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
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assembly

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x86

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cpu-architecture

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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?

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