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/*
* Copyright 2021 Google LLC
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "src/sksl/ir/SkSLExpressionStatement.h"
#include "include/core/SkTypes.h"
#include "src/sksl/SkSLAnalysis.h"
#include "src/sksl/SkSLContext.h"
#include "src/sksl/SkSLProgramSettings.h"
#include "src/sksl/ir/SkSLBinaryExpression.h"
#include "src/sksl/ir/SkSLNop.h"
#include "src/sksl/ir/SkSLVariableReference.h"
namespace SkSL {
std::unique_ptr<Statement> ExpressionStatement::Convert(const Context& context,
std::unique_ptr<Expression> expr) {
// Expression-statements need to represent a complete expression.
// Report an error on intermediate expressions, like FunctionReference or TypeReference.
if (expr->isIncomplete(context)) {
return nullptr;
}
return ExpressionStatement::Make(context, std::move(expr));
}
std::unique_ptr<Statement> ExpressionStatement::Make(const Context& context,
std::unique_ptr<Expression> expr) {
SkASSERT(!expr->isIncomplete(context));
if (context.fConfig->fSettings.fOptimize) {
// Expression-statements without any side effect can be replaced with a Nop.
if (!Analysis::HasSideEffects(*expr)) {
return Nop::Make();
}
// If this is an assignment statement like `a += b;`, the ref-kind of `a` will be set as
// read-write; `a` is written-to by the +=, and read-from by the consumer of the expression.
// We can demote the ref-kind to "write" safely, because the result of the expression is
// discarded; that is, `a` is never actually read-from.
if (expr->is<BinaryExpression>()) {
BinaryExpression& binary = expr->as<BinaryExpression>();
if (VariableReference* assignedVar = binary.isAssignmentIntoVariable()) {
if (assignedVar->refKind() == VariableRefKind::kReadWrite) {
assignedVar->setRefKind(VariableRefKind::kWrite);
}
}
}
}
return std::make_unique<ExpressionStatement>(std::move(expr));
}
} // namespace SkSL
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