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

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Mathieu Desnoyers wrote:
* H. Peter Anvin ([email protected]) wrote:
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".


Ah! yep, I see, so we say:

1 byte : "=q"
2 bytes : "=r"
4 bytes : "=r"
8 bytes : "=r"

? (si and di appear to be legal for 2 and 4 bytes in 32-bit mode)


That's right.

	-hpa
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