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* [Bug target/51274] New: Starting with GCC 4.5, powerpc generated different code for x != 0. @ 2011-11-22 23:42 meissner at gcc dot gnu.org 2011-11-22 23:57 ` [Bug target/51274] " meissner at gcc dot gnu.org ` (2 more replies) 0 siblings, 3 replies; 4+ messages in thread From: meissner at gcc dot gnu.org @ 2011-11-22 23:42 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51274 Bug #: 51274 Summary: Starting with GCC 4.5, powerpc generated different code for x != 0. Classification: Unclassified Product: gcc Version: 4.5.0 Status: UNCONFIRMED Severity: minor Priority: P3 Component: target AssignedTo: unassigned@gcc.gnu.org ReportedBy: meissner@gcc.gnu.org Host: powerpc64-linux power-linux Target: powerpc64-linux Build: powerpc64-linux In doing some investigation for optimizations of comparisons for power7, I noticed that starting with GCC 4.5, the compiler no longer generates the code it used to for setting x = (y != 0). In the rs6000.md file, these optimizations start with the insn "ne0si". In the 4.4 time frame, for -m32 (and for -m32 -mpowerpc64, which is PR 36557), gcc would generate: addic 9,3,-1 subfe 0,9,3 However, it wouldn't generate this code for -m64. Starting with 4.5, it generates the code for !(x == 0), or: cntlzw 3,3 srwi 3,3,5 xori 3,3,1 We should either remove the insns in rs6000.md that no longer are matching, or fix them so they do match. I suspect that the longer code sequence is actually faster on the newer processors, since you don't need to track the carry between the two insns. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/51274] Starting with GCC 4.5, powerpc generated different code for x != 0. 2011-11-22 23:42 [Bug target/51274] New: Starting with GCC 4.5, powerpc generated different code for x != 0 meissner at gcc dot gnu.org @ 2011-11-22 23:57 ` meissner at gcc dot gnu.org 2012-09-26 5:19 ` segher at gcc dot gnu.org 2012-09-26 5:35 ` segher at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: meissner at gcc dot gnu.org @ 2011-11-22 23:57 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51274 --- Comment #1 from Michael Meissner <meissner at gcc dot gnu.org> 2011-11-22 23:12:43 UTC --- Created attachment 25889 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=25889 Example test case ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/51274] Starting with GCC 4.5, powerpc generated different code for x != 0. 2011-11-22 23:42 [Bug target/51274] New: Starting with GCC 4.5, powerpc generated different code for x != 0 meissner at gcc dot gnu.org 2011-11-22 23:57 ` [Bug target/51274] " meissner at gcc dot gnu.org @ 2012-09-26 5:19 ` segher at gcc dot gnu.org 2012-09-26 5:35 ` segher at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: segher at gcc dot gnu.org @ 2012-09-26 5:19 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51274 --- Comment #2 from Segher Boessenkool <segher at gcc dot gnu.org> 2012-09-26 05:18:49 UTC --- Author: segher Date: Wed Sep 26 05:18:43 2012 New Revision: 191752 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=191752 Log: gcc/ PR target/51274 PR target/53087 * config/rs6000/rs6000.md (ne0si): Remove unnecessary earlyclobber. Merge with... (ne0di): ... to... (ne0_<mode>): New. (plus_ne0si): Merge with... (plus_ne0di): ... to... (plus_ne0_<mode>): New. (compare_plus_ne0si): Merge with... (compare_plus_ne0di)... to... (compare_plus_ne0_<mode>): New. (compare_plus_ne0_<mode>_1): New. (plus_ne0si_compare): Merge with... (plus_ne0di_compare)... to... (plus_ne0_<mode>_compare): New. gcc/testsuite/ PR target/51274 PR target/53087 * gcc.target/powerpc/ppc-ne0-1.c: New. Added: trunk/gcc/testsuite/gcc.target/powerpc/ppc-ne0-1.c Modified: trunk/gcc/ChangeLog trunk/gcc/config/rs6000/rs6000.md trunk/gcc/testsuite/ChangeLog ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/51274] Starting with GCC 4.5, powerpc generated different code for x != 0. 2011-11-22 23:42 [Bug target/51274] New: Starting with GCC 4.5, powerpc generated different code for x != 0 meissner at gcc dot gnu.org 2011-11-22 23:57 ` [Bug target/51274] " meissner at gcc dot gnu.org 2012-09-26 5:19 ` segher at gcc dot gnu.org @ 2012-09-26 5:35 ` segher at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: segher at gcc dot gnu.org @ 2012-09-26 5:35 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51274 Segher Boessenkool <segher at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED CC| |segher at gcc dot gnu.org Resolution| |FIXED --- Comment #3 from Segher Boessenkool <segher at gcc dot gnu.org> 2012-09-26 05:35:06 UTC --- Fixed. ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2012-09-26 5:35 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2011-11-22 23:42 [Bug target/51274] New: Starting with GCC 4.5, powerpc generated different code for x != 0 meissner at gcc dot gnu.org 2011-11-22 23:57 ` [Bug target/51274] " meissner at gcc dot gnu.org 2012-09-26 5:19 ` segher at gcc dot gnu.org 2012-09-26 5:35 ` segher at gcc dot gnu.org
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