Fix unguarded uses of tree_to_uhwi

This patch uses tree_fits_uhwi_p to protect a previously unguarded
use of tree_to_uhwi.  Previously we would ICE for variable-sized types.

2017-09-20  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* tree.c (find_atomic_core_type): Check tree_fits_uhwi_p before
	calling tree_to_uhwi.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r253057

gcc/ChangeLog

@@ -2,6 +2,13 @@
 	    Alan Hayward  <alan.hayward@arm.com>
 	    David Sherwood  <david.sherwood@arm.com>
 
+	* tree.c (find_atomic_core_type): Check tree_fits_uhwi_p before
+	calling tree_to_uhwi.
+
+2017-09-21  Richard Sandiford  <richard.sandiford@linaro.org>
+	    Alan Hayward  <alan.hayward@arm.com>
+	    David Sherwood  <david.sherwood@arm.com>
+
 	* tree-ssa-ccp.c (get_value_for_expr): Use a positive test for
 	INTEGER_CST rather than a negative test for ADDR_EXPR.
 

gcc/tree.c

@@ -5821,11 +5821,10 @@ find_atomic_core_type (tree type)
   tree base_atomic_type;
 
   /* Only handle complete types.  */
-  if (TYPE_SIZE (type) == NULL_TREE)
+  if (!tree_fits_uhwi_p (TYPE_SIZE (type)))
     return NULL_TREE;
 
-  HOST_WIDE_INT type_size = tree_to_uhwi (TYPE_SIZE (type));
-  switch (type_size)
+  switch (tree_to_uhwi (TYPE_SIZE (type)))
     {
     case 8:
       base_atomic_type = atomicQI_type_node;