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update memset16/32 inlining heuristics

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I spent some time looking at perf.skia.org and it looks like we can do better.

It is weird, weird, weird that on x86, we see three completely different behaviors:
  - x86 Android: inlining better for small N, custom better for large N;
  - Windows:     inlining better for large N, custom better for small N;
  - other x86:   inlining generally better

BUG=skia:4316,chromium:516426

(Temporary, plan to revert.)
TBR=reed@google.com

Review URL: https://codereview.chromium.org/1357193002
This commit is contained in:
mtklein 2015-09-20 15:02:15 -07:00 committed by Commit bot
parent 0e7ca50756
commit b68fa409fc
1 changed files with 17 additions and 15 deletions
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32
include/core/SkUtils.h
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@ -17,13 +17,11 @@ namespace SkOpts {
///////////////////////////////////////////////////////////////////////////////
// The inlining heuristics below were determined using bench/MemsetBench.cpp
// on a x86 desktop, a Nexus 7 with and without NEON, and a Nexus 9:
// - on x86, inlining was never faster,
// - on ARMv7, inlining was faster for N<=10. Putting this check inside the NEON
// code was not helpful; it's got to be here outside.
// - NEON code generation for ARMv8 with GCC 4.9 is terrible,
// making the NEON code ~8x slower that just a serial loop.
// Inlining heuristics were determined by using perf.skia.org and bench/MemsetBench.cpp.
// When using MSVC, inline is better >= 1K and worse <= 100. The Nexus Player was the opposite.
// Otherwise, when NEON or SSE is available to GCC or Clang, they can handle it best.
// See https://code.google.com/p/chromium/issues/detail?id=516426#c15 for more details.
// See also skia:4316; it might be a good idea to use rep stosw/stosd here.
/** Similar to memset(), but it assigns a 16bit value into the buffer.
@param buffer The memory to have value copied into it
@ -31,10 +29,12 @@ namespace SkOpts {
@param count The number of times value should be copied into the buffer.
*/
static inline void sk_memset16(uint16_t buffer[], uint16_t value, int count) {
#if defined(SK_CPU_ARM64)
while (count --> 0) { *buffer++ = value; } return;
#elif defined(SK_CPU_ARM32)
if (count <= 10) { while (count --> 0) { *buffer++ = value; } return; }
#if defined(_MSC_VER)
if (count > 300) { while (count --> 0) { *buffer++ = value; } return; }
#elif defined(SK_BUILD_FOR_ANDROID) && defined(SK_CPU_X86)
if (count < 300) { while (count --> 0) { *buffer++ = value; } return; }
#elif defined(SK_ARM_HAS_NEON) || SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
{ while (count --> 0) { *buffer++ = value; } return; }
#endif
SkOpts::memset16(buffer, value, count);
}
@ -45,10 +45,12 @@ static inline void sk_memset16(uint16_t buffer[], uint16_t value, int count) {
@param count The number of times value should be copied into the buffer.
*/
static inline void sk_memset32(uint32_t buffer[], uint32_t value, int count) {
#if defined(SK_CPU_ARM64)
while (count --> 0) { *buffer++ = value; } return;
#elif defined(SK_CPU_ARM32)
if (count <= 10) { while (count --> 0) { *buffer++ = value; } return; }
#if defined(_MSC_VER)
if (count > 300) { while (count --> 0) { *buffer++ = value; } return; }
#elif defined(SK_BUILD_FOR_ANDROID) && defined(SK_CPU_X86)
if (count < 300) { while (count --> 0) { *buffer++ = value; } return; }
#elif defined(SK_ARM_HAS_NEON) || SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
{ while (count --> 0) { *buffer++ = value; } return; }
#endif
SkOpts::memset32(buffer, value, count);
}