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Re: Arranging for -Os to imply -mpreferred-stack-boundary=2 on x86

To: Geert Bosch <bosch at gnat dot com>
Subject: Re: Arranging for -Os to imply -mpreferred-stack-boundary=2 on x86
From: Richard Henderson <rth at redhat dot com>
Date: Wed, 24 Oct 2001 14:12:09 -0700
Cc: Alexandre Oliva <aoliva at redhat dot com>, gcc-patches at gcc dot gnu dot org
References: <20011024135739.C20239@redhat.com> <Pine.GSO.4.10.10110241658450.23444-100000@nile.gnat.com>

On Wed, Oct 24, 2001 at 05:08:00PM -0400, Geert Bosch wrote:
> Yes, but without the alignment you'd have %ebp available as general
> register, you would not need to save/restore it and set it up.
> So, the cost of aligning the stack-pointer is one register and five 
> instructions. How do you end up with only one instruction?

Because we currently default to -fno-omit-frame-pointer for x86.
So we currently never have %ebp available as a general register.


r~

Follow-Ups:
- Re: Arranging for -Os to imply -mpreferred-stack-boundary=2 on x86
  - From: Alexandre Oliva

References:
- Re: Arranging for -Os to imply -mpreferred-stack-boundary=2 on x86
  - From: Richard Henderson
- Re: Arranging for -Os to imply -mpreferred-stack-boundary=2 on x86
  - From: Geert Bosch

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