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Re: [PATCH] PR 85822 - Fix handling of negative constants
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Alexander Monakov <amonakov at ispras dot ru>,Yuri Gribov <tetra2005 at gmail dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>,marxin at gcc dot gnu dot org,Marc Glisse <marc dot glisse at inria dot fr>
- Date: Sun, 20 May 2018 14:19:27 +0200
- Subject: Re: [PATCH] PR 85822 - Fix handling of negative constants
- References: <CAJOtW+6myAAbf2ouaZ=w3Kv4iKTaokhAyptRuVdd5SnE7iU3yg@mail.gmail.com> <alpine.LNX.2.20.13.1805201454260.12860@monopod.intra.ispras.ru>
On May 20, 2018 2:01:24 PM GMT+02:00, Alexander Monakov <amonakov@ispras.ru> wrote:
>On Sun, 20 May 2018, Yuri Gribov wrote:
>
>> Hi all,
>>
>> This fixes PR 85822 by removing incorrect reversal of condition in
>VRP
>> assertion. Bootstrapped and regtested on x86_64.
>>
>> Ok for trunk?
>
>Please address the following issues:
>
>Use correct PR reference in Changelog.
>
>Double-check the comment before the function, I think NE_EXPR and
>EQ_EXPR
>should be swapped there.
>
>Address Richard's request from the bug report:
>
>>> Ok, please make sure to say why not doing anything special for
>negative
>>> numbers is ok.
>
>Note there are at least three special cases that are handled
>incorrectly either
>before or after the patch:
>
> - not two's complement integers
GCC doesn't support these.
> - mask being 0
> - mask being ~0
>
>Alexander