[Bug optimization/11861] New: Optimization error on 'while' control condition

[dan dot gehlhaar at pfizer dot com]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11861

           Summary: Optimization error on 'while' control condition
           Product: gcc
           Version: 3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dan dot gehlhaar at pfizer dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i386-redhat-linux
  GCC host triplet: i386-redhat-linux
GCC target triplet: i386-redhat-linux

I ran into a case where a -O2 build gave an incorrect result, while
-g worked fine.  The problem was traced to a while loop conditional.
If the conditional was broken down into individually-evaluated statements
rather than being all inline, it worked.  .i files for both broken (test.i)
and fixed (test_works.i) files are attached.

Expected output (get this w/o -O2): 'Token is: 8.2'
Actual output (get this w/ -O2): 'Token is: 8'

Compilation was with:

gcc -v -save-temps -O2 test.c -o testTok

Output is as follows:

Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/3.2/specs
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --
infodir=/usr/share/info --enable-shared --enable-threads=posix --disable-
checking --host=i386-redhat-linux --with-system-zlib --enable-__cxa_atexit
Thread model: posix
gcc version 3.2 20020903 (Red Hat Linux 8.0 3.2-7)
 /usr/lib/gcc-lib/i386-redhat-linux/3.2/cpp0 -lang-c -v -D__GNUC__=3 -
D__GNUC_MINOR__=2 -D__GNUC_PATCHLEVEL__=0 -D__GXX_ABI_VERSION=102 -D__ELF__ -
Dunix -D__gnu_linux__ -Dlinux -D__ELF__ -D__unix__ -D__gnu_linux__ -D__linux__ -
D__unix -D__linux -Asystem=posix -D__OPTIMIZE__ -D__STDC_HOSTED__=1 -Acpu=i386 -
Amachine=i386 -Di386 -D__i386 -D__i386__ -D__tune_i386__ test.c test.i
GNU CPP version 3.2 20020903 (Red Hat Linux 8.0 3.2-7) (cpplib) (i386 Linux/ELF)
ignoring nonexistent directory "/usr/i386-redhat-linux/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/lib/gcc-lib/i386-redhat-linux/3.2/include
 /usr/include
End of search list.
 /usr/lib/gcc-lib/i386-redhat-linux/3.2/cc1 -fpreprocessed test.i -quiet -
dumpbase test.c -O2 -version -o test.s
GNU CPP version 3.2 20020903 (Red Hat Linux 8.0 3.2-7) (cpplib) (i386 Linux/ELF)
GNU C version 3.2 20020903 (Red Hat Linux 8.0 3.2-7) (i386-redhat-linux)
	compiled by GNU C version 3.2 20020903 (Red Hat Linux 8.0 3.2-7).
 as -V -Qy -o test.o test.s
GNU assembler version 2.13.90.0.2 (i386-redhat-linux) using BFD version 
2.13.90.0.2 20020802
 /usr/lib/gcc-lib/i386-redhat-linux/3.2/collect2 --eh-frame-hdr -m elf_i386 -
dynamic-linker /lib/ld-linux.so.2 -o testTok /usr/lib/gcc-lib/i386-redhat-
linux/3.2/../../../crt1.o /usr/lib/gcc-lib/i386-redhat-
linux/3.2/../../../crti.o /usr/lib/gcc-lib/i386-redhat-linux/3.2/crtbegin.o -
L/usr/lib/gcc-lib/i386-redhat-linux/3.2 -L/usr/lib/gcc-lib/i386-redhat-
linux/3.2/../../.. test.o -lgcc -lgcc_eh -lc -lgcc -lgcc_eh /usr/lib/gcc-
lib/i386-redhat-linux/3.2/crtend.o /usr/lib/gcc-lib/i386-redhat-
linux/3.2/../../../crtn.o