir_analyze_instruction_ctz(IrAnalyze *ira, Stage1ZirInstCt
 
 static Stage1AirInst *ir_analyze_instruction_clz(IrAnalyze *ira, Stage1ZirInstClz *instruction) {
     Error err;
-    
+
     ZigType *int_type = ir_resolve_int_type(ira, instruction->type->child);
     if (type_is_invalid(int_type))
         return ira->codegen->invalid_inst_gen;
@@ -16242,7 +16242,7 @@ static Stage1AirInst *ir_analyze_instruction_clz(IrAnalyze *ira, Stage1ZirInstCl
             return ira->codegen->invalid_inst_gen;
         if (val->special == ConstValSpecialUndef)
             return ir_const_undef(ira, instruction->base.scope, instruction->base.source_node, ira->codegen->builtin_types.entry_num_lit_int);
-        
+
         if (is_vector) {
             ZigType *smallest_vec_type = get_vector_type(ira->codegen, vector_len, smallest_type);
             Stage1AirInst *result = ir_const(ira, instruction->base.scope, instruction->base.source_node, smallest_vec_type);
@@ -16276,7 +16276,7 @@ static Stage1AirInst *ir_analyze_instruction_clz(IrAnalyze *ira, Stage1ZirInstCl
 
 static Stage1AirInst *ir_analyze_instruction_pop_count(IrAnalyze *ira, Stage1ZirInstPopCount *instruction) {
     Error err;
-    
+
     ZigType *int_type = ir_resolve_int_type(ira, instruction->type->child);
     if (type_is_invalid(int_type))
         return ira->codegen->invalid_inst_gen;
@@ -16318,7 +16318,7 @@ static Stage1AirInst *ir_analyze_instruction_pop_count(IrAnalyze *ira, Stage1Zir
             return ira->codegen->invalid_inst_gen;
         if (val->special == ConstValSpecialUndef)
             return ir_const_undef(ira, instruction->base.scope, instruction->base.source_node, ira->codegen->builtin_types.entry_num_lit_int);
-        
+
         if (is_vector) {
             ZigType *smallest_vec_type = get_vector_type(ira->codegen, vector_len, smallest_type);
             Stage1AirInst *result = ir_const(ira, instruction->base.scope, instruction->base.source_node, smallest_vec_type);
@@ -17904,7 +17904,7 @@ static ZigValue *create_ptr_like_type_info(IrAnalyze *ira, Scope *scope, AstNode
     result->special = ConstValSpecialStatic;
     result->type = type_info_pointer_type;
 
-    ZigValue **fields = alloc_const_vals_ptrs(ira->codegen, 7);
+    ZigValue **fields = alloc_const_vals_ptrs(ira->codegen, 8);
     result->data.x_struct.fields = fields;
 
     // size: Size
@@ -17939,24 +17939,29 @@ static ZigValue *create_ptr_like_type_info(IrAnalyze *ira, Scope *scope, AstNode
         lazy_align_of->base.id = LazyValueIdAlignOf;
         lazy_align_of->target_type = ir_const_type(ira, scope, source_node, attrs_type->data.pointer.child_type);
     }
-    // child: type
+    // address_space: AddressSpace,
-    ensure_field_index(result->type, "child", 4);
+    ensure_field_index(result->type, "address_space", 4);
     fields[4]->special = ConstValSpecialStatic;
-    fields[4]->type = ira->codegen->builtin_types.entry_type;
+    fields[4]->type = get_builtin_type(ira->codegen, "AddressSpace");
-    fields[4]->data.x_type = attrs_type->data.pointer.child_type;
+    bigint_init_unsigned(&fields[4]->data.x_enum_tag, AddressSpaceGeneric);
-    // is_allowzero: bool
+    // child: type
-    ensure_field_index(result->type, "is_allowzero", 5);
+    ensure_field_index(result->type, "child", 5);
     fields[5]->special = ConstValSpecialStatic;
-    fields[5]->type = ira->codegen->builtin_types.entry_bool;
+    fields[5]->type = ira->codegen->builtin_types.entry_type;
-    fields[5]->data.x_bool = attrs_type->data.pointer.allow_zero;
+    fields[5]->data.x_type = attrs_type->data.pointer.child_type;
-    // sentinel: anytype
+    // is_allowzero: bool
-    ensure_field_index(result->type, "sentinel", 6);
+    ensure_field_index(result->type, "is_allowzero", 6);
     fields[6]->special = ConstValSpecialStatic;
+    fields[6]->type = ira->codegen->builtin_types.entry_bool;
+    fields[6]->data.x_bool = attrs_type->data.pointer.allow_zero;
+    // sentinel: anytype
+    ensure_field_index(result->type, "sentinel", 7);
+    fields[7]->special = ConstValSpecialStatic;
     if (attrs_type->data.pointer.sentinel != nullptr) {
-        fields[6]->type = get_optional_type(ira->codegen, attrs_type->data.pointer.child_type);
+        fields[7]->type = get_optional_type(ira->codegen, attrs_type->data.pointer.child_type);
-        set_optional_payload(fields[6], attrs_type->data.pointer.sentinel);
+        set_optional_payload(fields[7], attrs_type->data.pointer.sentinel);
     } else {
-        fields[6]->type = ira->codegen->builtin_types.entry_null;
+        fields[7]->type = ira->codegen->builtin_types.entry_null;
     }
 
     return result;
@@ -18465,7 +18470,7 @@ static Error ir_make_type_info_value(IrAnalyze *ira, Scope *scope, AstNode *sour
                 result->special = ConstValSpecialStatic;
                 result->type = ir_type_info_get_type(ira, "Fn", nullptr);
 
-                ZigValue **fields = alloc_const_vals_ptrs(ira->codegen, 6);
+                ZigValue **fields = alloc_const_vals_ptrs(ira->codegen, 7);
                 result->data.x_struct.fields = fields;
 
                 // calling_convention: TypeInfo.CallingConvention
@@ -18826,11 +18831,11 @@ static ZigType *type_info_to_type(IrAnalyze *ira, Scope *scope, AstNode *source_
                 assert(size_value->type == ir_type_info_get_type(ira, "Size", type_info_pointer_type));
                 BuiltinPtrSize size_enum_index = (BuiltinPtrSize)bigint_as_u32(&size_value->data.x_enum_tag);
                 PtrLen ptr_len = size_enum_index_to_ptr_len(size_enum_index);
-                ZigType *elem_type = get_const_field_meta_type(ira, source_node, payload, "child", 4);
+                ZigType *elem_type = get_const_field_meta_type(ira, source_node, payload, "child", 5);
                 if (type_is_invalid(elem_type))
                     return ira->codegen->invalid_inst_gen->value->type;
                 ZigValue *sentinel;
-                if ((err = get_const_field_sentinel(ira, scope, source_node, payload, "sentinel", 6,
+                if ((err = get_const_field_sentinel(ira, scope, source_node, payload, "sentinel", 7,
                                 elem_type, &sentinel)))
                 {
                     return ira->codegen->invalid_inst_gen->value->type;
@@ -18845,6 +18850,19 @@ static ZigType *type_info_to_type(IrAnalyze *ira, Scope *scope, AstNode *source_
                 if (alignment == nullptr)
                     return ira->codegen->invalid_inst_gen->value->type;
 
+                ZigValue *as_value = get_const_field(ira, source_node, payload, "address_space", 4);
+                if (as_value == nullptr)
+                    return ira->codegen->invalid_inst_gen->value->type;
+                assert(as_value->special == ConstValSpecialStatic);
+                assert(as_value->type == get_builtin_type(ira->codegen, "AddressSpace"));
+                AddressSpace as = (AddressSpace)bigint_as_u32(&as_value->data.x_enum_tag);
+                if (as != AddressSpaceGeneric) {
+                    ir_add_error_node(ira, source_node, buf_sprintf(
+                        "address space '%s' not available in stage 1 compiler, must be .generic",
+                        address_space_name(as)));
+                    return ira->codegen->invalid_inst_gen->value->type;
+                }
+
                 bool is_const;
                 if ((err = get_const_field_bool(ira, source_node, payload, "is_const", 1, &is_const)))
                     return ira->codegen->invalid_inst_gen->value->type;
@@ -18857,13 +18875,12 @@ static ZigType *type_info_to_type(IrAnalyze *ira, Scope *scope, AstNode *source_
                 }
 
                 bool is_allowzero;
-                if ((err = get_const_field_bool(ira, source_node, payload, "is_allowzero", 5,
+                if ((err = get_const_field_bool(ira, source_node, payload, "is_allowzero", 6,
                                 &is_allowzero)))
                 {
                     return ira->codegen->invalid_inst_gen->value->type;
                 }
 
-
                 ZigType *ptr_type = get_pointer_to_type_extra2(ira->codegen,
                     elem_type,
                     is_const,

src/target.zig

@@ -544,3 +544,21 @@ pub fn largestAtomicBits(target: std.Target) u32 {
         .x86_64 => 128,
     };
 }
+
+pub fn defaultAddressSpace(
+    target: std.Target,
+    context: enum {
+        /// Query the default address space for global constant values.
+        global_constant,
+        /// Query the default address space for global mutable values.
+        global_mutable,
+        /// Query the default address space for function-local values.
+        local,
+        /// Query the default address space for functions themselves.
+        function,
+    },
+) std.builtin.AddressSpace {
+    _ = target;
+    _ = context;
+    return .generic;
+}

src/translate_c/ast.zig

@@ -2614,6 +2614,7 @@ fn renderVar(c: *Context, node: Node) !NodeIndex {
                     .type_node = type_node,
                     .align_node = align_node,
                     .section_node = section_node,
+                    .addrspace_node = 0,
                 }),
                 .rhs = init_node,
             },
@@ -2705,6 +2706,7 @@ fn renderFunc(c: *Context, node: Node) !NodeIndex {
                     .lhs = try c.addExtra(std.zig.Ast.Node.FnProtoOne{
                         .param = params.items[0],
                         .align_expr = align_expr,
+                        .addrspace_expr = 0, // TODO
                         .section_expr = section_expr,
                         .callconv_expr = callconv_expr,
                     }),
@@ -2720,6 +2722,7 @@ fn renderFunc(c: *Context, node: Node) !NodeIndex {
                         .params_start = span.start,
                         .params_end = span.end,
                         .align_expr = align_expr,
+                        .addrspace_expr = 0, // TODO
                         .section_expr = section_expr,
                         .callconv_expr = callconv_expr,
                     }),

src/type.zig

@@ -127,6 +127,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             => return .Enum,
@@ -288,6 +289,7 @@ pub const Type = extern union {
                 .pointee_type = Type.initTag(.comptime_int),
                 .sentinel = null,
                 .@"align" = 0,
+                .@"addrspace" = .generic,
                 .bit_offset = 0,
                 .host_size = 0,
                 .@"allowzero" = false,
@@ -299,6 +301,7 @@ pub const Type = extern union {
                 .pointee_type = Type.initTag(.u8),
                 .sentinel = null,
                 .@"align" = 0,
+                .@"addrspace" = .generic,
                 .bit_offset = 0,
                 .host_size = 0,
                 .@"allowzero" = false,
@@ -310,6 +313,7 @@ pub const Type = extern union {
                 .pointee_type = self.castPointer().?.data,
                 .sentinel = null,
                 .@"align" = 0,
+                .@"addrspace" = .generic,
                 .bit_offset = 0,
                 .host_size = 0,
                 .@"allowzero" = false,
@@ -321,6 +325,7 @@ pub const Type = extern union {
                 .pointee_type = self.castPointer().?.data,
                 .sentinel = null,
                 .@"align" = 0,
+                .@"addrspace" = .generic,
                 .bit_offset = 0,
                 .host_size = 0,
                 .@"allowzero" = false,
@@ -332,6 +337,7 @@ pub const Type = extern union {
                 .pointee_type = self.castPointer().?.data,
                 .sentinel = null,
                 .@"align" = 0,
+                .@"addrspace" = .generic,
                 .bit_offset = 0,
                 .host_size = 0,
                 .@"allowzero" = false,
@@ -343,6 +349,7 @@ pub const Type = extern union {
                 .pointee_type = Type.initTag(.u8),
                 .sentinel = null,
                 .@"align" = 0,
+                .@"addrspace" = .generic,
                 .bit_offset = 0,
                 .host_size = 0,
                 .@"allowzero" = false,
@@ -354,6 +361,7 @@ pub const Type = extern union {
                 .pointee_type = self.castPointer().?.data,
                 .sentinel = null,
                 .@"align" = 0,
+                .@"addrspace" = .generic,
                 .bit_offset = 0,
                 .host_size = 0,
                 .@"allowzero" = false,
@@ -365,6 +373,7 @@ pub const Type = extern union {
                 .pointee_type = Type.initTag(.u8),
                 .sentinel = null,
                 .@"align" = 0,
+                .@"addrspace" = .generic,
                 .bit_offset = 0,
                 .host_size = 0,
                 .@"allowzero" = false,
@@ -376,6 +385,7 @@ pub const Type = extern union {
                 .pointee_type = self.castPointer().?.data,
                 .sentinel = null,
                 .@"align" = 0,
+                .@"addrspace" = .generic,
                 .bit_offset = 0,
                 .host_size = 0,
                 .@"allowzero" = false,
@@ -387,6 +397,7 @@ pub const Type = extern union {
                 .pointee_type = self.castPointer().?.data,
                 .sentinel = null,
                 .@"align" = 0,
+                .@"addrspace" = .generic,
                 .bit_offset = 0,
                 .host_size = 0,
                 .@"allowzero" = false,
@@ -398,6 +409,7 @@ pub const Type = extern union {
                 .pointee_type = self.castPointer().?.data,
                 .sentinel = null,
                 .@"align" = 0,
+                .@"addrspace" = .generic,
                 .bit_offset = 0,
                 .host_size = 0,
                 .@"allowzero" = false,
@@ -409,6 +421,7 @@ pub const Type = extern union {
                 .pointee_type = self.castPointer().?.data,
                 .sentinel = null,
                 .@"align" = 0,
+                .@"addrspace" = .generic,
                 .bit_offset = 0,
                 .host_size = 0,
                 .@"allowzero" = false,
@@ -461,6 +474,8 @@ pub const Type = extern union {
                     return false;
                 if (info_a.host_size != info_b.host_size)
                     return false;
+                if (info_a.@"addrspace" != info_b.@"addrspace")
+                    return false;
 
                 const sentinel_a = info_a.sentinel;
                 const sentinel_b = info_b.sentinel;
@@ -746,6 +761,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             .call_options,
@@ -835,6 +851,7 @@ pub const Type = extern union {
                     .pointee_type = try payload.pointee_type.copy(allocator),
                     .sentinel = sent,
                     .@"align" = payload.@"align",
+                    .@"addrspace" = payload.@"addrspace",
                     .bit_offset = payload.bit_offset,
                     .host_size = payload.host_size,
                     .@"allowzero" = payload.@"allowzero",
@@ -958,6 +975,7 @@ pub const Type = extern union {
                 .atomic_order => return writer.writeAll("std.builtin.AtomicOrder"),
                 .atomic_rmw_op => return writer.writeAll("std.builtin.AtomicRmwOp"),
                 .calling_convention => return writer.writeAll("std.builtin.CallingConvention"),
+                .address_space => return writer.writeAll("std.builtin.AddressSpace"),
                 .float_mode => return writer.writeAll("std.builtin.FloatMode"),
                 .reduce_op => return writer.writeAll("std.builtin.ReduceOp"),
                 .call_options => return writer.writeAll("std.builtin.CallOptions"),
@@ -1111,6 +1129,9 @@ pub const Type = extern union {
                         }
                         try writer.writeAll(") ");
                     }
+                    if (payload.@"addrspace" != .generic) {
+                        try writer.print("addrspace(.{s}) ", .{@tagName(payload.@"addrspace")});
+                    }
                     if (!payload.mutable) try writer.writeAll("const ");
                     if (payload.@"volatile") try writer.writeAll("volatile ");
                     if (payload.@"allowzero") try writer.writeAll("allowzero ");
@@ -1186,6 +1207,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             .call_options,
@@ -1301,6 +1323,7 @@ pub const Type = extern union {
             .atomic_order => return Value.initTag(.atomic_order_type),
             .atomic_rmw_op => return Value.initTag(.atomic_rmw_op_type),
             .calling_convention => return Value.initTag(.calling_convention_type),
+            .address_space => return Value.initTag(.address_space_type),
             .float_mode => return Value.initTag(.float_mode_type),
             .reduce_op => return Value.initTag(.reduce_op_type),
             .call_options => return Value.initTag(.call_options_type),
@@ -1362,6 +1385,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             .call_options,
@@ -1496,6 +1520,30 @@ pub const Type = extern union {
         }
     }
 
+    pub fn ptrAddressSpace(self: Type) std.builtin.AddressSpace {
+        return switch (self.tag()) {
+            .single_const_pointer_to_comptime_int,
+            .const_slice_u8,
+            .single_const_pointer,
+            .single_mut_pointer,
+            .many_const_pointer,
+            .many_mut_pointer,
+            .c_const_pointer,
+            .c_mut_pointer,
+            .const_slice,
+            .mut_slice,
+            .inferred_alloc_const,
+            .inferred_alloc_mut,
+            .manyptr_u8,
+            .manyptr_const_u8,
+            => .generic,
+
+            .pointer => self.castTag(.pointer).?.data.@"addrspace",
+
+            else => unreachable,
+        };
+    }
+
     /// Asserts that hasCodeGenBits() is true.
     pub fn abiAlignment(self: Type, target: Target) u32 {
         return switch (self.tag()) {
@@ -1508,6 +1556,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             .call_options,
@@ -1734,6 +1783,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             .call_options,
@@ -2019,6 +2069,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             .call_options,
@@ -2105,42 +2156,82 @@ pub const Type = extern union {
         };
     }
 
-    pub fn slicePtrFieldType(self: Type, buffer: *Payload.ElemType) Type {
+    pub const SlicePtrFieldTypeBuffer = union {
+        elem_type: Payload.ElemType,
+        pointer: Payload.Pointer,
+    };
+
+    pub fn slicePtrFieldType(self: Type, buffer: *SlicePtrFieldTypeBuffer) Type {
         switch (self.tag()) {
             .const_slice_u8 => return Type.initTag(.manyptr_const_u8),
 
             .const_slice => {
                 const elem_type = self.castTag(.const_slice).?.data;
                 buffer.* = .{
-                    .base = .{ .tag = .many_const_pointer },
+                    .elem_type = .{
-                    .data = elem_type,
+                        .base = .{ .tag = .many_const_pointer },
+                        .data = elem_type,
+                    },
                 };
-                return Type.initPayload(&buffer.base);
+                return Type.initPayload(&buffer.elem_type.base);
             },
             .mut_slice => {
                 const elem_type = self.castTag(.mut_slice).?.data;
                 buffer.* = .{
-                    .base = .{ .tag = .many_mut_pointer },
+                    .elem_type = .{
-                    .data = elem_type,
+                        .base = .{ .tag = .many_mut_pointer },
+                        .data = elem_type,
+                    },
                 };
-                return Type.initPayload(&buffer.base);
+                return Type.initPayload(&buffer.elem_type.base);
             },
 
             .pointer => {
                 const payload = self.castTag(.pointer).?.data;
                 assert(payload.size == .Slice);
-                if (payload.mutable) {
+
+                if (payload.sentinel != null or
+                    payload.@"align" != 0 or
+                    payload.@"addrspace" != .generic or
+                    payload.bit_offset != 0 or
+                    payload.host_size != 0 or
+                    payload.@"allowzero" or
+                    payload.@"volatile")
+                {
                     buffer.* = .{
-                        .base = .{ .tag = .many_mut_pointer },
+                        .pointer = .{
-                        .data = payload.pointee_type,
+                            .data = .{
+                                .pointee_type = payload.pointee_type,
+                                .sentinel = payload.sentinel,
+                                .@"align" = payload.@"align",
+                                .@"addrspace" = payload.@"addrspace",
+                                .bit_offset = payload.bit_offset,
+                                .host_size = payload.host_size,
+                                .@"allowzero" = payload.@"allowzero",
+                                .mutable = payload.mutable,
+                                .@"volatile" = payload.@"volatile",
+                                .size = .Many,
+                            },
+                        },
                     };
+                    return Type.initPayload(&buffer.pointer.base);
+                } else if (payload.mutable) {
+                    buffer.* = .{
+                        .elem_type = .{
+                            .base = .{ .tag = .many_mut_pointer },
+                            .data = payload.pointee_type,
+                        },
+                    };
+                    return Type.initPayload(&buffer.elem_type.base);
                 } else {
                     buffer.* = .{
-                        .base = .{ .tag = .many_const_pointer },
+                        .elem_type = .{
-                        .data = payload.pointee_type,
+                            .base = .{ .tag = .many_const_pointer },
+                            .data = payload.pointee_type,
+                        },
                     };
+                    return Type.initPayload(&buffer.elem_type.base);
                 }
-                return Type.initPayload(&buffer.base);
             },
 
             else => unreachable,
@@ -2793,6 +2884,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             .call_options,
@@ -3000,6 +3092,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             .call_options,
@@ -3024,6 +3117,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             .call_options,
@@ -3047,6 +3141,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             .call_options,
@@ -3100,6 +3195,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             .call_options,
@@ -3155,6 +3251,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             .call_options,
@@ -3192,6 +3289,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             .call_options,
@@ -3242,6 +3340,7 @@ pub const Type = extern union {
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,
+            .address_space,
             .float_mode,
             .reduce_op,
             .call_options,
@@ -3302,6 +3401,7 @@ pub const Type = extern union {
         atomic_order,
         atomic_rmw_op,
         calling_convention,
+        address_space,
         float_mode,
         reduce_op,
         call_options,
@@ -3425,6 +3525,7 @@ pub const Type = extern union {
                 .atomic_order,
                 .atomic_rmw_op,
                 .calling_convention,
+                .address_space,
                 .float_mode,
                 .reduce_op,
                 .call_options,
@@ -3580,6 +3681,7 @@ pub const Type = extern union {
                 sentinel: ?Value,
                 /// If zero use pointee_type.AbiAlign()
                 @"align": u32,
+                @"addrspace": std.builtin.AddressSpace,
                 bit_offset: u16,
                 host_size: u16,
                 @"allowzero": bool,

src/value.zig

@@ -63,6 +63,7 @@ pub const Value = extern union {
         atomic_order_type,
         atomic_rmw_op_type,
         calling_convention_type,
+        address_space_type,
         float_mode_type,
         reduce_op_type,
         call_options_type,
@@ -226,6 +227,7 @@ pub const Value = extern union {
                 .atomic_order_type,
                 .atomic_rmw_op_type,
                 .calling_convention_type,
+                .address_space_type,
                 .float_mode_type,
                 .reduce_op_type,
                 .call_options_type,
@@ -412,6 +414,7 @@ pub const Value = extern union {
             .atomic_order_type,
             .atomic_rmw_op_type,
             .calling_convention_type,
+            .address_space_type,
             .float_mode_type,
             .reduce_op_type,
             .call_options_type,
@@ -625,6 +628,7 @@ pub const Value = extern union {
             .atomic_order_type => return out_stream.writeAll("std.builtin.AtomicOrder"),
             .atomic_rmw_op_type => return out_stream.writeAll("std.builtin.AtomicRmwOp"),
             .calling_convention_type => return out_stream.writeAll("std.builtin.CallingConvention"),
+            .address_space_type => return out_stream.writeAll("std.builtin.AddressSpace"),
             .float_mode_type => return out_stream.writeAll("std.builtin.FloatMode"),
             .reduce_op_type => return out_stream.writeAll("std.builtin.ReduceOp"),
             .call_options_type => return out_stream.writeAll("std.builtin.CallOptions"),
@@ -792,6 +796,7 @@ pub const Value = extern union {
             .atomic_order_type => Type.initTag(.atomic_order),
             .atomic_rmw_op_type => Type.initTag(.atomic_rmw_op),
             .calling_convention_type => Type.initTag(.calling_convention),
+            .address_space_type => Type.initTag(.address_space),
             .float_mode_type => Type.initTag(.float_mode),
             .reduce_op_type => Type.initTag(.reduce_op),
             .call_options_type => Type.initTag(.call_options),

src/zig_llvm.cpp

@@ -416,6 +416,11 @@ ZIG_EXTERN_C LLVMTypeRef ZigLLVMTokenTypeInContext(LLVMContextRef context_ref) {
   return wrap(Type::getTokenTy(*unwrap(context_ref)));
 }
 
+LLVMValueRef ZigLLVMAddFunctionInAddressSpace(LLVMModuleRef M, const char *Name, LLVMTypeRef FunctionTy, unsigned AddressSpace) {
+    Function* func = Function::Create(unwrap<FunctionType>(FunctionTy), GlobalValue::ExternalLinkage, AddressSpace, Name, unwrap(M));
+    return wrap(func);
+}
+
 LLVMValueRef ZigLLVMBuildCall(LLVMBuilderRef B, LLVMValueRef Fn, LLVMValueRef *Args,
         unsigned NumArgs, ZigLLVM_CallingConv CC, ZigLLVM_CallAttr attr, const char *Name)
 {

src/zig_llvm.h

@@ -65,6 +65,9 @@ ZIG_EXTERN_C LLVMTargetMachineRef ZigLLVMCreateTargetMachine(LLVMTargetRef T, co
 
 ZIG_EXTERN_C LLVMTypeRef ZigLLVMTokenTypeInContext(LLVMContextRef context_ref);
 
+ZIG_EXTERN_C LLVMValueRef ZigLLVMAddFunctionInAddressSpace(LLVMModuleRef M, const char *Name,
+        LLVMTypeRef FunctionTy, unsigned AddressSpace);
+
 enum ZigLLVM_CallingConv {
     ZigLLVM_C = 0,
     ZigLLVM_Fast = 8,

test/behavior/type.zig

@@ -137,6 +137,7 @@ test "@Type create slice with null sentinel" {
             .is_volatile = false,
             .is_allowzero = false,
             .alignment = 8,
+            .address_space = .generic,
             .child = *i32,
             .sentinel = null,
         },

test/cases.zig

@@ -1807,4 +1807,16 @@ pub fn addCases(ctx: *TestContext) !void {
             \\}
         , "");
     }
+
+    {
+        var case = ctx.exe("setting an address space on a local variable", linux_x64);
+        case.addError(
+            \\export fn entry() i32 {
+            \\    var foo: i32 addrspace(".general") = 1234;
+            \\    return foo;
+            \\}
+        , &[_][]const u8{
+            ":2:28: error: cannot set address space of local variable 'foo'",
+        });
+    }
 }

test/compile_errors.zig

@@ -711,6 +711,7 @@ pub fn addCases(ctx: *TestContext) !void {
         \\        .is_const = false,
         \\        .is_volatile = false,
         \\        .alignment = 1,
+        \\        .address_space = .generic,
         \\        .child = u8,
         \\        .is_allowzero = false,
         \\        .sentinel = 0,
@@ -720,6 +721,23 @@ pub fn addCases(ctx: *TestContext) !void {
         "tmp.zig:2:16: error: sentinels are only allowed on slices and unknown-length pointers",
     });
 
+    ctx.objErrStage1("@Type(.Pointer) with invalid address space ",
+        \\export fn entry() void {
+        \\    _ = @Type(.{ .Pointer = .{
+        \\        .size = .One,
+        \\        .is_const = false,
+        \\        .is_volatile = false,
+        \\        .alignment = 1,
+        \\        .address_space = .gs,
+        \\        .child = u8,
+        \\        .is_allowzero = false,
+        \\        .sentinel = null,
+        \\    }});
+        \\}
+    , &[_][]const u8{
+        "tmp.zig:2:16: error: address space 'gs' not available in stage 1 compiler, must be .generic",
+    });
+
     ctx.testErrStage1("helpful return type error message",
         \\export fn foo() u32 {
         \\    return error.Ohno;

test/stage2/llvm.zig

@@ -242,4 +242,184 @@ pub fn addCases(ctx: *TestContext) !void {
             \\}
         , "");
     }
+
+    {
+        var case = ctx.exeUsingLlvmBackend("invalid address space coercion", linux_x64);
+        case.addError(
+            \\fn entry(a: *addrspace(.gs) i32) *i32 {
+            \\    return a;
+            \\}
+            \\pub export fn main() void { _ = entry; }
+        , &[_][]const u8{
+            ":2:12: error: expected *i32, found *addrspace(.gs) i32",
+        });
+    }
+
+    {
+        var case = ctx.exeUsingLlvmBackend("pointer keeps address space", linux_x64);
+        case.compiles(
+            \\fn entry(a: *addrspace(.gs) i32) *addrspace(.gs) i32 {
+            \\    return a;
+            \\}
+            \\pub export fn main() void { _ = entry; }
+        );
+    }
+
+    {
+        var case = ctx.exeUsingLlvmBackend("pointer to explicit generic address space coerces to implicit pointer", linux_x64);
+        case.compiles(
+            \\fn entry(a: *addrspace(.generic) i32) *i32 {
+            \\    return a;
+            \\}
+            \\pub export fn main() void { _ = entry; }
+        );
+    }
+
+    {
+        var case = ctx.exeUsingLlvmBackend("pointers with different address spaces", linux_x64);
+        case.addError(
+            \\fn entry(a: *addrspace(.gs) i32) *addrspace(.fs) i32 {
+            \\    return a;
+            \\}
+            \\pub export fn main() void { _ = entry; }
+        , &[_][]const u8{
+            ":2:12: error: expected *addrspace(.fs) i32, found *addrspace(.gs) i32",
+        });
+    }
+
+    {
+        var case = ctx.exeUsingLlvmBackend("pointers with different address spaces", linux_x64);
+        case.addError(
+            \\fn entry(a: ?*addrspace(.gs) i32) *i32 {
+            \\    return a.?;
+            \\}
+            \\pub export fn main() void { _ = entry; }
+        , &[_][]const u8{
+            ":2:13: error: expected *i32, found *addrspace(.gs) i32",
+        });
+    }
+
+    {
+        var case = ctx.exeUsingLlvmBackend("invalid pointer keeps address space when taking address of dereference", linux_x64);
+        case.addError(
+            \\fn entry(a: *addrspace(.gs) i32) *i32 {
+            \\    return &a.*;
+            \\}
+            \\pub export fn main() void { _ = entry; }
+        , &[_][]const u8{
+            ":2:12: error: expected *i32, found *addrspace(.gs) i32",
+        });
+    }
+
+    {
+        var case = ctx.exeUsingLlvmBackend("pointer keeps address space when taking address of dereference", linux_x64);
+        case.compiles(
+            \\fn entry(a: *addrspace(.gs) i32) *addrspace(.gs) i32 {
+            \\    return &a.*;
+            \\}
+            \\pub export fn main() void { _ = entry; }
+        );
+    }
+
+    {
+        var case = ctx.exeUsingLlvmBackend("address spaces pointer access chaining: array pointer", linux_x64);
+        case.compiles(
+            \\fn entry(a: *addrspace(.gs) [1]i32) *addrspace(.gs) i32 {
+            \\    return &a[0];
+            \\}
+            \\pub export fn main() void { _ = entry; }
+        );
+    }
+
+    {
+        var case = ctx.exeUsingLlvmBackend("address spaces pointer access chaining: pointer to optional array", linux_x64);
+        case.compiles(
+            \\fn entry(a: *addrspace(.gs) ?[1]i32) *addrspace(.gs) i32 {
+            \\    return &a.*.?[0];
+            \\}
+            \\pub export fn main() void { _ = entry; }
+        );
+    }
+
+    {
+        var case = ctx.exeUsingLlvmBackend("address spaces pointer access chaining: struct pointer", linux_x64);
+        case.compiles(
+            \\const A = struct{ a: i32 };
+            \\fn entry(a: *addrspace(.gs) A) *addrspace(.gs) i32 {
+            \\    return &a.a;
+            \\}
+            \\pub export fn main() void { _ = entry; }
+        );
+    }
+
+    {
+        var case = ctx.exeUsingLlvmBackend("address spaces pointer access chaining: complex", linux_x64);
+        case.compiles(
+            \\const A = struct{ a: ?[1]i32 };
+            \\fn entry(a: *addrspace(.gs) [1]A) *addrspace(.gs) i32 {
+            \\    return &a[0].a.?[0];
+            \\}
+            \\pub export fn main() void { _ = entry; }
+        );
+    }
+
+    {
+        var case = ctx.exeUsingLlvmBackend("dereferencing through multiple pointers with address spaces", linux_x64);
+        case.compiles(
+            \\fn entry(a: *addrspace(.fs) *addrspace(.gs) *i32) *i32 {
+            \\    return a.*.*;
+            \\}
+            \\pub export fn main() void { _ = entry; }
+        );
+    }
+
+    {
+        var case = ctx.exeUsingLlvmBackend("f segment address space reading and writing", linux_x64);
+        case.addCompareOutput(
+            \\fn assert(ok: bool) void {
+            \\    if (!ok) unreachable;
+            \\}
+            \\
+            \\fn setFs(value: c_ulong) void {
+            \\    asm volatile (
+            \\        \\syscall
+            \\        :
+            \\        : [number] "{rax}" (158),
+            \\          [code] "{rdi}" (0x1002),
+            \\          [val] "{rsi}" (value),
+            \\        : "rcx", "r11", "memory"
+            \\    );
+            \\}
+            \\
+            \\fn getFs() c_ulong {
+            \\    var result: c_ulong = undefined;
+            \\    asm volatile (
+            \\        \\syscall
+            \\        :
+            \\        : [number] "{rax}" (158),
+            \\          [code] "{rdi}" (0x1003),
+            \\          [ptr] "{rsi}" (@ptrToInt(&result)),
+            \\        : "rcx", "r11", "memory"
+            \\    );
+            \\    return result;
+            \\}
+            \\
+            \\var test_value: u64 = 12345;
+            \\
+            \\pub export fn main() c_int {
+            \\    const orig_fs = getFs();
+            \\
+            \\    setFs(@ptrToInt(&test_value));
+            \\    assert(getFs() == @ptrToInt(&test_value));
+            \\
+            \\    var test_ptr = @intToPtr(*allowzero addrspace(.fs) u64, 0);
+            \\    assert(test_ptr.* == 12345);
+            \\    test_ptr.* = 98765;
+            \\    assert(test_value == 98765);
+            \\
+            \\    setFs(orig_fs);
+            \\    return 0;
+            \\}
+        , "");
+    }
 }