re PR debug/48204 (ICE: in decimal_to_decnumber, at dfp.c:115 with -fno-tree-ccp -fno-tree-dominator-opts -fno-tree-fre -g)

	PR debug/48204
	* simplify-rtx.c (simplify_const_unary_operation): Call
	real_convert when changing mode class with FLOAT_EXTEND.

	* gcc.dg/dfp/pr48204.c: New test.

From-SVN: r171423