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From: "rearnsha at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/54829] bad optimization: sub followed by cmp w/ zero (x86 & ARM)
Date: Sat, 13 Oct 2012 16:18:00 -0000	[thread overview]
Message-ID: <bug-54829-4-Pru4thBtqx@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-54829-4@http.gcc.gnu.org/bugzilla/>


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54829

--- Comment #6 from Richard Earnshaw <rearnsha at gcc dot gnu.org> 2012-10-13 16:18:03 UTC ---
Note also that flag setting behaviour of the PPC instruction essentially is a
comparison of the result against zero.  On ARM the flags are set as if the two
input operands were compared; that's not the same as comparing the result with
zero.


  parent reply	other threads:[~2012-10-13 16:18 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-05 23:16 [Bug target/54829] New: " daniel.santos at pobox dot com
2012-10-05 23:40 ` [Bug target/54829] " pinskia at gcc dot gnu.org
2012-10-06 13:31 ` [Bug target/54829] bad optimization: sub followed by cmp w/ zero (ARM) hjl.tools at gmail dot com
2012-10-06 15:56 ` [Bug target/54829] bad optimization: sub followed by cmp w/ zero (x86 & ARM) daniel.santos at pobox dot com
2012-10-06 15:57 ` daniel.santos at pobox dot com
2012-10-13 16:05 ` rearnsha at gcc dot gnu.org
2012-10-13 16:18 ` rearnsha at gcc dot gnu.org [this message]
2012-11-15 21:56 ` daniel.santos at pobox dot com
2013-08-05 21:04 ` rearnsha at gcc dot gnu.org
2015-02-15  6:17 ` daniel.santos at pobox dot com

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