Hello, again,
Today, I found that it would be a bit serious with Clang 17.
Niels Möller <ni...@lysator.liu.se> wrote:
> even if 32-bit x86 is not a high priority these days
I was not clear enough. It's not only for 32-bit Intel with MSVC, but
also for 64-bit Intel with MSVC, as well as ARM and ARM64 with MSVC.
Well, for this case, it's not that serious as it's only a conditional
jump.
* * *
I checked other compilers today.
With Clang 17, the entire loop is skipped when CND == 0 (64-bit Intel,
32-bit Intel, 64-bit ARM, 32-bit ARM, etc.). For 64-bit
Intel, here is the result:
x86-64 clang 17.0.1:
https://godbolt.org/z/6cYcn6Y1b
This would be a bit serious.
With GCC 13.2, access to 'ap[i]' may be conditionally executed for some
architectures (64-bit Intel, 32-bit Intel, etc., but not for 64-bit ARM
and 32-bit ARM), instead of accessed _and_ masked. For 64-bit Intel,
here is the result:
x86-64 gcc 13.2:
https://godbolt.org/z/6En8M5GTz
This may affect the cache access pattern.
(We can use '-O3 -m32' to see code for 32-bit Intel.)
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