[PATCH, PR 61540] Do not ICE on impossible devirtualization

[Martin Jambor <mjambor at suse dot cz>]

Hi,

I was quite surprised we still had an assert checking that the target
of a virtual call derived by ipa-cp is among possible ones derived by
ipa-devirt.  This is not true for various down-casts and I managed to
trigger it in PR 61540 (where the testcase purposefully invokes
undefined behavior but we should not ICE).

Fixed thusly.  Bootstrapped and tested on x86_64-linux.  OK for trunk
and the 4.9 branch?

Thanks,

Martin


2014-06-17  Martin Jambor  <mjambor@suse.cz>

	PR ipa/61540
	* ipa-prop.c (impossible_devirt_target): New function.
	(try_make_edge_direct_virtual_call): Use it, also instead of
	asserting.

testsuite/
	* g++.dg/ipa/pr61540.C: New test.

diff --git a/gcc/ipa-prop.c b/gcc/ipa-prop.c
index b67deed..f5ec67a 100644
--- a/gcc/ipa-prop.c
+++ b/gcc/ipa-prop.c
@@ -2912,6 +2912,29 @@ try_make_edge_direct_simple_call (struct cgraph_edge *ie,
   return cs;
 }
 
+/* Return the target to be used in cases of impossible devirtualization.  IE
+   and target (the latter can be NULL) are dumped when dumping is enabled.  */
+
+static tree
+impossible_devirt_target (struct cgraph_edge *ie, tree target)
+{
+  if (dump_file)
+    {
+      if (target)
+	fprintf (dump_file,
+		 "Type inconsident devirtualization: %s/%i->%s\n",
+		 ie->caller->name (), ie->caller->order,
+		 IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (target)));
+      else
+	fprintf (dump_file,
+		 "No devirtualization target in %s/%i\n",
+		 ie->caller->name (), ie->caller->order);
+    }
+  tree new_target = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+  cgraph_get_create_node (new_target);
+  return new_target;
+}
+
 /* Try to find a destination for indirect edge IE that corresponds to a virtual
    call based on a formal parameter which is described by jump function JFUNC
    and if it can be determined, make it direct and return the direct edge.
@@ -2946,15 +2969,7 @@ try_make_edge_direct_virtual_call (struct cgraph_edge *ie,
 		   && DECL_FUNCTION_CODE (target) == BUILT_IN_UNREACHABLE)
 		  || !possible_polymorphic_call_target_p
 		       (ie, cgraph_get_node (target)))
-		{
-		  if (dump_file)
-		    fprintf (dump_file,
-			     "Type inconsident devirtualization: %s/%i->%s\n",
-			     ie->caller->name (), ie->caller->order,
-			     IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (target)));
-		  target = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
-		  cgraph_get_create_node (target);
-		}
+		target = impossible_devirt_target (ie, target);
 	      return ipa_make_edge_direct_to_target (ie, target);
 	    }
 	}
@@ -2984,10 +2999,7 @@ try_make_edge_direct_virtual_call (struct cgraph_edge *ie,
       if (targets.length () == 1)
 	target = targets[0]->decl;
       else
-	{
-          target = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
-	  cgraph_get_create_node (target);
-	}
+	target = impossible_devirt_target (ie, NULL_TREE);
     }
   else
     {
@@ -3002,10 +3014,8 @@ try_make_edge_direct_virtual_call (struct cgraph_edge *ie,
 
   if (target)
     {
-#ifdef ENABLE_CHECKING
-      gcc_assert (possible_polymorphic_call_target_p
-	 (ie, cgraph_get_node (target)));
-#endif
+      if (!possible_polymorphic_call_target_p (ie, cgraph_get_node (target)))
+	return ipa_make_edge_direct_to_target (ie, target);
       return ipa_make_edge_direct_to_target (ie, target);
     }
   else
diff --git a/gcc/testsuite/g++.dg/ipa/pr61540.C b/gcc/testsuite/g++.dg/ipa/pr61540.C
new file mode 100644
index 0000000..d298964
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ipa/pr61540.C
@@ -0,0 +1,41 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fno-early-inlining -fdump-ipa-cp" } */
+
+struct data {
+  data(int) {}
+};
+
+struct top {
+  virtual int topf() {}
+};
+
+struct intermediate: top {
+    int topf() /* override */ { return 0; }
+};
+
+struct child1: top {
+    void childf()
+    {
+        data d(topf());
+    }
+};
+
+struct child2: intermediate {};
+
+void test(top& t)
+{
+    child1& c = static_cast<child1&>(t);
+    c.childf();
+    child2 d;
+    test(d);
+}
+
+int main (int argc, char **argv)
+{
+  child1 c;
+  test (c);
+  return 0;
+}
+
+/* { dg-final { scan-ipa-dump "Type inconsident devirtualization" "cp" } } */
+/* { dg-final { cleanup-ipa-dump "cp" } } */