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* [Bug regression/16458] New: PowerPC - redundant compare @ 2004-07-09 18:05 gcc-bugzilla at gcc dot gnu dot org 2004-07-09 18:42 ` [Bug rtl-optimization/16458] " pinskia at gcc dot gnu dot org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: gcc-bugzilla at gcc dot gnu dot org @ 2004-07-09 18:05 UTC (permalink / raw) To: gcc-bugs Description: A non-optimal compare sequence is illustrated. Two compares are being done, one signed and the other unsigned. One unsigned compare would suffice. Duplicate using gcc 3.5 and command line: gcc -O3 -m64 -c test.c Testcase: unsigned int a, b; int foo () { if (a == b) return 1; if (a > b) return 2; if (a < b) return 3; if (a != b) return 4; return 0; } Assembly: ld 9,.LC1@toc(2) li 3,1 ld 11,.LC0@toc(2) lwz 10,0(9) lwz 0,0(11) cmpw 7,0,10 - signed compare of a and b cmplw 6,0,10 - unsigned compare of a and b beqlr- 7 - (a == b uses signed compare) li 3,2 bgtlr- 6 - (a > b uses unsigned compare) li 3,4 bgelr- 6 - (a != b uses unsigned compare) li 3,3 blr -- Summary: PowerPC - redundant compare 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=16458 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug rtl-optimization/16458] PowerPC - redundant compare 2004-07-09 18:05 [Bug regression/16458] New: PowerPC - redundant compare gcc-bugzilla at gcc dot gnu dot org @ 2004-07-09 18:42 ` pinskia at gcc dot gnu dot org 2004-11-10 10:27 ` [Bug middle-end/16458] " nathan at gcc dot gnu dot org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu dot org @ 2004-07-09 18:42 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-07-09 18:42 ------- Confirmed, any PPC has this trouble, 32 bit or not. This looks more like a middle-end problem or a target because when converting unsigned == unsigned from tree to RTL, it changes it to be a signed comparison. -- What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Component|regression |rtl-optimization Ever Confirmed| |1 GCC build triplet|powerpc64-linux | GCC host triplet|powerpc64-linux | GCC target triplet|powerpc64-linux |powerpc*-* Keywords| |missed-optimization Last reconfirmed|0000-00-00 00:00:00 |2004-07-09 18:42:00 date| | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16458 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/16458] PowerPC - redundant compare 2004-07-09 18:05 [Bug regression/16458] New: PowerPC - redundant compare gcc-bugzilla at gcc dot gnu dot org 2004-07-09 18:42 ` [Bug rtl-optimization/16458] " pinskia at gcc dot gnu dot org @ 2004-11-10 10:27 ` nathan at gcc dot gnu dot org 2004-11-11 8:39 ` nathan at gcc dot gnu dot org 2004-11-11 8:41 ` cvs-commit at gcc dot gnu dot org 3 siblings, 0 replies; 5+ messages in thread From: nathan at gcc dot gnu dot org @ 2004-11-10 10:27 UTC (permalink / raw) To: gcc-bugs -- What |Removed |Added ---------------------------------------------------------------------------- AssignedTo|unassigned at gcc dot gnu |nathan at gcc dot gnu dot |dot org |org Status|NEW |ASSIGNED http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16458 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/16458] PowerPC - redundant compare 2004-07-09 18:05 [Bug regression/16458] New: PowerPC - redundant compare gcc-bugzilla at gcc dot gnu dot org 2004-07-09 18:42 ` [Bug rtl-optimization/16458] " pinskia at gcc dot gnu dot org 2004-11-10 10:27 ` [Bug middle-end/16458] " nathan at gcc dot gnu dot org @ 2004-11-11 8:39 ` nathan at gcc dot gnu dot org 2004-11-11 8:41 ` cvs-commit at gcc dot gnu dot org 3 siblings, 0 replies; 5+ messages in thread From: nathan at gcc dot gnu dot org @ 2004-11-11 8:39 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From nathan at gcc dot gnu dot org 2004-11-11 08:39 ------- 2004-11-11 Nathan Sidwell <nathan@codesourcery.com> PR target/16458 * config/rs6000/rs6000.c (rs6000_generate_compare): Generate an unsigned equality compare when we know the operands are unsigned. this is a partial fix, the remainder is dependent on 18395, IMO -- What |Removed |Added ---------------------------------------------------------------------------- BugsThisDependsOn| |18395 AssignedTo|nathan at gcc dot gnu dot |unassigned at gcc dot gnu |org |dot org Status|ASSIGNED |NEW http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16458 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/16458] PowerPC - redundant compare 2004-07-09 18:05 [Bug regression/16458] New: PowerPC - redundant compare gcc-bugzilla at gcc dot gnu dot org ` (2 preceding siblings ...) 2004-11-11 8:39 ` nathan at gcc dot gnu dot org @ 2004-11-11 8:41 ` cvs-commit at gcc dot gnu dot org 3 siblings, 0 replies; 5+ messages in thread From: cvs-commit at gcc dot gnu dot org @ 2004-11-11 8:41 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From cvs-commit at gcc dot gnu dot org 2004-11-11 08:41 ------- Subject: Bug 16458 CVSROOT: /cvs/gcc Module name: gcc Changes by: nathan@gcc.gnu.org 2004-11-11 08:40:43 Modified files: gcc : ChangeLog gcc/config/rs6000: rs6000.c gcc/testsuite : ChangeLog Added files: gcc/testsuite/gcc.dg: ppc-compare-1.c Log message: .: PR target/16458 * config/rs6000/rs6000.c (rs6000_generate_compare): Generate an unsigned equality compare when we know the operands are unsigned. testsuite: PR target/16458 * gcc.dg/ppc-compare-1.c: New. Patches: http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.6271&r2=2.6272 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/config/rs6000/rs6000.c.diff?cvsroot=gcc&r1=1.739&r2=1.740 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&r1=1.4574&r2=1.4575 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.dg/ppc-compare-1.c.diff?cvsroot=gcc&r1=NONE&r2=1.1 -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16458 ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2004-11-11 8:41 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2004-07-09 18:05 [Bug regression/16458] New: PowerPC - redundant compare gcc-bugzilla at gcc dot gnu dot org 2004-07-09 18:42 ` [Bug rtl-optimization/16458] " pinskia at gcc dot gnu dot org 2004-11-10 10:27 ` [Bug middle-end/16458] " nathan at gcc dot gnu dot org 2004-11-11 8:39 ` nathan at gcc dot gnu dot org 2004-11-11 8:41 ` cvs-commit at gcc dot gnu dot org
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