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

From: "H.J. Lu" <hjl dot tools at gmail dot com>
To: Paolo Bonzini <bonzini at gnu dot org>
Cc: Uros Bizjak <ubizjak at gmail dot com>, gcc-patches at gcc dot gnu dot org, rth at redhat dot com
Date: Tue, 5 Jan 2010 08:00:01 -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 Tue, Jan 5, 2010 at 7:55 AM, Paolo Bonzini <bonzini@gnu.org> wrote:
>>> I see no other way to fixup the underflow. Some comments below:
>
> You can always subtract (or XOR) the sign bit to turn an unsigned value to
> the corresponding signed value. ?The attached patch (on top of the code
> before H.J.'s patch) fixes the C testcase in the PR, but I didn't test it
> further and I don't have time unfortunately.
>

What is the the corresponding signed value of unsigned 0x8000000?


-- 
H.J.

Follow-Ups:
- Re: PATCH: PR target/42542: Vectorizer produces incorrect results on max of signed intergers
  - From: Paolo Bonzini

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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