backport: re PR rtl-optimization/77919 (ICE converting DC to V2DF mode)

backport: re PR rtl-optimization/77919 (ICE converting DC to V2DF mode)

	Backported from mainline
	2016-10-29  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/77919
	* expr.c (expand_expr_real_1) <normal_inner_ref>: Only avoid forcing
	into memory if both modes are complex and their inner modes have the
	same precision.  If the two modes are different complex modes, convert
	each part separately and generate a new CONCAT.

	* g++.dg/torture/pr77919-2.C: New test.

From-SVN: r248619