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While we can, restrict SkFixedAlloc/SkFallbackAlloc to POD.

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This trims the overhead down to a uniform 4 bytes.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4786

Change-Id: I92127a0c2d6c23a4a372eca39842e22195d2dc99
Reviewed-on: https://skia-review.googlesource.com/4786
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
This commit is contained in:
Mike Klein 2016-11-15 10:26:44 -05:00 committed by Skia Commit-Bot
parent f530586c41
commit 1ee70359a1
5 changed files with 81 additions and 83 deletions
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4
src/core/SkColorShader.cpp
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@ -317,7 +317,7 @@ bool SkColor4Shader::Color4Context::onChooseBlitProcs(const SkImageInfo& info, B
bool SkColorShader::onAppendStages(SkRasterPipeline* p,
SkColorSpace* dst,
SkFallbackAlloc* scratch) const {
auto color = scratch->make<SkPM4f>(SkPM4f_from_SkColor(fColor, dst));
auto color = scratch->copy(SkPM4f_from_SkColor(fColor, dst));
p->append(SkRasterPipeline::move_src_dst);
p->append(SkRasterPipeline::constant_color, color);
if (!append_gamut_transform(p, scratch,
@ -331,7 +331,7 @@ bool SkColorShader::onAppendStages(SkRasterPipeline* p,
bool SkColor4Shader::onAppendStages(SkRasterPipeline* p,
SkColorSpace* dst,
SkFallbackAlloc* scratch) const {
auto color = scratch->make<SkPM4f>(fColor4.premul());
auto color = scratch->copy(fColor4.premul());
p->append(SkRasterPipeline::move_src_dst);
p->append(SkRasterPipeline::constant_color, color);
if (!append_gamut_transform(p, scratch, fColorSpace.get(), dst)) {

43
src/core/SkFixedAlloc.cpp
View File

@ -11,23 +11,37 @@ SkFixedAlloc::SkFixedAlloc(void* ptr, size_t len)
: fBuffer((char*)ptr), fUsed(0), fLimit(len) {}
void SkFixedAlloc::undo() {
// This function is essentially make() in reverse.
// First, read the Footer we stamped at the end.
Footer footer;
memcpy(&footer, fBuffer + fUsed - sizeof(Footer), sizeof(Footer));
// That tells us where the T starts and how to destroy it.
footer.dtor(fBuffer + fUsed - sizeof(Footer) - footer.len);
// We can reuse bytes that stored the Footer, the T, and any that we skipped for alignment.
fUsed -= sizeof(Footer) + footer.len + footer.skip;
uint32_t skip_and_size;
memcpy(&skip_and_size, fBuffer + fUsed - 4, 4);
fUsed -= skip_and_size + 4;
}
void SkFixedAlloc::reset() {
while (fUsed) {
this->undo();
fUsed = 0;
}
void* SkFixedAlloc::alloc(size_t size, size_t align) {
auto aligned = ((uintptr_t)(fBuffer+fUsed) + align-1) & ~(align-1);
size_t skip = aligned - (uintptr_t)(fBuffer+fUsed);
if (!SkTFitsIn<uint32_t>(skip + size) ||
fUsed + skip + size + 4 > fLimit) {
return nullptr;
}
// Skip ahead until aligned.
fUsed += skip;
// Allocate size bytes.
void* ptr = (fBuffer+fUsed);
fUsed += size;
// Stamp a footer that we can use to clean up.
uint32_t skip_and_size = SkToU32(skip + size);
memcpy(fBuffer+fUsed, &skip_and_size, 4);
fUsed += 4;
return ptr;
}
@ -37,8 +51,7 @@ void SkFallbackAlloc::undo() {
if (fHeapAllocs.empty()) {
return fFixedAlloc->undo();
}
HeapAlloc alloc = fHeapAllocs.back();
alloc.deleter(alloc.ptr);
sk_free(fHeapAllocs.back());
fHeapAllocs.pop_back();
}

85
src/core/SkFixedAlloc.h
View File

@ -11,54 +11,51 @@
#include "SkTFitsIn.h"
#include "SkTypes.h"
#include <new>
#include <type_traits>
#include <utility>
#include <vector>
// SkFixedAlloc allocates objects out of a fixed-size buffer and destroys them when destroyed.
// Before GCC 5, is_trivially_copyable had a pre-standard name.
#if defined(__GLIBCXX__) && (__GLIBCXX__ < 20150801)
namespace std {
template <typename T>
using is_trivially_copyable = has_trivial_copy_constructor<T>;
}
#endif
// SkFixedAlloc allocates POD objects out of a fixed-size buffer.
class SkFixedAlloc {
public:
SkFixedAlloc(void* ptr, size_t len);
~SkFixedAlloc() { this->reset(); }
// Allocates a new T in the buffer if possible. If not, returns nullptr.
// Allocates space suitable for a T. If we can't, returns nullptr.
template <typename T>
void* alloc() {
static_assert(std::is_standard_layout <T>::value
&& std::is_trivially_copyable<T>::value, "");
return this->alloc(sizeof(T), alignof(T));
}
template <typename T, typename... Args>
T* make(Args&&... args) {
auto aligned = ((uintptr_t)(fBuffer+fUsed) + alignof(T) - 1) & ~(alignof(T)-1);
size_t skip = aligned - (uintptr_t)(fBuffer+fUsed);
if (!SkTFitsIn<uint32_t>(skip) ||
!SkTFitsIn<uint32_t>(sizeof(T)) ||
fUsed + skip + sizeof(T) + sizeof(Footer) > fLimit) {
if (auto ptr = this->alloc<T>()) {
return new (ptr) T(std::forward<Args>(args)...);
}
return nullptr;
}
// Skip ahead until our buffer is aligned for T.
fUsed += skip;
template <typename T>
T* copy(const T& src) { return this->make<T>(src); }
// Create the T.
auto ptr = (T*)(fBuffer+fUsed);
new (ptr) T(std::forward<Args>(args)...);
fUsed += sizeof(T);
// Stamp a footer after the T that we can use to clean it up.
Footer footer = { [](void* ptr) { ((T*)ptr)->~T(); }, SkToU32(skip), SkToU32(sizeof(T)) };
memcpy(fBuffer+fUsed, &footer, sizeof(Footer));
fUsed += sizeof(Footer);
return ptr;
}
// Destroys the last object allocated and frees its space in the buffer.
// Frees the space of the last object allocated.
void undo();
// Destroys all objects and frees all space in the buffer.
// Frees all space in the buffer.
void reset();
private:
struct Footer {
void (*dtor)(void*);
uint32_t skip, len;
};
void* alloc(size_t, size_t);
char* fBuffer;
size_t fUsed, fLimit;
@ -69,34 +66,34 @@ public:
explicit SkFallbackAlloc(SkFixedAlloc*);
~SkFallbackAlloc() { this->reset(); }
// Allocates a new T with the SkFixedAlloc if possible. If not, uses the heap.
template <typename T, typename... Args>
T* make(Args&&... args) {
// Once we go heap we never go back to fixed. This keeps destructor ordering sane.
template <typename T>
void* alloc() {
// Once we go heap we never go back to fixed. This keeps undo() working.
if (fHeapAllocs.empty()) {
if (T* ptr = fFixedAlloc->make<T>(std::forward<Args>(args)...)) {
if (void* ptr = fFixedAlloc->alloc<T>()) {
return ptr;
}
}
auto ptr = new T(std::forward<Args>(args)...);
fHeapAllocs.push_back({[](void* ptr) { delete (T*)ptr; }, ptr});
void* ptr = sk_malloc_throw(sizeof(T));
fHeapAllocs.push_back(ptr);
return ptr;
}
// Destroys the last object allocated and frees any space it used in the SkFixedAlloc.
template <typename T, typename... Args>
T* make(Args&&... args) { return new (this->alloc<T>()) T(std::forward<Args>(args)...); }
template <typename T>
T* copy(const T& src) { return this->make<T>(src); }
// Frees the last object allocated, including any space it used in the SkFixedAlloc.
void undo();
// Destroys all objects and frees all space in the SkFixedAlloc.
// Frees all objects and all space in the SkFixedAlloc.
void reset();
private:
struct HeapAlloc {
void (*deleter)(void*);
void* ptr;
};
SkFixedAlloc* fFixedAlloc;
std::vector<HeapAlloc> fHeapAllocs;
std::vector<void*> fHeapAllocs;
};
#endif//SkFixedAlloc_DEFINED

2
src/core/SkModeColorFilter.cpp
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@ -90,7 +90,7 @@ bool SkModeColorFilter::onAppendStages(SkRasterPipeline* p,
SkColorSpace* dst,
SkFallbackAlloc* scratch,
bool shaderIsOpaque) const {
auto color = scratch->make<SkPM4f>(SkPM4f_from_SkColor(fColor, dst));
auto color = scratch->copy(SkPM4f_from_SkColor(fColor, dst));
p->append(SkRasterPipeline::move_src_dst);
p->append(SkRasterPipeline::constant_color, color);

20
tests/FixedAllocTest.cpp
View File

@ -10,11 +10,10 @@
namespace {
static int created, destroyed;
static int created;
struct Foo {
Foo(int X, float Y) : x(X), y(Y) { created++; }
~Foo() { destroyed++; }
int x;
float y;
@ -38,21 +37,15 @@ DEF_TEST(FixedAlloc, r) {
REPORTER_ASSERT(r, foo->x == 3);
REPORTER_ASSERT(r, foo->y == 4.0f);
REPORTER_ASSERT(r, created == 1);
REPORTER_ASSERT(r, destroyed == 0);
Foo* bar = fa.make<Foo>(8, 1.0f);
REPORTER_ASSERT(r, bar);
REPORTER_ASSERT(r, bar->x == 8);
REPORTER_ASSERT(r, bar->y == 1.0f);
REPORTER_ASSERT(r, created == 2);
REPORTER_ASSERT(r, destroyed == 0);
fa.undo();
REPORTER_ASSERT(r, created == 2);
REPORTER_ASSERT(r, destroyed == 1);
}
REPORTER_ASSERT(r, created == 2);
REPORTER_ASSERT(r, destroyed == 2);
{
// Test alignment gurantees.
@ -62,15 +55,10 @@ DEF_TEST(FixedAlloc, r) {
Foo* foo = fa.make<Foo>(3, 4.0f);
REPORTER_ASSERT(r, SkIsAlign4((uintptr_t)foo));
REPORTER_ASSERT(r, created == 3);
REPORTER_ASSERT(r, destroyed == 2);
// Might as well test reset() while we're at it.
fa.reset();
REPORTER_ASSERT(r, created == 3);
REPORTER_ASSERT(r, destroyed == 3);
}
REPORTER_ASSERT(r, created == 3);
REPORTER_ASSERT(r, destroyed == 3);
}
DEF_TEST(FallbackAlloc, r) {
@ -79,8 +67,8 @@ DEF_TEST(FallbackAlloc, r) {
SkFixedAlloc fixed(buf, sizeof(buf));
bool fixed_failed = false;
for (int i = 0; i < 32; i++) {
// (Remember, there is some overhead to each make() call.)
fixed_failed = fixed_failed || (fixed.make<int>(i) == nullptr);
// (Remember, there is some overhead to each copy() call.)
fixed_failed = fixed_failed || (fixed.copy(i) == nullptr);
}
REPORTER_ASSERT(r, fixed_failed);
@ -91,7 +79,7 @@ DEF_TEST(FallbackAlloc, r) {
bool fallback_failed = false;
for (int i = 0; i < 32; i++) {
fallback_failed = fallback_failed || (fallback.make<int>(i) == nullptr);
fallback_failed = fallback_failed || (fallback.copy(i) == nullptr);
}
REPORTER_ASSERT(r, !fallback_failed);