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

[Richard Sandiford]

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.

Tested on aarch64-linux-gnu with SVE (with and without follow-on
patches) and x86_64-linux-gnu.  OK to install?

Richard


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

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

Index: gcc/gimplify.c
===================================================================
--- gcc/gimplify.c      2019-08-08 18:11:51.411313290 +0100
+++ gcc/gimplify.c      2019-09-18 07:52:22.799034800 +0100
@@ -1754,11 +1754,12 @@ gimplify_decl_expr (tree *stmt_p, gimple
       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;