Author: Severi Salminen
Date: 12:25:55 01/31/02
Hi! This is what I got from intel about bsf/bsr instructions. I asked this: "In what situations bsf/bsr eax,VARIABLE changes the contents of eax, if VARIABLE is 0?" This is what they say: "Although the value appears unchanged in some cases, the definition of this instruction applies to all IA-32 processors starting with the Intel 386. That stated, the BSR and BSF instructions both work as defined on all processors previously noted. So even though it might be deterministic in a specific implementation, no information will be provided on special cases." So practically I got no info at all. Still it is just speculation to try to guess if there are systems where eax might be changed. In Requiem I make a small test (which of course can't cover all situations) to see if bsf/bsr changes eax in above situation and exit if this is that case. Severi
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