[Bug c/66853] New: sanitized gcc shows bug in rtlanal.c:4911 shift exponent too large because bitwitdth==0

[zeccav at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66853

            Bug ID: 66853
           Summary: sanitized gcc shows bug in rtlanal.c:4911 shift
                    exponent too large because bitwitdth==0
           Product: gcc
           Version: 5.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zeccav at gmail dot com
  Target Milestone: ---

This appears to be a duplicate for 64327
Sanitized version of gcc 5.1.0 shows a bug in the following

/* from gcc file fixopts.c */
/* must be compiled with -O2 */
/*gcc-5.1.0/gcc/rtlanal.c:4911:48: runtime error: shift exponent 4294967295 is
too large for 64-bit type 'long unsigned int'*/
/*on source line "return nonzero & ((unsigned HOST_WIDE_INT) 1 << (bitwidth -
1))"*/
/* because unsigned int bitwidth is zero and bitwitdth-1 is 4294967295 on my
x86-64 */
/* I did double check with:
 *   bitwidth = GET_MODE_PRECISION (mode);
 *   gcc_assert(bitwidth);
*/
/* the bug appears compiling fixopts.c crc32.c md5.c and many Fedora 21 kernel
files*/
int strcmp(const char *s1, const char *s2);
int  fixinc_mode; /* must be outside main for bug to appear */
int main (void)
{
 const char *pz;
 if (strcmp (pz, "true") ) fixinc_mode = 0;
}