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Re: [PATCH] PR 16373: -fomit-frame-pointer when optimizing on x86
- From: Paul Brook <paul at codesourcery dot com>
- To: gcc at gcc dot gnu dot org
- Cc: Andi Kleen <ak at muc dot de>, Roger Sayle <roger at eyesopen dot com>
- Date: Mon, 12 Jul 2004 13:06:51 +0100
- Subject: Re: [PATCH] PR 16373: -fomit-frame-pointer when optimizing on x86
- Organization: CodeSourcery
- References: <Pine.LNX.email@example.com> <Pine.LNX.firstname.lastname@example.org> <email@example.com>
On Monday 12 July 2004 04:53, Andi Kleen wrote:
> Roger Sayle <firstname.lastname@example.org> writes:
> > On Sun, 11 Jul 2004, Joseph S. Myers wrote:
> >> Performance statistics (compile time, run time and code size)? After
> >> all, the point of this change is presumably that it improves
> >> performance.
> > Do you have any doubt at all that this patch won't improve run-time,
> > reduce code size and speed up a bootstrapped compiler? :>
> It won't reduce code size - ebp references are smaller than esp
> references. This means if the function does more than four or five
> local variable references it will be bigger.
> But it will be likely faster.
However you also have ebp available as a general purpose register, which will
tend to mean less spills, reducing both code size and stack usage.