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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/var_for_dynamic_index.h"
#include <utility>
#include "src/tint/program_builder.h"
#include "src/tint/transform/utils/hoist_to_decl_before.h"
namespace tint::transform {
VarForDynamicIndex::VarForDynamicIndex() = default;
VarForDynamicIndex::~VarForDynamicIndex() = default;
Transform::ApplyResult VarForDynamicIndex::Apply(const Program* src,
const DataMap&,
DataMap&) const {
ProgramBuilder b;
CloneContext ctx{&b, src, /* auto_clone_symbols */ true};
HoistToDeclBefore hoist_to_decl_before(ctx);
// Extracts array and matrix values that are dynamically indexed to a
// temporary `var` local that is then indexed.
auto dynamic_index_to_var = [&](const ast::IndexAccessorExpression* access_expr) {
auto* index_expr = access_expr->index;
auto* object_expr = access_expr->object;
auto& sem = src->Sem();
if (sem.Get(index_expr)->ConstantValue()) {
// Index expression resolves to a compile time value.
// As this isn't a dynamic index, we can ignore this.
return true;
}
auto* indexed = sem.Get(object_expr);
if (!indexed->Type()->IsAnyOf<sem::Array, sem::Matrix>()) {
// We only care about array and matrices.
return true;
}
// TODO(bclayton): group multiple accesses in the same object.
// e.g. arr[i] + arr[i+1] // Don't create two vars for this
return hoist_to_decl_before.Add(indexed, object_expr, HoistToDeclBefore::VariableKind::kVar,
"var_for_index");
};
bool index_accessor_found = false;
for (auto* node : src->ASTNodes().Objects()) {
if (auto* access_expr = node->As<ast::IndexAccessorExpression>()) {
if (!dynamic_index_to_var(access_expr)) {
return Program(std::move(b));
}
index_accessor_found = true;
}
}
if (!index_accessor_found) {
return SkipTransform;
}
ctx.Clone();
return Program(std::move(b));
}
} // namespace tint::transform