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Re: [PATCH] Optimize andl $0xffffffff, %eax

From: Jakub Jelinek <jakub at redhat dot com>
To: Richard Guenther <richard dot guenther at gmail dot com>
Cc: Uros Bizjak <ubizjak at gmail dot com>, Jan Hubicka <jh at suse dot cz>, Richard Henderson <rth at redhat dot com>, gcc-patches at gcc dot gnu dot org
Date: Fri, 22 May 2009 11:38:25 +0200
Subject: Re: [PATCH] Optimize andl $0xffffffff, %eax
References: <20090521131653.GL5781@tyan-ft48-01.lab.bos.redhat.com> <84fc9c000905210844o1051ddb4ga4fea640998a38f1@mail.gmail.com>
Reply-to: Jakub Jelinek <jakub at redhat dot com>

On Thu, May 21, 2009 at 05:44:09PM +0200, Richard Guenther wrote:
> > Bootstrapped/regtested on x86_64-linux, ok for trunk?
> 
> Hm, isn't that something simplify-rtx should do?  Transform
> (and:SI reg 0xfffff) to (zero-extend:SI (subreg ...))?

I fear that's too risky, on most targets zero_extend?i?i2 is implemented
using and, so if simplify-rtx canonicalizes that to zero-extend, we
risk oscillating forever between the two.

	Jakub

Follow-Ups:
- Re: [PATCH] Optimize andl $0xffffffff, %eax
  - From: Adam Nemet
- Re: [PATCH] Optimize andl $0xffffffff, %eax
  - From: Paolo Bonzini

References:
- [PATCH] Optimize andl $0xffffffff, %eax
  - From: Jakub Jelinek
- Re: [PATCH] Optimize andl $0xffffffff, %eax
  - From: Richard Guenther

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