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/SkSLConstructorMatrixResize.h"
9
10 #include "src/sksl/ir/SkSLConstructor.h"
11 #include "src/sksl/ir/SkSLType.h"
12
13 namespace SkSL {
14
Make(const Context & context,int offset,const Type & type,std::unique_ptr<Expression> arg)15 std::unique_ptr<Expression> ConstructorMatrixResize::Make(const Context& context,
16 int offset,
17 const Type& type,
18 std::unique_ptr<Expression> arg) {
19 SkASSERT(type.isMatrix());
20 SkASSERT(arg->type().componentType() == type.componentType());
21
22 // If the matrix isn't actually changing size, return it as-is.
23 if (type.rows() == arg->type().rows() && type.columns() == arg->type().columns()) {
24 return arg;
25 }
26
27 return std::make_unique<ConstructorMatrixResize>(offset, type, std::move(arg));
28 }
29
getConstantSubexpression(int n) const30 const Expression* ConstructorMatrixResize::getConstantSubexpression(int n) const {
31 int rows = this->type().rows();
32 int row = n % rows;
33 int col = n / rows;
34
35 SkASSERT(col >= 0);
36 SkASSERT(row >= 0);
37 SkASSERT(col < this->type().columns());
38 SkASSERT(row < this->type().rows());
39
40 // GLSL resize matrices are of the form:
41 // |m m 0|
42 // |m m 0|
43 // |0 0 1|
44 // Where `m` is the matrix being wrapped, and other cells contain the identity matrix.
45
46 // Forward `getConstantSubexpression` to the wrapped matrix if the position is in its bounds.
47 if (col < this->argument()->type().columns() && row < this->argument()->type().rows()) {
48 // Recalculate `n` in terms of the inner matrix's dimensions.
49 n = row + (col * this->argument()->type().rows());
50 return this->argument()->getConstantSubexpression(n);
51 }
52
53 // Synthesize an identity matrix for out-of-bounds positions.
54 return (col == row) ? &fOneLiteral : &fZeroLiteral;
55 }
56
57 } // namespace SkSL
58