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From: "hjl.tools at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/50131] Optimize x = -1 with "or" for -O
Date: Sat, 20 Aug 2011 20:04:00 -0000	[thread overview]
Message-ID: <bug-50131-4-Xl2dnGyuZM@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-50131-4@http.gcc.gnu.org/bugzilla/>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50131

--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> 2011-08-20 19:44:49 UTC ---
(In reply to comment #2)
> Is or $-1, reg on all CPUs equally expensive to mov $-1, reg though (as or
> generally needs the previous reg content while mov does not; I know some CPUs
> special case xor reg, reg, but I doubt or $-1, reg is special cased)?

We should add a new x86 optimization flag and turn it on
only if it helps for the processor to be optimized.


  parent reply	other threads:[~2011-08-20 19:45 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-08-19 20:58 [Bug target/50131] New: " hjl.tools at gmail dot com
2011-08-19 21:19 ` [Bug target/50131] " hjl.tools at gmail dot com
2011-08-20  8:37 ` jakub at gcc dot gnu.org
2011-08-20 20:04 ` hjl.tools at gmail dot com [this message]
2011-08-21  9:20 ` rguenth at gcc dot gnu.org
2011-08-23 14:57 ` hjl.tools at gmail dot com
2021-12-15  1:34 ` pinskia at gcc dot gnu.org

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