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Re: [PATCH] Convert __builtin_expect to __glibc_(un)likely throughout elf/.
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Zack Weinberg <zackw at panix dot com>
- Cc: <libc-alpha at sourceware dot org>, <schwab at suse dot de>
- Date: Mon, 4 Jun 2018 14:36:13 +0000
- Subject: Re: [PATCH] Convert __builtin_expect to __glibc_(un)likely throughout elf/.
- References: <20180602220831.25016-1-zackw@panix.com>
On Sat, 2 Jun 2018, Zack Weinberg wrote:
> I would appreciate someone checking over this patch very carefully
> indeed. In a whole bunch of places, __builtin_expect was used in a
> way that did not map mechanically to the newer convention. The test
> suite caught one mistake; I'm not confident I didn't make any more.
I think this means there is a case for splitting this patch up into a part
that doesn't change installed stripped shared libraries (on one platform -
so at least the sense of comparisons etc. is unchanged on that platform
after the patch, even if likely/unlikely could be wrong sometimes without
being detected by such a comparison of installed stripped shared
libraries), and a part that does (presumably because the mapping isn't
purely mechanical so compiler IR changes enough to result in different
code generated), with the latter needing more careful review that no
semantics have changed.
--
Joseph S. Myers
joseph@codesourcery.com