[PATCH] PowerPC - Add a faster way to read the Time Base register

[Ryan S. Arnold]

On Tue, Feb 14, 2012 at 4:53 PM, Richard Henderson <rth@twiddle.net> wrote:
> On 02/14/2012 02:33 PM, Ryan S. Arnold wrote:
>>> > Is there a good reason why you're stringify-ing this constant
>>> > rather than just writing "mfspr %0, 268"?  You certainly don't
>>> > want to be polluting the namespace with an unadorned "STRINGIFY".
>> We didn't want a naked (non-descriptive) opcode parameter.  There must
>> be a way to do this that takes the definition as a variable, like
>> perhaps the following (totally untested) code:
>>
>>     __asm__ volatile (                                         \
>>                      "mfspr %[tb], %2\n" \
>>                      : [tb]"=r" (__tb)                         \
>>                      : "i" (SPRN_TBRL)  );
>>
>>
>
> Why didn't you want this?  Certainly that's what hp-timing.h does.
>
> And why expose SPRN_TBRL at all?  It doesn't really do the user any good.

Actually, you're right.  I was thinking of myself as the maintainer,
and not of the actual users who doesn't need that information.

Ryan S. Arnold