Re: MS/CW-style inline assembly for GCC

[Robert Dewar <dewar at gnat dot com>]

Neil Booth wrote:

> Robert Dewar wrote:-
>
>
> > Robert Dewar wrote:
> >
> >
> > > For reference, the code on the x86 should look something like
> > > (in Intel syntax):
> > >
> > >    lp:   mov  eax, [ebx]
> > >          adc  eax, [ecx]
> > >          inc  ebx
> > >          inc  ecx
> > >          loop lp
> >
> > that's the code that was wrong, should be
> >
> >
> > >     lp:   mov  eax, [ebx]
> > >           adc  eax, [ecx]
> > >           lea  ebx, [ebx+4]
> > >           lea  ecx, [ecx+4]
> > >           loop lp
>
>
> Except that loop decrements ecx and loops if non-zero, so I
> think you've still got some work to do 8-)

OK, well I did say look something like :-)
Yes indeed we need to use some other register
than ecx for the second index register. Might
also be nice to store the result :-) Just goes to show
that dashing off code in email is a hazzardous
occupation. How about

         lp:   lodsw
               adc     eax, [ebx]
               lea     ebx, [ebx+4]
               stosw
               loop    lp

Here source registers are esi,ebx and destination register is edi

Did someone check what GCC generates for the C code?