Horton

Thread

Commits

  1. Optimize vector8_has_le() on AArch64.

  2. Fix broken cast on MSVC

  1. a couple of small patches for simd.h

    Nathan Bossart <nathandbossart@gmail.com> — 2025-09-22T21:44:20Z

    0001 essentially reverts commit c6a43c2, and instead fixes the problem
(MSVC dislikes casts to the same type) by omitting the cast in the
problematic line in pg_lfind32().  While working on optimizing hex_encode()
and hex_decode() [0], I noticed that implicit conversions sufficed.

0002 optimizes vector8_has_le() on AArch64 by using vminvq_u8().  I needed
vector8_has_ge() for the hex_encode()/hex_decode() work and noticed this
opportunity.

[0] https://commitfest.postgresql.org/patch/5538/

-- 
nathan

  2. Re: a couple of small patches for simd.h

    John Naylor <johncnaylorls@gmail.com> — 2025-09-24T01:04:59Z

    On Tue, Sep 23, 2025 at 4:44 AM Nathan Bossart <nathandbossart@gmail.com> wrote:
>
> 0001 essentially reverts commit c6a43c2, and instead fixes the problem
> (MSVC dislikes casts to the same type) by omitting the cast in the
> problematic line in pg_lfind32().  While working on optimizing hex_encode()
> and hex_decode() [0], I noticed that implicit conversions sufficed.

I don't remember why that cast was there, but I suggest testing on gcc
/ aarch64 if you haven't already.

As for 0002, +1 for more succinct expressions when the hardware supports it.

--
John Naylor
Amazon Web Services

  3. Re: a couple of small patches for simd.h

    Nathan Bossart <nathandbossart@gmail.com> — 2025-09-24T17:41:11Z

    On Wed, Sep 24, 2025 at 08:04:59AM +0700, John Naylor wrote:
> On Tue, Sep 23, 2025 at 4:44 AM Nathan Bossart <nathandbossart@gmail.com> wrote:
>> 0001 essentially reverts commit c6a43c2, and instead fixes the problem
>> (MSVC dislikes casts to the same type) by omitting the cast in the
>> problematic line in pg_lfind32().  While working on optimizing hex_encode()
>> and hex_decode() [0], I noticed that implicit conversions sufficed.
> 
> I don't remember why that cast was there, but I suggest testing on gcc
> / aarch64 if you haven't already.

Ah, I thought CI was testing that, but apparently it is not.  After some
basic testing in godbolt.org, I see that leaving out the cast makes
gcc/arm64 unhappy, and adding the cast makes msvc/x64 unhappy.  gcc has a
-flax-vector-conversions option that fixes it, but the documentation for
that option [0] cautions against using it.  So, 0001 is bogus, and I need
to figure out how to get the hex_{encode,decode} patches working for
gcc/arm64...

[0] https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html#index-flax-vector-conversions

-- 
nathan

  4. Re: a couple of small patches for simd.h

    Nathan Bossart <nathandbossart@gmail.com> — 2025-09-25T19:10:19Z

    Here's a new version of 0002 with a modified SSE2 implementation, as
discussed elsewhere [0].  This allows us to remove vector8_ssub().

[0] https://postgr.es/m/aNWO7L43UevRErw_%40nathan

-- 
nathan

  5. Re: a couple of small patches for simd.h

    Nathan Bossart <nathandbossart@gmail.com> — 2025-09-25T21:27:35Z

    On Thu, Sep 25, 2025 at 02:10:19PM -0500, Nathan Bossart wrote:
> Here's a new version of 0002 with a modified SSE2 implementation, as
> discussed elsewhere [0].  This allows us to remove vector8_ssub().

Sorry for the noise.  v3 fixes the mixed-declarations-and-code problems.

-- 
nathan

  6. Re: a couple of small patches for simd.h

    Nathan Bossart <nathandbossart@gmail.com> — 2025-10-02T17:36:12Z

    On Thu, Sep 25, 2025 at 04:27:35PM -0500, Nathan Bossart wrote:
> On Thu, Sep 25, 2025 at 02:10:19PM -0500, Nathan Bossart wrote:
>> Here's a new version of 0002 with a modified SSE2 implementation, as
>> discussed elsewhere [0].  This allows us to remove vector8_ssub().
> 
> Sorry for the noise.  v3 fixes the mixed-declarations-and-code problems.

Barring objections, I plan to commit this soon.  Probably tomorrow.

-- 
nathan

  7. Re: a couple of small patches for simd.h

    John Naylor <johncnaylorls@gmail.com> — 2025-10-03T07:40:22Z

    On Fri, Oct 3, 2025 at 12:36 AM Nathan Bossart <nathandbossart@gmail.com> wrote:
> Barring objections, I plan to commit this soon.  Probably tomorrow.

LGTM.

-- 
John Naylor
Amazon Web Services

  8. Re: a couple of small patches for simd.h

    Nathan Bossart <nathandbossart@gmail.com> — 2025-10-03T19:04:10Z

    On Fri, Oct 03, 2025 at 02:40:22PM +0700, John Naylor wrote:
> LGTM.

Committed, thanks for reviewing.

-- 
nathan