[RFC/PATCH] Make powerpc64 use __thread for per-cpu variables

[Paul Mackerras]

Richard Henderson writes:

> How do you plan to address the compiler optimizing
> 
> 	__thread int foo;
> 	{
> 	  use(foo);
> 	  schedule();
> 	  use(foo);
> 	}
> 
> into
> 
> 	{
> 	  int *tmp = &foo;	// tls arithmetic here
> 	  use(*tmp);
> 	  schedule();
> 	  use(*tmp);
> 	}

Hmmm...  Would it be sufficient to use a RELOC_HIDE in __get_cpu_var,
like this?

#define __get_cpu_var(x)	(*(RELOC_HIDE(&per_cpu__##x, 0)))

Paul.