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Re: [PATCH] PR 16373: -fomit-frame-pointer when optimizing on x86
- From: Zack Weinberg <zack at codesourcery dot com>
- To: Roger Sayle <roger at eyesopen dot com>
- Cc: Richard Henderson <rth at redhat dot com>, Jakub Jelinek <jakub at redhat dot com>, <gcc-patches at gcc dot gnu dot org>
- Date: Fri, 16 Jul 2004 10:30:19 -0700
- Subject: Re: [PATCH] PR 16373: -fomit-frame-pointer when optimizing on x86
- References: <Pine.LNX.4.44.0407160956200.17849-100000@www.eyesopen.com>
Roger Sayle <roger@eyesopen.com> writes:
> Hence, I believe that the correct way to obtain that not insignificant
> 2.5% improvement in SPECint2000 performance above, is for the i386 to
> treat %ebp as a fixed (non general purpose) register in the scheme that
> I described earlier. This would allow frame pointers to be eliminated
> both from leaf and non-leaf functions, and would resolve the issue
> above of non-call exceptions in a leaf functions (not unusual for gcj).
Since this scheme doesn't make %ebp available as a general register, I
will be very surprised if it actually gets the same 2.5% performance
improvement.
What was wrong with making -fomit-frame-pointer imply
-fasynchronous-unwind-tables? People concerned with code size can
turn it back off again.
zw