Re: how to inline "ROR/ROL" asm instructions in C ?? (help wanted)

Marcus Watts (mdw@umich.edu)
Thu, 08 Oct 98 01:37:31 -0400

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David R. Conrad writes:

> 2.6.2 is pretty old. Did you mean 2.7.2?

I meant 2.6.2, and yes it's old. It was handy, and didn't seem
like behavior that was likely to go away. I mentioned the version
in case the behavior was different in other versions.

David R. Conrad also writes:
...
>
> .ident "GCC: (GNU) egcs-2.91.57 19980901 (egcs-1.1 release)"
>
> So apparently they have fixed the inability to do rotates by a variable
> number of bits, but they haven't addressed the issue of addition vs. or.

Evidently, the behavior *did* change. Somebody should mention
this to Theodore Ts'o and/or the linux folks, because his /dev/random
driver for linux (drivers/char/random.c, at least as of linux 2.1.124)
has an inline function "rotate_left" that uses __asm for i386, to get
around this no longer missing feature in gcc.

                                        -Marcus Watts
                                        UM ITD PD&D Umich Systems Group

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