String copy idiom.

[Joe Orost]

In article <3448 at alice.UUCP> ark at alice.UUCP (Andrew Koenig) writes:
>If s and t are char pointers in registers,
>
>	while (*s++ = *t++) ;
>
>generates the best code I could possibly imagine.
>
>	while ((*s = *t) != '\0') {s++; t++;}
>
>is considerably worse.  Try it with register variables on your compiler.

Ok, I did.  The second sequence generates less code than the first sequence
on our machine (Perkin-Elmer).  This is due to the fact that our machine
doesn't support auto-increment in hardware.  The C compiler has to "fake" it.

					regards,
					joe

--
Full-Name:  Joseph M. Orost
UUCP:       ..!{decvax,ucbvax,ihnp4}!vax135!petsd!joe
ARPA:	    vax135!petsd!joe at BERKELEY
US Mail:    MS 313; Perkin-Elmer; 106 Apple St; Tinton Falls, NJ 07724
Phone:      (201) 870-5844
Location:   40 19'49" N / 74 04'37" W