User's Manual

32 Copy Frequently De-referenced Pointer Arguments to Local Variables
AMD Athlon™ Processor x86 Code Optimization
22007E/0—November 1999
Example 1 (Avoid):
//assumes pointers are different and q!=r
void isqrt ( unsigned long a,
unsigned long *q,
unsigned long *r)
{
*q = a;
if (a > 0)
{
while (*q > (*r = a / *q))
{
*q = (*q + *r) >> 1;
}
}
*r = a - *q * *q;
}
Example 2 (Preferred):
//assumes pointers are different and q!=r
void isqrt ( unsigned long a,
unsigned long *q,
unsigned long *r)
{
unsigned long qq, rr;
qq = a;
if (a > 0)
{
while (qq > (rr = a / qq))
{
qq = (qq + rr) >> 1;
}
}
rr = a - qq * qq;
*q = qq;
*r = rr;
}