Use consistent compatibility checks in vectorizable_shift

The validation phase of vectorizable_shift used TYPE_MODE to check
whether the shift amount vector was compatible with the shifted vector:

      if ((op1_vectype == NULL_TREE
	   || TYPE_MODE (op1_vectype) != TYPE_MODE (vectype))
 	  && (!slp_node
 	      || SLP_TREE_DEF_TYPE
 		   (SLP_TREE_CHILDREN (slp_node)[1]) != vect_constant_def))

But the generation phase was stricter and required the element types to
be equivalent:

		   && !useless_type_conversion_p (TREE_TYPE (vectype),
						  TREE_TYPE (op1)))

This difference led to an ICE with a later patch.

The first condition seems a bit too lax given that the function
supports vect_worthwhile_without_simd_p, where two different vector
types could have the same integer mode.  But it seems too strict
to reject signed shifts by unsigned amounts or unsigned shifts by
signed amounts; verify_gimple_assign_binary is happy with those.

This patch therefore goes for a middle ground of checking both TYPE_MODE
and TYPE_VECTOR_SUBPARTS, using the same condition in both places.

2019-11-14  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-vect-stmts.c (vectorizable_shift): Check the number
	of vector elements as well as the type mode when deciding
	whether an op1_vectype is compatible.  Reuse the result of
	this check when generating vector statements.

From-SVN: r278235

gcc/ChangeLog

 2019-11-14  Richard Sandiford  <richard.sandiford@arm.com>
 
+	* tree-vect-stmts.c (vectorizable_shift): Check the number
+	of vector elements as well as the type mode when deciding
+	whether an op1_vectype is compatible.  Reuse the result of
+	this check when generating vector statements.
+
+2019-11-14  Richard Sandiford  <richard.sandiford@arm.com>
+
 	* tree-vect-stmts.c (get_vectype_for_scalar_type_and_size): If
 	targetm.vectorize.preferred_simd_mode returns an integer mode,
 	use mode_for_vector to decide what the vector type's mode

gcc/tree-vect-stmts.c

@@ -5544,6 +5544,7 @@ vectorizable_shift (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
   bool scalar_shift_arg = true;
   bb_vec_info bb_vinfo = STMT_VINFO_BB_VINFO (stmt_info);
   vec_info *vinfo = stmt_info->vinfo;
+  bool incompatible_op1_vectype_p = false;
 
   if (!STMT_VINFO_RELEVANT_P (stmt_info) && !bb_vinfo)
     return false;
@@ -5688,8 +5689,12 @@ vectorizable_shift (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
 
       if (!op1_vectype)
 	op1_vectype = get_same_sized_vectype (TREE_TYPE (op1), vectype_out);
-      if ((op1_vectype == NULL_TREE
-	   || TYPE_MODE (op1_vectype) != TYPE_MODE (vectype))
+      incompatible_op1_vectype_p
+	= (op1_vectype == NULL_TREE
+	   || maybe_ne (TYPE_VECTOR_SUBPARTS (op1_vectype),
+			TYPE_VECTOR_SUBPARTS (vectype))
+	   || TYPE_MODE (op1_vectype) != TYPE_MODE (vectype));
+      if (incompatible_op1_vectype_p
 	  && (!slp_node
 	      || SLP_TREE_DEF_TYPE
 		   (SLP_TREE_CHILDREN (slp_node)[1]) != vect_constant_def))
@@ -5835,9 +5840,7 @@ vectorizable_shift (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
                     }
                 }
             }
-	  else if (slp_node
-		   && !useless_type_conversion_p (TREE_TYPE (vectype),
-						  TREE_TYPE (op1)))
+	  else if (slp_node && incompatible_op1_vectype_p)
 	    {
 	      if (was_scalar_shift_arg)
 		{