transform: Add FoldTrivialSingleUseLets
This transform is intended to clean up the output of the SPIR-V reader, so that we can pattern match loops that can be transformed into a for-loop. Bug: tint:952 Change-Id: Iba58e4e1f6e20daaf7715e493df53346cdb7c89f Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/56766 Kokoro: Kokoro <noreply+kokoro@google.com> Reviewed-by: David Neto <dneto@google.com> Commit-Queue: David Neto <dneto@google.com> Auto-Submit: Ben Clayton <bclayton@google.com>
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@ -26,6 +26,7 @@
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#include "src/sem/type_manager.h"
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#include "src/transform/binding_remapper.h"
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#include "src/transform/first_index_offset.h"
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#include "src/transform/fold_trivial_single_use_lets.h"
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#include "src/transform/manager.h"
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#include "src/transform/renamer.h"
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#include "src/transform/robustness.h"
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@ -88,6 +88,7 @@ const char kUsage[] = R"(Usage: tint [options] <input-file>
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--transform <name list> -- Runs transforms, name list is comma separated
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Available transforms:
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first_index_offset
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fold_trivial_single_use_lets
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renamer
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robustness
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--parse-only -- Stop after parsing the input
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@ -708,6 +709,8 @@ int main(int argc, const char** argv) {
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transform_inputs.Add<tint::transform::FirstIndexOffset::BindingPoint>(0,
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0);
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transform_manager.Add<tint::transform::FirstIndexOffset>();
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} else if (name == "fold_trivial_single_use_lets") {
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transform_manager.Add<tint::transform::FoldTrivialSingleUseLets>();
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} else if (name == "renamer") {
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transform_manager.Add<tint::transform::Renamer>();
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} else if (name == "robustness") {
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@ -568,6 +568,8 @@ libtint_source_set("libtint_core_all_src") {
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"transform/first_index_offset.h",
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"transform/fold_constants.cc",
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"transform/fold_constants.h",
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"transform/fold_trivial_single_use_lets.cc",
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"transform/fold_trivial_single_use_lets.h",
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"transform/inline_pointer_lets.cc",
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"transform/inline_pointer_lets.h",
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"transform/manager.cc",
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@ -293,6 +293,8 @@ set(TINT_LIB_SRCS
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transform/first_index_offset.h
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transform/fold_constants.cc
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transform/fold_constants.h
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transform/fold_trivial_single_use_lets.cc
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transform/fold_trivial_single_use_lets.h
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transform/inline_pointer_lets.cc
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transform/inline_pointer_lets.h
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transform/manager.cc
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@ -875,6 +877,7 @@ if(${TINT_BUILD_TESTS})
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transform/external_texture_transform_test.cc
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transform/first_index_offset_test.cc
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transform/fold_constants_test.cc
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transform/fold_trivial_single_use_lets_test.cc
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transform/inline_pointer_lets_test.cc
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transform/pad_array_elements_test.cc
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transform/promote_initializers_to_const_var_test.cc
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@ -0,0 +1,93 @@
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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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@ -0,0 +1,59 @@
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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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#ifndef SRC_TRANSFORM_FOLD_TRIVIAL_SINGLE_USE_LETS_H_
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#define SRC_TRANSFORM_FOLD_TRIVIAL_SINGLE_USE_LETS_H_
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#include <string>
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#include <unordered_map>
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#include "src/transform/transform.h"
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namespace tint {
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namespace transform {
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/// FoldTrivialSingleUseLets is an optimizer for folding away trivial `let`
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/// statements into their single place of use. This transform is intended to
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/// clean up the SSA `let`s produced by the SPIR-V reader.
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/// `let`s can only be folded if:
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/// * There is a single usage of the `let` value.
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/// * The `let` is constructed with a ScalarConstructorExpression, or with an
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/// IdentifierExpression.
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/// * There are only other foldable `let`s between the `let` declaration and its
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/// single usage.
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/// These rules prevent any hoisting of the let that may affect execution
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/// behaviour.
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class FoldTrivialSingleUseLets
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: public Castable<FoldTrivialSingleUseLets, Transform> {
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public:
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/// Constructor
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FoldTrivialSingleUseLets();
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/// Destructor
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~FoldTrivialSingleUseLets() override;
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protected:
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/// Runs the transform using the CloneContext built for transforming a
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/// program. Run() is responsible for calling Clone() on the CloneContext.
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/// @param ctx the CloneContext primed with the input program and
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/// ProgramBuilder
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/// @param inputs optional extra transform-specific input data
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/// @param outputs optional extra transform-specific output data
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void Run(CloneContext& ctx, const DataMap& inputs, DataMap& outputs) override;
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};
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} // namespace transform
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} // namespace tint
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#endif // SRC_TRANSFORM_FOLD_TRIVIAL_SINGLE_USE_LETS_H_
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@ -0,0 +1,149 @@
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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/transform/test_helper.h"
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namespace tint {
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namespace transform {
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namespace {
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using FoldTrivialSingleUseLetsTest = TransformTest;
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TEST_F(FoldTrivialSingleUseLetsTest, EmptyModule) {
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auto* src = "";
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auto* expect = "";
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auto got = Run<FoldTrivialSingleUseLets>(src);
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EXPECT_EQ(expect, str(got));
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}
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TEST_F(FoldTrivialSingleUseLetsTest, Single) {
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auto* src = R"(
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fn f() {
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let x = 1;
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ignore(x);
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}
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)";
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auto* expect = R"(
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fn f() {
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ignore(1);
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}
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)";
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auto got = Run<FoldTrivialSingleUseLets>(src);
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EXPECT_EQ(expect, str(got));
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}
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TEST_F(FoldTrivialSingleUseLetsTest, Multiple) {
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auto* src = R"(
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fn f() {
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let x = 1;
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let y = 2;
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let z = 3;
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ignore(x + y + z);
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}
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)";
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auto* expect = R"(
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fn f() {
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ignore(((1 + 2) + 3));
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}
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)";
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auto got = Run<FoldTrivialSingleUseLets>(src);
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EXPECT_EQ(expect, str(got));
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}
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TEST_F(FoldTrivialSingleUseLetsTest, Chained) {
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auto* src = R"(
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fn f() {
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let x = 1;
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let y = x;
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let z = y;
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ignore(z);
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}
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)";
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auto* expect = R"(
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fn f() {
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ignore(1);
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}
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)";
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auto got = Run<FoldTrivialSingleUseLets>(src);
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EXPECT_EQ(expect, str(got));
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}
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TEST_F(FoldTrivialSingleUseLetsTest, NoFold_NonTrivialLet) {
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auto* src = R"(
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fn function_with_posssible_side_effect() -> i32 {
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return 1;
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}
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fn f() {
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let x = 1;
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let y = function_with_posssible_side_effect();
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ignore((x + y));
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}
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)";
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auto* expect = src;
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auto got = Run<FoldTrivialSingleUseLets>(src);
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EXPECT_EQ(expect, str(got));
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}
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TEST_F(FoldTrivialSingleUseLetsTest, NoFold_UseInSubBlock) {
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auto* src = R"(
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fn f() {
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let x = 1;
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{
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ignore(x);
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}
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}
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)";
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auto* expect = src;
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auto got = Run<FoldTrivialSingleUseLets>(src);
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EXPECT_EQ(expect, str(got));
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}
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TEST_F(FoldTrivialSingleUseLetsTest, NoFold_MultipleUses) {
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auto* src = R"(
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fn f() {
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let x = 1;
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ignore((x + x));
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}
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)";
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auto* expect = src;
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auto got = Run<FoldTrivialSingleUseLets>(src);
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EXPECT_EQ(expect, str(got));
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}
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} // namespace
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} // namespace transform
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} // namespace tint
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@ -284,6 +284,8 @@ tint_unittests_source_set("tint_unittests_core_src") {
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"../src/transform/decompose_memory_access_test.cc",
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"../src/transform/external_texture_transform_test.cc",
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"../src/transform/first_index_offset_test.cc",
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"../src/transform/fold_constants_test.cc",
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"../src/transform/fold_trivial_single_use_lets_test.cc",
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"../src/transform/inline_pointer_lets_test.cc",
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"../src/transform/pad_array_elements_test.cc",
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"../src/transform/promote_initializers_to_const_var_test.cc",
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