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// Copyright 2022 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/promote_initializers_to_let.h"
#include <utility>
#include "src/tint/program_builder.h"
#include "src/tint/sem/call.h"
#include "src/tint/sem/statement.h"
#include "src/tint/sem/type_initializer.h"
#include "src/tint/transform/utils/hoist_to_decl_before.h"
TINT_INSTANTIATE_TYPEINFO(tint::transform::PromoteInitializersToLet);
namespace tint::transform {
PromoteInitializersToLet::PromoteInitializersToLet() = default;
PromoteInitializersToLet::~PromoteInitializersToLet() = default;
Transform::ApplyResult PromoteInitializersToLet::Apply(const Program* src,
const DataMap&,
DataMap&) const {
ProgramBuilder b;
CloneContext ctx{&b, src, /* auto_clone_symbols */ true};
HoistToDeclBefore hoist_to_decl_before(ctx);
bool any_promoted = false;
// Hoists array and structure initializers to a constant variable, declared
// just before the statement of usage.
auto promote = [&](const sem::Expression* expr) {
auto* sem_stmt = expr->Stmt();
if (!sem_stmt) {
// Expression is outside of a statement. This usually means the
// expression is part of a global (module-scope) constant declaration.
// These must be constexpr, and so cannot contain the type of
// expressions that must be sanitized.
return true;
}
auto* stmt = sem_stmt->Declaration();
if (auto* src_var_decl = stmt->As<ast::VariableDeclStatement>()) {
if (src_var_decl->variable->initializer == expr->Declaration()) {
// This statement is just a variable declaration with the
// initializer as the initializer value. This is what we're
// attempting to transform to, and so ignore.
return true;
}
}
auto* src_ty = expr->Type();
if (!src_ty->IsAnyOf<sem::Array, sem::Struct>()) {
// We only care about array and struct initializers
return true;
}
any_promoted = true;
return hoist_to_decl_before.Add(expr, expr->Declaration(), true);
};
for (auto* node : src->ASTNodes().Objects()) {
bool ok = Switch(
node, //
[&](const ast::CallExpression* expr) {
if (auto* sem = src->Sem().Get(expr)) {
auto* ctor = sem->UnwrapMaterialize()->As<sem::Call>();
if (ctor->Target()->Is<sem::TypeInitializer>()) {
return promote(sem);
}
}
return true;
},
[&](const ast::IdentifierExpression* expr) {
if (auto* sem = src->Sem().Get(expr)) {
if (auto* user = sem->UnwrapMaterialize()->As<sem::VariableUser>()) {
// Identifier resolves to a variable
if (auto* stmt = user->Stmt()) {
if (auto* decl = stmt->Declaration()->As<ast::VariableDeclStatement>();
decl && decl->variable->Is<ast::Const>()) {
// The identifier is used on the RHS of a 'const' declaration.
// Ignore.
return true;
}
}
if (user->Variable()->Declaration()->Is<ast::Const>()) {
// The identifier resolves to a 'const' variable, but isn't used to
// initialize another 'const'. This needs promoting.
return promote(user);
}
}
}
return true;
},
[&](Default) { return true; });
if (!ok) {
return Program(std::move(b));
}
}
if (!any_promoted) {
return SkipTransform;
}
ctx.Clone();
return Program(std::move(b));
}
} // namespace tint::transform