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Re: [PATCH] x86, bitops, variable_test_bit should return 1 not -1 on a match

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  Re: [PATCH] x86, bitops, variable_test_bit should return 1 not -1  on a match Prarit Bhargava <prarit@redhat.com> - 2015-10-08 13:50 +0200

#1242263 — Re: [PATCH] x86, bitops, variable_test_bit should return 1 not -1 on a match

On 08/21/2015 04:08 AM, H. Peter Anvin wrote:
> Wrong fix, though.  Instead we should change it to use the set instruction, which would also make it easier to use the CC_SET/CC_OUT proposed macros to use assembly out in the future.
> 
> The downside with set is that it only sets a single byte, the upside is that it always outputs 0 or 1, and apparently if the output variable is your bool gcc can use that for optimization.
> 

hpa, I didn't realize your comment was suggesting a change.  I've done a google
search on "gcc bool optimization" (and various incantations of that) and didn't
find anything that lead me in the direction of making a change.  Could you
elaborate on what the issue is?

Thanks,

P.
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