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From: "nathan at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/16796] PowerPC - Unnecessary Floating Point Register Copy
Date: Wed, 10 Nov 2004 11:01:00 -0000	[thread overview]
Message-ID: <20041110110110.17311.qmail@sourceware.org> (raw)
In-Reply-To: <20040728170038.16796.steinmtz@us.ibm.com>


------- Additional Comments From nathan at gcc dot gnu dot org  2004-11-10 11:01 -------
The fault is not the register allocator, is is a problem introduced by flow2 and
the existance of conditional returns on PPC.  During register allocation
there is one exit block.  The returns are 'x, x, x+x & x', thus the global
allocator sets the exit block to copy 'x' to the return register.  flow2
replaces some of those branches to the exit block with conditional returns,
because 'x' resides in both DF:33 and DF:32.  The remaining use of the exit
is the load from the union into DF:32, the location of 'x' during the function.



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16796


  parent reply	other threads:[~2004-11-10 11:01 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-07-28 17:01 [Bug other/16796] New: " gcc-bugzilla at gcc dot gnu dot org
2004-07-28 17:36 ` [Bug target/16796] " bangerth at dealii dot org
2004-07-28 18:31 ` falk at debian dot org
2004-07-29  5:37 ` [Bug rtl-optimization/16796] " pinskia at gcc dot gnu dot org
2004-10-08 13:11 ` pinskia at gcc dot gnu dot org
2004-11-10 11:01 ` nathan at gcc dot gnu dot org [this message]
2004-11-10 12:28 ` nathan at gcc dot gnu dot org
2004-11-11  8:47 ` nathan at gcc dot gnu dot org
2004-11-11  8:49 ` cvs-commit at gcc dot gnu dot org
     [not found] <bug-16796-8614@http.gcc.gnu.org/bugzilla/>
2005-10-04  6:26 ` pinskia at gcc dot gnu dot org
2005-11-02 17:16 ` pinskia at gcc dot gnu dot org
2006-06-08  6:10 ` pinskia at gcc dot gnu dot org
2008-09-14  4:09 ` pinskia at gcc dot gnu dot org

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