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Re: PATCH: PR target/42542: Vectorizer produces incorrect results on max of signed intergers

From: Richard Henderson <rth at redhat dot com>
To: Paolo Bonzini <bonzini at gnu dot org>
Cc: "H.J. Lu" <hjl dot tools at gmail dot com>, Uros Bizjak <ubizjak at gmail dot com>, gcc-patches at gcc dot gnu dot org
Date: Tue, 05 Jan 2010 08:16:32 -0800
Subject: Re: PATCH: PR target/42542: Vectorizer produces incorrect results on max of signed intergers
References: <20091230154815.GA31664@lucon.org> <5787cf471001040617w66f6e7echa6004ff36c694d83@mail.gmail.com> <6dc9ffc81001040717v191581e1u1e9579933f8f1371@mail.gmail.com> <4B4360F5.101@gnu.org>

On 01/05/2010 07:55 AM, Paolo Bonzini wrote:

You can always subtract (or XOR) the sign bit to turn an unsigned value
to the corresponding signed value.

While the two operations in this case are identical, I think it's clearer to use SUB than XOR. And yes, this mapping works well.

r~

References:
- Re: PATCH: PR target/42542: Vectorizer produces incorrect results on max of signed intergers
  - From: Uros Bizjak
- Re: PATCH: PR target/42542: Vectorizer produces incorrect results on max of signed intergers
  - From: H.J. Lu
- Re: PATCH: PR target/42542: Vectorizer produces incorrect results on max of signed intergers
  - From: Paolo Bonzini

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