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

H. Peter Anvin
2007-11-14T01:05:51Z

Mathieu Desnoyers wrote:
>
> Ok, so the most flexible solution that I see, that should fit for both
> i386 and x86_64 would be :
>
>
> 1 byte : "=Q" : Any register accessible as rh: a, b, c, and d.
> 2, 4 bytes : "=R" : Legacy register—the eight integer registers available
> on all i386 processors (a, b, c, d, si, di, bp, sp).
> 8 bytes : (only for x86_64)
> "=r" : A register operand is allowed provided that it is in a
> general register.
>
> That should make sure x86_64 won't try to use REX prefixed opcodes for
> 1, 2 and 4 bytes values.
>
> Does it make sense ?
>

That's probably the best bet.

-hpa