AMD 250 manual 190

Software Optimization Guide for AMD64 Processors 25112 Rev. 3.06 September 2005

int main(void)

{

fprintf(stderr, "\n");

fprintf(stderr, "Signed division by constant\n"); fprintf(stderr, "===========================\n\n");

fprintf(stderr, "enter divisor: "); scanf("%ld", &d); fprintf(stderr, "\n");

e = d;

d = labs(d);

if (d == 0) goto printed_code;

if (e == (-1)) {

printf("; dividend: register or memory location\n"); printf("\n");

printf("NEG dividend\n"); printf("\n");

printf("; quotient replaced dividend\n"); goto printed_code;

}

if (d == 2) {

printf("; dividend expected in EAX\n");

printf("\n");
printf("CMP	EAX, 080000000h\n");
printf("SBB	EAX, -1\n");
printf("SAR	EAX, 1\n");
if (e < 0) printf("NEG		EAX\n");

printf("\n");

printf("; quotient now in EAX\n"); goto printed_code;

}

if (!(d & (d - 1))) {

printf("; dividend expected in EAX\n");

printf("\n");
printf("CDQ\n");
printf("AND	EDX, 0%08lXh\n", (d-1));
printf("ADD	EAX, EDX\n");
if (log2(d))	printf("SAR	EAX, %d\n", log2(d));
if (e < 0)	printf("NEG	EAX\n");
printf("\n");

printf("; quotient now in EAX\n"); goto printed_code;

}

/* Determine algorithm (a), multiplier (m), and shift factor (s) for 32-bit signed integer division. Based on: Granlund, T.; Montgomery, P.L.:

190 Integer Optimizations Chapter 8