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From: "svfuerst at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/43883] missed optimization of constant __int128_t modulus
Date: Fri, 30 Apr 2010 20:31:00 -0000	[thread overview]
Message-ID: <20100430203031.1229.qmail@sourceware.org> (raw)
In-Reply-To: <bug-43883-18995@http.gcc.gnu.org/bugzilla/>



------- Comment #6 from svfuerst at gmail dot com  2010-04-30 20:30 -------
For posterity, I might as well note that with the sbb added on the end we don't
need the initial mov instruction if we do some register renaming.  This leaves
the, hopefully optimal this time, five-instruction fragment as the goal:

shr    $0x3f,%rsi
lea    (%rdi,%rsi,1),%rax
and    $0x1,%eax
sub    %rsi,%rax
sbb    %rdx,%rdx


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43883


  parent reply	other threads:[~2010-04-30 20:31 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-04-25  5:06 [Bug middle-end/43883] New: " svfuerst at gmail dot com
2010-04-25 20:09 ` [Bug target/43883] " rguenth at gcc dot gnu dot org
2010-04-30  9:25 ` ubizjak at gmail dot com
2010-04-30 16:13 ` svfuerst at gmail dot com
2010-04-30 16:33 ` svfuerst at gmail dot com
2010-04-30 19:00 ` [Bug middle-end/43883] " ubizjak at gmail dot com
2010-04-30 20:31 ` svfuerst at gmail dot com [this message]
     [not found] <bug-43883-4@http.gcc.gnu.org/bugzilla/>
2021-12-23  0:46 ` pinskia at gcc dot gnu.org
2021-12-23  0:51 ` pinskia at gcc dot gnu.org

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