On 2017-04-05 06:05, James Almer wrote: > On 4/4/2017 10:53 PM, James Darnley wrote: >> Haswell: >> - 1.02x faster (405±0.7 vs. 397±0.8 decicycles) compared with mmxext >> >> Skylake-U: >> - 1.06x faster (498±1.8 vs. 470±1.3 decicycles) compared with mmxext >> --- >> libavcodec/x86/h264_idct.asm | 20 ++++++++++++++++++++ >> libavcodec/x86/h264dsp_init.c | 2 ++ >> 2 files changed, 22 insertions(+) >> >> diff --git a/libavcodec/x86/h264_idct.asm b/libavcodec/x86/h264_idct.asm >> index 24fb4d2..7fd57d3 100644 >> --- a/libavcodec/x86/h264_idct.asm >> +++ b/libavcodec/x86/h264_idct.asm >> @@ -1158,7 +1158,27 @@ INIT_XMM avx >> movd [%7+%8], %4 >> %endmacro >> >> +%macro DC_ADD_INIT 1 >> + add %1d, 32 >> + sar %1d, 6 >> + movd m0, %1d >> + SPLATW m0, m0, 0 > > Considering DC_ADD_MMXEXT_OP works with dwords, a single pshuflw should be > enough. This macro calls two instructions to fill the entire XMM register, > and there's no need for that.
Noted, I made that change butit doesn't seemto change much in terms of performance. > You could for that matter try to optimize DC_ADD_MMXEXT_OP a bit, combining > said dwords with punpk* into fewer registers to reduce the amount of padd* > and psub* needed afterwards. See ADD_RES_MMX_4_8 in hevc_add_res.asm Noted. Maybe in the future. > And again, SSE2 first, AVX only if measurably faster. But since you're not > making use of the wider XMM regs here at all, the only chips that will see > any real speed up are those slow in mmx (like Skylake seems to be). Yorkfield gets no benefit from sse2 (575±0.4 vs. 574±0.3 decicycles). Haswell gets most of its benefit from sse2 (404±0.6 vs. 390±0.3 vs. 388±0.3). Skylake-U gets all of its speedup from sse2 (533±3.0 vs 488±2.0 vs 497±1.4). Nehalem and 64-bit also gets no benefit from sse2. Again: SSE2 yay or nay? Maybe I should just drop this; I'm not sure 5 cycles is worth it. (I will now go and modify my script to divide the recorded decicycle count by 10.) >> +cglobal h264_idct_dc_add_8, 3, 4, 0, dst_, block_, stride_ ^ Fixed this bug. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel