| // Copyright 2021 The Tint Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| #include "src/tint/transform/remove_phonies.h" |
| |
| #include <memory> |
| #include <unordered_map> |
| #include <utility> |
| #include <vector> |
| |
| #include "src/tint/ast/traverse_expressions.h" |
| #include "src/tint/program_builder.h" |
| #include "src/tint/sem/block_statement.h" |
| #include "src/tint/sem/function.h" |
| #include "src/tint/sem/statement.h" |
| #include "src/tint/sem/variable.h" |
| #include "src/tint/utils/map.h" |
| #include "src/tint/utils/scoped_assignment.h" |
| |
| TINT_INSTANTIATE_TYPEINFO(tint::transform::RemovePhonies); |
| |
| namespace tint::transform { |
| namespace { |
| |
| using SinkSignature = std::vector<const sem::Type*>; |
| |
| } // namespace |
| |
| RemovePhonies::RemovePhonies() = default; |
| |
| RemovePhonies::~RemovePhonies() = default; |
| |
| Transform::ApplyResult RemovePhonies::Apply(const Program* src, const DataMap&, DataMap&) const { |
| ProgramBuilder b; |
| CloneContext ctx{&b, src, /* auto_clone_symbols */ true}; |
| |
| auto& sem = src->Sem(); |
| |
| utils::Hashmap<SinkSignature, Symbol, 8, utils::Hasher<SinkSignature>> sinks; |
| |
| bool made_changes = false; |
| for (auto* node : src->ASTNodes().Objects()) { |
| Switch( |
| node, |
| [&](const ast::AssignmentStatement* stmt) { |
| if (stmt->lhs->Is<ast::PhonyExpression>()) { |
| made_changes = true; |
| |
| std::vector<const ast::Expression*> side_effects; |
| if (!ast::TraverseExpressions( |
| stmt->rhs, b.Diagnostics(), [&](const ast::CallExpression* expr) { |
| // ast::CallExpression may map to a function or builtin call |
| // (both may have side-effects), or a type initializer or |
| // type conversion (both do not have side effects). |
| auto* call = sem.Get<sem::Call>(expr); |
| if (!call) { |
| // Semantic node must be a Materialize, in which case the |
| // expression was creation-time (compile time), so could not |
| // have side effects. Just skip. |
| return ast::TraverseAction::Skip; |
| } |
| if (call->Target()->IsAnyOf<sem::Function, sem::Builtin>() && |
| call->HasSideEffects()) { |
| side_effects.push_back(expr); |
| return ast::TraverseAction::Skip; |
| } |
| return ast::TraverseAction::Descend; |
| })) { |
| return; |
| } |
| |
| if (side_effects.empty()) { |
| // Phony assignment with no side effects. |
| // Just remove it. |
| RemoveStatement(ctx, stmt); |
| return; |
| } |
| |
| if (side_effects.size() == 1) { |
| if (auto* call = side_effects[0]->As<ast::CallExpression>()) { |
| // Phony assignment with single call side effect. |
| // Replace phony assignment with call. |
| ctx.Replace(stmt, [&, call] { return b.CallStmt(ctx.Clone(call)); }); |
| return; |
| } |
| } |
| |
| // Phony assignment with multiple side effects. |
| // Generate a call to a placeholder function with the side |
| // effects as arguments. |
| ctx.Replace(stmt, [&, side_effects] { |
| SinkSignature sig; |
| for (auto* arg : side_effects) { |
| sig.push_back(sem.Get(arg)->Type()->UnwrapRef()); |
| } |
| auto sink = sinks.GetOrCreate(sig, [&] { |
| auto name = b.Symbols().New("phony_sink"); |
| utils::Vector<const ast::Parameter*, 8> params; |
| for (auto* ty : sig) { |
| auto* ast_ty = CreateASTTypeFor(ctx, ty); |
| params.Push(b.Param("p" + std::to_string(params.Length()), ast_ty)); |
| } |
| b.Func(name, params, b.ty.void_(), {}); |
| return name; |
| }); |
| utils::Vector<const ast::Expression*, 8> args; |
| for (auto* arg : side_effects) { |
| args.Push(ctx.Clone(arg)); |
| } |
| return b.CallStmt(b.Call(sink, args)); |
| }); |
| } |
| }, |
| [&](const ast::CallStatement* stmt) { |
| // Remove call statements to const value-returning functions. |
| // TODO(crbug.com/tint/1637): Remove if `stmt->expr` has no side-effects. |
| auto* sem_expr = sem.Get(stmt->expr); |
| if ((sem_expr->ConstantValue() != nullptr) && !sem_expr->HasSideEffects()) { |
| made_changes = true; |
| ctx.Remove(sem.Get(stmt)->Block()->Declaration()->statements, stmt); |
| } |
| }); |
| } |
| |
| if (!made_changes) { |
| return SkipTransform; |
| } |
| |
| ctx.Clone(); |
| return Program(std::move(b)); |
| } |
| |
| } // namespace tint::transform |