| /* |
| * Copyright 2020 Google LLC |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "src/sksl/SkSLConstantFolder.h" |
| |
| #include <limits> |
| |
| #include "include/sksl/SkSLErrorReporter.h" |
| #include "src/sksl/SkSLAnalysis.h" |
| #include "src/sksl/SkSLContext.h" |
| #include "src/sksl/SkSLProgramSettings.h" |
| #include "src/sksl/ir/SkSLBinaryExpression.h" |
| #include "src/sksl/ir/SkSLConstructor.h" |
| #include "src/sksl/ir/SkSLConstructorCompound.h" |
| #include "src/sksl/ir/SkSLConstructorSplat.h" |
| #include "src/sksl/ir/SkSLExpression.h" |
| #include "src/sksl/ir/SkSLLiteral.h" |
| #include "src/sksl/ir/SkSLPrefixExpression.h" |
| #include "src/sksl/ir/SkSLType.h" |
| #include "src/sksl/ir/SkSLVariable.h" |
| #include "src/sksl/ir/SkSLVariableReference.h" |
| |
| namespace SkSL { |
| |
| static bool is_vec_or_mat(const Type& type) { |
| switch (type.typeKind()) { |
| case Type::TypeKind::kMatrix: |
| case Type::TypeKind::kVector: |
| return true; |
| |
| default: |
| return false; |
| } |
| } |
| |
| static std::unique_ptr<Expression> eliminate_no_op_boolean(const Expression& left, |
| Operator op, |
| const Expression& right) { |
| bool rightVal = right.as<Literal>().boolValue(); |
| |
| // Detect no-op Boolean expressions and optimize them away. |
| if ((op.kind() == Token::Kind::TK_LOGICALAND && rightVal) || // (expr && true) -> (expr) |
| (op.kind() == Token::Kind::TK_LOGICALOR && !rightVal) || // (expr || false) -> (expr) |
| (op.kind() == Token::Kind::TK_LOGICALXOR && !rightVal) || // (expr ^^ false) -> (expr) |
| (op.kind() == Token::Kind::TK_EQEQ && rightVal) || // (expr == true) -> (expr) |
| (op.kind() == Token::Kind::TK_NEQ && !rightVal)) { // (expr != false) -> (expr) |
| |
| return left.clone(); |
| } |
| |
| return nullptr; |
| } |
| |
| static std::unique_ptr<Expression> short_circuit_boolean(const Expression& left, |
| Operator op, |
| const Expression& right) { |
| bool leftVal = left.as<Literal>().boolValue(); |
| |
| // When the literal is on the left, we can sometimes eliminate the other expression entirely. |
| if ((op.kind() == Token::Kind::TK_LOGICALAND && !leftVal) || // (false && expr) -> (false) |
| (op.kind() == Token::Kind::TK_LOGICALOR && leftVal)) { // (true || expr) -> (true) |
| |
| return left.clone(); |
| } |
| |
| // We can't eliminate the right-side expression via short-circuit, but we might still be able to |
| // simplify away a no-op expression. |
| return eliminate_no_op_boolean(right, op, left); |
| } |
| |
| static std::unique_ptr<Expression> simplify_constant_equality(const Context& context, |
| const Expression& left, |
| Operator op, |
| const Expression& right) { |
| if (op.kind() == Token::Kind::TK_EQEQ || op.kind() == Token::Kind::TK_NEQ) { |
| bool equality = (op.kind() == Token::Kind::TK_EQEQ); |
| |
| switch (left.compareConstant(right)) { |
| case Expression::ComparisonResult::kNotEqual: |
| equality = !equality; |
| [[fallthrough]]; |
| |
| case Expression::ComparisonResult::kEqual: |
| return Literal::MakeBool(context, left.fLine, equality); |
| |
| case Expression::ComparisonResult::kUnknown: |
| break; |
| } |
| } |
| return nullptr; |
| } |
| |
| static std::unique_ptr<Expression> simplify_matrix_times_matrix(const Context& context, |
| const Expression& left, |
| const Expression& right) { |
| const Type& leftType = left.type(); |
| const Type& rightType = right.type(); |
| |
| SkASSERT(leftType.isMatrix()); |
| SkASSERT(rightType.isMatrix()); |
| |
| const Type& componentType = leftType.componentType(); |
| SkASSERT(componentType.matches(rightType.componentType())); |
| |
| const int leftColumns = leftType.columns(), |
| leftRows = leftType.rows(), |
| rightColumns = rightType.columns(), |
| rightRows = rightType.rows(), |
| outColumns = rightColumns, |
| outRows = leftRows; |
| SkASSERT(leftColumns == rightRows); |
| const Type& resultType = componentType.toCompound(context, outColumns, outRows); |
| |
| // Fetch the left matrix. |
| double leftVals[4][4]; |
| for (int c = 0; c < leftColumns; ++c) { |
| for (int r = 0; r < leftRows; ++r) { |
| leftVals[c][r] = *left.getConstantValue((c * leftRows) + r); |
| } |
| } |
| // Fetch the right matrix. |
| double rightVals[4][4]; |
| for (int c = 0; c < rightColumns; ++c) { |
| for (int r = 0; r < rightRows; ++r) { |
| rightVals[c][r] = *right.getConstantValue((c * rightRows) + r); |
| } |
| } |
| |
| ExpressionArray args; |
| args.reserve_back(outColumns * outRows); |
| for (int c = 0; c < outColumns; ++c) { |
| for (int r = 0; r < outRows; ++r) { |
| // Compute a dot product for this position. |
| double val = 0; |
| for (int dotIdx = 0; dotIdx < leftColumns; ++dotIdx) { |
| val += leftVals[dotIdx][r] * rightVals[c][dotIdx]; |
| } |
| args.push_back(Literal::Make(left.fLine, val, &componentType)); |
| } |
| } |
| |
| return ConstructorCompound::Make(context, left.fLine, resultType, std::move(args)); |
| } |
| |
| static std::unique_ptr<Expression> simplify_componentwise(const Context& context, |
| const Expression& left, |
| Operator op, |
| const Expression& right) { |
| SkASSERT(is_vec_or_mat(left.type())); |
| SkASSERT(left.type().matches(right.type())); |
| const Type& type = left.type(); |
| |
| // Handle equality operations: == != |
| if (std::unique_ptr<Expression> result = simplify_constant_equality(context, left, op, right)) { |
| return result; |
| } |
| |
| // Handle floating-point arithmetic: + - * / |
| using FoldFn = double (*)(double, double); |
| FoldFn foldFn; |
| switch (op.kind()) { |
| case Token::Kind::TK_PLUS: foldFn = +[](double a, double b) { return a + b; }; break; |
| case Token::Kind::TK_MINUS: foldFn = +[](double a, double b) { return a - b; }; break; |
| case Token::Kind::TK_STAR: foldFn = +[](double a, double b) { return a * b; }; break; |
| case Token::Kind::TK_SLASH: foldFn = +[](double a, double b) { return a / b; }; break; |
| default: |
| return nullptr; |
| } |
| |
| const Type& componentType = type.componentType(); |
| SkASSERT(componentType.isNumber()); |
| |
| double minimumValue = -INFINITY, maximumValue = INFINITY; |
| if (componentType.isInteger()) { |
| minimumValue = componentType.minimumValue(); |
| maximumValue = componentType.maximumValue(); |
| } |
| |
| ExpressionArray args; |
| int numSlots = type.slotCount(); |
| args.reserve_back(numSlots); |
| for (int i = 0; i < numSlots; i++) { |
| double value = foldFn(*left.getConstantValue(i), *right.getConstantValue(i)); |
| if (value < minimumValue || value > maximumValue) { |
| return nullptr; |
| } |
| |
| args.push_back(Literal::Make(left.fLine, value, &componentType)); |
| } |
| return ConstructorCompound::Make(context, left.fLine, type, std::move(args)); |
| } |
| |
| static std::unique_ptr<Expression> splat_scalar(const Context& context, |
| const Expression& scalar, |
| const Type& type) { |
| if (type.isVector()) { |
| return ConstructorSplat::Make(context, scalar.fLine, type, scalar.clone()); |
| } |
| if (type.isMatrix()) { |
| int numSlots = type.slotCount(); |
| ExpressionArray splatMatrix; |
| splatMatrix.reserve_back(numSlots); |
| for (int index = 0; index < numSlots; ++index) { |
| splatMatrix.push_back(scalar.clone()); |
| } |
| return ConstructorCompound::Make(context, scalar.fLine, type, std::move(splatMatrix)); |
| } |
| SkDEBUGFAILF("unsupported type %s", type.description().c_str()); |
| return nullptr; |
| } |
| |
| static std::unique_ptr<Expression> cast_expression(const Context& context, |
| const Expression& expr, |
| const Type& type) { |
| ExpressionArray ctorArgs; |
| ctorArgs.push_back(expr.clone()); |
| return Constructor::Convert(context, expr.fLine, type, std::move(ctorArgs)); |
| } |
| |
| bool ConstantFolder::GetConstantInt(const Expression& value, SKSL_INT* out) { |
| const Expression* expr = GetConstantValueForVariable(value); |
| if (!expr->isIntLiteral()) { |
| return false; |
| } |
| *out = expr->as<Literal>().intValue(); |
| return true; |
| } |
| |
| bool ConstantFolder::GetConstantValue(const Expression& value, double* out) { |
| const Expression* expr = GetConstantValueForVariable(value); |
| if (!expr->is<Literal>()) { |
| return false; |
| } |
| *out = expr->as<Literal>().value(); |
| return true; |
| } |
| |
| static bool contains_constant_zero(const Expression& expr) { |
| int numSlots = expr.type().slotCount(); |
| for (int index = 0; index < numSlots; ++index) { |
| std::optional<double> slotVal = expr.getConstantValue(index); |
| if (slotVal.has_value() && *slotVal == 0.0) { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| static bool is_constant_value(const Expression& expr, double value) { |
| int numSlots = expr.type().slotCount(); |
| for (int index = 0; index < numSlots; ++index) { |
| std::optional<double> slotVal = expr.getConstantValue(index); |
| if (!slotVal.has_value() || *slotVal != value) { |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| static bool error_on_divide_by_zero(const Context& context, int line, Operator op, |
| const Expression& right) { |
| switch (op.kind()) { |
| case Token::Kind::TK_SLASH: |
| case Token::Kind::TK_SLASHEQ: |
| case Token::Kind::TK_PERCENT: |
| case Token::Kind::TK_PERCENTEQ: |
| if (contains_constant_zero(right)) { |
| context.fErrors->error(line, "division by zero"); |
| return true; |
| } |
| return false; |
| default: |
| return false; |
| } |
| } |
| |
| const Expression* ConstantFolder::GetConstantValueForVariable(const Expression& inExpr) { |
| for (const Expression* expr = &inExpr;;) { |
| if (!expr->is<VariableReference>()) { |
| break; |
| } |
| const VariableReference& varRef = expr->as<VariableReference>(); |
| if (varRef.refKind() != VariableRefKind::kRead) { |
| break; |
| } |
| const Variable& var = *varRef.variable(); |
| if (!(var.modifiers().fFlags & Modifiers::kConst_Flag)) { |
| break; |
| } |
| expr = var.initialValue(); |
| if (!expr) { |
| // Function parameters can be const but won't have an initial value. |
| break; |
| } |
| if (expr->isCompileTimeConstant()) { |
| return expr; |
| } |
| } |
| // We didn't find a compile-time constant at the end. Return the expression as-is. |
| return &inExpr; |
| } |
| |
| std::unique_ptr<Expression> ConstantFolder::MakeConstantValueForVariable( |
| std::unique_ptr<Expression> expr) { |
| const Expression* constantExpr = GetConstantValueForVariable(*expr); |
| if (constantExpr != expr.get()) { |
| expr = constantExpr->clone(); |
| } |
| return expr; |
| } |
| |
| static std::unique_ptr<Expression> simplify_no_op_arithmetic(const Context& context, |
| const Expression& left, |
| Operator op, |
| const Expression& right, |
| const Type& resultType) { |
| switch (op.kind()) { |
| case Token::Kind::TK_PLUS: |
| if (is_constant_value(right, 0.0)) { // x + 0 |
| return cast_expression(context, left, resultType); |
| } |
| if (is_constant_value(left, 0.0)) { // 0 + x |
| return cast_expression(context, right, resultType); |
| } |
| break; |
| |
| case Token::Kind::TK_STAR: |
| if (is_constant_value(right, 1.0)) { // x * 1 |
| return cast_expression(context, left, resultType); |
| } |
| if (is_constant_value(left, 1.0)) { // 1 * x |
| return cast_expression(context, right, resultType); |
| } |
| if (is_constant_value(right, 0.0) && !left.hasSideEffects()) { // x * 0 |
| return cast_expression(context, right, resultType); |
| } |
| if (is_constant_value(left, 0.0) && !right.hasSideEffects()) { // 0 * x |
| return cast_expression(context, left, resultType); |
| } |
| break; |
| |
| case Token::Kind::TK_MINUS: |
| if (is_constant_value(right, 0.0)) { // x - 0 |
| return cast_expression(context, left, resultType); |
| } |
| if (is_constant_value(left, 0.0)) { // 0 - x (to `-x`) |
| if (std::unique_ptr<Expression> val = cast_expression(context, right, resultType)) { |
| return PrefixExpression::Make(context, Token::Kind::TK_MINUS, std::move(val)); |
| } |
| } |
| break; |
| |
| case Token::Kind::TK_SLASH: |
| if (is_constant_value(right, 1.0)) { // x / 1 |
| return cast_expression(context, left, resultType); |
| } |
| break; |
| |
| case Token::Kind::TK_PLUSEQ: |
| case Token::Kind::TK_MINUSEQ: |
| if (is_constant_value(right, 0.0)) { // x += 0, x -= 0 |
| if (std::unique_ptr<Expression> var = cast_expression(context, left, resultType)) { |
| Analysis::UpdateVariableRefKind(var.get(), VariableRefKind::kRead); |
| return var; |
| } |
| } |
| break; |
| |
| case Token::Kind::TK_STAREQ: |
| case Token::Kind::TK_SLASHEQ: |
| if (is_constant_value(right, 1.0)) { // x *= 1, x /= 1 |
| if (std::unique_ptr<Expression> var = cast_expression(context, left, resultType)) { |
| Analysis::UpdateVariableRefKind(var.get(), VariableRefKind::kRead); |
| return var; |
| } |
| } |
| break; |
| |
| default: |
| break; |
| } |
| |
| return nullptr; |
| } |
| |
| template <typename T> |
| static std::unique_ptr<Expression> fold_float_expression(int line, |
| T result, |
| const Type* resultType) { |
| // If constant-folding this expression would generate a NaN/infinite result, leave it as-is. |
| if constexpr (!std::is_same<T, bool>::value) { |
| if (!std::isfinite(result)) { |
| return nullptr; |
| } |
| } |
| |
| return Literal::Make(line, result, resultType); |
| } |
| |
| template <typename T> |
| static std::unique_ptr<Expression> fold_int_expression(int line, |
| T result, |
| const Type* resultType) { |
| // If constant-folding this expression would overflow the result type, leave it as-is. |
| if constexpr (!std::is_same<T, bool>::value) { |
| if (result < resultType->minimumValue() || result > resultType->maximumValue()) { |
| return nullptr; |
| } |
| } |
| |
| return Literal::Make(line, result, resultType); |
| } |
| |
| std::unique_ptr<Expression> ConstantFolder::Simplify(const Context& context, |
| int line, |
| const Expression& leftExpr, |
| Operator op, |
| const Expression& rightExpr, |
| const Type& resultType) { |
| // Replace constant variables with their literal values. |
| const Expression* left = GetConstantValueForVariable(leftExpr); |
| const Expression* right = GetConstantValueForVariable(rightExpr); |
| |
| // If this is the comma operator, the left side is evaluated but not otherwise used in any way. |
| // So if the left side has no side effects, it can just be eliminated entirely. |
| if (op.kind() == Token::Kind::TK_COMMA && !left->hasSideEffects()) { |
| return right->clone(); |
| } |
| |
| // If this is the assignment operator, and both sides are the same trivial expression, this is |
| // self-assignment (i.e., `var = var`) and can be reduced to just a variable reference (`var`). |
| // This can happen when other parts of the assignment are optimized away. |
| if (op.kind() == Token::Kind::TK_EQ && Analysis::IsSameExpressionTree(*left, *right)) { |
| return right->clone(); |
| } |
| |
| // Simplify the expression when both sides are constant Boolean literals. |
| if (left->isBoolLiteral() && right->isBoolLiteral()) { |
| bool leftVal = left->as<Literal>().boolValue(); |
| bool rightVal = right->as<Literal>().boolValue(); |
| bool result; |
| switch (op.kind()) { |
| case Token::Kind::TK_LOGICALAND: result = leftVal && rightVal; break; |
| case Token::Kind::TK_LOGICALOR: result = leftVal || rightVal; break; |
| case Token::Kind::TK_LOGICALXOR: result = leftVal ^ rightVal; break; |
| case Token::Kind::TK_EQEQ: result = leftVal == rightVal; break; |
| case Token::Kind::TK_NEQ: result = leftVal != rightVal; break; |
| default: return nullptr; |
| } |
| return Literal::MakeBool(context, line, result); |
| } |
| |
| // If the left side is a Boolean literal, apply short-circuit optimizations. |
| if (left->isBoolLiteral()) { |
| return short_circuit_boolean(*left, op, *right); |
| } |
| |
| // If the right side is a Boolean literal... |
| if (right->isBoolLiteral()) { |
| // ... and the left side has no side effects... |
| if (!left->hasSideEffects()) { |
| // We can reverse the expressions and short-circuit optimizations are still valid. |
| return short_circuit_boolean(*right, op, *left); |
| } |
| |
| // We can't use short-circuiting, but we can still optimize away no-op Boolean expressions. |
| return eliminate_no_op_boolean(*left, op, *right); |
| } |
| |
| if (op.kind() == Token::Kind::TK_EQEQ && Analysis::IsSameExpressionTree(*left, *right)) { |
| // With == comparison, if both sides are the same trivial expression, this is self- |
| // comparison and is always true. (We are not concerned with NaN.) |
| return Literal::MakeBool(context, leftExpr.fLine, /*value=*/true); |
| } |
| |
| if (op.kind() == Token::Kind::TK_NEQ && Analysis::IsSameExpressionTree(*left, *right)) { |
| // With != comparison, if both sides are the same trivial expression, this is self- |
| // comparison and is always false. (We are not concerned with NaN.) |
| return Literal::MakeBool(context, leftExpr.fLine, /*value=*/false); |
| } |
| |
| if (error_on_divide_by_zero(context, line, op, *right)) { |
| return nullptr; |
| } |
| |
| // Optimize away no-op arithmetic like `x * 1`, `x *= 1`, `x + 0`, `x * 0`, `0 / x`, etc. |
| const Type& leftType = left->type(); |
| const Type& rightType = right->type(); |
| if ((leftType.isScalar() || leftType.isVector()) && |
| (rightType.isScalar() || rightType.isVector())) { |
| std::unique_ptr<Expression> expr = simplify_no_op_arithmetic(context, *left, op, *right, |
| resultType); |
| if (expr) { |
| return expr; |
| } |
| } |
| |
| // Other than the cases above, constant folding requires both sides to be constant. |
| if (!left->isCompileTimeConstant() || !right->isCompileTimeConstant()) { |
| return nullptr; |
| } |
| |
| // Note that fold_int_expression returns null if the result would overflow its type. |
| using SKSL_UINT = uint64_t; |
| if (left->isIntLiteral() && right->isIntLiteral()) { |
| SKSL_INT leftVal = left->as<Literal>().intValue(); |
| SKSL_INT rightVal = right->as<Literal>().intValue(); |
| |
| #define RESULT(Op) fold_int_expression(line, \ |
| (SKSL_INT)(leftVal) Op (SKSL_INT)(rightVal), &resultType) |
| #define URESULT(Op) fold_int_expression(line, \ |
| (SKSL_INT)((SKSL_UINT)(leftVal) Op (SKSL_UINT)(rightVal)), &resultType) |
| switch (op.kind()) { |
| case Token::Kind::TK_PLUS: return URESULT(+); |
| case Token::Kind::TK_MINUS: return URESULT(-); |
| case Token::Kind::TK_STAR: return URESULT(*); |
| case Token::Kind::TK_SLASH: |
| if (leftVal == std::numeric_limits<SKSL_INT>::min() && rightVal == -1) { |
| context.fErrors->error(line, "arithmetic overflow"); |
| return nullptr; |
| } |
| return RESULT(/); |
| case Token::Kind::TK_PERCENT: |
| if (leftVal == std::numeric_limits<SKSL_INT>::min() && rightVal == -1) { |
| context.fErrors->error(line, "arithmetic overflow"); |
| return nullptr; |
| } |
| return RESULT(%); |
| case Token::Kind::TK_BITWISEAND: return RESULT(&); |
| case Token::Kind::TK_BITWISEOR: return RESULT(|); |
| case Token::Kind::TK_BITWISEXOR: return RESULT(^); |
| case Token::Kind::TK_EQEQ: return RESULT(==); |
| case Token::Kind::TK_NEQ: return RESULT(!=); |
| case Token::Kind::TK_GT: return RESULT(>); |
| case Token::Kind::TK_GTEQ: return RESULT(>=); |
| case Token::Kind::TK_LT: return RESULT(<); |
| case Token::Kind::TK_LTEQ: return RESULT(<=); |
| case Token::Kind::TK_SHL: |
| if (rightVal >= 0 && rightVal <= 31) { |
| // Left-shifting a negative (or really, any signed) value is undefined behavior |
| // in C++, but not GLSL. Do the shift on unsigned values, to avoid UBSAN. |
| return URESULT(<<); |
| } |
| context.fErrors->error(line, "shift value out of range"); |
| return nullptr; |
| case Token::Kind::TK_SHR: |
| if (rightVal >= 0 && rightVal <= 31) { |
| return RESULT(>>); |
| } |
| context.fErrors->error(line, "shift value out of range"); |
| return nullptr; |
| |
| default: |
| return nullptr; |
| } |
| #undef RESULT |
| #undef URESULT |
| } |
| |
| // Perform constant folding on pairs of floating-point literals. |
| if (left->isFloatLiteral() && right->isFloatLiteral()) { |
| SKSL_FLOAT leftVal = left->as<Literal>().floatValue(); |
| SKSL_FLOAT rightVal = right->as<Literal>().floatValue(); |
| |
| #define RESULT(Op) fold_float_expression(line, leftVal Op rightVal, &resultType) |
| switch (op.kind()) { |
| case Token::Kind::TK_PLUS: return RESULT(+); |
| case Token::Kind::TK_MINUS: return RESULT(-); |
| case Token::Kind::TK_STAR: return RESULT(*); |
| case Token::Kind::TK_SLASH: return RESULT(/); |
| case Token::Kind::TK_EQEQ: return RESULT(==); |
| case Token::Kind::TK_NEQ: return RESULT(!=); |
| case Token::Kind::TK_GT: return RESULT(>); |
| case Token::Kind::TK_GTEQ: return RESULT(>=); |
| case Token::Kind::TK_LT: return RESULT(<); |
| case Token::Kind::TK_LTEQ: return RESULT(<=); |
| default: return nullptr; |
| } |
| #undef RESULT |
| } |
| |
| // Perform matrix * matrix multiplication. |
| if (op.kind() == Token::Kind::TK_STAR && leftType.isMatrix() && rightType.isMatrix()) { |
| return simplify_matrix_times_matrix(context, *left, *right); |
| } |
| |
| // Perform constant folding on pairs of vectors/matrices. |
| if (is_vec_or_mat(leftType) && leftType.matches(rightType)) { |
| return simplify_componentwise(context, *left, op, *right); |
| } |
| |
| // Perform constant folding on vectors/matrices against scalars, e.g.: half4(2) + 2 |
| if (rightType.isScalar() && is_vec_or_mat(leftType) && |
| leftType.componentType().matches(rightType)) { |
| return simplify_componentwise(context, *left, op, |
| *splat_scalar(context, *right, left->type())); |
| } |
| |
| // Perform constant folding on scalars against vectors/matrices, e.g.: 2 + half4(2) |
| if (leftType.isScalar() && is_vec_or_mat(rightType) && |
| rightType.componentType().matches(leftType)) { |
| return simplify_componentwise(context, *splat_scalar(context, *left, right->type()), |
| op, *right); |
| } |
| |
| // Perform constant folding on pairs of matrices or arrays. |
| if ((leftType.isMatrix() && rightType.isMatrix()) || |
| (leftType.isArray() && rightType.isArray())) { |
| return simplify_constant_equality(context, *left, op, *right); |
| } |
| |
| // We aren't able to constant-fold. |
| return nullptr; |
| } |
| |
| } // namespace SkSL |
