> Grant Grundler wrote:
> > On Thu, Jun 26, 2008 at 07:28:03AM +0100, Joel Soete wrote:
> >> Just for remind:
> >>
> >> Joel Soete wrote:
> >> >
> >> >
> >> [snip]
> >> >>> But this time, it seems not consider assembly:
> >> >>> asm volatile ("lci %%r0(%%sr1, %1), %0" : "=r" (ci) : "r"
> >> >>> (vba));
> >> >>> asm volatile ("extru %1,19,12,%0" : "+r" (ci) : "r" (ci));
> >> >>> asm volatile ("depw %1,15,12,%0" : "+r" (pa) : "r" (ci));
> >> >>>
> >> >>> as a 'volatile' block and insert line 1c:
> >>
> >> This seems to make better what I want:
> >> __asm__ __volatile__ (
> >> "lci %%r0(%%sr1, %2), %0\n"
> >> "\textru %0,19,12,%0\n"
> >> "\tdepw %0,15,12,%1\n"
> >> : "+r" (ci), "+r" (pa)
> >> : "r" (vba)
> >> : "memory"
> >
> > Why the "memory"? This asm code isn't modifying memory at all.
> >
> well I certainly still have wrongly understand what "memory" clobber means but for me "pa" is a memory location modified
> (the plus sign in '"+r" (pa)' and that either after 64bit computation or 32bit initialization pa=0).
The "+r" constraint indicates a register operand that is both read and written.
However, "ci" and "pa" are not read, so the constraints for them should be
"=r". None of the instructions modify memory, so the "memory" clobber
is unnecessary.
> so why not simply get rid of its declaration (btw save a line of code ;-)) and just use a common temporay reg as r19?
r19 is the pic register in 64-bit mode and can't be used without saving
and restoring it.
Dave
--
J. David Anglin dave.anglin@xxxxxxxxxxxxxx
National Research Council of Canada (613) 990-0752 (FAX: 952-6602)
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