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- /*
- * Copyright 2016 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
- #ifndef SKIASL_MEMORYLAYOUT
- #define SKIASL_MEMORYLAYOUT
- #include "src/sksl/ir/SkSLType.h"
- namespace SkSL {
- class MemoryLayout {
- public:
- enum Standard {
- k140_Standard,
- k430_Standard,
- kMetal_Standard
- };
- MemoryLayout(Standard std)
- : fStd(std) {}
- static size_t vector_alignment(size_t componentSize, int columns) {
- return componentSize * (columns + columns % 2);
- }
- /**
- * Rounds up to the nearest multiple of 16 if in std140, otherwise returns the parameter
- * unchanged (std140 requires various things to be rounded up to the nearest multiple of 16,
- * std430 does not).
- */
- size_t roundUpIfNeeded(size_t raw) const {
- switch (fStd) {
- case k140_Standard: return (raw + 15) & ~15;
- case k430_Standard: return raw;
- case kMetal_Standard: return raw;
- }
- ABORT("unreachable");
- }
- /**
- * Returns a type's required alignment when used as a standalone variable.
- */
- size_t alignment(const Type& type) const {
- // See OpenGL Spec 7.6.2.2 Standard Uniform Block Layout
- switch (type.kind()) {
- case Type::kScalar_Kind:
- return this->size(type);
- case Type::kVector_Kind:
- return vector_alignment(this->size(type.componentType()), type.columns());
- case Type::kMatrix_Kind:
- return this->roundUpIfNeeded(vector_alignment(this->size(type.componentType()),
- type.rows()));
- case Type::kArray_Kind:
- return this->roundUpIfNeeded(this->alignment(type.componentType()));
- case Type::kStruct_Kind: {
- size_t result = 0;
- for (const auto& f : type.fields()) {
- size_t alignment = this->alignment(*f.fType);
- if (alignment > result) {
- result = alignment;
- }
- }
- return this->roundUpIfNeeded(result);
- }
- default:
- ABORT("cannot determine size of type %s", type.name().c_str());
- }
- }
- /**
- * For matrices and arrays, returns the number of bytes from the start of one entry (row, in
- * the case of matrices) to the start of the next.
- */
- size_t stride(const Type& type) const {
- switch (type.kind()) {
- case Type::kMatrix_Kind: {
- size_t base = vector_alignment(this->size(type.componentType()), type.rows());
- return this->roundUpIfNeeded(base);
- }
- case Type::kArray_Kind: {
- int align = this->alignment(type.componentType());
- int stride = this->size(type.componentType()) + align - 1;
- stride -= stride % align;
- return this->roundUpIfNeeded(stride);
- }
- default:
- ABORT("type does not have a stride");
- }
- }
- /**
- * Returns the size of a type in bytes.
- */
- size_t size(const Type& type) const {
- switch (type.kind()) {
- case Type::kScalar_Kind:
- if (type.name() == "bool") {
- return 1;
- }
- // FIXME need to take precision into account, once we figure out how we want to
- // handle it...
- return 4;
- case Type::kVector_Kind:
- if (fStd == kMetal_Standard && type.columns() == 3) {
- return 4 * this->size(type.componentType());
- }
- return type.columns() * this->size(type.componentType());
- case Type::kMatrix_Kind: // fall through
- case Type::kArray_Kind:
- return type.columns() * this->stride(type);
- case Type::kStruct_Kind: {
- size_t total = 0;
- for (const auto& f : type.fields()) {
- size_t alignment = this->alignment(*f.fType);
- if (total % alignment != 0) {
- total += alignment - total % alignment;
- }
- SkASSERT(total % alignment == 0);
- total += this->size(*f.fType);
- }
- size_t alignment = this->alignment(type);
- SkASSERT(!type.fields().size() ||
- (0 == alignment % this->alignment(*type.fields()[0].fType)));
- return (total + alignment - 1) & ~(alignment - 1);
- }
- default:
- ABORT("cannot determine size of type %s", type.name().c_str());
- }
- }
- const Standard fStd;
- };
- } // namespace
- #endif
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