Author: Bruce Moreland
Date: 14:30:27 10/23/00
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On October 23, 2000 at 12:29:27, Oliver Roese wrote: >On October 23, 2000 at 01:09:02, Landon Rabern wrote: > >>is it faster to cast to a char or to AND by 0xff, or to do they take the same >>number of clock cycles? >> >>Thanks, >> >>Landon W. Rabern > >Since "(unsigned char) u" and "u & 0xff" are equivalent expressions in C (or >arent they??) and nearly equivalent in other languages you surely cant tell >that, without looking on the assembler output of your compiler. >In C dont ever use char, there are implicitely converted to ints and that could >hurt. If the compiler can decide not to convert, slow 86-instructions must be >used. Hard to tell, what is slowest. > >Oliver I know that with the original pentium, in 32-bit mode, 32-bit and 8-bit operations were fine, but 16-bit operations were bad. I don't know if 8-bit operations are now bad, but if they are, it has been since sometime after the Pentium Pro. bruce
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