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
clone() const23 std::unique_ptr<Statement> IfStatement::clone() const {
24 return std::make_unique<IfStatement>(fPosition, this->test()->clone(), this->ifTrue()->clone(),
25 this->ifFalse() ? this->ifFalse()->clone() : nullptr);
26 }
27
description() const28 std::string IfStatement::description() const {
29 std::string result;
30 result += "if (" + this->test()->description() + ") " + this->ifTrue()->description();
31 if (this->ifFalse()) {
32 result += " else " + this->ifFalse()->description();
33 }
34 return result;
35 }
36
Convert(const Context & context,Position pos,std::unique_ptr<Expression> test,std::unique_ptr<Statement> ifTrue,std::unique_ptr<Statement> ifFalse)37 std::unique_ptr<Statement> IfStatement::Convert(const Context& context,
38 Position pos,
39 std::unique_ptr<Expression> test,
40 std::unique_ptr<Statement> ifTrue,
41 std::unique_ptr<Statement> ifFalse) {
42 test = context.fTypes.fBool->coerceExpression(std::move(test), context);
43 if (!test) {
44 return nullptr;
45 }
46 SkASSERT(ifTrue);
47 if (Analysis::DetectVarDeclarationWithoutScope(*ifTrue, context.fErrors)) {
48 return nullptr;
49 }
50 if (ifFalse && Analysis::DetectVarDeclarationWithoutScope(*ifFalse, context.fErrors)) {
51 return nullptr;
52 }
53 return IfStatement::Make(context, pos, std::move(test), std::move(ifTrue), std::move(ifFalse));
54 }
55
replace_empty_with_nop(std::unique_ptr<Statement> stmt,bool isEmpty)56 static std::unique_ptr<Statement> replace_empty_with_nop(std::unique_ptr<Statement> stmt,
57 bool isEmpty) {
58 return (stmt && (!isEmpty || stmt->is<Nop>())) ? std::move(stmt)
59 : Nop::Make();
60 }
61
Make(const Context & context,Position pos,std::unique_ptr<Expression> test,std::unique_ptr<Statement> ifTrue,std::unique_ptr<Statement> ifFalse)62 std::unique_ptr<Statement> IfStatement::Make(const Context& context,
63 Position pos,
64 std::unique_ptr<Expression> test,
65 std::unique_ptr<Statement> ifTrue,
66 std::unique_ptr<Statement> ifFalse) {
67 SkASSERT(test->type().matches(*context.fTypes.fBool));
68 SkASSERT(!Analysis::DetectVarDeclarationWithoutScope(*ifTrue));
69 SkASSERT(!ifFalse || !Analysis::DetectVarDeclarationWithoutScope(*ifFalse));
70
71 const bool optimize = context.fConfig->fSettings.fOptimize;
72 bool trueIsEmpty = false;
73 bool falseIsEmpty = false;
74
75 if (optimize) {
76 // If both sides are empty, the if statement can be reduced to its test expression.
77 trueIsEmpty = ifTrue->isEmpty();
78 falseIsEmpty = !ifFalse || ifFalse->isEmpty();
79 if (trueIsEmpty && falseIsEmpty) {
80 return ExpressionStatement::Make(context, std::move(test));
81 }
82 }
83
84 if (optimize) {
85 // Static Boolean values can fold down to a single branch.
86 const Expression* testValue = ConstantFolder::GetConstantValueForVariable(*test);
87 if (testValue->isBoolLiteral()) {
88 if (testValue->as<Literal>().boolValue()) {
89 return replace_empty_with_nop(std::move(ifTrue), trueIsEmpty);
90 } else {
91 return replace_empty_with_nop(std::move(ifFalse), falseIsEmpty);
92 }
93 }
94 }
95
96 if (optimize) {
97 // Replace an empty if-true branches with Nop; eliminate empty if-false branches entirely.
98 ifTrue = replace_empty_with_nop(std::move(ifTrue), trueIsEmpty);
99 if (falseIsEmpty) {
100 ifFalse = nullptr;
101 }
102 }
103
104 return std::make_unique<IfStatement>(
105 pos, std::move(test), std::move(ifTrue), std::move(ifFalse));
106 }
107
108 } // namespace SkSL
109