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Hamming Distance using 16 bit accumulators

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Summing 16 bit hamming codes restricts the maximum length,
but saves an inner loop instruction.  The outer loop can sum the
values.

32 bit Neon
Now BenchmarkHammingDistance_Opt (78 ms)
Was BenchmarkHammingDistance_Opt (92 ms)

64 bit Neon
Now BenchmarkHammingDistance_Opt (85 ms)
Was BenchmarkHammingDistance_Opt (92 ms)

R=wangcheng@google.com
TBR=kjellander@chromium.org
BUG=libyuv:701
TEST=BenchmarkHammingDistance

Change-Id: Ie40f0eac2f3339c33b833b42af5d394b122066ae
Reviewed-on: https://chromium-review.googlesource.com/526932
Reviewed-by: Frank Barchard <fbarchard@google.com>
Reviewed-by: Cheng Wang <wangcheng@google.com>
Commit-Queue: Frank Barchard <fbarchard@google.com>
This commit is contained in:
Frank Barchard 2017-06-07 15:19:25 -07:00 committed by Commit Bot
parent 790e0634a8
commit d981495b42
4 changed files with 11 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
README.chromium
View File

@ -1,6 +1,6 @@
Name: libyuv
URL: http://code.google.com/p/libyuv/
Version: 1659
Version: 1660
License: BSD
License File: LICENSE

2
include/libyuv/version.h
View File

@ -11,6 +11,6 @@
#ifndef INCLUDE_LIBYUV_VERSION_H_
#define INCLUDE_LIBYUV_VERSION_H_
#define LIBYUV_VERSION 1659
#define LIBYUV_VERSION 1660
#endif // INCLUDE_LIBYUV_VERSION_H_

11
source/compare_neon.cc
View File

@ -22,12 +22,12 @@ extern "C" {
!defined(__aarch64__)
// 256 bits at a time
// uses short accumulator which restricts count to 131 KB
uint32 HammingDistance_NEON(const uint8* src_a, const uint8* src_b, int count) {
uint32 diff;
asm volatile (
// Load constants.
"vmov.u8 q4, #0 \n" // accumulator
"vmov.u16 q4, #0 \n" // accumulator
"1: \n"
"vld1.8 {q0, q1}, [%0]! \n"
@ -38,13 +38,12 @@ uint32 HammingDistance_NEON(const uint8* src_a, const uint8* src_b, int count) {
"vcnt.i8 q1, q1 \n"
"subs %2, %2, #32 \n"
"vadd.u8 q0, q0, q1 \n" // 16 byte counts
"vpaddl.u8 q0, q0 \n" // 8 shorts
"vpadal.u16 q4, q0 \n" // 4 ints
"vpadal.u8 q4, q0 \n" // 8 shorts
"bgt 1b \n"
"vpadd.u32 d0, d8, d9 \n"
"vpaddl.u16 q0, q4 \n" // 4 ints
"vpadd.u32 d0, d0, d1 \n"
"vpadd.u32 d0, d0, d0 \n"
// Move distance to return register.
"vmov.32 %3, d0[0] \n"
: "+r"(src_a),

8
source/compare_neon64.cc
View File

@ -21,10 +21,11 @@ extern "C" {
#if !defined(LIBYUV_DISABLE_NEON) && defined(__aarch64__)
// 256 bits at a time
// uses short accumulator which restricts count to 131 KB
uint32 HammingDistance_NEON(const uint8* src_a, const uint8* src_b, int count) {
uint32 diff;
asm volatile (
"movi v4.4s, #0 \n"
"movi v4.8h, #0 \n"
"1: \n"
"ld1 {v0.16b, v1.16b}, [%0], #32 \n"
@ -35,11 +36,10 @@ uint32 HammingDistance_NEON(const uint8* src_a, const uint8* src_b, int count) {
"cnt v1.16b, v1.16b \n"
"subs %w2, %w2, #32 \n"
"add v0.16b, v0.16b, v1.16b \n"
"uaddlp v0.8h, v0.16b \n"
"uadalp v4.4s, v0.8h \n"
"uadalp v4.8h, v0.16b \n"
"b.gt 1b \n"
"addv s4, v4.4s \n"
"uaddlv s4, v4.8h \n"
"fmov %w3, s4 \n"
: "+r"(src_a),
"+r"(src_b),