[lkml]   [2009]   [Jan]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: gcc inlining heuristics was Re: [PATCH -v7][RFC]: mutex: implement adaptive spinning
Andi Kleen wrote:
> On Sun, Jan 11, 2009 at 04:21:03PM -0800, Linus Torvalds wrote:
>> On Mon, 12 Jan 2009, Andi Kleen wrote:
>>> so at least least for this case it works. Your case also doesn't work
>>> for me. So it looks like gcc didn't like something you did in your test
>>> program.
>> I very intentionally used _different_ types.
>> If you use the same type, gcc will apparenrly happily say "hey, I can
>> combine two variables of the same type with different liveness into the
>> same variable".
> Confirmed.
>> But that's not the interesting case.
> Weird. I wonder where this strange restriction comes from.

Something at the back of my mind said "aliasing".

$ gcc linus.c -O2 -S ; grep subl linus.s
subl $1624, %esp
$ gcc linus.c -O2 -S -fno-strict-aliasing; grep subl linus.s
subl $824, %esp

That's with 4.3.2.

This footer brought to you by insane German lawmakers.
Analog Devices GmbH Wilhelm-Wagenfeld-Str. 6 80807 Muenchen
Sitz der Gesellschaft Muenchen, Registergericht Muenchen HRB 40368
Geschaeftsfuehrer Thomas Wessel, William A. Martin, Margaret Seif

 \ /
  Last update: 2009-01-12 19:51    [W:0.238 / U:12.584 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site