RE: [PATCH] ARMv7 Oprofile support

["Woodruff, Richard" <r-woodruff2@xxxxxx>]

> > One thing I noticed was I think the patch should add the "memory"
> > qualifier to clobber list for asm's calls with output operands (=r).
> > There is a little bit of mixed C where the compiler should be told to
> > make sure to update local variables which may be in memory.
>
> Why?  Merely reading a register doesn't affect memory.

The comment was if the local variable 'val' which could be allocated in memory needs updating.

        u32 val;
        asm volatile("mrc p15, 0, %0, c9, c12, 3" : "=r" (val));
        val &= FLAG_MASK;
        volatile("mrc p15, 0, %0, c9, c12, 3" : "=r" (val));

Can you always be assured that val will stick in a register and not be pushed on the stack (memory)?

I had rearranged some of the code and was seeing values not propagating as expected.

Regards,
Richard W.


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