[PATCH] Remove unnecessary VLA restriction in copy_forbidden (PR middle-end/42874)

[Jakub Jelinek]

Hi!

As mentioned in the PR, this check has been added many years ago when
tree-inline.c didn't handle VL type remapping properly.
GCC until 4.4 has been ignoring this restriction for always_inline
functions, and inlining them successfully, and OpenMP code remaps such types
for years as well.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2010-01-27  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/42874
	* tree-inline.c (cannot_copy_type_1): Removed.
	(copy_forbidden): Don't forbid copying of functions containing
	records/unions with variable length fields.

	* gcc.dg/vla-22.c: New test.

--- gcc/tree-inline.c.jj	2010-01-20 13:58:18.000000000 +0100
+++ gcc/tree-inline.c	2010-01-27 09:52:55.000000000 +0100
@@ -2730,39 +2730,6 @@ has_label_address_in_static_1 (tree *nod
   return NULL_TREE;
 }
 
-/* Callback through walk_tree.  Determine if we've got an aggregate
-   type that we can't support; return non-null if so.  */
-
-static tree
-cannot_copy_type_1 (tree *nodep, int *walk_subtrees ATTRIBUTE_UNUSED,
-                    void *data ATTRIBUTE_UNUSED)
-{
-  tree t, node = *nodep;
-
-  if (TREE_CODE (node) == RECORD_TYPE || TREE_CODE (node) == UNION_TYPE)
-    {
-      /* We cannot inline a function of the form
-
-	   void F (int i) { struct S { int ar[i]; } s; }
-
-	 Attempting to do so produces a catch-22.
-	 If walk_tree examines the TYPE_FIELDS chain of RECORD_TYPE/
-	 UNION_TYPE nodes, then it goes into infinite recursion on a
-	 structure containing a pointer to its own type.  If it doesn't,
-	 then the type node for S doesn't get adjusted properly when
-	 F is inlined.
-
-	 ??? This is likely no longer true, but it's too late in the 4.0
-	 cycle to try to find out.  This should be checked for 4.1.  */
-      for (t = TYPE_FIELDS (node); t; t = TREE_CHAIN (t))
-	if (variably_modified_type_p (TREE_TYPE (t), NULL))
-	  return node;
-    }
-
-  return NULL_TREE;
-}
-
-
 /* Determine if the function can be copied.  If so return NULL.  If
    not return a string describng the reason for failure.  */
 
@@ -2805,16 +2772,6 @@ copy_forbidden (struct function *fun, tr
 		      "address of local label in a static variable");
 	  goto fail;
 	}
-
-      if (!TREE_STATIC (decl) && !DECL_EXTERNAL (decl)
-	  && variably_modified_type_p (TREE_TYPE (decl), NULL)
-	  && walk_tree_without_duplicates (&TREE_TYPE (decl),
-					   cannot_copy_type_1, NULL))
-	{
-	  reason = G_("function %q+F can never be copied "
-		      "because it uses variable sized variables");
-	  goto fail;
-	}
     }
 
  fail:
--- gcc/testsuite/gcc.dg/vla-22.c.jj	2010-01-27 10:00:54.000000000 +0100
+++ gcc/testsuite/gcc.dg/vla-22.c	2010-01-27 10:03:46.000000000 +0100
@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+extern void bar (int *);
+
+static inline __attribute__((always_inline))
+int
+foo (int i)
+{
+  struct S {
+    int ar[1][i];
+  } s;
+
+  s.ar[0][0] = 0;
+  bar (&s.ar[0][0]);
+}
+
+void
+baz (int i)
+{
+  foo (i + 2);
+}

	Jakub