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* [Bug c/39755] New: inline memcpy() incorrectly optimized on MIPS target
@ 2009-04-13 19:52 msieweke at broadcom dot com
2009-04-14 10:14 ` [Bug c/39755] " rguenth at gcc dot gnu dot org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: msieweke at broadcom dot com @ 2009-04-13 19:52 UTC (permalink / raw)
To: gcc-bugs
In one case the C compiler can optimize away an inline memcpy() on a
MIPS target. The problem was duplicated with GCC 3.2.1 and 3.3.3.
The problem does not affect x86 targets or GCC 4.x (tested on 4.2.4).
The MIPS cross-compiler runs under RHEL. Tested MIPS cross-compilers
under Cygwin and Mingw with the same results.
This is the test code and the resulting output. The "if" statement and
16-byte memcpy() are optimized away, leaving only the 4-byte memcpy.
Compile with: mipsisa32-elf-gcc -O2 -c test.c
---------------------------
#include <string.h>
typedef struct {
char C[16];
int E;
} st;
void f( st *S, char* c );
void f( st *S, char* c )
{
if ( S->E == 6 )
memcpy( &S->C, c, 16 );
else
memcpy( &S->C, c, 4 );
}
---------------------------
00000000 <f>:
0: 88a20000 lwl v0,0(a1)
4: 98a20003 lwr v0,3(a1)
8: a8820000 swl v0,0(a0)
c: 03e00008 jr ra
10: b8820003 swr v0,3(a0)
---------------------------
Compiler info:
$ mipsisa32-elf-gcc -v
Reading specs from
/tools/ecos/3.2.1_opt/Linux/opt/ecos/gnutools/mipsisa32-elf/bin/../lib/gcc-lib/mipsisa32-elf/3.2.1/specs
Configured with: /home/msieweke/ecos20/gnutools-src/gcc-3.2.1/configure
--target=mipsisa32-elf --prefix=/home/msieweke/gnutools_321
--enable-languages=c,c++ --enable-gofast --with-gnu-as --with-gnu-ld
--with-newlib
--with-gxx-include-dir=/home/msieweke/gnutools_321/mipsisa32-elf/include -v
Thread model: single
gcc version 3.2.1
--
Summary: inline memcpy() incorrectly optimized on MIPS target
Product: gcc
Version: 3.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: msieweke at broadcom dot com
GCC build triplet: i386-gnu-linux
GCC host triplet: i386-gnu-linux
GCC target triplet: mipsisa32-elf
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39755
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/39755] inline memcpy() incorrectly optimized on MIPS target
2009-04-13 19:52 [Bug c/39755] New: inline memcpy() incorrectly optimized on MIPS target msieweke at broadcom dot com
@ 2009-04-14 10:14 ` rguenth at gcc dot gnu dot org
2009-04-16 15:06 ` msieweke at broadcom dot com
2009-04-16 15:56 ` rguenth at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2009-04-14 10:14 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from rguenth at gcc dot gnu dot org 2009-04-14 10:13 -------
GCC 3.2.1 is no longer maintained, please reproduce with at least GCC 4.3.3.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |WAITING
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39755
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/39755] inline memcpy() incorrectly optimized on MIPS target
2009-04-13 19:52 [Bug c/39755] New: inline memcpy() incorrectly optimized on MIPS target msieweke at broadcom dot com
2009-04-14 10:14 ` [Bug c/39755] " rguenth at gcc dot gnu dot org
@ 2009-04-16 15:06 ` msieweke at broadcom dot com
2009-04-16 15:56 ` rguenth at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: msieweke at broadcom dot com @ 2009-04-16 15:06 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from msieweke at broadcom dot com 2009-04-16 15:06 -------
As mentioned in the original report, the bug doesn't exist in GCC 4.x.x. It
has since been tested with GCC 3.4.4, where the bug is fixed.
GCC 3.2.x - broken
GCC 3.3.x - broken
GCC 3.4.x - fixed
GCC 4.x.x - fixed
For a number of reasons, we're stuck using GCC 3.2.1 with only minor updates.
I tried porting parts of the MIPS code generator from 3.4.4 into 3.2.1, but
this is a larger project than it appears. I don't expect anyone to spend much
time fixing this, but I would appreciate a hint about how I might approach
a fix.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39755
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/39755] inline memcpy() incorrectly optimized on MIPS target
2009-04-13 19:52 [Bug c/39755] New: inline memcpy() incorrectly optimized on MIPS target msieweke at broadcom dot com
2009-04-14 10:14 ` [Bug c/39755] " rguenth at gcc dot gnu dot org
2009-04-16 15:06 ` msieweke at broadcom dot com
@ 2009-04-16 15:56 ` rguenth at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2009-04-16 15:56 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from rguenth at gcc dot gnu dot org 2009-04-16 15:56 -------
Try bisecting the changes to cherry-pick the one fixing the bug.
Fixed in GCC 3.4.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |RESOLVED
Resolution| |FIXED
Target Milestone|--- |3.4.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39755
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2009-04-16 15:56 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2009-04-13 19:52 [Bug c/39755] New: inline memcpy() incorrectly optimized on MIPS target msieweke at broadcom dot com
2009-04-14 10:14 ` [Bug c/39755] " rguenth at gcc dot gnu dot org
2009-04-16 15:06 ` msieweke at broadcom dot com
2009-04-16 15:56 ` rguenth at gcc dot gnu dot org
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