Re: Bug with PPC 32-bit inline assembler [4.1.1 and 4.3.2]

[Tom St Denis <tstdenis at ellipticsemi dot com>]

Andrew Haley wrote:
> Tom St Denis wrote:
> > #define SQRADDSC(i, j)            \
> > asm(                              \
> >   " mullw  %0,%3,%4        \n\t" \
> >   " mulhwu %1,%3,%4        \n\t" \
> >   " xor    %2,%2,%2        \n\t" \
> > :"=r"(sc0), "=r"(sc1), "=r"(sc2): "r"(i),"r"(j) : "%cc");
> >
> > #endif
> >     
> This isn't a bug: look for "earlyclobber" in the documentation.
>   

Adding =&r worked, however ... (this is the part where I complain 
perhaps needlessly :-) )

This doesn't make sense.  In the subsequent line "mulhwu ..." I 
specifically asked for %3,%4 which is i and j respectively.  Yet, 
without early clobber it gives me sc0.    To me that sounds like a bug.  
Maybe it's not the way the inline asm is "meant" to be used, but to 
someone who reads the code it's not obvious that %3 no longer means i.  
Semantically it's as if I used "%1,%0,%4" as the operands for the 2nd line.

Either way, thank you for pointing me in the right direction.

Tom