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Re: CC0 to CCmode conversion

From: James E Wilson <wilson at specifixinc dot com>
To: Denis Chertykov <denisc at overta dot ru>
Cc: gcc at gcc dot gnu dot org
Date: Tue, 22 Mar 2005 12:04:21 -0800
Subject: Re: CC0 to CCmode conversion
References: <auto-000020618887@overta.ru>

Denis Chertykov wrote:

I think that sequence of compare + cond-jump will exists in any
compiler pass.

Combine can optimize away compares, if you have other instructions that set the condition code register to useful values. This optimization will only work correctly if instructions that set or clobber the cc are properly marked.

If no instructions are marked as setting the cc (other than compares), then this will probably work, but you won't get any optimization from combine, and may get worse code than before. -- Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com

References:
- CC0 to CCmode conversion
  - From: Denis Chertykov

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