[PATCH] Fix PR92088

[Richard Biener <rguenther at suse dot de>]

The following works around a middle-end limitation not being able
to deal with by value-passing of VLAs transparently during inlining
(but only DECL_BY_REFERENCE is handled) in the C frontend by marking
said functions as not inlinable.  This avoids ICEs later.

Bootstrapped and tested on x86_64-unknown-linux-gnu.

OK for trunk?

Thanks,
Richard.

2019-11-09  Richard Biener  <rguenther@suse.de>

	PR c/92088
	c/
	* c-decl.c (grokdeclarator): Prevent inlining of nested
	function with VLA arguments.

	* builtins.c (compute_objsize): Deal with VLAs.

	* gcc.dg/torture/pr92088-1.c: New testcase.
	* gcc.dg/torture/pr92088-2.c: Likewise.

Index: gcc/builtins.c
===================================================================
--- gcc/builtins.c	(revision 277906)
+++ gcc/builtins.c	(working copy)
@@ -3708,7 +3708,8 @@ compute_objsize (tree dest, int ostype,
   if (DECL_P (ref))
     {
       *pdecl = ref;
-      return DECL_SIZE_UNIT (ref);
+      if (tree size = DECL_SIZE_UNIT (ref))
+	return TREE_CODE (size) == INTEGER_CST ? size : NULL_TREE;
     }
 
   tree type = TREE_TYPE (dest);
Index: gcc/c/c-decl.c
===================================================================
--- gcc/c/c-decl.c	(revision 277906)
+++ gcc/c/c-decl.c	(working copy)
@@ -7304,6 +7304,23 @@ grokdeclarator (const struct c_declarato
 	      	    "no linkage");
       }
 
+    /* For nested functions disqualify ones taking VLAs by value
+       from inlining since the middle-end cannot deal with this.
+       ???  We should arrange for those to be passed by reference
+       with emitting the copy on the caller side in the frontend.  */
+    if (storage_class == csc_none
+	&& TREE_CODE (type) == FUNCTION_TYPE)
+      for (tree al = TYPE_ARG_TYPES (type); al; al = TREE_CHAIN (al))
+	{
+	  tree arg = TREE_VALUE (al);
+	  if (arg != error_mark_node
+	      && C_TYPE_VARIABLE_SIZE (TREE_VALUE (al)))
+	    {
+	      DECL_UNINLINABLE (decl) = 1;
+	      break;
+	    }
+	}
+
     /* Record `register' declaration for warnings on &
        and in case doing stupid register allocation.  */
 
Index: gcc/testsuite/gcc.dg/torture/pr92088-1.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr92088-1.c	(revision 0)
+++ gcc/testsuite/gcc.dg/torture/pr92088-1.c	(working copy)
@@ -0,0 +1,22 @@
+/* { dg-do run } */
+
+int __attribute__((noipa))
+g (char *p)
+{
+  return p[9];
+}
+int main (int argc, char **argv)
+{
+  struct S {
+    char toto[argc + 16];
+  };
+  int f (struct S arg) {
+      __builtin_strcpy(arg.toto, "helloworld");
+      return g (arg.toto);
+  }
+  struct S bob;
+  __builtin_strcpy(bob.toto, "coucoucoucou");
+  if (f(bob) != 'd' || __builtin_strcmp (bob.toto, "coucoucoucou"))
+    __builtin_abort ();
+  return 0;
+}
Index: gcc/testsuite/gcc.dg/torture/pr92088-2.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr92088-2.c	(revision 0)
+++ gcc/testsuite/gcc.dg/torture/pr92088-2.c	(working copy)
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+
+void foo(int n)
+{
+  struct X { int a[n]; } y;
+
+  struct X baz (struct X x)
+    {
+      x.a[0] = 1;
+      return x;
+    }
+
+  y.a[0] = 0;
+  y = baz(y);
+  if (y.a[0] != 1)
+    __builtin_abort ();
+}