RCL/RCR

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hckr83

Joined: 12 Nov 2006
Posts: 86
Location: usa

hckr83 05 Jan 2008, 17:15

For RCL and RCR, do these instructions set the carry flag to 0 or do they rotate in what CF already is into the result?

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05 Jan 2008, 17:15

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 05 Jan 2008, 18:31

The value of CF prior to execution goes into result and the bit that gets out after doing the operation is copied into the flag.

Code:

mov eax, $80000000
xor edx, edx

shl eax, 1 ; EAX = $00000000; EDX = $00000000; CF = 1
rcr edx, 1 ; EAX = $00000000; EDX = $80000000; CF = 0

[edit]Changed first instruction to other that shows my point more clear Razz

[/edit]

Last edited by LocoDelAssembly on 05 Jan 2008, 18:42; edited 1 time in total

05 Jan 2008, 18:31

asmfan

Joined: 11 Aug 2006
Posts: 392
Location: Russian

asmfan 05 Jan 2008, 18:38

LocoDelAssembly wrote:

mov eax, $80000000
xor edx, edx

rol eax, 1 ; EAX = $00000001; EDX = $00000000; CF = 1
rcr edx, 1 ; EAX = $00000000; EDX = $80000000; CF = 0

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05 Jan 2008, 18:38

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 05 Jan 2008, 18:44

There is another error just in the comment below Wink

I have changed the instruction. Thanks for point that out.

05 Jan 2008, 18:44

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