optimization/5076: gcc3 regression: yet another strength reduction bug

[gbeauchesne at mandrakesoft dot com]

>Number:         5076
>Category:       optimization
>Synopsis:       gcc3 regression: yet another strength reduction bug
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Tue Dec 11 08:16:00 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     Gwenole Beauchesne
>Release:        3.0.X, 3.1, "2.96"
>Organization:
>Environment:
i586-mandrake-linux-gnu
ia64-mandrake-linux-gnu
>Description:
The attached test case is extracted/reduced from PR 2847 that was closed earlier. gcc3 series compilers are affected, unlike gcc-2.95.X. (gcc-"2.96" is affected too).

* Failures on ix86:

[gbeauchesne@thalys vrac]$ CC="gcc-$(gcc31-version)" sh bugstrength.c
Reading specs from /usr//bin/../lib/gcc-lib/i586-mandrake-linux-gnu/3.1/specs
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --enable-shared --enable-threads=posix --disable-checking --enable-long-long --enable-cstdio=stdio --enable-clocale=generic --with-gxx-include-dir=/usr/include/g++-v31 --enable-languages=c,c++ --program-suffix=-3.1 --enable-objc-gc --host=i586-mandrake-linux-gnu
Thread model: posix
gcc version 3.1 20011203 (experimental)
CC: gcc-3.1; CFLAGS: -O1
> > PASS
CC: gcc-3.1; CFLAGS: -O1 -fstrength-reduce
> > FAIL
CC: gcc-3.1; CFLAGS: -O2
> > FAIL
CC: gcc-3.1; CFLAGS: -O2 -fno-strength-reduce
> > PASS

[gbeauchesne@thalys vrac]$ CC="gcc-$(gcc3-version)" sh bugstrength.c
Reading specs from /usr//bin/../lib/gcc-lib/i586-mandrake-linux-gnu/3.0.2/specs
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --enable-shared --enable-threads=posix --disable-checking --enable-long-long --enable-cstdio=stdio --enable-clocale=generic --enable-languages=c,c++,f77,objc,java --program-suffix=-3.0.2 --enable-objc-gc --host=i586-mandrake-linux-gnu
Thread model: posix
gcc version 3.0.2
CC: gcc-3.0.2; CFLAGS: -O1
> > PASS
CC: gcc-3.0.2; CFLAGS: -O1 -fstrength-reduce
> > FAIL
CC: gcc-3.0.2; CFLAGS: -O2
> > FAIL
CC: gcc-3.0.2; CFLAGS: -O2 -fno-strength-reduce
> > PASS

* Similar failures on ia64:

[gb@lion vrac]$ CC=gcc-3.0.2 sh bugstrength.c
Reading specs from /usr/lib/gcc-lib/ia64-mandrake-linux-gnu/3.0.2/specs
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --enable-shared --enable-threads=posix --disable-checking --enable-long-long --enable-cstdio=stdio --enable-clocale=generic --enable-languages=c,c++,f77,objc,java --program-suffix=-3.0.2 --enable-objc-gc --host=ia64-mandrake-linux-gnu
Thread model: posix
gcc version 3.0.2
CC: gcc-3.0.2; CFLAGS: -O1
> > PASS
CC: gcc-3.0.2; CFLAGS: -O1 -fstrength-reduce
> > FAIL
CC: gcc-3.0.2; CFLAGS: -O2
> > FAIL
CC: gcc-3.0.2; CFLAGS: -O2 -fno-strength-reduce
> > PASS

* Success on powerpc-mandrake-linux-gnu with gcc-2.95.X:

Reading specs from /usr/lib/gcc-lib/ppc-mandrake-linux/2.95.3/specs
gcc version 2.95.3 20010315 (release - Linux-Mandrake 8.0 for PPC)
CC: gcc; CFLAGS: -O1
> > PASS
CC: gcc; CFLAGS: -O1 -fstrength-reduce
> > PASS
CC: gcc; CFLAGS: -O2
> > PASS
CC: gcc; CFLAGS: -O2 -fno-strength-reduce
> > PASS
>How-To-Repeat:
Compile attachment with -O1 -fstrength-reduce to exhibit an abort() in the resulting executable. Alternatively, type "sh ./bugstrength.c"
>Fix:
Don't use strength reduction.
>Release-Note:
>Audit-Trail:
>Unformatted:
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Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="bugstrength.c"

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