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Re: volatile function

On 01/25/2011 09:04 AM, kevin diggs wrote:
Hi,

The function in question is returning the value of the PLL config
register in a PowerPC 750GX. I wanted to make sure that the optimizer
does not move or eliminate the call. I thought that is one of the uses
of the volatile qualifier???

Thanks!

kevin

static inline volatile unsigned int get_PLL(void)
{
unsigned int ret;

         __asm__ __volatile__ ("mfspr %0,%1":
                 "=r"(ret):
                 "i"(SPRN_HID1)
         );

         return ret;
}


I think that SPRN_HID1 has to be declared as volatile
(if that has a meaning at all in your case) for gcc
to force the load in all cases (my .02 euros, I don't
know your target asm, I don't know what SPRN_HID1 is).

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