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From: "gcc-bugzilla at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug regression/16457] New: PowerPC - Combine two rldicr instructions into a single rlwinm. Date: Fri, 09 Jul 2004 18:05:00 -0000 [thread overview] Message-ID: <20040709175338.16457.steinmtz@us.ibm.com> (raw) Description: A non-optimal code sequence is illustrated. Two rlidcr instructions could be replaced by a single rlwinm. Duplicate using gcc 3.5 and command line: gcc -O3 -m64 -c test.c Testcase: char *q; void foo (char *p) { unsigned int x; q = p - (x & ~1); } Assembly: rldicr 0,0,32,31 ld 9,.LC0@toc(2) rldicr 0,0,32,62 subf 3,0,3 std 3,0(9) blr The two rldicr instructions can be combined into one rlwinm with the resulting code looking like this: ld 9,.LC0@toc(2) rlwinm 0,0,0,0,30 subf 3,0,3 std 3,0(9) blr -- Summary: PowerPC - Combine two rldicr instructions into a single rlwinm. Product: gcc Version: 3.5.0 Status: UNCONFIRMED Severity: enhancement Priority: P1 Component: regression AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: steinmtz at us dot ibm dot com CC: gcc-bugs at gcc dot gnu dot org,steinmtz at us dot ibm dot com GCC build triplet: powerpc64-linux GCC host triplet: powerpc64-linux GCC target triplet: powerpc64-linux http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16457
next reply other threads:[~2004-07-09 18:05 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2004-07-09 18:05 gcc-bugzilla at gcc dot gnu dot org [this message] 2004-07-09 18:57 ` [Bug target/16457] " pinskia at gcc dot gnu dot org 2004-07-09 19:12 ` pinskia at gcc dot gnu dot org 2004-11-03 14:50 ` nathan at gcc dot gnu dot org 2004-11-03 15:41 ` pinskia at gcc dot gnu dot org 2004-11-11 16:59 ` nathan at gcc dot gnu dot org 2004-11-11 17:01 ` pinskia at gcc dot gnu dot org 2004-11-11 17:04 ` cvs-commit at gcc dot gnu dot org
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