regrename speedup

[Eric Botcazou]

> Could install now, or could wait for the clean results (without this and
> the previous regrename patch) which should take another 24 hours or so.

At your convenience, we aren't in a hurry.  Patch is OK if you update 

	  /* Simplify the code below by rewriting things to reflect
	     matching constraints.  Also promote OP_OUT to OP_INOUT
	     in predicated instructions.  */

in build_def_use, something like "... but only for register operands that are 
already tracked, so that we can create a chain when the first SET makes a 
register live".

-- 
Eric Botcazou