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* [Bug other/26474] New: compiling 'long long' math with optimization gives bad results
@ 2006-02-26 17:19 eran dot nissenhaus at mobileye dot com
2006-02-26 18:39 ` [Bug other/26474] " pinskia at gcc dot gnu dot org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: eran dot nissenhaus at mobileye dot com @ 2006-02-26 17:19 UTC (permalink / raw)
To: gcc-bugs
Hello,
Tested with two compilers:
1. powerpc-7400-linux-gnu-g++ version 3.3.4
2. powerpc-linux-g++ version 3.3.2
the following code gives correct results when compiled with no optimization:
"Add siy: -3252329895"
Compiling with any of the optimization levels gives bad results:
"Add siy: 39697343065"
it looks like a sign-extension problem.
turning on the #define works-around the problem in a mysterious way.
Regrds,
Eran.
#include <cstdio>
void add(long* yy, long* xx, int n);
int main() {
const int N = 10;
long yy[N] = {-5,-1,-2,-3,-4,-5,-6,-7,-8,-9};
long xx[N] = {-1,-2,-3,-4,-5,-6,-7,-8,-9,10};
add(yy, xx, N);
return 0;
}
void add(long* yy, long* xx, int n) {
long long siy=0;
for(int i = 0; i < n; i++) {
long y = yy[i];
#if 0 // workaround
long ipy = -(1<<30)/y;
long long iy = ipy;
iy = -iy;
#else
long iy = (1<<30)/y;
#endif
siy += iy;
}
printf("Add siy: %lld \n",siy);
}
--
Summary: compiling 'long long' math with optimization gives bad
results
Product: gcc
Version: 3.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: other
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: eran dot nissenhaus at mobileye dot com
GCC build triplet: 3.2.1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26474
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug other/26474] compiling 'long long' math with optimization gives bad results
2006-02-26 17:19 [Bug other/26474] New: compiling 'long long' math with optimization gives bad results eran dot nissenhaus at mobileye dot com
@ 2006-02-26 18:39 ` pinskia at gcc dot gnu dot org
2006-02-27 8:35 ` eran dot nissenhaus at mobileye dot com
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2006-02-26 18:39 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from pinskia at gcc dot gnu dot org 2006-02-26 17:22 -------
Can you give the full output of:
powerpc-7400-linux-gnu-g++ -v
and
powerpc-linux-g++ -v
?
Thanks,
Andrew
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26474
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug other/26474] compiling 'long long' math with optimization gives bad results
2006-02-26 17:19 [Bug other/26474] New: compiling 'long long' math with optimization gives bad results eran dot nissenhaus at mobileye dot com
2006-02-26 18:39 ` [Bug other/26474] " pinskia at gcc dot gnu dot org
@ 2006-02-27 8:35 ` eran dot nissenhaus at mobileye dot com
2006-02-27 11:48 ` [Bug target/26474] " rguenth at gcc dot gnu dot org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: eran dot nissenhaus at mobileye dot com @ 2006-02-27 8:35 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from eran dot nissenhaus at mobileye dot com 2006-02-27 06:46 -------
(In reply to comment #1)
> Can you give the full output of:
> powerpc-7400-linux-gnu-g++ -v
> and
> powerpc-linux-g++ -v
> ?
> Thanks,
> Andrew
>
Here goes:
% /opt/Arabella/bin/powerpc-linux-g++ -v
Reading specs from /opt/Arabella/lib/gcc-lib/powerpc-linux/3.3.2/specs
Configured with: ../../../SRC/gcc-3.3.2/configure --target=powerpc-linux
--with-gnu-as --with-gnu-ld --prefix=/opt/Arabella
--mandir=/opt/Arabella/share/man --infodir=/opt/Arabella/share/info
--with-gxx-include-dir=/opt/Arabella/include/c++/3.3.2 --disable-nls
--enable-shared --enable-languages=c,c++ --enable-threads=posix
--enable-multilib --enable-__cxa_atexit --enable-clocale=gnu --enable-c-mbchar
--enable-version-specific-runtime-libs --with-dwarf2 --with-headers
Thread model: posix
gcc version 3.3.2
%
/opt/crosstool/gcc-3.3.4-glibc-2.2.5/powerpc-7400-linux-gnu/bin/powerpc-7400-linux-gnu-g++
-v
Reading specs from
/opt/crosstool/gcc-3.3.4-glibc-2.2.5/powerpc-7400-linux-gnu/lib/gcc-lib/powerpc-7400-linux-gnu/3.3.4/specs
Configured with:
/homes/avrozen/downloads/crosstool-0.37/build/powerpc-7400-linux-gnu/gcc-3.3.4-glibc-2.2.5/gcc-3.3.4/configure
--target=powerpc-7400-linux-gnu --host=i686-host_pc-linux-gnu
--prefix=/opt/crosstool/gcc-3.3.4-glibc-2.2.5/powerpc-7400-linux-gnu
--with-cpu=7400 --enable-altivec --enable-cxx-flags=-mcpu=7400
--disable-libunwind-exceptions --disable-c-mbchar
--with-headers=/opt/crosstool/gcc-3.3.4-glibc-2.2.5/powerpc-7400-linux-gnu/powerpc-7400-linux-gnu/include
--with-local-prefix=/opt/crosstool/gcc-3.3.4-glibc-2.2.5/powerpc-7400-linux-gnu/powerpc-7400-linux-gnu
--disable-nls --enable-threads=posix --enable-symvers=gnu --enable-__cxa_atexit
--enable-languages=c,c++ --enable-shared --enable-c99 --enable-long-long
Thread model: posix
gcc version 3.3.4
Thanks,
Eran
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26474
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug target/26474] compiling 'long long' math with optimization gives bad results
2006-02-26 17:19 [Bug other/26474] New: compiling 'long long' math with optimization gives bad results eran dot nissenhaus at mobileye dot com
2006-02-26 18:39 ` [Bug other/26474] " pinskia at gcc dot gnu dot org
2006-02-27 8:35 ` eran dot nissenhaus at mobileye dot com
@ 2006-02-27 11:48 ` rguenth at gcc dot gnu dot org
2006-02-27 12:03 ` rguenth at gcc dot gnu dot org
2006-02-27 13:48 ` rguenth at gcc dot gnu dot org
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2006-02-27 11:48 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from rguenth at gcc dot gnu dot org 2006-02-27 11:42 -------
Works for me on i686 for all gcc > 3.3.3 and 2.95. Works for me on ppc64 with
4.1.0. So this is at least ppc specific.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|other |target
GCC build triplet|3.2.1 |
GCC target triplet| |ppc-linux
Keywords| |wrong-code
Known to work| |4.1.0
Version|3.2.1 |3.3.4
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26474
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug target/26474] compiling 'long long' math with optimization gives bad results
2006-02-26 17:19 [Bug other/26474] New: compiling 'long long' math with optimization gives bad results eran dot nissenhaus at mobileye dot com
` (2 preceding siblings ...)
2006-02-27 11:48 ` [Bug target/26474] " rguenth at gcc dot gnu dot org
@ 2006-02-27 12:03 ` rguenth at gcc dot gnu dot org
2006-02-27 13:48 ` rguenth at gcc dot gnu dot org
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2006-02-27 12:03 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from rguenth at gcc dot gnu dot org 2006-02-27 11:47 -------
Confirmed for 3.3.3-hammer on ppc32 (ppc64 works). 4.0.2 is fine.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Known to fail| |3.3.3
Known to work|4.1.0 |4.0.2 4.1.0
Last reconfirmed|0000-00-00 00:00:00 |2006-02-27 11:47:58
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26474
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug target/26474] compiling 'long long' math with optimization gives bad results
2006-02-26 17:19 [Bug other/26474] New: compiling 'long long' math with optimization gives bad results eran dot nissenhaus at mobileye dot com
` (3 preceding siblings ...)
2006-02-27 12:03 ` rguenth at gcc dot gnu dot org
@ 2006-02-27 13:48 ` rguenth at gcc dot gnu dot org
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2006-02-27 13:48 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from rguenth at gcc dot gnu dot org 2006-02-27 13:28 -------
Fixed at least on the 3.4 branch.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Known to work|4.0.2 4.1.0 |3.4.6 4.0.2 4.1.0
Resolution| |FIXED
Target Milestone|--- |3.4.6
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26474
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2006-02-27 13:28 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2006-02-26 17:19 [Bug other/26474] New: compiling 'long long' math with optimization gives bad results eran dot nissenhaus at mobileye dot com
2006-02-26 18:39 ` [Bug other/26474] " pinskia at gcc dot gnu dot org
2006-02-27 8:35 ` eran dot nissenhaus at mobileye dot com
2006-02-27 11:48 ` [Bug target/26474] " rguenth at gcc dot gnu dot org
2006-02-27 12:03 ` rguenth at gcc dot gnu dot org
2006-02-27 13:48 ` rguenth at gcc dot gnu dot org
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