Author: Larry Griffiths
Date: 10:14:04 01/27/99
Go up one level in this thread
On January 27, 1999 at 02:20:17, Bruce Moreland wrote: > >On January 27, 1999 at 02:18:41, Bruce Moreland wrote: > >> >>On January 27, 1999 at 01:32:28, Eugene Nalimov wrote: >> >>>On January 26, 1999 at 22:38:37, James Robertson wrote: >>> >>>>Once again I show my absolute ignorance of assembly with these two questions: >>>>I am trying to acces the 3rd [+ 4th] byte of a register. How? E.g., what is next >>>>after al, ah, ? >>>>How do I pop something off the stack without moving the stack pointer? >>>> >>>>Thanks, >>>>James >>> >>>1. Use shift instruction. E.g. >>> shr eax, 16 >>> mov byte ptr [esi], al >>> You can also use rotate instruction (it'll not destruct >>> other bytes): >>> ror eax, 16 >>> mov byte ptr [esi], al >>> ror eax, 16 >>> But if I remember it correctly, rotate is worse than shift >>> (cannot be executed in parallel) on both Pentium and P6 family. >> >>The shift also sucks, AFAIK. >> >>>2. mov reg32, dword ptr [esp] >> >>esp - 4, right? But can you say [esp - 4]? I seem to remember that you can't. > >I'm wrong, stack grows toward zero. > >bruce [esp - 4] should work ok. Larry
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