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From: "Joey dot ye at intel dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/39148] -Os increase code size when stack is aligned
Date: Thu, 12 Feb 2009 02:33:00 -0000	[thread overview]
Message-ID: <20090212023336.29347.qmail@sourceware.org> (raw)
In-Reply-To: <bug-39148-682@http.gcc.gnu.org/bugzilla/>



------- Comment #6 from Joey dot ye at intel dot com  2009-02-12 02:33 -------
(In reply to comment #5)
> If ACCUMULATE_OUTGOING_ARGS is off, ECX will be used
> for stack alignment and it may lead to code size
> increase due to register spill since ia32 has very
> few registers.
The code increase resulted from stack realign are mainly from prologue
increase. ECX is only used as hard register in prologue/epilogue and the impact
to function body is low.

If ACCUMULATE_OUTGOING_ARGS does increase code size, then for big functions,
benefit of !ACCUMULATE_OUTGOING_ARGS will offset increase of prologue/epilogue.

So simply enable ACCUMULATE_OUTGOING_ARGS for stack realign isn't be the best
option for all cases either.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39148


  parent reply	other threads:[~2009-02-12  2:33 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-02-10 20:19 [Bug target/39148] New: " hjl dot tools at gmail dot com
2009-02-10 20:19 ` [Bug target/39148] " hjl dot tools at gmail dot com
2009-02-10 20:46 ` hjl dot tools at gmail dot com
2009-02-11 15:54 ` hjl dot tools at gmail dot com
2009-02-11 17:12 ` jakub at gcc dot gnu dot org
2009-02-11 17:16 ` hjl dot tools at gmail dot com
2009-02-12  0:45 ` hjl dot tools at gmail dot com
2009-02-12  2:33 ` Joey dot ye at intel dot com [this message]
2009-02-12  2:37 ` hjl dot tools at gmail dot com

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