Handle poly_int vector sizes in get_vec_alignment_for_array_type

[Richard Sandiford]

get_vectype_for_scalar_type returns a variable-length vector type
for SVE, whereas get_vec_alignment_for_array_type assumed it would
always be an INTEGER_CST.

This is needed to build libstdc++-v3/src/closures.cc for SVE
(and probably many other places besides -- this was just the
first hit).

Tested on aarch64-linux-gnu, x86_64-linux-gnu and powerpc64le-linux-gnu.
Also tested by comparing the before-and-after assembly output for at
least one target per CPU directory.  OK to install?

Thanks,
Richard


2018-01-12  Richard Sandiford  <richard.sandif...@linaro.org>

gcc/
        * tree-vectorizer.c (get_vec_alignment_for_array_type): Handle
        polynomial type sizes.

Index: gcc/tree-vectorizer.c
===================================================================
--- gcc/tree-vectorizer.c       2018-01-10 08:43:40.053367209 +0000
+++ gcc/tree-vectorizer.c       2018-01-12 12:56:30.428743723 +0000
@@ -1015,12 +1015,13 @@ static unsigned get_vec_alignment_for_ty
 get_vec_alignment_for_array_type (tree type) 
 {
   gcc_assert (TREE_CODE (type) == ARRAY_TYPE);
+  poly_uint64 array_size, vector_size;
 
   tree vectype = get_vectype_for_scalar_type (strip_array_types (type));
   if (!vectype
-      || !TYPE_SIZE (type)
-      || TREE_CODE (TYPE_SIZE (type)) != INTEGER_CST
-      || tree_int_cst_lt (TYPE_SIZE (type), TYPE_SIZE (vectype)))
+      || !poly_int_tree_p (TYPE_SIZE (type), &array_size)
+      || !poly_int_tree_p (TYPE_SIZE (vectype), &vector_size)
+      || maybe_lt (array_size, vector_size))
     return 0;
 
   return TYPE_ALIGN (vectype);