Assembly or ....

[Richard A. O'Keefe]

In article <21440 at apple.Apple.COM> desnoyer at Apple.COM (Peter Desnoyers) writes:
>In article <1034 at l.cc.purdue.edu> cik at l.cc.purdue.edu (Herman Rubin) writes:
>>[about the iq, r := x div y, x mod y instruction]

>The operation mentioned was either poorly defined, or merely consisted of:
>  convert a, b to int
>  div a,b -> int quotient, remainder
>  convert remainder to float

Wrong.  The important thing is that the remainder is
	remainder = a - b*INT(a/b)
I am sure that the IEEE floating-point committee would be interested to
learn that it is not a "natural divide-type operation"; this is
precisely the IEEE drem(a,b) function.  Quoting the SunOS manual:
	drem(x, y) returns the remainder r := x - n*y where n is the
	integer nearest the exact value of x/y; moreover if |n-x/y|=1/2
	then n is even.  Consequently the remainder is computed exactly
	and |r| <= |y|/2.  ... drem(x, 0) returns a NaN.

This is obviously a range reduction operator.  Oddly enough, on most
present-day machines, there is a good excuse for _not_ returning the
quotient (n) as well:  with 64-bit floats and 32-bit integers there
is no reason to expect n to be representable as a machine "integer".
Both results would have to be floats.  And in its use as a range
reduction operation, you normally aren't interested in n.