Neil:

Your not kidding...that is pretty obtuse...

Thanks for pointing out using ClockCycles() instead, certainly much
easier for accessing the time base register this way.

robert

-----Original Message-----
From: Neil Schellenberger [mailto:community-noreply@qnx.com] 
Sent: Wednesday, June 10, 2009 6:05 PM
To: general-toolchain
Subject: Re: How to embed (PPC405) assembly in C function

Hi Robert,

The gcc extended inline assembly constraint language isn't for the faint
of heart ;-)  It's not particularly well documented; what there is can
be found, e.g., here:

http://gcc.gnu.org/onlinedocs/gcc-4.4.0/gcc/Extended-Asm.html#Extended-A
sm

In your case you could probably use something like (WARNING: UNCOMPILED
AND UNTESTED):

  uint32_t lo, hi, hi2;
  __asm__ __volatile__(
    "1:mftbu %[hi];"
    "mftb %[lo];"
    "mftbu %[hi2];"
    "cmplw %[hi],%[hi2];"
    "bne 1b;"
    : [hi] "=r" (hi),
      [lo] "=r" (lo),
      [hi2] "=r" (hi2));

If this is Neutrino user mode, you might want to consider ClockCycles()
instead.  (And note also the SMP warning there.)

Regards,
Neil

On Wed, 2009-06-10 at 17:03 -0400, Robert D'Attilio wrote:
> Hi:
> 
> I need to read some hardware special purpose registers that can only
accessed using assembly instructions. Would anyone have some code
snippets that would illustrate doing this. I do have some example macros
taken from the IPL code that look like the following:
> 
> #define set_dcr(dcr,val) 					\
> 		__asm__ __volatile__( 				\
> 			".ifdef PPC_CPUOP_ENABLED;"		\
> 			".cpu 403;"
\
> 			".endif;"
\
> 			"mtdcr %0,%1"
\
> 			: : "i" (dcr), "r" (val) )
> 
> But 1) I need to embed several instructions and 2) not clear on the
above syntax .
> 
> thanks
> 
> PS
> 
> Here is the assembly I"m trying to embed
> 
> loop:
>   mftbu Rx
>   mftb Ry
>   mftbu Rz
>   cmpw Rz, Rx
>   bne loop
> 
> Note I realize I'll have to find some vacant registers to use for Rx,
Ry and Rz
> 
> _______________________________________________
> General
> http://community.qnx.com/sf/go/post31437
> 

_______________________________________________
General
http://community.qnx.com/sf/go/post31445