Re: [patch 5/8] Immediate Values - x86 Optimization

[H. Peter Anvin]

Mathieu Desnoyers wrote:
> > - Use "=g" constraint for char immediate value inline assembly.
> >
> > "=g" is the same as "=rmi" which is inherently bogus.  In your actual code 
> > you use "=r", the correct constraint is "=q".
>
> q
>     Any register accessible as rl. In 32-bit mode, a, b, c, and d; in 64-bit mode, any integer register. 
>
>
> I am worried that "=q" might exclude the si and di registers in 32-bit mode.
>
> What exactly is wrong with "=r" ?

For "char" (8-bit) values, sp/bp/si/di are illegal in 32-bit mode.

Hence "=q".

	-hpa
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