Two Birds with One Stone

[Walter Bright]

In article <864 at kuling.UUCP> thomas at kuling.UUCP (Thomas H{meenaho) writes:
>In article <874 at dataioDataio.UUCP> bright at dataio.UUCP (Walter Bright writes:
>>Almost but not quite true. A compiler CANNOT normally replace a divide
>>by a right-shift if it is an integer divide. This is because a right
>>shift of a negative integer is not the same as a divide.
>However most useable processors provide arithmetic shifts which will give
>the right result even if it is a signed divide.

Ok, try this program:

main()
{
	printf("-3/2 = %d\n-3 >> 1 = %d\n",(-3)/2,(-3) >> 1);
}

I think you'll find the results are different, even when the compiler
does an arithmetic right shift! (The difference is the direction in
which rounding occurs.)