Re: Rotate Left from C

"Torben Ægidius Mogensen" <>
24 Oct 2002 23:57:31 -0400

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From: "Torben Ægidius Mogensen" <>
Newsgroups: comp.compilers
Date: 24 Oct 2002 23:57:31 -0400
Organization: Department of Computer Science, University of Copenhagen
References: 02-10-065
Keywords: architecture
Posted-Date: 24 Oct 2002 23:57:30 EDT

The moderator inquires:
> [How many machines still have rotate instructions? I thought they had
> gone out of fashion. Yes, I know the Pentium does, but its instruction
> set dates from the 1970s. -John]

ARM has rotates: 32-bit rotates by any amount and a 33-bit rotate
right by 1 (using the carry flag as the 33rd bit). The standard ARM
compiler will (or would, I haven't checked the latest versions)
generate a rotate instruction from a specific combination of shifts
and OR.

Torben Mogensen (

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