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/SkSLIfStatement.h"
9
10 #include "include/core/SkTypes.h"
11 #include "src/sksl/SkSLAnalysis.h"
12 #include "src/sksl/SkSLBuiltinTypes.h"
13 #include "src/sksl/SkSLConstantFolder.h"
14 #include "src/sksl/SkSLContext.h"
15 #include "src/sksl/SkSLProgramSettings.h"
16 #include "src/sksl/ir/SkSLExpressionStatement.h"
17 #include "src/sksl/ir/SkSLLiteral.h"
18 #include "src/sksl/ir/SkSLNop.h"
19 #include "src/sksl/ir/SkSLType.h"
20
21 namespace SkSL {
22
description() const23 std::string IfStatement::description() const {
24 std::string result;
25 result += "if (" + this->test()->description() + ") " + this->ifTrue()->description();
26 if (this->ifFalse()) {
27 result += " else " + this->ifFalse()->description();
28 }
29 return result;
30 }
31
Convert(const Context & context,Position pos,std::unique_ptr<Expression> test,std::unique_ptr<Statement> ifTrue,std::unique_ptr<Statement> ifFalse)32 std::unique_ptr<Statement> IfStatement::Convert(const Context& context,
33 Position pos,
34 std::unique_ptr<Expression> test,
35 std::unique_ptr<Statement> ifTrue,
36 std::unique_ptr<Statement> ifFalse) {
37 test = context.fTypes.fBool->coerceExpression(std::move(test), context);
38 if (!test) {
39 return nullptr;
40 }
41 SkASSERT(ifTrue);
42 if (Analysis::DetectVarDeclarationWithoutScope(*ifTrue, context.fErrors)) {
43 return nullptr;
44 }
45 if (ifFalse && Analysis::DetectVarDeclarationWithoutScope(*ifFalse, context.fErrors)) {
46 return nullptr;
47 }
48 return IfStatement::Make(context, pos, std::move(test), std::move(ifTrue), std::move(ifFalse));
49 }
50
replace_empty_with_nop(std::unique_ptr<Statement> stmt,bool isEmpty)51 static std::unique_ptr<Statement> replace_empty_with_nop(std::unique_ptr<Statement> stmt,
52 bool isEmpty) {
53 return (stmt && (!isEmpty || stmt->is<Nop>())) ? std::move(stmt)
54 : Nop::Make();
55 }
56
Make(const Context & context,Position pos,std::unique_ptr<Expression> test,std::unique_ptr<Statement> ifTrue,std::unique_ptr<Statement> ifFalse)57 std::unique_ptr<Statement> IfStatement::Make(const Context& context,
58 Position pos,
59 std::unique_ptr<Expression> test,
60 std::unique_ptr<Statement> ifTrue,
61 std::unique_ptr<Statement> ifFalse) {
62 SkASSERT(test->type().matches(*context.fTypes.fBool));
63 SkASSERT(!Analysis::DetectVarDeclarationWithoutScope(*ifTrue));
64 SkASSERT(!ifFalse || !Analysis::DetectVarDeclarationWithoutScope(*ifFalse));
65
66 const bool optimize = context.fConfig->fSettings.fOptimize;
67 bool trueIsEmpty = false;
68 bool falseIsEmpty = false;
69
70 if (optimize) {
71 // If both sides are empty, the if statement can be reduced to its test expression.
72 trueIsEmpty = ifTrue->isEmpty();
73 falseIsEmpty = !ifFalse || ifFalse->isEmpty();
74 if (trueIsEmpty && falseIsEmpty) {
75 return ExpressionStatement::Make(context, std::move(test));
76 }
77 }
78
79 if (optimize) {
80 // Static Boolean values can fold down to a single branch.
81 const Expression* testValue = ConstantFolder::GetConstantValueForVariable(*test);
82 if (testValue->isBoolLiteral()) {
83 if (testValue->as<Literal>().boolValue()) {
84 return replace_empty_with_nop(std::move(ifTrue), trueIsEmpty);
85 } else {
86 return replace_empty_with_nop(std::move(ifFalse), falseIsEmpty);
87 }
88 }
89 }
90
91 if (optimize) {
92 // Replace an empty if-true branches with Nop; eliminate empty if-false branches entirely.
93 ifTrue = replace_empty_with_nop(std::move(ifTrue), trueIsEmpty);
94 if (falseIsEmpty) {
95 ifFalse = nullptr;
96 }
97 }
98
99 return std::make_unique<IfStatement>(
100 pos, std::move(test), std::move(ifTrue), std::move(ifFalse));
101 }
102
103 } // namespace SkSL
104