[Bug c/14375] New: bad code gen for pointer inc with &&

[gcc-bugzilla at gcc dot gnu dot org]

	in a for loop computing a logical and, a second pointer appears
not to increment correctly.  Code demonstrating problem and fix is attached.
The bug is activated by leaving GCC3_BUGFIX set to zero.  The bug
appears in gcc 3.2.3 and gcc 3.3.3.


#include <stdio.h>

#define GCC3_BUGFIX 0

void andlog(int* dest, int* src,
            int count)

{
   int* term;

   #if (GCC3_BUGFIX)
   for (term=dest+count; dest<term; dest++,src++)
      *dest = (*dest) && (*src);
   #else 
   /* GCC3X (3.2.3 and 3.3.3) do not increment src right on x86
      in this sequence */
   for (term=dest+count; dest<term; dest++)
      *dest = (*dest) && (*src++);
   #endif
}

int main()

{
   int i1[] = {
0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 
1,  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 
1,  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1  };

   int i2[] = {
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 
1,  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 
1,  1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0  };

   int i;

   andlog(i1,i2,65);

   for (i=0; i<65; i++)
      printf("and = %d  should be %d\n",i1[i],i1[i] && i2[i]);

   return(0);
}

Environment:
System: Linux madhatter 2.6.3 #2 Sat Feb 21 14:38:40 EST 2004 i686 unknown unknown GNU/Linux
Architecture: i686

	
host: i486-slackware-linux-gnu
build: i486-slackware-linux-gnu
target: i486-slackware-linux-gnu
configured with: ../gcc-3.3.3/configure --prefix=/usr --enable-shared --enable-threads=posix --enable-__cxa_atexit --disable-checking --with-gnu-ld --verbose --target=i486-slackware-linux --host=i486-slackware-linux

How-To-Repeat:
	compile attached program on gcc3.2.3 or gcc3.3.3 and run it.  Last
4 compares are bad.
------- Additional Comments From tjb at watson dot ibm dot com  2004-03-01 23:12 -------
Fix:
	recode if using GCC3.

-- 
           Summary: bad code gen for pointer inc with &&
           Product: gcc
           Version: 3.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tjb at watson dot ibm dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i486-slackware-linux-gnu
  GCC host triplet: i486-slackware-linux-gnu
GCC target triplet: i486-slackware-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14375