94 lines
2.9 KiB
C++
94 lines
2.9 KiB
C++
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// Copyright 2021 The Tint Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "src/transform/fold_trivial_single_use_lets.h"
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#include "src/program_builder.h"
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#include "src/sem/block_statement.h"
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#include "src/sem/function.h"
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#include "src/sem/statement.h"
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#include "src/sem/variable.h"
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#include "src/utils/scoped_assignment.h"
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TINT_INSTANTIATE_TYPEINFO(tint::transform::FoldTrivialSingleUseLets);
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namespace tint {
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namespace transform {
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namespace {
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ast::VariableDeclStatement* AsTrivialLetDecl(ast::Statement* stmt) {
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auto* var_decl = stmt->As<ast::VariableDeclStatement>();
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if (!var_decl) {
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return nullptr;
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}
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auto* var = var_decl->variable();
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if (!var->is_const()) {
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return nullptr;
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}
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auto* ctor = var->constructor();
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if (!IsAnyOf<ast::IdentifierExpression, ast::ScalarConstructorExpression>(
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ctor)) {
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return nullptr;
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}
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return var_decl;
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}
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} // namespace
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FoldTrivialSingleUseLets::FoldTrivialSingleUseLets() = default;
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FoldTrivialSingleUseLets::~FoldTrivialSingleUseLets() = default;
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void FoldTrivialSingleUseLets::Run(CloneContext& ctx,
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const DataMap&,
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DataMap&) {
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for (auto* node : ctx.src->ASTNodes().Objects()) {
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if (auto* block = node->As<ast::BlockStatement>()) {
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auto& stmts = block->statements();
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for (size_t stmt_idx = 0; stmt_idx < stmts.size(); stmt_idx++) {
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auto* stmt = stmts[stmt_idx];
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if (auto* let_decl = AsTrivialLetDecl(stmt)) {
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auto* let = let_decl->variable();
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auto* sem_let = ctx.src->Sem().Get(let);
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auto& users = sem_let->Users();
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if (users.size() != 1) {
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continue; // Does not have a single user.
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}
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auto* user = users[0];
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auto* user_stmt = user->Stmt()->Declaration();
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for (size_t i = stmt_idx; i < stmts.size(); i++) {
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if (user_stmt == stmts[i]) {
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auto* user_expr = user->Declaration();
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ctx.Remove(stmts, let_decl);
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ctx.Replace(user_expr, ctx.Clone(let->constructor()));
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}
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if (!AsTrivialLetDecl(stmts[i])) {
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// Stop if we hit a statement that isn't the single use of the
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// let, and isn't a let itself.
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break;
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}
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}
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}
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}
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}
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}
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ctx.Clone();
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}
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} // namespace transform
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} // namespace tint
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