SPIR-V: Spec generator

tools/gen_spirv_spec.zig

@@ -0,0 +1,245 @@
+const std = @import("std");
+const Writer = std.ArrayList(u8).Writer;
+
+//! See https://www.khronos.org/registry/spir-v/specs/unified1/MachineReadableGrammar.html
+//! and the files in https://github.com/KhronosGroup/SPIRV-Headers/blob/master/include/spirv/unified1/
+//! Note: Non-canonical casing in these structs used to match SPIR-V spec json.
+const Registry = union(enum) {
+    core: CoreRegistry,
+    extension: ExtensionRegistry,
+};
+
+const CoreRegistry = struct {
+    copyright: [][]const u8,
+    /// Hexadecimal representation of the magic number
+    magic_number: []const u8,
+    major_version: u32,
+    minor_version: u32,
+    revision: u32,
+    instruction_printing_class: []InstructionPrintingClass,
+    instructions: []Instruction,
+    operand_kinds: []OperandKind,
+};
+
+const ExtensionRegistry = struct {
+    copyright: [][]const u8,
+    version: u32,
+    revision: u32,
+    instructions: []Instruction,
+    operand_kinds: []OperandKind = &[_]OperandKind{},
+};
+
+const InstructionPrintingClass = struct {
+    tag: []const u8,
+    heading: ?[]const u8 = null,
+};
+
+const Instruction = struct {
+    opname: []const u8,
+    class: ?[]const u8 = null, // Note: Only available in the core registry.
+    opcode: u32,
+    operands: []Operand = &[_]Operand{},
+    capabilities: [][]const u8 = &[_][]const u8{},
+    extensions: [][]const u8 = &[_][]const u8{},
+    version: ?[]const u8 = null,
+
+    lastVersion: ?[]const u8 = null,
+};
+
+const Operand = struct {
+    kind: []const u8,
+    /// If this field is 'null', the operand is only expected once.
+    quantifier: ?Quantifier = null,
+    name: []const u8 = "",
+};
+
+const Quantifier = enum {
+    /// zero or once
+    @"?",
+    /// zero or more
+    @"*",
+};
+
+const OperandCategory = enum {
+    BitEnum,
+    ValueEnum,
+    Id,
+    Literal,
+    Composite,
+};
+
+const OperandKind = struct {
+    category: OperandCategory,
+    /// The name
+    kind: []const u8,
+    doc: ?[]const u8 = null,
+    enumerants: ?[]Enumerant = null,
+    bases: ?[]const []const u8 = null,
+};
+
+const Enumerant = struct {
+    enumerant: []const u8,
+    value: union(enum) {
+        bitflag: []const u8, // Hexadecimal representation of the value
+        int: u31,
+    },
+    capabilities: [][]const u8 = &[_][]const u8{},
+    /// Valid for .ValueEnum and .BitEnum
+    extensions: [][]const u8 = &[_][]const u8{},
+    /// `quantifier` will always be `null`.
+    parameters: []Operand = &[_]Operand{},
+    version: ?[]const u8 = null,
+    lastVersion: ?[]const u8 = null,
+};
+
+pub fn main() !void {
+    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+    defer arena.deinit();
+    const allocator = &arena.allocator;
+
+    const args = try std.process.argsAlloc(allocator);
+    if (args.len != 2) {
+        usageAndExit(std.io.getStdErr(), args[0], 1);
+    }
+
+    const spec_path = args[1];
+    const spec = try std.fs.cwd().readFileAlloc(allocator, spec_path, std.math.maxInt(usize));
+
+    var tokens = std.json.TokenStream.init(spec);
+    var registry = try std.json.parse(Registry, &tokens, .{.allocator = allocator});
+
+    var buf = std.ArrayList(u8).init(allocator);
+    defer buf.deinit();
+
+    try render(buf.writer(), registry);
+
+    const tree = try std.zig.parse(allocator, buf.items);
+    _ = try std.zig.render(allocator, std.io.getStdOut().writer(), tree);
+}
+
+fn render(writer: Writer, registry: Registry) !void {
+    switch (registry) {
+        .core => |core_reg| {
+            try renderCopyRight(writer, core_reg.copyright);
+            try writer.print(
+                \\const Version = @import("builtin").Version;
+                \\pub const version = Version{{.major = {}, .minor = {}, .patch = {}}};
+                \\pub const magic_number: u32 = {s};
+                \\
+                , .{ core_reg.major_version, core_reg.minor_version, core_reg.revision, core_reg.magic_number },
+            );
+            try renderOpcodes(writer, core_reg.instructions);
+            try renderOperandKinds(writer, core_reg.operand_kinds);
+        },
+        .extension => |ext_reg| {
+            try renderCopyRight(writer, ext_reg.copyright);
+            try writer.print(
+                \\const Version = @import("builtin").Version;
+                \\pub const version = Version{{.major = {}, .minor = 0, .patch = {}}};
+                \\
+                , .{ ext_reg.version, ext_reg.revision },
+            );
+            try renderOpcodes(writer, ext_reg.instructions);
+            try renderOperandKinds(writer, ext_reg.operand_kinds);
+        }
+    }
+}
+
+fn renderCopyRight(writer: Writer, copyright: []const []const u8) !void {
+    for (copyright) |line| {
+        try writer.print("// {s}\n", .{ line });
+    }
+}
+
+fn renderOpcodes(writer: Writer, instructions: []const Instruction) !void {
+    try writer.writeAll("pub const Opcode = extern enum(u16) {\n");
+    for (instructions) |instr| {
+        try writer.print("{} = {},\n", .{ std.zig.fmtId(instr.opname), instr.opcode });
+    }
+    try writer.writeAll("_,\n};\n");
+}
+
+fn renderOperandKinds(writer: Writer, kinds: []const OperandKind) !void {
+    for (kinds) |kind| {
+        switch (kind.category) {
+            .ValueEnum => try renderValueEnum(writer, kind),
+            .BitEnum => try renderBitEnum(writer, kind),
+            else => {},
+        }
+    }
+}
+
+fn renderValueEnum(writer: Writer, enumeration: OperandKind) !void {
+    try writer.print("pub const {s} = extern enum(u32) {{\n", .{ enumeration.kind });
+
+    const enumerants = enumeration.enumerants orelse return error.InvalidRegistry;
+    for (enumerants) |enumerant| {
+        if (enumerant.value != .int) return error.InvalidRegistry;
+
+        try writer.print("{} = {},\n", .{ std.zig.fmtId(enumerant.enumerant), enumerant.value.int });
+    }
+
+    try writer.writeAll("_,\n};\n");
+}
+
+fn renderBitEnum(writer: Writer, enumeration: OperandKind) !void {
+    try writer.print("pub const {s} = packed struct {{\n", .{ enumeration.kind });
+
+    var flags_by_bitpos = [_]?[]const u8{null} ** 32;
+    const enumerants = enumeration.enumerants orelse return error.InvalidRegistry;
+    for (enumerants) |enumerant| {
+        if (enumerant.value != .bitflag) return error.InvalidRegistry;
+        const value = try parseHexInt(enumerant.value.bitflag);
+        if (@popCount(u32, value) != 1) {
+            continue; // Skip combinations and 'none' items
+        }
+
+        var bitpos = std.math.log2_int(u32, value);
+        if (flags_by_bitpos[bitpos]) |*existing|{
+            // Keep the shortest
+            if (enumerant.enumerant.len < existing.len)
+                existing.* = enumerant.enumerant;
+        } else {
+            flags_by_bitpos[bitpos] = enumerant.enumerant;
+        }
+    }
+
+    for (flags_by_bitpos) |maybe_flag_name, bitpos| {
+        if (maybe_flag_name) |flag_name| {
+            try writer.writeAll(flag_name);
+        } else {
+            try writer.print("_reserved_bit_{}", .{bitpos});
+        }
+
+        try writer.writeAll(": bool ");
+        if (bitpos == 0) { // Force alignment to integer boundaries
+            try writer.writeAll("align(@alignOf(u32)) ");
+        }
+        try writer.writeAll("= false, ");
+    }
+
+    try writer.writeAll("};\n");
+}
+
+fn parseHexInt(text: []const u8) !u31 {
+    const prefix = "0x";
+    if (!std.mem.startsWith(u8, text, prefix))
+        return error.InvalidHexInt;
+    return try std.fmt.parseInt(u31, text[prefix.len ..], 16);
+}
+
+fn usageAndExit(file: std.fs.File, arg0: []const u8, code: u8) noreturn {
+    file.writer().print(
+        \\Usage: {s} <spirv json spec>
+        \\
+        \\Generates Zig bindings for a SPIR-V specification .json (either core or
+        \\extinst versions). The result, printed to stdout, should be used to update
+        \\files in src/codegen/spirv.
+        \\
+        \\The relevant specifications can be obtained from the SPIR-V registry:
+        \\https://github.com/KhronosGroup/SPIRV-Headers/blob/master/include/spirv/unified1/
+        \\
+        , .{arg0}
+    ) catch std.process.exit(1);
+    std.process.exit(code);
+}