1 /* 2 * Copyright 2022 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/base/SkEnumBitMask.h" 9 #include "src/sksl/SkSLAnalysis.h" 10 #include "src/sksl/analysis/SkSLProgramUsage.h" 11 #include "src/sksl/ir/SkSLModifierFlags.h" 12 #include "src/sksl/ir/SkSLVariable.h" 13 #include "src/sksl/transform/SkSLTransform.h" 14 15 namespace SkSL { 16 17 class Expression; 18 AddConstToVarModifiers(const Variable & var,const Expression * initialValue,const ProgramUsage * usage)19ModifierFlags Transform::AddConstToVarModifiers(const Variable& var, 20 const Expression* initialValue, 21 const ProgramUsage* usage) { 22 // If the variable is already marked as `const`, keep our existing modifiers. 23 ModifierFlags flags = var.modifierFlags(); 24 if (flags.isConst()) { 25 return flags; 26 } 27 // If the variable doesn't have a compile-time-constant initial value, we can't `const` it. 28 if (!initialValue || !Analysis::IsCompileTimeConstant(*initialValue)) { 29 return flags; 30 } 31 // This only works for variables that are written-to a single time. 32 ProgramUsage::VariableCounts counts = usage->get(var); 33 if (counts.fWrite != 1) { 34 return flags; 35 } 36 // Add `const` to our variable's modifier flags, making it eligible for constant-folding. 37 return flags | ModifierFlag::kConst; 38 } 39 40 } // namespace SkSL 41