2018-04-23  Eric Botcazou  <ebotcazou@adacore.com>

	PR middle-end/85496
	* expr.c (store_field): In the bitfield case, if the value comes from
	a function call and is returned in registers by means of a PARALLEL,
	do not change the mode of the temporary unless BLKmode and VOIDmode.

	* g++.dg/torture/pr85496.C: New test.

--- gcc/testsuite/g++.dg/torture/pr85496.C	(nonexistent)
+++ gcc/testsuite/g++.dg/torture/pr85496.C	(revision 259576)
@@ -0,0 +1,18 @@
+// PR middle-end/85496
+// Reported by Marek Polacek <mpolacek@gcc.gnu.org>
+
+template <typename> class complex;
+template <typename _Tp> complex<_Tp> operator*(complex<_Tp>, complex<_Tp>);
+template <> struct complex<float> { _Complex float _M_value; };
+class A {
+  complex<float> _f0, _f1;
+
+public:
+  complex<float> &m_fn1() { return _f1; }
+};
+complex<float> a;
+void cos() {
+  A b;
+  complex<float> c;
+  b.m_fn1() = c * a;
+}
--- gcc/expr.c	(revision 259575)
+++ gcc/expr.c	(revision 259576)
@@ -6893,8 +6893,9 @@
       if (GET_CODE (temp) == PARALLEL)
 	{
 	  HOST_WIDE_INT size = int_size_in_bytes (TREE_TYPE (exp));
-	  machine_mode temp_mode
-	    = smallest_mode_for_size (size * BITS_PER_UNIT, MODE_INT);
+	  machine_mode temp_mode = GET_MODE (temp);
+	  if (temp_mode == BLKmode || temp_mode == VOIDmode)
+	    temp_mode = smallest_mode_for_size (size * BITS_PER_UNIT, MODE_INT);
 	  rtx temp_target = gen_reg_rtx (temp_mode);
 	  emit_group_store (temp_target, temp, TREE_TYPE (exp), size);
 	  temp = temp_target;