[PATCH, PR 45934 3/5] Identify the new dynamic type after change

[Martin Jambor <mjambor at suse dot cz>]

This patch adds code attempting to identify of the new dynamic type
after it has been changed, which has been missing in the previous
patch.  All the details are in the previous email.

Just for the record, this has been also bootstrapped and tested
(without the last patch applied) on x86-64-linux and has passed make
check-c++ on i686.

Thanks,

Martin


2010-12-09  Martin Jambor  <mjambor@suse.cz>

	* ipa-prop.c (type_change_info): New fields object, known_current_type
	and multiple_types_encountered.
	(extr_type_from_vtbl_ptr_store): New function.
	(check_stmt_for_type_change): Use it, set multiple_types_encountered if
        the result is different from the prvious one.
	(detect_type_change): Set up new fields in tci, build knonw type
	jump functions if the new type chan be identified.

	* testsuite/g++.dg/ipa/devirt-c-1.C: Add dump scans.
	* testsuite/g++.dg/ipa/devirt-c-2.C: Likewise.
	* testsuite/g++.dg/ipa/devirt-c-3.C: Likewise.
	* testsuite/g++.dg/ipa/devirt-c-4.C: Likewise.
	* testsuite/g++.dg/ipa/devirt-c-8.C: New test.


Index: icln/gcc/ipa-prop.c
===================================================================
--- icln.orig/gcc/ipa-prop.c
+++ icln/gcc/ipa-prop.c
@@ -355,8 +355,17 @@ ipa_print_all_jump_functions (FILE *f)
 
 struct type_change_info
 {
+  /* The declaration or SSA_NAME pointer of the base that we are checking for
+     type change.  */
+  tree object;
+  /* If we actually can tell the type that the object has changed to, it is
+     stored in this field.  Otherwise it remains NULL_TREE.  */
+  tree known_current_type;
   /* Set to true if dynamic type change has been detected.  */
   bool type_maybe_changed;
+  /* Set to true if multiple types have been encountered.  known_current_type
+     must be disregarded in that case.  */
+  bool multiple_types_encountered;
 };
 
 /* Return true if STMT can modify a virtual method table pointer.
@@ -415,6 +424,49 @@ stmt_may_be_vtbl_ptr_store (gimple stmt)
   return true;
 }
 
+/* If STMT can be proved to be an assignment to the virtual method table
+   pointer of ANALYZED_OBJ and the type associated witht the new table
+   identified, return the type.  Otherwise return NULL_TREE.  */
+
+static tree
+extr_type_from_vtbl_ptr_store (gimple stmt, tree analyzed_obj)
+{
+  tree lhs, t, obj;
+
+  if (!is_gimple_assign (stmt))
+    return NULL_TREE;
+
+  lhs = gimple_assign_lhs (stmt);
+
+  if (TREE_CODE (lhs) != COMPONENT_REF)
+    return NULL_TREE;
+   obj = lhs;
+
+   if (!DECL_VIRTUAL_P (TREE_OPERAND (lhs, 1)))
+     return NULL_TREE;
+
+   do
+     {
+       obj = TREE_OPERAND (obj, 0);
+     }
+   while (TREE_CODE (obj) == COMPONENT_REF);
+   if (TREE_CODE (obj) == MEM_REF)
+     obj = TREE_OPERAND (obj, 0);
+   if (TREE_CODE (obj) == ADDR_EXPR)
+     obj = TREE_OPERAND (obj, 0);
+   if (obj != analyzed_obj)
+     return NULL_TREE;
+
+   t = gimple_assign_rhs1 (stmt);
+   if (TREE_CODE (t) != ADDR_EXPR)
+     return NULL_TREE;
+   t = get_base_address (TREE_OPERAND (t, 0));
+   if (!t || TREE_CODE (t) != VAR_DECL || !DECL_VIRTUAL_P (t))
+     return NULL_TREE;
+
+   return DECL_CONTEXT (t);
+}
+
 /* Callbeck of walk_aliased_vdefs and a helper function for
    detect_type_change to check whether a particular statement may modify
    the virtual table pointer, and if possible also determine the new type of
@@ -429,6 +481,12 @@ check_stmt_for_type_change (ao_ref *ao A
 
   if (stmt_may_be_vtbl_ptr_store (stmt))
     {
+      tree type;
+      type = extr_type_from_vtbl_ptr_store (stmt, tci->object);
+      if (tci->type_maybe_changed
+	  && type != tci->known_current_type)
+	tci->multiple_types_encountered = true;
+      tci->known_current_type = type;
       tci->type_maybe_changed = true;
       return true;
     }
@@ -448,6 +506,7 @@ detect_type_change (tree arg, tree base,
 		    struct ipa_jump_func *jfunc, HOST_WIDE_INT offset)
 {
   struct type_change_info tci;
+  tree type;
   ao_ref ao;
 
   gcc_checking_assert (DECL_P (arg)
@@ -458,8 +517,6 @@ detect_type_change (tree arg, tree base,
   if (!gimple_vuse (call))
     return false;
 
-  tci.type_maybe_changed = false;
-
   ao.ref = arg;
   ao.base = base;
   ao.offset = offset;
@@ -468,12 +525,38 @@ detect_type_change (tree arg, tree base,
   ao.ref_alias_set = -1;
   ao.base_alias_set = -1;
 
+  type = TREE_TYPE (arg);
+  while (handled_component_p (arg))
+    arg = TREE_OPERAND (arg, 0);
+  if (TREE_CODE (arg) == MEM_REF)
+    arg = TREE_OPERAND (arg, 0);
+  if (TREE_CODE (arg) == ADDR_EXPR)
+    arg = TREE_OPERAND (arg, 0);
+  tci.object = arg;
+  tci.known_current_type = NULL_TREE;
+  tci.type_maybe_changed = false;
+  tci.multiple_types_encountered = false;
+
   walk_aliased_vdefs (&ao, gimple_vuse (call), check_stmt_for_type_change,
 		      &tci, NULL);
   if (!tci.type_maybe_changed)
     return false;
 
-  jfunc->type = IPA_JF_UNKNOWN;
+ if (!tci.known_current_type || tci.multiple_types_encountered)
+   jfunc->type = IPA_JF_UNKNOWN;
+ else
+   {
+     tree new_binfo = get_binfo_at_offset (TYPE_BINFO (tci.known_current_type),
+					   offset, type);
+     if (new_binfo)
+	{
+	  jfunc->type = IPA_JF_KNOWN_TYPE;
+	  jfunc->value.base_binfo = new_binfo;
+	}
+     else
+       jfunc->type = IPA_JF_UNKNOWN;
+   }
+
   return true;
 }
 
Index: icln/gcc/testsuite/g++.dg/ipa/devirt-c-1.C
===================================================================
--- icln.orig/gcc/testsuite/g++.dg/ipa/devirt-c-1.C
+++ icln/gcc/testsuite/g++.dg/ipa/devirt-c-1.C
@@ -1,7 +1,7 @@
 /* Verify that ipa-cp correctly detects the dynamic type of an object
    under construction when doing devirtualization.  */
 /* { dg-do run } */
-/* { dg-options "-O3 -fno-early-inlining -fno-inline"  } */
+/* { dg-options "-O3 -fno-early-inlining -fno-inline -fdump-ipa-cp -fdump-tree-optimized"  } */
 
 extern "C" void abort (void);
 
@@ -69,3 +69,8 @@ int main (int argc, char *argv[])
     bah ();
   return 0;
 }
+
+/* { dg-final { scan-ipa-dump "Discovered a virtual call to a known target.*A::foo"  "cp"  } } */
+/* { dg-final { scan-tree-dump-times "OBJ_TYPE_REF" 0 "optimized"} } */
+/* { dg-final { cleanup-ipa-dump "cp" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: icln/gcc/testsuite/g++.dg/ipa/devirt-c-2.C
===================================================================
--- icln.orig/gcc/testsuite/g++.dg/ipa/devirt-c-2.C
+++ icln/gcc/testsuite/g++.dg/ipa/devirt-c-2.C
@@ -1,7 +1,7 @@
 /* Verify that ipa-cp correctly detects the dynamic type of an object
    under construction when doing devirtualization.  */
 /* { dg-do run } */
-/* { dg-options "-O3 -fno-early-inlining -fno-inline"  } */
+/* { dg-options "-O3 -fno-early-inlining -fno-inline -fdump-ipa-cp -fdump-tree-optimized"  } */
 
 extern "C" void abort (void);
 
@@ -77,3 +77,8 @@ int main (int argc, char *argv[])
     bah ();
   return 0;
 }
+
+/* { dg-final { scan-ipa-dump "Discovered a virtual call to a known target.*A::foo"  "cp"  } } */
+/* { dg-final { scan-tree-dump-times "OBJ_TYPE_REF" 0 "optimized"} } */
+/* { dg-final { cleanup-ipa-dump "cp" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: icln/gcc/testsuite/g++.dg/ipa/devirt-c-3.C
===================================================================
--- icln.orig/gcc/testsuite/g++.dg/ipa/devirt-c-3.C
+++ icln/gcc/testsuite/g++.dg/ipa/devirt-c-3.C
@@ -1,7 +1,7 @@
 /* Verify that ipa-cp correctly detects the dynamic type of an object
    under construction when doing devirtualization.  */
 /* { dg-do run } */
-/* { dg-options "-O3 -fno-inline"  } */
+/* { dg-options "-O3 -fno-inline -fdump-ipa-cp -fdump-tree-optimized"  } */
 
 extern "C" void abort (void);
 
@@ -78,3 +78,8 @@ int main (int argc, char *argv[])
     bah ();
   return 0;
 }
+
+/* { dg-final { scan-ipa-dump "Discovered a virtual call to a known target.*A::foo"  "cp"  } } */
+/* { dg-final { scan-tree-dump-times "OBJ_TYPE_REF" 0 "optimized"} } */
+/* { dg-final { cleanup-ipa-dump "cp" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: icln/gcc/testsuite/g++.dg/ipa/devirt-c-4.C
===================================================================
--- icln.orig/gcc/testsuite/g++.dg/ipa/devirt-c-4.C
+++ icln/gcc/testsuite/g++.dg/ipa/devirt-c-4.C
@@ -1,7 +1,7 @@
 /* Verify that ipa-cp correctly detects the dynamic type of an object
    under construction when doing devirtualization.  */
 /* { dg-do run } */
-/* { dg-options "-O3 -fno-inline"  } */
+/* { dg-options "-O3 -fno-inline -fdump-tree-optimized"  } */
 
 extern "C" void abort (void);
 
@@ -108,3 +108,6 @@ int main (int argc, char *argv[])
     bah ();
   return 0;
 }
+
+/* { dg-final { scan-tree-dump-times "OBJ_TYPE_REF" 0 "optimized"} } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: icln/gcc/tree.h
===================================================================
--- icln.orig/gcc/tree.h
+++ icln/gcc/tree.h
@@ -2565,7 +2565,9 @@ struct function;
     nodes, this points to either the FUNCTION_DECL for the containing
     function, the RECORD_TYPE or UNION_TYPE for the containing type, or
     NULL_TREE or a TRANSLATION_UNIT_DECL if the given decl has "file
-    scope".  */
+    scope".  In particular, for VAR_DECLs which are virtual table pointers
+    (they have DECL_VIRTUAL set), we use DECL_CONTEXT to determine the type
+    they belong to.  */
 #define DECL_CONTEXT(NODE) (DECL_MINIMAL_CHECK (NODE)->decl_minimal.context)
 #define DECL_FIELD_CONTEXT(NODE) \
   (FIELD_DECL_CHECK (NODE)->decl_minimal.context)
Index: icln/gcc/testsuite/g++.dg/ipa/devirt-c-8.C
===================================================================
--- /dev/null
+++ icln/gcc/testsuite/g++.dg/ipa/devirt-c-8.C
@@ -0,0 +1,87 @@
+/* Verify that ipa-cp will not get confused by placement new constructing an
+   object within another one when looking for dynamic type change .  */
+/* { dg-do run } */
+/* { dg-options "-O3"  } */
+
+extern "C" void abort (void);
+namespace std {
+  typedef __SIZE_TYPE__ size_t;
+}
+inline void* __attribute__ ((always_inline))
+operator new(std::size_t, void* __p) throw()
+{
+  return __p;
+}
+
+class A
+{
+public:
+  char data[256];
+  A();
+  virtual int foo (int i);
+};
+
+class B : public A
+{
+public:
+  virtual int foo (int i);
+};
+
+class C
+{
+public:
+  C();
+  virtual double foo (double i);
+};
+
+int A::foo (int i)
+{
+  return i + 1;
+}
+
+int B::foo (int i)
+{
+  return i + 2;
+}
+
+double C::foo (double i)
+{
+  return i + 3.5;
+}
+
+static int __attribute__ ((noinline)) middleman (class A *obj, int i)
+{
+  return obj->foo (i);
+}
+
+int __attribute__ ((noinline,noclone)) get_input(void)
+{
+  return 1;
+}
+
+__attribute__ ((always_inline)) C::C ()
+{
+}
+
+A::A ()
+{
+}
+
+static  __attribute__ ((noinline)) void bah ()
+{
+  class B b;
+
+  C *c = new ((void *) &b.data) C;
+
+  if (middleman (&b, get_input ()) != 3)
+    abort ();
+}
+
+int main (int argc, char *argv[])
+{
+  int i;
+
+  for (i = 0; i < 10; i++)
+    bah ();
+  return 0;
+}