match.pd: Add patterns convering two conversions in a row from fold-const.c.

match.pd: Add patterns convering two conversions in a row from fold-const.c.

2014-11-09  Richard Biener  <rguenther@suse.de>

	* match.pd: Add patterns convering two conversions in a row
	from fold-const.c.
	* fold-const.c (fold_unary_loc): Remove them here.
	* tree-ssa-forwprop.c (combine_conversions): Likewise.
	* genmatch.c (dt_node::gen_kids): Check whether we may
	follow SSA use-def chains.

	* g++.dg/cpp0x/constexpr-reinterpret1.C: XFAIL.
	* gcc.dg/tree-ssa/pr21031.c: XFAIL.

From-SVN: r217260