[Bug c/25332] New: 64 bit multiplication incorrectly folded.

[jyates at netezza dot com]

/*
 * Compile -O0 (no optimization)
 */

#include <stdio.h>

typedef int int32;
typedef long long int64;


int main ()
{
    int32 i = 1;                /* hence (2*i)-1 below is 1... */
#define K 0x800000003LL         /* 64 bit constant; low 32 are 3; high 32 are 8
*/

    printf("%016llx (gcc 2.96 bad:  0000000000000003)\n", K * (         (2*i) -
       1  ));
    printf("%016llx (gcc 2.96 bad:  0000000000000003)\n", K * (         (2*i) -
       1LL));
    printf("%016llx (gcc 2.96 bad:  0000000000000003)\n", K * (         (2*i) -
(int64)1  ));

    printf("%016llx (gcc 2.96 bad:  fffffff800000003)\n", K * (  (int64)(2*i) -
       1  ));
    printf("%016llx (gcc 2.96 bad:  fffffff800000003)\n", K * (  (int64)(2*i) -
       1LL));
    printf("%016llx (gcc 2.96 bad:  fffffff800000003)\n", K * (  (int64)(2*i) -
(int64)1  ));

    printf("%016llx (gcc 2.96 good: 0000000800000003)\n", K * (2*(int64)(  i) -
       1  ));
}


-- 
           Summary: 64 bit multiplication incorrectly folded.
           Product: gcc
           Version: 2.96
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jyates at netezza dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25332