1 // Copyright 2021 The Tint Authors.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #include "src/transform/remove_phonies.h"
16
17 #include <memory>
18 #include <unordered_map>
19 #include <utility>
20 #include <vector>
21
22 #include "src/ast/traverse_expressions.h"
23 #include "src/program_builder.h"
24 #include "src/sem/block_statement.h"
25 #include "src/sem/function.h"
26 #include "src/sem/statement.h"
27 #include "src/sem/variable.h"
28 #include "src/utils/map.h"
29 #include "src/utils/scoped_assignment.h"
30
31 TINT_INSTANTIATE_TYPEINFO(tint::transform::RemovePhonies);
32
33 namespace tint {
34 namespace transform {
35 namespace {
36
37 struct SinkSignature {
38 std::vector<const sem::Type*> types;
39
operator ==tint::transform::__anonb664b07f0111::SinkSignature40 bool operator==(const SinkSignature& other) const {
41 if (types.size() != other.types.size()) {
42 return false;
43 }
44 for (size_t i = 0; i < types.size(); i++) {
45 if (types[i] != other.types[i]) {
46 return false;
47 }
48 }
49 return true;
50 }
51
52 struct Hasher {
53 /// @param sig the CallTargetSignature to hash
54 /// @return the hash value
operator ()tint::transform::__anonb664b07f0111::SinkSignature::Hasher55 std::size_t operator()(const SinkSignature& sig) const {
56 size_t hash = tint::utils::Hash(sig.types.size());
57 for (auto* ty : sig.types) {
58 tint::utils::HashCombine(&hash, ty);
59 }
60 return hash;
61 }
62 };
63 };
64
65 } // namespace
66
67 RemovePhonies::RemovePhonies() = default;
68
69 RemovePhonies::~RemovePhonies() = default;
70
Run(CloneContext & ctx,const DataMap &,DataMap &)71 void RemovePhonies::Run(CloneContext& ctx, const DataMap&, DataMap&) {
72 auto& sem = ctx.src->Sem();
73
74 std::unordered_map<SinkSignature, Symbol, SinkSignature::Hasher> sinks;
75
76 for (auto* node : ctx.src->ASTNodes().Objects()) {
77 if (auto* stmt = node->As<ast::AssignmentStatement>()) {
78 if (stmt->lhs->Is<ast::PhonyExpression>()) {
79 std::vector<const ast::Expression*> side_effects;
80 if (!ast::TraverseExpressions(
81 stmt->rhs, ctx.dst->Diagnostics(),
82 [&](const ast::CallExpression* call) {
83 // ast::CallExpression may map to a function or intrinsic call
84 // (both may have side-effects), or a type constructor or
85 // type conversion (both do not have side effects).
86 if (sem.Get(call)
87 ->Target()
88 ->IsAnyOf<sem::Function, sem::Intrinsic>()) {
89 side_effects.push_back(call);
90 return ast::TraverseAction::Skip;
91 }
92 return ast::TraverseAction::Descend;
93 })) {
94 return;
95 }
96
97 if (side_effects.empty()) {
98 // Phony assignment with no side effects.
99 // Just remove it.
100 RemoveStatement(ctx, stmt);
101 continue;
102 }
103
104 if (side_effects.size() == 1) {
105 if (auto* call = side_effects[0]->As<ast::CallExpression>()) {
106 // Phony assignment with single call side effect.
107 // Replace phony assignment with call.
108 ctx.Replace(
109 stmt, [&, call] { return ctx.dst->CallStmt(ctx.Clone(call)); });
110 continue;
111 }
112 }
113
114 // Phony assignment with multiple side effects.
115 // Generate a call to a dummy function with the side effects as
116 // arguments.
117 ctx.Replace(stmt, [&, side_effects] {
118 SinkSignature sig;
119 for (auto* arg : side_effects) {
120 sig.types.push_back(sem.Get(arg)->Type()->UnwrapRef());
121 }
122 auto sink = utils::GetOrCreate(sinks, sig, [&] {
123 auto name = ctx.dst->Symbols().New("phony_sink");
124 ast::VariableList params;
125 for (auto* ty : sig.types) {
126 auto* ast_ty = CreateASTTypeFor(ctx, ty);
127 params.push_back(
128 ctx.dst->Param("p" + std::to_string(params.size()), ast_ty));
129 }
130 ctx.dst->Func(name, params, ctx.dst->ty.void_(), {});
131 return name;
132 });
133 ast::ExpressionList args;
134 for (auto* arg : side_effects) {
135 args.push_back(ctx.Clone(arg));
136 }
137 return ctx.dst->CallStmt(ctx.dst->Call(sink, args));
138 });
139 }
140 }
141 }
142
143 ctx.Clone();
144 }
145
146 } // namespace transform
147 } // namespace tint
148