Use ssizetype selectors for autovectorised VEC_PERM_EXPRs

The previous patches mean that there's no reason that constant
VEC_PERM_EXPRs need to have the same shape as the data inputs.
This patch makes the autovectoriser use sizetype elements instead,
so that indices don't get truncated for large or variable-length
vectors.

2018-01-02  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* tree-cfg.c (verify_gimple_assign_ternary): Allow the size of
	the selector elements to be different from the data elements
	if the selector is a VECTOR_CST.
	* tree-vect-stmts.c (vect_gen_perm_mask_any): Use a vector of
	ssizetype for the selector.

From-SVN: r256100

gcc/ChangeLog

 2018-01-02  Richard Sandiford  <richard.sandiford@linaro.org>
 
+	* tree-cfg.c (verify_gimple_assign_ternary): Allow the size of
+	the selector elements to be different from the data elements
+	if the selector is a VECTOR_CST.
+	* tree-vect-stmts.c (vect_gen_perm_mask_any): Use a vector of
+	ssizetype for the selector.
+
+2018-01-02  Richard Sandiford  <richard.sandiford@linaro.org>
+
 	* optabs.c (shift_amt_for_vec_perm_mask): Try using series_p
 	before testing each element individually.
 	* tree-vect-generic.c (lower_vec_perm): Likewise.

gcc/tree-cfg.c

@@ -4428,8 +4428,11 @@ verify_gimple_assign_ternary (gassign *stmt)
 	}
 
       if (TREE_CODE (TREE_TYPE (rhs3_type)) != INTEGER_TYPE
-	  || GET_MODE_BITSIZE (SCALAR_INT_TYPE_MODE (TREE_TYPE (rhs3_type)))
-	     != GET_MODE_BITSIZE (SCALAR_TYPE_MODE (TREE_TYPE (rhs1_type))))
+	  || (TREE_CODE (rhs3) != VECTOR_CST
+	      && (GET_MODE_BITSIZE (SCALAR_INT_TYPE_MODE
+				    (TREE_TYPE (rhs3_type)))
+		  != GET_MODE_BITSIZE (SCALAR_TYPE_MODE
+				       (TREE_TYPE (rhs1_type))))))
 	{
 	  error ("invalid mask type in vector permute expression");
 	  debug_generic_expr (lhs_type);

gcc/tree-vect-stmts.c

@@ -6535,11 +6535,12 @@ vectorizable_store (gimple *stmt, gimple_stmt_iterator *gsi, gimple **vec_stmt,
 tree
 vect_gen_perm_mask_any (tree vectype, const vec_perm_indices &sel)
 {
-  tree mask_elt_type, mask_type;
+  tree mask_type;
+
+  unsigned int nunits = sel.length ();
+  gcc_assert (nunits == TYPE_VECTOR_SUBPARTS (vectype));
 
-  mask_elt_type = lang_hooks.types.type_for_mode
-    (int_mode_for_mode (TYPE_MODE (TREE_TYPE (vectype))).require (), 1);
-  mask_type = get_vectype_for_scalar_type (mask_elt_type);
+  mask_type = build_vector_type (ssizetype, nunits);
   return vec_perm_indices_to_tree (mask_type, sel);
 }