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Re: [autovect] [patch] Improve generated vector comparisons

From: "Richard Guenther" <richard dot guenther at gmail dot com>
To: "Victor Kaplansky" <VICTORK at il dot ibm dot com>
Cc: gcc-patches at gcc dot gnu dot org
Date: Mon, 22 May 2006 16:58:41 +0200
Subject: Re: [autovect] [patch] Improve generated vector comparisons
References: <OFC74AFDBE.DFF15178-ONC2257176.004C8449-C2257176.004E22C9@il.ibm.com>

On 5/22/06, Victor Kaplansky <VICTORK@il.ibm.com> wrote:

This improves vector comparisons generated by vectorizer fro ALTIVEC.
As ALTIVEC has only GT and EQ vector instructions for short and char
integers,
we replace

      x = (a <= b) ? y : z;
by
      x = (a > b) ? z : y;

and
      x = (a >= b) ? y : z;
is replaced by
      x = (b > a) ? z : y;

Without this change, back-end generates 3 instructions ((a > b) || (a ==
b))
for (a >= b) vector comparison.

You should really do this at expand time.

Richard.

References:
- [autovect] [patch] Improve generated vector comparisons
  - From: Victor Kaplansky

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