Messages in this thread | | | Date | Tue, 13 Nov 2007 14:24:45 -0500 | From | Mathieu Desnoyers <> | Subject | Re: [patch 5/8] Immediate Values - x86 Optimization |
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* H. Peter Anvin (hpa@zytor.com) 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". >
Hi Peter,
Yup, =g wasn't what I was looking for at all, the header comment is bogus.
From http://gcc.gnu.org/onlinedocs/gcc/Simple-Constraints.html#Simple-Constraints
`r' A register operand is allowed provided that it is in a general register.
From http://gcc.gnu.org/onlinedocs/gcc/Machine-Constraints.html#Machine-Constraints Intel 386 config/i386/constraints.md
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" ?
> -hpa
-- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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