diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 3d3707d44e8d..f580b4eb1969 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2018-06-19  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR target/86197
+	* config/rs6000/rs6000.md (rs6000_discover_homogeneous_aggregate): An
+	ieee128 argument takes up only one (vector) register, not two (floating
+	point) registers.
+
 2018-06-19  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gimplify.c (gimplify_init_constructor): Really never clear for an
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 31c5bcff50d3..11ef766a531a 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -10887,12 +10887,12 @@ rs6000_discover_homogeneous_aggregate (machine_mode mode, const_tree type,
 
       if (field_count > 0)
 	{
-	  int n_regs = (SCALAR_FLOAT_MODE_P (field_mode) ?
-			(GET_MODE_SIZE (field_mode) + 7) >> 3 : 1);
+	  int reg_size = ALTIVEC_OR_VSX_VECTOR_MODE (field_mode) ? 16 : 8;
+	  int field_size = ROUND_UP (GET_MODE_SIZE (field_mode), reg_size);
 
 	  /* The ELFv2 ABI allows homogeneous aggregates to occupy
 	     up to AGGR_ARG_NUM_REG registers.  */
-	  if (field_count * n_regs <= AGGR_ARG_NUM_REG)
+	  if (field_count * field_size <= AGGR_ARG_NUM_REG * reg_size)
 	    {
 	      if (elt_mode)
 		*elt_mode = field_mode;