Re: a couple of small patches for simd.h - Mailing list pgsql-hackers

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