The following patch allows shrink-wrapping to succeed in the presence of
non-volatile CR save/restore. The movesi_from_cr define_insn used to
list all CRs as used, even though it's only the non-volatile values that
we are interested in saving/restoring. This prevented the prolog from
being moved past the early exit test because that compare was defining a
register used in the prolog (a volatile CR). The patch removes the
mentions of the volatile CRs and renames the functions involved so that
it's hopefully clear they are for prolog generation only.

Bootstrap/regtest on powerpc64le-linux with no new regressions. Ok for
trunk?

-Pat



2017-08-28  Pat Haugen  <pthaugen@us.ibm.com>

	* config/rs6000/rs6000.c (rs6000_emit_prolog_move_from_cr): Rename from
	rs6000_emit_move_from_cr and call renamed function.
	(rs6000_emit_prologue): Call renamed functions.
	* config/rs6000/rs6000.md (prolog_movesi_from_cr): Rename from
	prolog_movesi_from_cr, remove volatile CRs.


testsuite/ChangeLog:
2017-08-28  Pat Haugen  <pthaugen@us.ibm.com>

	* gcc.target/powerpc/cr_shrink-wrap.c: New.