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      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 // represents a swizzle component of constant 0, as in x.rgb0
     20 const int SKSL_SWIZZLE_0 = -2;
     21 
     22 // represents a swizzle component of constant 1, as in x.rgb1
     23 const int SKSL_SWIZZLE_1 = -1;
     24 
     25 /**
     26  * Given a type and a swizzle component count, returns the type that will result from swizzling. For
     27  * instance, swizzling a float3 with two components will result in a float2. It is possible to
     28  * swizzle with more components than the source vector, as in 'float2(1).xxxx'.
     29  */
     30 static const Type& get_type(const Context& context, Expression& value, size_t count) {
     31     const Type& base = value.fType.componentType();
     32     if (count == 1) {
     33         return base;
     34     }
     35     if (base == *context.fFloat_Type) {
     36         switch (count) {
     37             case 2: return *context.fFloat2_Type;
     38             case 3: return *context.fFloat3_Type;
     39             case 4: return *context.fFloat4_Type;
     40         }
     41     } else if (base == *context.fHalf_Type) {
     42         switch (count) {
     43             case 2: return *context.fHalf2_Type;
     44             case 3: return *context.fHalf3_Type;
     45             case 4: return *context.fHalf4_Type;
     46         }
     47     } else if (base == *context.fDouble_Type) {
     48         switch (count) {
     49             case 2: return *context.fDouble2_Type;
     50             case 3: return *context.fDouble3_Type;
     51             case 4: return *context.fDouble4_Type;
     52         }
     53     } else if (base == *context.fInt_Type) {
     54         switch (count) {
     55             case 2: return *context.fInt2_Type;
     56             case 3: return *context.fInt3_Type;
     57             case 4: return *context.fInt4_Type;
     58         }
     59     } else if (base == *context.fShort_Type) {
     60         switch (count) {
     61             case 2: return *context.fShort2_Type;
     62             case 3: return *context.fShort3_Type;
     63             case 4: return *context.fShort4_Type;
     64         }
     65     } else if (base == *context.fByte_Type) {
     66         switch (count) {
     67             case 2: return *context.fByte2_Type;
     68             case 3: return *context.fByte3_Type;
     69             case 4: return *context.fByte4_Type;
     70         }
     71     } else if (base == *context.fUInt_Type) {
     72         switch (count) {
     73             case 2: return *context.fUInt2_Type;
     74             case 3: return *context.fUInt3_Type;
     75             case 4: return *context.fUInt4_Type;
     76         }
     77     } else if (base == *context.fUShort_Type) {
     78         switch (count) {
     79             case 2: return *context.fUShort2_Type;
     80             case 3: return *context.fUShort3_Type;
     81             case 4: return *context.fUShort4_Type;
     82         }
     83     } else if (base == *context.fUByte_Type) {
     84         switch (count) {
     85             case 2: return *context.fUByte2_Type;
     86             case 3: return *context.fUByte3_Type;
     87             case 4: return *context.fUByte4_Type;
     88         }
     89     } else if (base == *context.fBool_Type) {
     90         switch (count) {
     91             case 2: return *context.fBool2_Type;
     92             case 3: return *context.fBool3_Type;
     93             case 4: return *context.fBool4_Type;
     94         }
     95     }
     96     ABORT("cannot swizzle %s\n", value.description().c_str());
     97 }
     98 
     99 /**
    100  * Represents a vector swizzle operation such as 'float2(1, 2, 3).zyx'.
    101  */
    102 struct Swizzle : public Expression {
    103     Swizzle(const Context& context, std::unique_ptr<Expression> base, std::vector<int> components)
    104     : INHERITED(base->fOffset, kSwizzle_Kind, get_type(context, *base, components.size()))
    105     , fBase(std::move(base))
    106     , fComponents(std::move(components)) {
    107         SkASSERT(fComponents.size() >= 1 && fComponents.size() <= 4);
    108     }
    109 
    110     std::unique_ptr<Expression> constantPropagate(const IRGenerator& irGenerator,
    111                                                   const DefinitionMap& definitions) override {
    112         if (fBase->fKind == Expression::kConstructor_Kind && fBase->isConstant()) {
    113             // we're swizzling a constant vector, e.g. float4(1).x. Simplify it.
    114             SkASSERT(fBase->fKind == Expression::kConstructor_Kind);
    115             if (fType.isInteger()) {
    116                 SkASSERT(fComponents.size() == 1);
    117                 int64_t value = ((Constructor&) *fBase).getIVecComponent(fComponents[0]);
    118                 return std::unique_ptr<Expression>(new IntLiteral(irGenerator.fContext,
    119                                                                   -1,
    120                                                                   value));
    121             } else if (fType.isFloat()) {
    122                 SkASSERT(fComponents.size() == 1);
    123                 double value = ((Constructor&) *fBase).getFVecComponent(fComponents[0]);
    124                 return std::unique_ptr<Expression>(new FloatLiteral(irGenerator.fContext,
    125                                                                     -1,
    126                                                                     value));
    127             }
    128         }
    129         return nullptr;
    130     }
    131 
    132     bool hasSideEffects() const override {
    133         return fBase->hasSideEffects();
    134     }
    135 
    136     std::unique_ptr<Expression> clone() const override {
    137         return std::unique_ptr<Expression>(new Swizzle(fType, fBase->clone(), fComponents));
    138     }
    139 
    140     String description() const override {
    141         String result = fBase->description() + ".";
    142         for (int x : fComponents) {
    143             result += "01xyzw"[x + 2];
    144         }
    145         return result;
    146     }
    147 
    148     std::unique_ptr<Expression> fBase;
    149     const std::vector<int> fComponents;
    150 
    151     typedef Expression INHERITED;
    152 
    153 private:
    154     Swizzle(const Type& type, std::unique_ptr<Expression> base, std::vector<int> components)
    155     : INHERITED(base->fOffset, kSwizzle_Kind, type)
    156     , fBase(std::move(base))
    157     , fComponents(std::move(components)) {
    158         SkASSERT(fComponents.size() >= 1 && fComponents.size() <= 4);
    159     }
    160 
    161 
    162 };
    163 
    164 } // namespace
    165 
    166 #endif
    167