[Bug c/40509] New: -fprofile-arcs changes behaviour

[p dot j dot bakker at brainspark dot nl]

Architecture: i386 / i486-linux-gnu
GCC Version: 4.3.3 (Debian 4.3.3-11)

Code should perform: Multiplication of two large number arrays. It has worked
in all test cases and production environments, but suddenly fails if profiling
is enabled. More specifically the -fprofile-arcs flag triggers the behaviour.

Example multiplies 10 and 1. 

Commandline for compilation of test code:
gcc bugrep.c -o bugrep
./bugrep
10 0
-and-
gcc -fprofile-arcs bugrep.c -o bugrep
./bugrep
1 0

The first answer is the right one obviously.
Small compilable snippet that triggers the behaviour.
-----
#include <stdio.h>

void func_hlp(int *s, int *d, int b)
{
    int c = 0, t = 0;

    asm( "movl   %%ebx, %0      " : "=m" (t));
    asm( "movl   %0, %%esi      " :: "m" (s));
    asm( "movl   %0, %%edi      " :: "m" (d));
    asm( "movl   %0, %%ecx      " :: "m" (c));
    asm( "movl   %0, %%ebx      " :: "m" (b));

    asm( "lodsl                 " );
    asm( "mull   %ebx           " );
    asm( "addl   %ecx,   %eax   " );
    asm( "adcl   $0,     %edx   " );
    asm( "addl   (%edi), %eax   " );
    asm( "adcl   $0,     %edx   " );
    asm( "movl   %edx,   %ecx   " );
    asm( "stosl                 " );

    asm( "movl   %0, %%ebx      " :: "m" (t));
    asm( "movl   %%ecx, %0      " : "=m" (c));
    asm( "movl   %%edi, %0      " : "=m" (d));
    asm( "movl   %%esi, %0      " : "=m" (s) ::
        "eax", "ecx", "edx", "esi", "edi" );

    t++;

    do {
        *d += c; c = ( *d < c ); d++;
    }
    while( c != 0 );
}

int main()
{
    int a[1] = { 1 }, b[1] = { 10 }, x[2] = { 0, 0 };

    func_hlp(a, x, b[0]);

    printf("%d %d\n", x[0], x[1]);

    return 0;
}
------

I attached both intermediate files (Both are identical!)

Result from gcc -v:
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.3.3-11'
--with-bugurl=file:///usr/share/doc/gcc-4.3/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared
--enable-multiarch --with-system-zlib --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix --enable-nls
--with-gxx-include-dir=/usr/include/c++/4.3 --program-suffix=-4.3
--enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-mpfr
--enable-targets=all --with-tune=generic --enable-checking=release
--build=i486-linux-gnu --host=i486-linux-gnu --target=i486-linux-gnu
Thread model: posix
gcc version 4.3.3 (Debian 4.3.3-11)
COLLECT_GCC_OPTIONS='-v' '-fprofile-arcs' '-save-temps' '-o' 'bugrep'
'-mtune=generic'
 /usr/lib/gcc/i486-linux-gnu/4.3.3/cc1 -E -quiet -v bugrep.c -mtune=generic
-fprofile-arcs -fpch-preprocess -o bugrep.i
ignoring nonexistent directory "/usr/local/include/i486-linux-gnu"
ignoring nonexistent directory
"/usr/lib/gcc/i486-linux-gnu/4.3.3/../../../../i486-linux-gnu/include"
ignoring nonexistent directory "/usr/include/i486-linux-gnu"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/lib/gcc/i486-linux-gnu/4.3.3/include
 /usr/lib/gcc/i486-linux-gnu/4.3.3/include-fixed
 /usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-fprofile-arcs' '-save-temps' '-o' 'bugrep'
'-mtune=generic'
 /usr/lib/gcc/i486-linux-gnu/4.3.3/cc1 -fpreprocessed bugrep.i -quiet -dumpbase
bugrep.c -mtune=generic -auxbase bugrep -version -fprofile-arcs -o bugrep.s
GNU C (Debian 4.3.3-11) version 4.3.3 (i486-linux-gnu)
        compiled by GNU C version 4.3.3, GMP version 4.2.4, MPFR version
2.4.1-p2.
warning: GMP header version 4.2.4 differs from library version 4.3.1.
GGC heuristics: --param ggc-min-expand=64 --param ggc-min-heapsize=64524
Compiler executable checksum: 51094b766d4f590b9eaf6e27a27bca3f
COLLECT_GCC_OPTIONS='-v' '-fprofile-arcs' '-save-temps' '-o' 'bugrep'
'-mtune=generic'
 as -V -Qy -o bugrep.o bugrep.s
GNU assembler version 2.19.1 (i486-linux-gnu) using BFD version (GNU Binutils
for Debian) 2.19.1
COMPILER_PATH=/usr/lib/gcc/i486-linux-gnu/4.3.3/:/usr/lib/gcc/i486-linux-gnu/4.3.3/:/usr/lib/gcc/i486-linux-gnu/:/usr/lib/gcc/i486-linux-gnu/4.3.3/:/usr/lib/gcc/i486-linux-gnu/:/usr/lib/gcc/i486-linux-gnu/4.3.3/:/usr/lib/gcc/i486-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/i486-linux-gnu/4.3.3/:/usr/lib/gcc/i486-linux-gnu/4.3.3/:/usr/lib/gcc/i486-linux-gnu/4.3.3/../../../../lib/:/lib/../lib/:/usr/lib/../lib/:/usr/lib/gcc/i486-linux-gnu/4.3.3/../../../:/lib/:/usr/lib/:/usr/lib/i486-linux-gnu/
COLLECT_GCC_OPTIONS='-v' '-fprofile-arcs' '-save-temps' '-o' 'bugrep'
'-mtune=generic'
 /usr/lib/gcc/i486-linux-gnu/4.3.3/collect2 --eh-frame-hdr -m elf_i386
--hash-style=both -dynamic-linker /lib/ld-linux.so.2 -o bugrep
/usr/lib/gcc/i486-linux-gnu/4.3.3/../../../../lib/crt1.o
/usr/lib/gcc/i486-linux-gnu/4.3.3/../../../../lib/crti.o
/usr/lib/gcc/i486-linux-gnu/4.3.3/crtbegin.o
-L/usr/lib/gcc/i486-linux-gnu/4.3.3 -L/usr/lib/gcc/i486-linux-gnu/4.3.3
-L/usr/lib/gcc/i486-linux-gnu/4.3.3/../../../../lib -L/lib/../lib
-L/usr/lib/../lib -L/usr/lib/gcc/i486-linux-gnu/4.3.3/../../..
-L/usr/lib/i486-linux-gnu bugrep.o -lgcov -lgcc --as-needed -lgcc_s
--no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed
/usr/lib/gcc/i486-linux-gnu/4.3.3/crtend.o
/usr/lib/gcc/i486-linux-gnu/4.3.3/../../../../lib/crtn.o


-- 
           Summary: -fprofile-arcs changes behaviour
           Product: gcc
           Version: 4.3.3
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: p dot j dot bakker at brainspark dot nl
 GCC build triplet: i486-linux-gnu
  GCC host triplet: i486-linux-gnu
GCC target triplet: i486-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40509