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From: Kugan <kugan.vivekanandarajah@linaro.org>
To: Richard Biener <richard.guenther@gmail.com>
Cc: Uros Bizjak <ubizjak@gmail.com>,
	 "gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>,
	Jakub Jelinek <jakub@redhat.com>
Subject: Re: [PATCH 2/2] Enable elimination of zext/sext
Date: Fri, 05 Sep 2014 01:33:00 -0000	[thread overview]
Message-ID: <540912E1.30505@linaro.org> (raw)
In-Reply-To: <CAFiYyc0D22fh2Votpebb=+oxPenJ9UznQYkeX8MRMLe0aTbPqw@mail.gmail.com>

>> Here is an attempt to do the value range computation in promoted_mode's
>> type when it is overflowing. Bootstrapped on x86-84.
> 
> Err - I think you misunderstood this as a suggestion to do this ;)
> value-ranges should be computed according to the type not according
> to the (promoted) mode.  Otherwise we will miss optimization
> opportunities.

Oops, sorry, I had my doubts about making trees aware of back-end stuff.

Coming back to the original problem, what would be the best approach to
handle this. Looking at the VRP pass, it seems to me that only MULT_EXPR
and LSHIFT_EXPR are truncating values this way. All other operation are
setting it to type_min, type_max. Can we rely on this ?

Is this error not showing up in PROMOTED_MODE <= word_mode (and
the mode precision of register from which we SUBREG is <= word_mode
precision) is just a coincidence. Can we rely on this?

Is there anyway we can fix this?

Thanks again,
Kugan



  reply	other threads:[~2014-09-05  1:33 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-27 10:01 Uros Bizjak
2014-08-27 10:07 ` Richard Biener
2014-08-27 10:32   ` Uros Bizjak
2014-08-27 10:32     ` Richard Biener
2014-09-01  8:48     ` Jakub Jelinek
2014-09-01  8:54       ` Uros Bizjak
2014-08-28  7:50   ` Kugan
2014-08-28  8:57     ` Richard Biener
2014-09-04  3:41       ` Kugan
2014-09-04 13:00         ` Richard Biener
2014-09-05  1:33           ` Kugan [this message]
2014-09-05  9:51             ` Richard Biener
2014-09-07  9:51               ` Kugan
2014-09-08  9:48                 ` Richard Biener
2014-09-09 10:06                   ` Kugan
2014-09-09 10:28                     ` Richard Biener
2014-11-09 23:30               ` [RFC] Elimination of zext/sext - type promotion pass Kugan
2014-11-10 12:56                 ` Richard Biener
2015-05-01  4:41                   ` Kugan
2015-05-08 12:48                     ` Richard Biener
2015-06-01 23:20                       ` Kugan
2015-06-19  2:55                         ` Kugan
2015-07-28 11:05                         ` Richard Biener
2015-08-05  0:12                           ` kugan
2015-08-05  9:10                             ` Richard Biener
2014-08-27 13:02 ` [PATCH 2/2] Enable elimination of zext/sext Kugan
2014-08-28  3:46   ` Kugan
2014-08-28  6:44     ` Marc Glisse
2014-08-28  7:29       ` Kugan
  -- strict thread matches above, loose matches on Subject: below --
2014-06-24 11:48 [PATCH 0/2] Zext/sext elimination using value range Kugan
2014-06-24 11:53 ` [PATCH 2/2] Enable elimination of zext/sext Kugan
2014-06-24 12:21   ` Jakub Jelinek
2014-06-25  8:15     ` Kugan
2014-06-25  8:36       ` Jakub Jelinek
2014-07-07  6:55         ` Kugan
2014-07-10 12:15           ` Richard Biener
2014-07-11 11:52             ` Kugan
2014-07-11 12:47               ` Richard Biener
2014-07-14  2:58                 ` Kugan
2014-07-14 20:11                   ` Bernhard Reutner-Fischer
2014-07-23 14:22                   ` Richard Biener
2014-08-01  4:51                     ` Kugan
2014-08-01 11:16                       ` Richard Biener
2014-08-01 16:04                         ` Kugan
2014-08-03 23:56                           ` Kugan
2014-08-05 14:18                           ` Richard Biener
2014-08-05 14:21                             ` Jakub Jelinek
2014-08-06 12:09                               ` Richard Biener
2014-08-06 13:22                                 ` Kugan
2014-08-06 13:29                                   ` Richard Biener
2014-08-07  5:25                                     ` Kugan
2014-08-07  8:09                                       ` Richard Biener

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