re PR rtl-optimization/42216 (changes in scheduling regress 464.h264ref 20%)

re PR rtl-optimization/42216 (changes in scheduling regress 464.h264ref 20%)

	PR rtl-optimization/42216
	* regrename.c (create_new_chain): New function, broken out from...
	(scan_rtx_reg): ... here.  Call it.  Handle the case where we are
	appending a use to an empty chain.
	(build_def_use): Remove previous changes that convert OP_INOUT to
	OP_OUT operands; instead detect the case where an OP_INOUT operand
	uses a previously untracked register and create an empty chain for
	it.

From-SVN: r157511