I'd like to give an example on a different use of the same
feature:
while(length--)
{
*d++ = *s++;
}
if(length == -1) /* the programmer will need to know the value
of length here. */
{
/* handle case where length was exactly 0, it's now -1 */
}
would become:
while(length--)
{
*d++ = *s++;
}
otherwise
{
/* handle case where length was exactly 0, it's now -1 */
}
---
A pseudo-assembly language version of a normal while-loop:
bra wstart /* this usually cost (something like) a
clock-cycle to start */
while:
copy.b s+,d+
wstart:
sub length,#1
bcc while
wend:
---
Different version of the above:
sub length,#1
bcs wend
while:
copy.b s+,d+
sub length,#1
bcc while
wend:
---
A pseudo-assembly language version of the 'otherwise' while-loop:
sub length,#1
bcs otherwise
while:
copy.b s+,d+
sub length,#1
bcc while
bra wend
otherwise:
/* handle zero-length */
wend:
-These are not real good examples, though. However, they do show
that the compiler would know that it can safely optimize the
expression-test, and almost for free get the 'otherwise', which
would cost only little extra CPU-time.
