authorgravatar for andrew@ziglang.orgAndrew Kelley <andrew@ziglang.org> 2023-11-03 21:31:32-07:00
committergravatar for andrew@ziglang.orgAndrew Kelley <andrew@ziglang.org> 2023-11-03 21:31:32-07:00
loga2f4adbd19ffea051a4fa0318bb0154e07660e55
treeee53ffcd4587ab34106470dd8895f8b39d26ad50
parent6aedddf900086543fa667d74ca4d1c266dbfcdf9

zig reduce: add "delete unused globals" transform

While walking the AST looking for reductions, notice if any globals are unreferenced, and if they are, add a transformation for removing the global.

3 files changed, 103 insertions(+), 12 deletions(-)

lib/std/zig/render.zig+7-1
......@@ -22,20 +22,25 @@ pub const Fixups = struct {
2222 /// with a function body of `@trap()` instead, with all parameters
2323 /// discarded.
2424 gut_functions: std.AutoHashMapUnmanaged(Ast.Node.Index, void) = .{},
25 /// These global declarations will be omitted.
26 omit_nodes: std.AutoHashMapUnmanaged(Ast.Node.Index, void) = .{},
2527
2628 pub fn count(f: Fixups) usize {
2729 return f.unused_var_decls.count() +
28 f.gut_functions.count();
30 f.gut_functions.count() +
31 f.omit_nodes.count();
2932 }
3033
3134 pub fn clearRetainingCapacity(f: *Fixups) void {
3235 f.unused_var_decls.clearRetainingCapacity();
3336 f.gut_functions.clearRetainingCapacity();
37 f.omit_nodes.clearRetainingCapacity();
3438 }
3539
3640 pub fn deinit(f: *Fixups, gpa: Allocator) void {
3741 f.unused_var_decls.deinit(gpa);
3842 f.gut_functions.deinit(gpa);
43 f.omit_nodes.deinit(gpa);
3944 f.* = undefined;
4045 }
4146};
......@@ -114,6 +119,7 @@ fn renderMember(
114119 const token_tags = tree.tokens.items(.tag);
115120 const main_tokens = tree.nodes.items(.main_token);
116121 const datas = tree.nodes.items(.data);
122 if (r.fixups.omit_nodes.contains(decl)) return;
117123 try renderDocComments(r, tree.firstToken(decl));
118124 switch (tree.nodes.items(.tag)[decl]) {
119125 .fn_decl => {
src/reduce.zig+5-2
......@@ -166,8 +166,8 @@ pub fn main(gpa: Allocator, arena: Allocator, args: []const []const u8) !void {
166166 try std.fs.cwd().writeFile(root_source_file_path, rendered.items);
167167
168168 const interestingness = try runCheck(arena, interestingness_argv.items);
169 std.debug.print("{d} random transformations: {s}\n", .{
170 subset_size, @tagName(interestingness),
169 std.debug.print("{d} random transformations: {s}. {d} remaining\n", .{
170 subset_size, @tagName(interestingness), transformations.items.len - start_index,
171171 });
172172 switch (interestingness) {
173173 .interesting => {
......@@ -250,6 +250,9 @@ fn transformationsToFixups(
250250 .gut_function => |fn_decl_node| {
251251 try fixups.gut_functions.put(gpa, fn_decl_node, {});
252252 },
253 .delete_node => |decl_node| {
254 try fixups.omit_nodes.put(gpa, decl_node, {});
255 },
253256 };
254257}
255258
src/reduce/Walk.zig+91-9
......@@ -5,11 +5,15 @@ const assert = std.debug.assert;
55
66ast: *const Ast,
77transformations: *std.ArrayList(Transformation),
8unreferenced_globals: std.StringArrayHashMapUnmanaged(Ast.Node.Index),
9gpa: std.mem.Allocator,
810
911pub const Transformation = union(enum) {
1012 /// Replace the fn decl AST Node with one whose body is only `@trap()` with
1113 /// discarded parameters.
1214 gut_function: Ast.Node.Index,
15 /// Omit a global declaration.
16 delete_node: Ast.Node.Index,
1317};
1418
1519pub const Error = error{OutOfMemory};
......@@ -21,16 +25,59 @@ pub fn findTransformations(ast: *const Ast, transformations: *std.ArrayList(Tran
2125 var walk: Walk = .{
2226 .ast = ast,
2327 .transformations = transformations,
28 .gpa = transformations.allocator,
29 .unreferenced_globals = .{},
2430 };
31 defer walk.unreferenced_globals.deinit(walk.gpa);
32
2533 try walkMembers(&walk, walk.ast.rootDecls());
34
35 const unreferenced_globals = walk.unreferenced_globals.values();
36 try transformations.ensureUnusedCapacity(unreferenced_globals.len);
37 for (unreferenced_globals) |node| {
38 transformations.appendAssumeCapacity(.{ .delete_node = node });
39 }
2640}
2741
2842fn walkMembers(w: *Walk, members: []const Ast.Node.Index) Error!void {
43 // First we scan for globals so that we can delete them while walking.
44 try scanDecls(w, members);
45
2946 for (members) |member| {
3047 try walkMember(w, member);
3148 }
3249}
3350
51fn scanDecls(w: *Walk, members: []const Ast.Node.Index) Error!void {
52 const ast = w.ast;
53 const gpa = w.gpa;
54 const node_tags = ast.nodes.items(.tag);
55 const main_tokens = ast.nodes.items(.main_token);
56 const token_tags = ast.tokens.items(.tag);
57
58 for (members) |member_node| {
59 const name_token = switch (node_tags[member_node]) {
60 .global_var_decl,
61 .local_var_decl,
62 .simple_var_decl,
63 .aligned_var_decl,
64 => main_tokens[member_node] + 1,
65
66 .fn_proto_simple,
67 .fn_proto_multi,
68 .fn_proto_one,
69 .fn_proto,
70 .fn_decl,
71 => main_tokens[member_node] + 1,
72
73 else => continue,
74 };
75 assert(token_tags[name_token] == .identifier);
76 const name_bytes = ast.tokenSlice(name_token);
77 try w.unreferenced_globals.put(gpa, name_bytes, member_node);
78 }
79}
80
3481fn walkMember(w: *Walk, decl: Ast.Node.Index) Error!void {
3582 const ast = w.ast;
3683 const datas = ast.nodes.items(.data);
......@@ -53,6 +100,7 @@ fn walkMember(w: *Walk, decl: Ast.Node.Index) Error!void {
53100 },
54101
55102 .@"usingnamespace" => {
103 try w.transformations.append(.{ .delete_node = decl });
56104 const expr = datas[decl].lhs;
57105 try walkExpression(w, expr);
58106 },
......@@ -61,9 +109,10 @@ fn walkMember(w: *Walk, decl: Ast.Node.Index) Error!void {
61109 .local_var_decl,
62110 .simple_var_decl,
63111 .aligned_var_decl,
64 => try walkVarDecl(w, ast.fullVarDecl(decl).?),
112 => try walkGlobalVarDecl(w, decl, ast.fullVarDecl(decl).?),
65113
66114 .test_decl => {
115 try w.transformations.append(.{ .delete_node = decl });
67116 try walkExpression(w, datas[decl].rhs);
68117 },
69118
......@@ -72,7 +121,10 @@ fn walkMember(w: *Walk, decl: Ast.Node.Index) Error!void {
72121 .container_field,
73122 => try walkContainerField(w, ast.fullContainerField(decl).?),
74123
75 .@"comptime" => try walkExpression(w, decl),
124 .@"comptime" => {
125 try w.transformations.append(.{ .delete_node = decl });
126 try walkExpression(w, decl);
127 },
76128
77129 .root => unreachable,
78130 else => unreachable,
......@@ -86,7 +138,7 @@ fn walkExpression(w: *Walk, node: Ast.Node.Index) Error!void {
86138 const node_tags = ast.nodes.items(.tag);
87139 const datas = ast.nodes.items(.data);
88140 switch (node_tags[node]) {
89 .identifier => {},
141 .identifier => try walkIdentifier(w, main_tokens[node]),
90142
91143 .number_literal,
92144 .char_literal,
......@@ -463,8 +515,32 @@ fn walkExpression(w: *Walk, node: Ast.Node.Index) Error!void {
463515 }
464516}
465517
518fn walkGlobalVarDecl(w: *Walk, decl_node: Ast.Node.Index, var_decl: Ast.full.VarDecl) Error!void {
519 _ = decl_node;
520
521 if (var_decl.ast.type_node != 0) {
522 try walkExpression(w, var_decl.ast.type_node);
523 }
524
525 if (var_decl.ast.align_node != 0) {
526 try walkExpression(w, var_decl.ast.align_node);
527 }
528
529 if (var_decl.ast.addrspace_node != 0) {
530 try walkExpression(w, var_decl.ast.addrspace_node);
531 }
532
533 if (var_decl.ast.section_node != 0) {
534 try walkExpression(w, var_decl.ast.section_node);
535 }
536
537 assert(var_decl.ast.init_node != 0);
538
539 return walkExpression(w, var_decl.ast.init_node);
540}
541
466542fn walkVarDecl(w: *Walk, var_decl: Ast.full.VarDecl) Error!void {
467 try walkIdentifier(w, var_decl.ast.mut_token + 1); // name
543 try walkIdentifierNew(w, var_decl.ast.mut_token + 1); // name
468544
469545 if (var_decl.ast.type_node != 0) {
470546 try walkExpression(w, var_decl.ast.type_node);
......@@ -571,9 +647,17 @@ fn walkSlice(
571647 }
572648}
573649
574fn walkIdentifier(w: *Walk, token_index: Ast.TokenIndex) Error!void {
650fn walkIdentifier(w: *Walk, name_ident: Ast.TokenIndex) Error!void {
651 const ast = w.ast;
652 const token_tags = ast.tokens.items(.tag);
653 assert(token_tags[name_ident] == .identifier);
654 const name_bytes = ast.tokenSlice(name_ident);
655 _ = w.unreferenced_globals.swapRemove(name_bytes);
656}
657
658fn walkIdentifierNew(w: *Walk, name_ident: Ast.TokenIndex) Error!void {
575659 _ = w;
576 _ = token_index;
660 _ = name_ident;
577661}
578662
579663fn walkContainerDecl(
......@@ -585,9 +669,7 @@ fn walkContainerDecl(
585669 if (container_decl.ast.arg != 0) {
586670 try walkExpression(w, container_decl.ast.arg);
587671 }
588 for (container_decl.ast.members) |member| {
589 try walkMember(w, member);
590 }
672 try walkMembers(w, container_decl.ast.members);
591673}
592674
593675fn walkBuiltinCall(