1 /*
2 * Copyright 2021 Google LLC
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #include "src/sksl/ir/SkSLExpressionStatement.h"
9
10 #include "include/core/SkTypes.h"
11 #include "src/sksl/SkSLAnalysis.h"
12 #include "src/sksl/SkSLContext.h"
13 #include "src/sksl/SkSLOperator.h"
14 #include "src/sksl/SkSLProgramSettings.h"
15 #include "src/sksl/ir/SkSLBinaryExpression.h"
16 #include "src/sksl/ir/SkSLNop.h"
17 #include "src/sksl/ir/SkSLVariableReference.h"
18
19 namespace SkSL {
20
Convert(const Context & context,std::unique_ptr<Expression> expr)21 std::unique_ptr<Statement> ExpressionStatement::Convert(const Context& context,
22 std::unique_ptr<Expression> expr) {
23 // Expression-statements need to represent a complete expression.
24 // Report an error on intermediate expressions, like FunctionReference or TypeReference.
25 if (expr->isIncomplete(context)) {
26 return nullptr;
27 }
28 return ExpressionStatement::Make(context, std::move(expr));
29 }
30
Make(const Context & context,std::unique_ptr<Expression> expr)31 std::unique_ptr<Statement> ExpressionStatement::Make(const Context& context,
32 std::unique_ptr<Expression> expr) {
33 SkASSERT(!expr->isIncomplete(context));
34
35 if (context.fConfig->fSettings.fOptimize) {
36 // Expression-statements without any side effect can be replaced with a Nop.
37 if (!Analysis::HasSideEffects(*expr)) {
38 return Nop::Make();
39 }
40
41 // If this is an assignment statement like `a += b;`, the ref-kind of `a` will be set as
42 // read-write; `a` is written-to by the +=, and read-from by the consumer of the expression.
43 // We can demote the ref-kind to "write" safely, because the result of the expression is
44 // discarded; that is, `a` is never actually read-from.
45 if (expr->is<BinaryExpression>()) {
46 BinaryExpression& binary = expr->as<BinaryExpression>();
47 if (VariableReference* assignedVar = binary.isAssignmentIntoVariable()) {
48 if (assignedVar->refKind() == VariableRefKind::kReadWrite) {
49 assignedVar->setRefKind(VariableRefKind::kWrite);
50 }
51 }
52 }
53 }
54
55 return std::make_unique<ExpressionStatement>(std::move(expr));
56 }
57
description() const58 std::string ExpressionStatement::description() const {
59 return this->expression()->description(OperatorPrecedence::kStatement) + ";";
60 }
61
62 } // namespace SkSL
63