Re: announce: my very first disassembler now available (GPL)

Alexei A. Frounze wrote:

Plain 90h, which would normally be XCHG EAX,EAX (and therefore
zero-extend EAX into RAX) is actually NOP.

I might have misspoken, but the appropriate REX followed by 0x90 isn't
a NOP, it's XCHG rAX, r8.


90 = nop = nop [would have been xchg eax,eax]
40 90 = rex nop = nop [would have been xchg eax,eax]
41 90 = rex.b nop = xchg eax,r8d
48 90 = rex.w nop = xchg rax,rax
49 90 = rex.wb nop = xchg rax,r8

-hpa
.