shifts and rotates by 1 on ix86

[Alan Modra]

On Wed, 10 May 2000, Alexander Sokolov wrote:

> On Wed, 10 May 2000, Alan Modra wrote:
> 
> > You can get the smaller opcode sequence by writing "shll %eax".
> 
> This should be documented in manual.

True.  Along with a few of other details too.

> > The reason gas does not do this automatically is that on certain processors,
> > eg. 486, the D1 E0 opcode sequence is slower than C1 E0 01.
> 
> Then why not to add directives like .386, .486 etc or a command line
> option to specify the target cpu type?

That's not such a bad idea, particularly if the directive also enabled 
warnings when someone tried to use an instruction not available on the
chosen cpu.

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