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/SkSLConstructorCompoundCast.h"
9
10 #include "include/core/SkTypes.h"
11 #include "src/sksl/SkSLAnalysis.h"
12 #include "src/sksl/SkSLConstantFolder.h"
13 #include "src/sksl/ir/SkSLConstructorCompound.h"
14 #include "src/sksl/ir/SkSLConstructorDiagonalMatrix.h"
15 #include "src/sksl/ir/SkSLConstructorScalarCast.h"
16 #include "src/sksl/ir/SkSLConstructorSplat.h"
17 #include "src/sksl/ir/SkSLType.h"
18
19 #include <cstddef>
20 #include <iterator>
21 #include <optional>
22
23 namespace SkSL {
24
cast_constant_composite(const Context & context,Position pos,const Type & destType,std::unique_ptr<Expression> constCtor)25 static std::unique_ptr<Expression> cast_constant_composite(const Context& context,
26 Position pos,
27 const Type& destType,
28 std::unique_ptr<Expression> constCtor) {
29 const Type& scalarType = destType.componentType();
30
31 // We generate nicer code for splats and diagonal matrices by handling them separately instead
32 // of relying on the constant-subexpression code below. This is not truly necessary but it makes
33 // our output look a little better; human beings prefer `half4(0)` to `half4(0, 0, 0, 0)`.
34 if (constCtor->is<ConstructorSplat>()) {
35 // This is a typecast of a splat containing a constant value, e.g. `half4(7)`. We can
36 // replace it with a splat of a different type, e.g. `int4(7)`.
37 ConstructorSplat& splat = constCtor->as<ConstructorSplat>();
38 return ConstructorSplat::Make(
39 context, pos, destType,
40 ConstructorScalarCast::Make(context, pos, scalarType, std::move(splat.argument())));
41 }
42
43 if (constCtor->is<ConstructorDiagonalMatrix>() && destType.isMatrix()) {
44 // This is a typecast of a constant diagonal matrix, e.g. `float3x3(2)`. We can replace it
45 // with a diagonal matrix of a different type, e.g. `half3x3(2)`.
46 ConstructorDiagonalMatrix& matrixCtor = constCtor->as<ConstructorDiagonalMatrix>();
47 return ConstructorDiagonalMatrix::Make(
48 context, pos, destType,
49 ConstructorScalarCast::Make(context, pos, scalarType,
50 std::move(matrixCtor.argument())));
51 }
52
53 // Create a compound Constructor(literal, ...) which typecasts each scalar value inside.
54 size_t numSlots = destType.slotCount();
55 SkASSERT(numSlots == constCtor->type().slotCount());
56
57 double typecastArgs[16];
58 SkASSERT(numSlots <= std::size(typecastArgs));
59 for (size_t index = 0; index < numSlots; ++index) {
60 std::optional<double> slotVal = constCtor->getConstantValue(index);
61 if (scalarType.checkForOutOfRangeLiteral(context, *slotVal, constCtor->fPosition)) {
62 // We've reported an error because the literal is out of range for this type. Zero out
63 // the value to avoid a cascade of errors.
64 *slotVal = 0.0;
65 }
66 typecastArgs[index] = *slotVal;
67 }
68
69 return ConstructorCompound::MakeFromConstants(context, pos, destType, typecastArgs);
70 }
71
Make(const Context & context,Position pos,const Type & type,std::unique_ptr<Expression> arg)72 std::unique_ptr<Expression> ConstructorCompoundCast::Make(const Context& context,
73 Position pos,
74 const Type& type,
75 std::unique_ptr<Expression> arg) {
76 // Only vectors or matrices of the same dimensions are allowed.
77 SkASSERT(type.isVector() || type.isMatrix());
78 SkASSERT(type.isAllowedInES2(context));
79 SkASSERT(arg->type().isVector() == type.isVector());
80 SkASSERT(arg->type().isMatrix() == type.isMatrix());
81 SkASSERT(type.columns() == arg->type().columns());
82 SkASSERT(type.rows() == arg->type().rows());
83
84 // If this is a no-op cast, return the expression as-is.
85 if (type.matches(arg->type())) {
86 arg->setPosition(pos);
87 return arg;
88 }
89 // Look up the value of constant variables. This allows constant-expressions like
90 // `int4(colorGreen)` to be replaced with the compile-time constant `int4(0, 1, 0, 1)`.
91 arg = ConstantFolder::MakeConstantValueForVariable(pos, std::move(arg));
92
93 // We can cast a vector of compile-time constants at compile-time.
94 if (Analysis::IsCompileTimeConstant(*arg)) {
95 return cast_constant_composite(context, pos, type, std::move(arg));
96 }
97 return std::make_unique<ConstructorCompoundCast>(pos, type, std::move(arg));
98 }
99
100 } // namespace SkSL
101