Don't treat variable-length vectors as VLAs during gimplification

Source-level SVE vectors should be gimplified in the same way
as normal fixed-length vectors rather than as VLAs.

This is tested by later SVE patches.

2019-09-18  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* gimplify.c (gimplify_decl_expr): Use poly_int_tree_p instead
	of checking specifically for INTEGER_CST.

From-SVN: r275870

gcc/ChangeLog

 2019-09-18  Richard Sandiford  <richard.sandiford@arm.com>
 
+	* gimplify.c (gimplify_decl_expr): Use poly_int_tree_p instead
+	of checking specifically for INTEGER_CST.
+
+2019-09-18  Richard Sandiford  <richard.sandiford@arm.com>
+
 	* stor-layout.c (compute_record_mode): Operate on poly_uint64
 	sizes instead of uhwi sizes.
 

gcc/gimplify.c

@@ -1754,11 +1754,12 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
       tree init = DECL_INITIAL (decl);
       bool is_vla = false;
 
-      if (TREE_CODE (DECL_SIZE_UNIT (decl)) != INTEGER_CST
+      poly_uint64 size;
+      if (!poly_int_tree_p (DECL_SIZE_UNIT (decl), &size)
 	  || (!TREE_STATIC (decl)
 	      && flag_stack_check == GENERIC_STACK_CHECK
-	      && compare_tree_int (DECL_SIZE_UNIT (decl),
-				   STACK_CHECK_MAX_VAR_SIZE) > 0))
+	      && maybe_gt (size,
+			   (unsigned HOST_WIDE_INT) STACK_CHECK_MAX_VAR_SIZE)))
 	{
 	  gimplify_vla_decl (decl, seq_p);
 	  is_vla = true;