rs6000: Fix vector homogeneous aggregates (PR86197)

The existing code allows only 4 vectors worth of ieee128 homogeneous
aggregates, but it should be 8.  This happens because at one spot it
is mistakenly qualified as being passed in floating point registers.


	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.

From-SVN: r261738

gcc/ChangeLog

+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

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;