zig/lib/compiler/reduce.zig

427 lines
17 KiB
Zig

const std = @import("std");
const mem = std.mem;
const Allocator = std.mem.Allocator;
const assert = std.debug.assert;
const Ast = std.zig.Ast;
const Walk = @import("reduce/Walk.zig");
const AstGen = std.zig.AstGen;
const Zir = std.zig.Zir;
const usage =
\\zig reduce [options] ./checker root_source_file.zig [-- [argv]]
\\
\\root_source_file.zig is relative to --main-mod-path.
\\
\\checker:
\\ An executable that communicates interestingness by returning these exit codes:
\\ exit(0): interesting
\\ exit(1): unknown (infinite loop or other mishap)
\\ exit(other): not interesting
\\
\\options:
\\ --seed [integer] Override the random seed. Defaults to 0
\\ --skip-smoke-test Skip interestingness check smoke test
\\ --mod [name]:[deps]:[src] Make a module available for dependency under the given name
\\ deps: [dep],[dep],...
\\ dep: [[import=]name]
\\ --deps [dep],[dep],... Set dependency names for the root package
\\ dep: [[import=]name]
\\ --main-mod-path Set the directory of the root module
\\
\\argv:
\\ Forwarded directly to the interestingness script.
\\
;
const Interestingness = enum { interesting, unknown, boring };
// Roadmap:
// - add thread pool
// - add support for parsing the module flags
// - more fancy transformations
// - @import inlining of modules
// - removing statements or blocks of code
// - replacing operands of `and` and `or` with `true` and `false`
// - replacing if conditions with `true` and `false`
// - reduce flags sent to the compiler
// - integrate with the build system?
pub fn main() !void {
var arena_instance = std.heap.ArenaAllocator.init(std.heap.page_allocator);
defer arena_instance.deinit();
const arena = arena_instance.allocator();
var general_purpose_allocator: std.heap.GeneralPurposeAllocator(.{}) = .init;
const gpa = general_purpose_allocator.allocator();
const args = try std.process.argsAlloc(arena);
var opt_checker_path: ?[]const u8 = null;
var opt_root_source_file_path: ?[]const u8 = null;
var argv: []const []const u8 = &.{};
var seed: u32 = 0;
var skip_smoke_test = false;
{
var i: usize = 1;
while (i < args.len) : (i += 1) {
const arg = args[i];
if (mem.startsWith(u8, arg, "-")) {
if (mem.eql(u8, arg, "-h") or mem.eql(u8, arg, "--help")) {
const stdout = std.io.getStdOut().writer();
try stdout.writeAll(usage);
return std.process.cleanExit();
} else if (mem.eql(u8, arg, "--")) {
argv = args[i + 1 ..];
break;
} else if (mem.eql(u8, arg, "--skip-smoke-test")) {
skip_smoke_test = true;
} else if (mem.eql(u8, arg, "--main-mod-path")) {
@panic("TODO: implement --main-mod-path");
} else if (mem.eql(u8, arg, "--mod")) {
@panic("TODO: implement --mod");
} else if (mem.eql(u8, arg, "--deps")) {
@panic("TODO: implement --deps");
} else if (mem.eql(u8, arg, "--seed")) {
i += 1;
if (i >= args.len) fatal("expected 32-bit integer after {s}", .{arg});
const next_arg = args[i];
seed = std.fmt.parseUnsigned(u32, next_arg, 0) catch |err| {
fatal("unable to parse seed '{s}' as 32-bit integer: {s}", .{
next_arg, @errorName(err),
});
};
} else {
fatal("unrecognized parameter: '{s}'", .{arg});
}
} else if (opt_checker_path == null) {
opt_checker_path = arg;
} else if (opt_root_source_file_path == null) {
opt_root_source_file_path = arg;
} else {
fatal("unexpected extra parameter: '{s}'", .{arg});
}
}
}
const checker_path = opt_checker_path orelse
fatal("missing interestingness checker argument; see -h for usage", .{});
const root_source_file_path = opt_root_source_file_path orelse
fatal("missing root source file path argument; see -h for usage", .{});
var interestingness_argv: std.ArrayListUnmanaged([]const u8) = .empty;
try interestingness_argv.ensureUnusedCapacity(arena, argv.len + 1);
interestingness_argv.appendAssumeCapacity(checker_path);
interestingness_argv.appendSliceAssumeCapacity(argv);
var rendered = std.ArrayList(u8).init(gpa);
defer rendered.deinit();
var astgen_input = std.ArrayList(u8).init(gpa);
defer astgen_input.deinit();
var tree = try parse(gpa, root_source_file_path);
defer {
gpa.free(tree.source);
tree.deinit(gpa);
}
if (!skip_smoke_test) {
std.debug.print("smoke testing the interestingness check...\n", .{});
switch (try runCheck(arena, interestingness_argv.items)) {
.interesting => {},
.boring, .unknown => |t| {
fatal("interestingness check returned {s} for unmodified input\n", .{
@tagName(t),
});
},
}
}
var fixups: Ast.Fixups = .{};
defer fixups.deinit(gpa);
var more_fixups: Ast.Fixups = .{};
defer more_fixups.deinit(gpa);
var rng = std.Random.DefaultPrng.init(seed);
// 1. Walk the AST of the source file looking for independent
// reductions and collecting them all into an array list.
// 2. Randomize the list of transformations. A future enhancement will add
// priority weights to the sorting but for now they are completely
// shuffled.
// 3. Apply a subset consisting of 1/2 of the transformations and check for
// interestingness.
// 4. If not interesting, half the subset size again and check again.
// 5. Repeat until the subset size is 1, then march the transformation
// index forward by 1 with each non-interesting attempt.
//
// At any point if a subset of transformations succeeds in producing an interesting
// result, restart the whole process, reparsing the AST and re-generating the list
// of all possible transformations and shuffling it again.
var transformations = std.ArrayList(Walk.Transformation).init(gpa);
defer transformations.deinit();
try Walk.findTransformations(arena, &tree, &transformations);
sortTransformations(transformations.items, rng.random());
fresh: while (transformations.items.len > 0) {
std.debug.print("found {d} possible transformations\n", .{
transformations.items.len,
});
var subset_size: usize = transformations.items.len;
var start_index: usize = 0;
while (start_index < transformations.items.len) {
const prev_subset_size = subset_size;
subset_size = @max(1, subset_size * 3 / 4);
if (prev_subset_size > 1 and subset_size == 1)
start_index = 0;
const this_set = transformations.items[start_index..][0..subset_size];
std.debug.print("trying {d} random transformations: ", .{subset_size});
for (this_set[0..@min(this_set.len, 20)]) |t| {
std.debug.print("{s} ", .{@tagName(t)});
}
std.debug.print("\n", .{});
try transformationsToFixups(gpa, arena, root_source_file_path, this_set, &fixups);
rendered.clearRetainingCapacity();
try tree.renderToArrayList(&rendered, fixups);
// The transformations we applied may have resulted in unused locals,
// in which case we would like to add the respective discards.
{
try astgen_input.resize(rendered.items.len);
@memcpy(astgen_input.items, rendered.items);
try astgen_input.append(0);
const source_with_null = astgen_input.items[0 .. astgen_input.items.len - 1 :0];
var astgen_tree = try Ast.parse(gpa, source_with_null, .zig);
defer astgen_tree.deinit(gpa);
if (astgen_tree.errors.len != 0) {
@panic("syntax errors occurred");
}
var zir = try AstGen.generate(gpa, astgen_tree);
defer zir.deinit(gpa);
if (zir.hasCompileErrors()) {
more_fixups.clearRetainingCapacity();
const payload_index = zir.extra[@intFromEnum(Zir.ExtraIndex.compile_errors)];
assert(payload_index != 0);
const header = zir.extraData(Zir.Inst.CompileErrors, payload_index);
var extra_index = header.end;
for (0..header.data.items_len) |_| {
const item = zir.extraData(Zir.Inst.CompileErrors.Item, extra_index);
extra_index = item.end;
const msg = zir.nullTerminatedString(item.data.msg);
if (mem.eql(u8, msg, "unused local constant") or
mem.eql(u8, msg, "unused local variable") or
mem.eql(u8, msg, "unused function parameter") or
mem.eql(u8, msg, "unused capture"))
{
const ident_token = item.data.token;
try more_fixups.unused_var_decls.put(gpa, ident_token, {});
} else {
std.debug.print("found other ZIR error: '{s}'\n", .{msg});
}
}
if (more_fixups.count() != 0) {
rendered.clearRetainingCapacity();
try astgen_tree.renderToArrayList(&rendered, more_fixups);
}
}
}
try std.fs.cwd().writeFile(.{ .sub_path = root_source_file_path, .data = rendered.items });
// std.debug.print("trying this code:\n{s}\n", .{rendered.items});
const interestingness = try runCheck(arena, interestingness_argv.items);
std.debug.print("{d} random transformations: {s}. {d}/{d}\n", .{
subset_size, @tagName(interestingness), start_index, transformations.items.len,
});
switch (interestingness) {
.interesting => {
const new_tree = try parse(gpa, root_source_file_path);
gpa.free(tree.source);
tree.deinit(gpa);
tree = new_tree;
try Walk.findTransformations(arena, &tree, &transformations);
sortTransformations(transformations.items, rng.random());
continue :fresh;
},
.unknown, .boring => {
// Continue to try the next set of transformations.
// If we tested only one transformation, move on to the next one.
if (subset_size == 1) {
start_index += 1;
} else {
start_index += subset_size;
if (start_index + subset_size > transformations.items.len) {
start_index = 0;
}
}
},
}
}
std.debug.print("all {d} remaining transformations are uninteresting\n", .{
transformations.items.len,
});
// Revert the source back to not be transformed.
fixups.clearRetainingCapacity();
rendered.clearRetainingCapacity();
try tree.renderToArrayList(&rendered, fixups);
try std.fs.cwd().writeFile(.{ .sub_path = root_source_file_path, .data = rendered.items });
return std.process.cleanExit();
}
std.debug.print("no more transformations found\n", .{});
return std.process.cleanExit();
}
fn sortTransformations(transformations: []Walk.Transformation, rng: std.Random) void {
rng.shuffle(Walk.Transformation, transformations);
// Stable sort based on priority to keep randomness as the secondary sort.
// TODO: introduce transformation priorities
// std.mem.sort(transformations);
}
fn termToInteresting(term: std.process.Child.Term) Interestingness {
return switch (term) {
.Exited => |code| switch (code) {
0 => .interesting,
1 => .unknown,
else => .boring,
},
else => b: {
std.debug.print("interestingness check aborted unexpectedly\n", .{});
break :b .boring;
},
};
}
fn runCheck(arena: std.mem.Allocator, argv: []const []const u8) !Interestingness {
const result = try std.process.Child.run(.{
.allocator = arena,
.argv = argv,
});
if (result.stderr.len != 0)
std.debug.print("{s}", .{result.stderr});
return termToInteresting(result.term);
}
fn transformationsToFixups(
gpa: Allocator,
arena: Allocator,
root_source_file_path: []const u8,
transforms: []const Walk.Transformation,
fixups: *Ast.Fixups,
) !void {
fixups.clearRetainingCapacity();
for (transforms) |t| switch (t) {
.gut_function => |fn_decl_node| {
try fixups.gut_functions.put(gpa, fn_decl_node, {});
},
.delete_node => |decl_node| {
try fixups.omit_nodes.put(gpa, decl_node, {});
},
.delete_var_decl => |delete_var_decl| {
try fixups.omit_nodes.put(gpa, delete_var_decl.var_decl_node, {});
for (delete_var_decl.references.items) |ident_node| {
try fixups.replace_nodes_with_string.put(gpa, ident_node, "undefined");
}
},
.replace_with_undef => |node| {
try fixups.replace_nodes_with_string.put(gpa, node, "undefined");
},
.replace_with_true => |node| {
try fixups.replace_nodes_with_string.put(gpa, node, "true");
},
.replace_with_false => |node| {
try fixups.replace_nodes_with_string.put(gpa, node, "false");
},
.replace_node => |r| {
try fixups.replace_nodes_with_node.put(gpa, r.to_replace, r.replacement);
},
.inline_imported_file => |inline_imported_file| {
const full_imported_path = try std.fs.path.join(gpa, &.{
std.fs.path.dirname(root_source_file_path) orelse ".",
inline_imported_file.imported_string,
});
defer gpa.free(full_imported_path);
var other_file_ast = try parse(gpa, full_imported_path);
defer {
gpa.free(other_file_ast.source);
other_file_ast.deinit(gpa);
}
var inlined_fixups: Ast.Fixups = .{};
defer inlined_fixups.deinit(gpa);
if (std.fs.path.dirname(inline_imported_file.imported_string)) |dirname| {
inlined_fixups.rebase_imported_paths = dirname;
}
for (inline_imported_file.in_scope_names.keys()) |name| {
// This name needs to be mangled in order to not cause an
// ambiguous reference error.
var i: u32 = 2;
const mangled = while (true) : (i += 1) {
const mangled = try std.fmt.allocPrint(gpa, "{s}{d}", .{ name, i });
if (!inline_imported_file.in_scope_names.contains(mangled))
break mangled;
gpa.free(mangled);
};
try inlined_fixups.rename_identifiers.put(gpa, name, mangled);
}
defer {
for (inlined_fixups.rename_identifiers.values()) |v| {
gpa.free(v);
}
}
var other_source = std.ArrayList(u8).init(gpa);
defer other_source.deinit();
try other_source.appendSlice("struct {\n");
try other_file_ast.renderToArrayList(&other_source, inlined_fixups);
try other_source.appendSlice("}");
try fixups.replace_nodes_with_string.put(
gpa,
inline_imported_file.builtin_call_node,
try arena.dupe(u8, other_source.items),
);
},
};
}
fn parse(gpa: Allocator, file_path: []const u8) !Ast {
const source_code = std.fs.cwd().readFileAllocOptions(
gpa,
file_path,
std.math.maxInt(u32),
null,
1,
0,
) catch |err| {
fatal("unable to open '{s}': {s}", .{ file_path, @errorName(err) });
};
errdefer gpa.free(source_code);
var tree = try Ast.parse(gpa, source_code, .zig);
errdefer tree.deinit(gpa);
if (tree.errors.len != 0) {
@panic("syntax errors occurred");
}
return tree;
}
fn fatal(comptime format: []const u8, args: anytype) noreturn {
std.log.err(format, args);
std.process.exit(1);
}