asm conflict question

Richard Bonomo bonomo@sal.wisc.edu
Wed Aug 9 16:53:00 GMT 2006


An Extended ASM manual!
Now that I know what to look for, I will
locate it.  Thanks for that bit of information!

Rich

On Wed, 9 Aug 2006, Andrew Haley wrote:

> Richard Bonomo writes:
> >
> >
> > On Wed, 9 Aug 2006, Andrew Haley wrote:
> >
> > <snip>
> >
> > > MM, wrong.  gcc might put something between the insns.  Ok, try
> > >
> > > #define disable() \
> > >     ({  int __Status; \
> > >     __asm__ volatile ("clra      ; save CPU status\n" \
> > >                       "tfr     cc,b\n" \
> > >                       "orcc    #0x50   ; disable interrupts" \
> > >                        : "=d" (__Status)); \
> > >     __Status; })
> > >
> >
> > OK, I get this error message:
> >
> > error: can't find a register in class `Q_REGS' while reloading `asm'
> >
> > which I think is generated by the companion "restore" function.
>
> OK.  Well, you have a worked example -- now you need to read the
> manual about Extended Asm and do the same with restore() that you did
> with disable().
>
> > Here are the 3 function definitions as they
> > currently stand:
> >
> > #define disable() \
> >       ({  int __Status; \
> >       __asm__ volatile ("clra      ; save CPU status\n" \
> >                         "tfr     cc,b\n" \
> >                         "orcc    #0x50   ; disable interrupts" \
> >                          : "=d" (__Status)); \
> >       __Status; })
> >
> > #define restore(X) \
> >      ({ int __Status = (X); \
> >      __asm__ ("tfr       b,cc    ; restore status" : : "d" (__Status) :
> > "d", "cc"); })  [NOTE that the line wrapped in this message]
> >
> > #define enable() \
> >      __asm__ ("andcc     #0xaf   ; enable interrupts")
> >
> >
> > The disable function is as you (Andrew) suggested.
> > The restore function and enable function definitions
> > are unchanged.
> >
> > BTW, I am not familiar with the syntax which was
> > and it being used.  What does (for example)
> > ("tfr       b,cc    ; restore status" : : "d" (__Status) :"d", "cc")
> > mean in this context?
>
> Here, register d is being used as an input and it's also being
> clobbered.  That doesn't seem right to me.  Something more like using
> "=d" as the ouput and a matching constraint "0" for the input might
> work better.
>
> Andrew.
>

-- 
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Richard Bonomo
UW Space Astronomy Laboratory
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web page URL: http://www.cae.wisc.edu/~bonomo
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