[PATCH] Improve and consolidate sparc PIC assembler.

[David Miller]

From: Torbjorn Granlund <tg at gmplib.org>
Date: Sun, 14 Apr 2013 19:21:36 +0200

> T3 and T4 are of course quite relevant, so we should take these into
> account.  If they run rdpc no slower than the thunk call, then we should
> use rdpc unconditionally.
> 
> I used this test program:

Ok, on T4, %pc reads are definitely faster:

call:	16sec
rdpc:	3sec

On T3:

call:	34sec
rdpc:	41sec

I bet on T3 a rdpc makes the cpu strand unavilable the next cycle.

In all the tests above I changed the %g1 initialization to be that
of the cpu in question's clock rate.

Since using rdpc avoids the whole issue of corrupting the return
address stack, it seems pretty desirable to move over to it.