On Wed, Mar 17, 2021 at 10:10:16AM -0400, Waiman Long wrote: > On 3/17/21 9:55 AM, Peter Zijlstra wrote: > > On Wed, Mar 17, 2021 at 09:43:20AM -0400, Waiman Long wrote: > > > > > Using gcc 8.4.1, the generated __mutex_lock function has the same size (with > > > last instruction at offset +5179) with or without this patch. Well, you can > > > say that this patch is an no-op wrt generated code. > > OK, then GCC has gotten better. Because back then I tried really hard > > but it wouldn't remove the if (ww_ctx) branches unless I had that extra > > const bool argument. > > > I think ww_mutex was merged in 2013. That is almost 8 years ago. It could > still be the case that older gcc compilers may not generate the right code. > I will try the RHEL7 gcc compiler (4.8.5) to see how it fares. I really don't care about code generation qualitee of anything before 8-ish at this point. That's already an old compiler. If you run on ancient compilers, you simply don't care about code quality.
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