Author: Larry Griffiths
Date: 16:58:35 01/27/99
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On January 27, 1999 at 14:50:59, James Robertson 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. >>2. mov reg32, dword ptr [esp] >> >>Eugene > >Ok.... that would work. Because I already have stuff stored in ax, and I know >the exact values I want to put into the 'e' part, I wrote: > >or eax,0xeeee0000 >and eax,0x0000ffff >or eax,0xeeee0000 > >where eeee=what I want to put in. This seems to work. Are there any problems I >am missing? > >James James, It looks to me like the above three instructions can be replaced by: mov eax,0xeeee0000 Larry
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