diff options
| author | Rémi Denis-Courmont <remi@remlab.net> | 2022-10-02 14:54:59 +0300 |
|---|---|---|
| committer | Lynne <dev@lynne.ee> | 2022-10-05 08:26:19 +0200 |
| commit | f0ef11ea835181c74afe11fea445790873d5f6bc (patch) | |
| tree | 864452d44ab968f39d198c1a4e8ac92636cdf1e0 /libavutil/hwcontext_opencl.c | |
| parent | 37d5ddc317c35bded22fee8d79020653781d8230 (diff) | |
| download | ffmpeg-f0ef11ea835181c74afe11fea445790873d5f6bc.tar.gz | |
lavc/bswapdsp: RISC-V B bswap_buf
Simply taking the Zbb REV8 instruction into use in a simple loop gives
some significant savings:
bswap_buf_c: 1081.0
bswap_buf_rvb_b: 771.0
But we can also use the 64-bit REV8 as a pseudo-SIMD instruction with
just one additional shift, and one fewer load, effectively doubling the
bandwidth. Consequently, this patch is useful even if the compile-time
target has Zbb enabled for C code:
bswap_buf_c: 1081.0
bswap_buf_rvb_b: 341.0 (this patch)
On the other hand, this approach fails miserably for bswap16_buf as the
ratio of shifts and stores becomes unfavorable compared to naïve C:
bswap16_buf_c: 1542.0
bswap16_buf_rvb_b: 1803.7
Unrolling to process 128 bits (4 samples) at a time actually worsens
performance ever so slightly:
bswap_buf_c: 1081.0
bswap_buf_rvb_b: 408.5
Diffstat (limited to 'libavutil/hwcontext_opencl.c')
0 files changed, 0 insertions, 0 deletions