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Re: [PATCH] teach phi-opt to produce -(a COND b)

From: Richard Henderson <rth at redhat dot com>
To: Paolo Bonzini <bonzini at gnu dot org>
Cc: gcc-patches at gcc dot gnu dot org, rguenther at suse dot de, ubizjak at gmail dot com
Date: Tue, 01 May 2012 10:40:22 -0700
Subject: Re: [PATCH] teach phi-opt to produce -(a COND b)
References: <1335520861-29252-1-git-send-email-bonzini@gnu.org>

On 04/27/2012 03:01 AM, Paolo Bonzini wrote:

This patch teaches phiopt to look at phis whose arguments are -1 and 0,
and produce negated setcc statements.

Is this really a win over a COND_EXPR, i.e. (a < b ? -1 : 0)?

There is quite a bit of logic inside the rtl and backend expansion of
cmove that would seem to be being bypassed by committing to this form.

r~

Follow-Ups:
- Re: [PATCH] teach phi-opt to produce -(a COND b)
  - From: Richard Guenther

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