Ensure the mode used to create split registers is suppported

gcc/
	PR target/78012
	* lra-constraints.c (split_reg): Check requested split mode
	is supported by the register.

From-SVN: r245601

gcc/ChangeLog

 2017-02-20  Matthew Fortune  <matthew.fortune@imgtec.com>
 
+	PR target/78012
+	* lra-constraints.c (split_reg): Check requested split mode
+	is supported by the register.
+
+2017-02-20  Matthew Fortune  <matthew.fortune@imgtec.com>
+
 	* lra-constraints.c (simplify_operand_subreg): Remove early
 	return false.
 

gcc/lra-constraints.c

@@ -5396,6 +5396,26 @@ split_reg (bool before_p, int original_regno, rtx_insn *insn,
 	    }
 	  return false;
 	}
+      /* Split_if_necessary can split hard registers used as part of a
+	 multi-register mode but splits each register individually.  The
+	 mode used for each independent register may not be supported
+	 so reject the split.  Splitting the wider mode should theoretically
+	 be possible but is not implemented.  */
+      if (! HARD_REGNO_MODE_OK (hard_regno, mode))
+	{
+	  if (lra_dump_file != NULL)
+	    {
+	      fprintf (lra_dump_file,
+		       "    Rejecting split of %d(%s): unsuitable mode %s\n",
+		       original_regno,
+		       reg_class_names[lra_get_allocno_class (original_regno)],
+		       GET_MODE_NAME (mode));
+	      fprintf
+		(lra_dump_file,
+		 "    ))))))))))))))))))))))))))))))))))))))))))))))))\n");
+	    }
+	  return false;
+	}
       new_reg = lra_create_new_reg (mode, original_reg, rclass, "split");
       reg_renumber[REGNO (new_reg)] = hard_regno;
     }