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flat assembler > Heap > jcc instruction

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CandyMan



Joined: 04 Sep 2009
Posts: 285
Location: film "CandyMan" directed through Bernard Rose OR Candy Shop
Code:
use16
org 0xFFF9
db 66h,72h,7Fh ;on Intel CPU this instruction jumps (jc) to 0x1007B, whether in AMD processors is it the same?    

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smaller is better
Post 21 Mar 2018, 18:43
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DimonSoft



Joined: 03 Mar 2010
Posts: 420
Location: Belarus
CandyMan wrote:
Code:
use16
org 0xFFF9
db 66h,72h,7Fh ;on Intel CPU this instruction jumps (jc) to 0x1007B, whether in AMD processors is it the same?    

From AMD SDM, although it might be just a part of the story. Why would you need to depend on such behaviour?
AMD SDM wrote:
If the jump is taken, the signed displacement is added to the rIP (of the following instruction) and the result is truncated to 16, 32, or 64 bits, depending on operand size.
Post 21 Mar 2018, 19:37
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CandyMan



Joined: 04 Sep 2009
Posts: 285
Location: film "CandyMan" directed through Bernard Rose OR Candy Shop
it is worthwhile reading documentation, thanks.
Post 21 Mar 2018, 21:52
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