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pal



Joined: 26 Aug 2008
Posts: 227
pal
What exactly is a rotating register Confused Someone said the term to me but I had no idea what they meant be it.

Any description/links would be appreciated.

Cheers, pal.
Post 04 Oct 2009, 15:20
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
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revolution
In what context was it said? It is hard to know what it means without the context.
Post 04 Oct 2009, 15:30
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bitshifter



Joined: 04 Dec 2007
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bitshifter
Maybe to rotate the bits within a register via ror or rol?
Post 04 Oct 2009, 18:21
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pal



Joined: 26 Aug 2008
Posts: 227
pal
I thought it was about literally rotating the registers using rol/ror/rcr/rcl but I'm not sure.

I'll try to get the person to explain what he means, but he literally said to me "Do you know what rotating registers are?". I thought of the rotating instruction mnemonics too. The only thing that I found relating to it is:

Code:
http://www.cs.nmsu.edu/~rvinyard/itanium/register_rotation.htm    


But it doesn't really explain much to be honest. I'll find out more when I speak to the guy again.

This is what he said:

Quote:

Chris []:
do you know what are rotating registers


He then said he wasn't listening though so I don't really know.
Post 04 Oct 2009, 19:12
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LocoDelAssembly
Your code has a bug


Joined: 06 May 2005
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LocoDelAssembly
Perhaps a different way of saying this?
Post 04 Oct 2009, 20:26
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Pirata Derek



Joined: 31 Oct 2008
Posts: 259
Location: Italy
Pirata Derek
ROTATING REGISTERS:
THe same rules are for different register sizes.



ROR - Rotate right:

Image




ROL - Rotate left:

Image




RCR - Rotate right with carry:

Image




RCL - Rotate left with carry:

Image




For more information go on wikipedia
Post 06 Oct 2009, 07:27
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17715
Location: In your JS exploiting you and your system
revolution
Pirata Derek: I think "rotating" is used as an adjective, not as a verb. But thanks for the pretty pics anyway.
Post 06 Oct 2009, 07:44
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Borsuc



Joined: 29 Dec 2005
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Borsuc
It probably means like the x86 FPU except that it "overflows" back to the original st0 register if you go over once it's full.
Post 06 Oct 2009, 14:10
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pal



Joined: 26 Aug 2008
Posts: 227
pal
Razz Nice pictures, but yeah I don't think it was that. I have to wait for him to come back on to see if he can explain it again.

Borsuc: that was another thing I thought of, the FPU style registers.
Post 06 Oct 2009, 22:02
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pal



Joined: 26 Aug 2008
Posts: 227
pal
OK Madis cleared it up for me. The rotating registers are from Itanium architecture, not Intel.


Last edited by pal on 07 Oct 2009, 11:21; edited 1 time in total
Post 07 Oct 2009, 11:15
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17715
Location: In your JS exploiting you and your system
revolution
IA64 does have 128 FPU and 128 CPU registers. Nothing new there. It also has a hardware supported register windowing facility - that could be the rotating register thing. But who knows, could be anything else also.

Anyhow, if you want to learn more about the (dead) IA64 architecture search for Itanium (and/or IA64 of course).
Post 07 Oct 2009, 11:20
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pal



Joined: 26 Aug 2008
Posts: 227
pal
Yeah my bad. The guy who said it to me didn't mention the IA-64 bit originally but said 64-bits, so I assumed he was using x86-64 bit. Either way I didn't know about IA-64 like that. Cheers all.
Post 07 Oct 2009, 11:33
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kohlrak



Joined: 21 Jul 2006
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kohlrak
Let's not forget that it could be a reference to alternate registers (the idea that there are more registers that we can access, but to reduce hardware restrictions, the registers we specify are aliased).
Post 08 Oct 2009, 04:15
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