What's the purpose of the rotate instructions (ROL, RCL on x86) ?

Posted by lgratian on Stack Overflow See other posts from Stack Overflow or by lgratian
Published on 2011-02-12T06:07:14Z Indexed on 2011/02/12 7:25 UTC
Read the original article Hit count: 169

Filed under:

assembly

|

x86

|

cpu-architecture

|

machine-instruction

I always wondered what's the purpose of the rotate instructions some CPUs have (ROL, RCL on x86, for example). What kind of software makes use of these instructions? I first thought they may be used for encryption/computing hash codes, but these libraries are written usually in C, which doesn't have operators that map to these instructions.
Has anybody found an use for them? Why where they added to the instructions set?

© Stack Overflow or respective owner

Related posts about assembly

More information wanted on error: CREATE ASSEMBLY for assembly failed because assembly failed verif

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a small application that uses SQL Server 2005 Express with CLR stored procedures. It has been successfully installed and runs on many computers running XP and Vista. To create the assembly the following SQL is executed (names changed to protect the innocent): CREATE ASSEMBLY myAssemblyName… >>> More
Installed SQL Server 2008 and now TFS is broken.

as seen on Server Fault - Search for 'Server Fault'
Hi, My W2K3 server was running TFS 2008 SP1, SQL Server 2005 Development edition. I installed SQL Server 2008 Standard. I installed it while leaving SQL Server 2005 alone. Upgrading was not possible due to the differences in editions of the SQL Servers. Now TFS is broken. On a client computer… >>> More
How to Specify AssemblyKeyFile Attribute in .NET Assembly and Issues

as seen on Microsoft .NET Support Team - Search for 'Microsoft .NET Support Team'
How to specify strong key file in assembly? Answer: You can specify snk file information using following line [assembly: AssemblyKeyFile(@"c:\Key2.snk")] Where to specify an strong key file (snk file)? Answer: You have two options to specify the AssemblyKeyFile infromation. 1. In… >>> More
Assembly Language Question: Display Characters to screen LIFO (Last In First Out) in assembly langua

as seen on Stack Overflow - Search for 'Stack Overflow'
Given a stack that displays characters to the screen First in First Out(FIFO), how do you switch it to display them Last in First Out(LIFO). Theoretically speaking... is it simply just sending the characters to print in reverse order? >>> More
c# - can you make a "weak" assembly reference to a strong named assembly

as seen on Stack Overflow - Search for 'Stack Overflow'
hi, for various reasons i would rather not use strong named (signed) assemblies in my project. however, one of the projects is referenced by a sharepoint web part which means it must be signed. is it possible to have this assembly signed but when I reference it from other projects, to do so using… >>> More

Related posts about x86

Windows Start Menu Not Staying on Top

as seen on Super User - Search for 'Super User'
Hey everyone. I've had this problem since Windows Vista. I did a clean install with Windows 7 and hoped it would fix the problem. Also swapped out the video card just to rule out a strange driver issue. Here's what's happening. After running for some period of time (usually a few hours), the… >>> More
Recompile a x86 code with LLVM to some faster one x86

as seen on Stack Overflow - Search for 'Stack Overflow'
Hello Is it possible to run LLVM compiler with input of x86 32bit code? There is a huge algorithm which I have no source code and I want to make it run faster on the same hardware. Can I translate it from x86 back to x86 with optimizations. This Code runs a long time, so I want to do static recompilation… >>> More
Install Additional Printer Drivers (x86) on Vista (x64) - Can't find suitable (x86) ntprint.inf

as seen on Super User - Search for 'Super User'
I have a printer connected to my computer that I'd like to share on my home network - shouldn't be a problem. The computer the printer is connected to is running Vista Ultimate x64. The computers I'm trying to share with are x86 Windows XP Professional and x86 Vista, so I need to install additional… >>> More
HP-UX (PA-RISC|Itanium) virtualisation on (x86-64|x86)

as seen on Server Fault - Search for 'Server Fault'
I'm looking for a way to run HP-UX (for educational purposes), but I don't have HP hardware right now. These options are not very suitable for me: HP TestDrive program - Looks like it was discontinued 2 years ago. Ski - looks like only CPU emulator. Is it worth trying? HPPAQEMU - Patch for old… >>> More
Injection of banners in my webbrowsers possible malware

as seen on Super User - Search for 'Super User'
Recently I have started to suspect that I have some kind of virus on my computer. There are 3 symptoms: Banners are being displayed on pages that doesn't use commercials, for instance when viewing screen-shots on Steam. It is only displayed after the rest of the page has been loaded and seems to be… >>> More