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Re: How to implement "unsigned long long __rdtsc ()" for x86?



Sent from my iPhone

On Jan 16, 2009, at 9:23 AM, "H.J. Lu" <hjl.tools@gmail.com> wrote:

Hi,

I am trying to implement

unsigned long long __rdtsc (void);

for RDTSC as an intrinsic.  It is easy to do it with asm statement.
But I am having a hard time to implement it as a gcc builtin.
The main problem is there is no input. It is impossible to write
a proper RTL for it.  Any suggestions?

unspec_volatile? I don't see any issues with a no input unspec_volatile the rs6000 backend uses that already.

Thanks,
Andrew Pinski



I am thinking about adding some fake readonly registers. Will
it work?

Thanks.


--
H.J.

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