sgiccbug.c

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/* NOCW */
/* sgibug.c */
/* bug found by Eric Young ([email protected]) May 95 */

#include <stdio.h>

/* This compiler bug it present on IRIX 5.3, 5.1 and 4.0.5 (these are
 * the only versions of IRIX I have access to.
 * defining FIXBUG removes the bug.
 * (bug is still present in IRIX 6.3 according to
 * Gage <[email protected]>
 */
 
/* Compare the output from
 * cc sgiccbug.c; ./a.out
 * and
 * cc -O sgiccbug.c; ./a.out
 */

static unsigned long a[4]={0x01234567,0x89ABCDEF,0xFEDCBA98,0x76543210};
static unsigned long b[4]={0x89ABCDEF,0xFEDCBA98,0x76543210,0x01234567};
static unsigned long c[4]={0x77777778,0x8ACF1357,0x88888888,0x7530ECA9};

main()
    {
    unsigned long r[4];
    sub(r,a,b);
    fprintf(stderr,"input a= %08X %08X %08X %08X\n",a[3],a[2],a[1],a[0]);
    fprintf(stderr,"input b= %08X %08X %08X %08X\n",b[3],b[2],b[1],b[0]);
    fprintf(stderr,"output = %08X %08X %08X %08X\n",r[3],r[2],r[1],r[0]);
    fprintf(stderr,"correct= %08X %08X %08X %08X\n",c[3],c[2],c[1],c[0]);
    }

int sub(r,a,b)
unsigned long *r,*a,*b;
    {
    register unsigned long t1,t2,*ap,*bp,*rp;
    int i,carry;
#ifdef FIXBUG
    unsigned long dummy;
#endif

    ap=a;
    bp=b;
    rp=r;
    carry=0;
    for (i=0; i<4; i++)
        {
        t1= *(ap++);
        t2= *(bp++);
        t1=(t1-t2);
#ifdef FIXBUG
        dummy=t1;
#endif
        *(rp++)=t1&0xffffffff;
        }
    }