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[AArch64] Add Neon dot-product implementation of HammingDistance

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We can use the Neon dot-product instructions as a slightly faster
widening accumulation. This also has the advantage of widening to 32
bits so avoids the risk of overflow present in the original Neon code.

Reduction in runtimes observed for HammingDistance compared to the
existing Neon code:

 Cortex-A55:  -4.4%
Cortex-A510: -26.5%
 Cortex-A76:  -8.1%
Cortex-A720: -15.5%
  Cortex-X1:  -4.1%
  Cortex-X2:  -5.1%

Bug: libyuv:977
Change-Id: I9e5e10d228c339d905cb2e668a9811ff0a6af5de
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/5490049
Reviewed-by: Frank Barchard <fbarchard@chromium.org>
Commit-Queue: Frank Barchard <fbarchard@chromium.org>
This commit is contained in:
George Steed 2024-04-25 09:28:31 +01:00 committed by libyuv LUCI CQ
parent 6433029df7
commit 95eed2b75f
3 changed files with 42 additions and 1 deletions
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6
include/libyuv/compare_row.h
View File

@ -78,12 +78,13 @@ extern "C" {
// The following are available for Neon:
#if !defined(LIBYUV_DISABLE_NEON) && \
(defined(__ARM_NEON__) || defined(LIBYUV_NEON) || defined(__aarch64__))
#define HAS_SUMSQUAREERROR_NEON
#define HAS_HAMMINGDISTANCE_NEON
#define HAS_SUMSQUAREERROR_NEON
#endif
// The following are available for AArch64 Neon:
#if !defined(LIBYUV_DISABLE_NEON) && defined(__aarch64__)
#define HAS_HAMMINGDISTANCE_NEON_DOTPROD
#define HAS_SUMSQUAREERROR_NEON_DOTPROD
#endif
@ -107,6 +108,9 @@ uint32_t HammingDistance_AVX2(const uint8_t* src_a,
uint32_t HammingDistance_NEON(const uint8_t* src_a,
const uint8_t* src_b,
int count);
uint32_t HammingDistance_NEON_DotProd(const uint8_t* src_a,
const uint8_t* src_b,
int count);
uint32_t HammingDistance_MSA(const uint8_t* src_a,
const uint8_t* src_b,
int count);

5
source/compare.cc
View File

@ -134,6 +134,11 @@ uint64_t ComputeHammingDistance(const uint8_t* src_a,
HammingDistance = HammingDistance_NEON;
}
#endif
#if defined(HAS_HAMMINGDISTANCE_NEON_DOTPROD)
if (TestCpuFlag(kCpuHasNeonDotProd)) {
HammingDistance = HammingDistance_NEON_DotProd;
}
#endif
#if defined(HAS_HAMMINGDISTANCE_SSSE3)
if (TestCpuFlag(kCpuHasSSSE3)) {
HammingDistance = HammingDistance_SSSE3;

32
source/compare_neon64.cc
View File

@ -86,6 +86,38 @@ uint32_t SumSquareError_NEON(const uint8_t* src_a,
return sse;
}
uint32_t HammingDistance_NEON_DotProd(const uint8_t* src_a,
const uint8_t* src_b,
int count) {
uint32_t diff;
asm volatile(
"movi v4.4s, #0 \n"
"movi v5.4s, #0 \n"
"movi v6.16b, #1 \n"
"1: \n"
"ldp q0, q1, [%0], #32 \n"
"ldp q2, q3, [%1], #32 \n"
"eor v0.16b, v0.16b, v2.16b \n"
"prfm pldl1keep, [%0, 448] \n" // prefetch 7 lines ahead
"eor v1.16b, v1.16b, v3.16b \n"
"cnt v0.16b, v0.16b \n"
"prfm pldl1keep, [%1, 448] \n"
"cnt v1.16b, v1.16b \n"
"subs %w2, %w2, #32 \n"
"udot v4.4s, v0.16b, v6.16b \n"
"udot v5.4s, v1.16b, v6.16b \n"
"b.gt 1b \n"
"add v0.4s, v4.4s, v5.4s \n"
"addv s0, v0.4s \n"
"fmov %w3, s0 \n"
: "+r"(src_a), "+r"(src_b), "+r"(count), "=r"(diff)
:
: "memory", "cc", "v0", "v1", "v2", "v3", "v4", "v5", "v6");
return diff;
}
uint32_t SumSquareError_NEON_DotProd(const uint8_t* src_a,
const uint8_t* src_b,
int count) {