Handle vectors that don't fit in an integer.

GCN vector sizes range between 64 and 512 bytes, none of which have
correspondingly sized integer modes.  This breaks a number of assumptions
throughout the compiler, but I don't really want to create modes just for this
purpose.

Instead, this patch fixes up the cases that I've found, so far, such that the
compiler tries something else, or fails to optimize, rather than just ICE.

2018-11-15  Andrew Stubbs  <ams@codesourcery.com>
            Kwok Cheung Yeung  <kcy@codesourcery.com>

	gcc/
	* tree-vect-stmts.c (vectorizable_store): Don't ICE when
	int_mode_for_size fails.
	(vectorizable_load): Likewise.

Co-Authored-By: Kwok Cheung Yeung <kcy@codesourcery.com>

From-SVN: r266190

gcc/ChangeLog

+2018-11-15  Andrew Stubbs  <ams@codesourcery.com>
+            Kwok Cheung Yeung  <kcy@codesourcery.com>
+
+	* tree-vect-stmts.c (vectorizable_store): Don't ICE when
+	int_mode_for_size fails.
+	(vectorizable_load): Likewise.
+
 2018-11-15  David Malcolm  <dmalcolm@redhat.com>
 
 	* doc/ux.texi (Group logically-related diagnostics): Move

gcc/tree-vect-stmts.c

@@ -6654,12 +6654,12 @@ vectorizable_store (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
 		     supported.  */
 		  unsigned lsize
 		    = group_size * GET_MODE_BITSIZE (elmode);
-		  elmode = int_mode_for_size (lsize, 0).require ();
 		  unsigned int lnunits = const_nunits / group_size;
 		  /* If we can't construct such a vector fall back to
 		     element extracts from the original vector type and
 		     element size stores.  */
-		  if (mode_for_vector (elmode, lnunits).exists (&vmode)
+		  if (int_mode_for_size (lsize, 0).exists (&elmode)
+		      && mode_for_vector (elmode, lnunits).exists (&vmode)
 		      && VECTOR_MODE_P (vmode)
 		      && targetm.vector_mode_supported_p (vmode)
 		      && (convert_optab_handler (vec_extract_optab,
@@ -7789,11 +7789,11 @@ vectorizable_load (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
 		     to a larger load.  */
 		  unsigned lsize
 		    = group_size * TYPE_PRECISION (TREE_TYPE (vectype));
-		  elmode = int_mode_for_size (lsize, 0).require ();
 		  unsigned int lnunits = const_nunits / group_size;
 		  /* If we can't construct such a vector fall back to
 		     element loads of the original vector type.  */
-		  if (mode_for_vector (elmode, lnunits).exists (&vmode)
+		  if (int_mode_for_size (lsize, 0).exists (&elmode)
+		      && mode_for_vector (elmode, lnunits).exists (&vmode)
 		      && VECTOR_MODE_P (vmode)
 		      && targetm.vector_mode_supported_p (vmode)
 		      && (convert_optab_handler (vec_init_optab, vmode, elmode)