1 /*
2 * Copyright 2016 Google Inc.
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 #ifndef SKSL_SWIZZLE
9 #define SKSL_SWIZZLE
10
11 #include "SkSLConstructor.h"
12 #include "SkSLContext.h"
13 #include "SkSLExpression.h"
14 #include "SkSLIRGenerator.h"
15 #include "SkSLUtil.h"
16
17 namespace SkSL {
18
19 /**
20 * Given a type and a swizzle component count, returns the type that will result from swizzling. For
21 * instance, swizzling a vec3 with two components will result in a vec2. It is possible to swizzle
22 * with more components than the source vector, as in 'vec2(1).xxxx'.
23 */
get_type(const Context & context,Expression & value,size_t count)24 static const Type& get_type(const Context& context, Expression& value, size_t count) {
25 const Type& base = value.fType.componentType();
26 if (count == 1) {
27 return base;
28 }
29 if (base == *context.fFloat_Type) {
30 switch (count) {
31 case 2: return *context.fVec2_Type;
32 case 3: return *context.fVec3_Type;
33 case 4: return *context.fVec4_Type;
34 }
35 } else if (base == *context.fDouble_Type) {
36 switch (count) {
37 case 2: return *context.fDVec2_Type;
38 case 3: return *context.fDVec3_Type;
39 case 4: return *context.fDVec4_Type;
40 }
41 } else if (base == *context.fInt_Type) {
42 switch (count) {
43 case 2: return *context.fIVec2_Type;
44 case 3: return *context.fIVec3_Type;
45 case 4: return *context.fIVec4_Type;
46 }
47 } else if (base == *context.fUInt_Type) {
48 switch (count) {
49 case 2: return *context.fUVec2_Type;
50 case 3: return *context.fUVec3_Type;
51 case 4: return *context.fUVec4_Type;
52 }
53 } else if (base == *context.fBool_Type) {
54 switch (count) {
55 case 2: return *context.fBVec2_Type;
56 case 3: return *context.fBVec3_Type;
57 case 4: return *context.fBVec4_Type;
58 }
59 }
60 ABORT("cannot swizzle %s\n", value.description().c_str());
61 }
62
63 /**
64 * Represents a vector swizzle operation such as 'vec2(1, 2, 3).zyx'.
65 */
66 struct Swizzle : public Expression {
SwizzleSwizzle67 Swizzle(const Context& context, std::unique_ptr<Expression> base, std::vector<int> components)
68 : INHERITED(base->fPosition, kSwizzle_Kind, get_type(context, *base, components.size()))
69 , fBase(std::move(base))
70 , fComponents(std::move(components)) {
71 ASSERT(fComponents.size() >= 1 && fComponents.size() <= 4);
72 }
73
constantPropagateSwizzle74 std::unique_ptr<Expression> constantPropagate(const IRGenerator& irGenerator,
75 const DefinitionMap& definitions) override {
76 if (fBase->fKind == Expression::kConstructor_Kind && fBase->isConstant()) {
77 // we're swizzling a constant vector, e.g. vec4(1).x. Simplify it.
78 ASSERT(fBase->fKind == Expression::kConstructor_Kind);
79 if (fType == *irGenerator.fContext.fInt_Type) {
80 ASSERT(fComponents.size() == 1);
81 int64_t value = ((Constructor&) *fBase).getIVecComponent(fComponents[0]);
82 return std::unique_ptr<Expression>(new IntLiteral(irGenerator.fContext,
83 Position(),
84 value));
85 } else if (fType == *irGenerator.fContext.fFloat_Type) {
86 ASSERT(fComponents.size() == 1);
87 double value = ((Constructor&) *fBase).getFVecComponent(fComponents[0]);
88 return std::unique_ptr<Expression>(new FloatLiteral(irGenerator.fContext,
89 Position(),
90 value));
91 }
92 }
93 return nullptr;
94 }
95
hasSideEffectsSwizzle96 bool hasSideEffects() const override {
97 return fBase->hasSideEffects();
98 }
99
descriptionSwizzle100 String description() const override {
101 String result = fBase->description() + ".";
102 for (int x : fComponents) {
103 result += "xyzw"[x];
104 }
105 return result;
106 }
107
108 std::unique_ptr<Expression> fBase;
109 const std::vector<int> fComponents;
110
111 typedef Expression INHERITED;
112 };
113
114 } // namespace
115
116 #endif
117