Fix ARM ICE for register var asm ("pc") (PR target/60606)

[Joseph S. Myers]

On Wed, 17 Sep 2014, Alan Lawrence wrote:

> We've just noticed this patch causes an ICE in
> gcc.c-torture/execute/scal-to-vec1.c at -O3 when running with -fPIC on
> arm-none-linux-gnueabi and arm-none-linux-gnueabihf; test logs:

Which part causes the ICE?  The arm_hard_regno_mode_ok change relating to 
modes assigned to CC_REGNUM, the arm_regno_class change relating to 
PC_REGNUM, or something else?  Either of those would indicate something 
very strange going on in LRA (maybe something else needs to change 
somewhere as well to stop attempts to use CC_REGNUM or PC_REGNUM 
inappropriately?).

-- 
Joseph S. Myers
joseph@codesourcery.com