| From: | John Naylor <johncnaylorls(at)gmail(dot)com> |
|---|---|
| To: | "Devulapalli, Raghuveer" <raghuveer(dot)devulapalli(at)intel(dot)com> |
| Cc: | Nathan Bossart <nathandbossart(at)gmail(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>, "Shankaran, Akash" <akash(dot)shankaran(at)intel(dot)com> |
| Subject: | Re: Improve CRC32C performance on SSE4.2 |
| Date: | 2025-03-25 13:18:41 |
| Message-ID: | CANWCAZY1Le1tpTZauY-JzbLpk=VSerP8=GZs36Cza9iJfRnn-A@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Mar 24, 2025 at 6:37 PM John Naylor <johncnaylorls(at)gmail(dot)com> wrote:
>
> I'll take a look at the configure
> checks soon, since I had some questions there.
One other thing I forgot to mention: The previous test function had
local constants that the compiler was able to fold, resulting in no
actual vector instructions being emitted:
movabs rdx, 12884901891
xor eax, eax
crc32 rax, rdx
crc32 rax, rdx
ret
That may be okay for practical purposes, but in the spirit of commit
fdb5dd6331e30 I changed it in v15 to use global variables and made
sure it emits what the function attributes are intended for:
vmovdqu64 zmm3, ZMMWORD PTR x[rip]
xor eax, eax
vpclmulqdq zmm0, zmm3, ZMMWORD PTR y[rip], 0
vextracti32x4 xmm2, zmm0, 1
vmovdqa64 xmm1, xmm0
vmovdqu64 ZMMWORD PTR y[rip], zmm0
vextracti32x4 xmm0, zmm0, 2
vpternlogq xmm1, xmm2, xmm0, 150
vmovq rdx, xmm1
crc32 rax, rdx
vzeroupper
ret
--
John Naylor
Amazon Web Services
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