On Fri, Nov 08, 2024 at 11:18:09PM +1300, David Rowley wrote: > I'm slightly worried due to the current rate we're receiving cleanup > suggestions that someone might come along and think they'd be doing us > a favour by submitting a patch to "fixup the inefficient bitwise-ORs > and use boolean-OR". Maybe a comment like the following might prevent > that from happening.
Not sure, but OK by me to tweak things more. > Can you share your test case for this? I tried with [1] and the > latest gcc does not seem to be smart enough to figure this out. I > tried adding some additional len checks that the compiler can use as a > cue and won't need to emit code for the checks providing the function > does get inlined. That was enough to get the compiler to not emit the > loops when they'll not be used. See the -DCHECK_LEN flag I'm passing > in the 2nd compiler window. I just don't know if putting something > like that into the code is a good idea as if the function wasn't > inlined for some reason, the extra len checks would have to be > compiled into the function. Feel free to use that (I hope it works), and see the difference once the aligned structure is 121 bytes or more: https://godbolt.org/z/94393nPGG At least, I can see that the SIMD loop is ignored. -- Michael
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