re PR tree-optimization/29738 (Missed constant propagation into loops)

re PR tree-optimization/29738 (Missed constant propagation into loops)

	PR tree-optimization/29738
	* tree-ssa-ccp.c: Remove UNKNOWN_VAL from comments.
	(ccp_lattice_t): Remove UNKNOWN_VAL.
	(dump_lattice_value, ccp_lattice_meet, ccp_visit_phi_node):
	Do not handle UNKNOWN_VAL.
	(get_default_value): Set initial value of virtual operands to
	VARYING.
	(get_value): Always use get_default_value on uninitialized
	operands.
	(set_value_varying, surely_varying_stmt_p): New functions.
	(set_lattice_value): Do not pass argument to get_value.
	Do not handle UNKNOWN_VAL.
	(likely_value): Follow the semantics described in the comment.
	(ccp_initialize): Use surely_varying_stmt_p.  Do not mark
	phi nodes DONT_SIMULATE_AGAIN.
	(ccp_fold): Do not pass argument to get_value.
	(fold_const_aggregate_ref, visit_assignment): Ditto.  Do not
	handle UNKNOWN_VAL.

	* gcc.dg/tree-ssa/ssa-ccp-14.c: New test.
	* gcc.dg/tree-ssa/ssa-ccp-15.c: New test.

From-SVN: r118602