public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [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
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).