[RFC PATCH 2/4] Folding of virtual calls

[Martin Jambor <mjambor at suse dot cz>]

Hi,

this patch has changed only slightly since I posted it last time but
needs to be applied before the next one is so I send it along again.

The change is that gimple_fold_obj_type_ref_known_binfo now accepts an
integer instead of tree version of the OBJ_TYPE_REF token.  I did this
because LTO streaming of integers is rather simpler (OTOH I still
need to stream type too to do indirect inlining of virtual calls, more
on that later).

Thanks,

Martin


2009-10-21  Martin Jambor  <mjambor@suse.cz>

	* gimple.c (get_base_binfo_for_type): New function.
	(get_relevant_ref_binfo_single_inh): New function.
	(get_relevant_ref_binfo_multi_inh): New function.
	(gimple_fold_obj_type_ref_known_binfo): New function.
	(gimple_fold_obj_type_ref): Get binfo from
	get_relevant_ref_binfo_single_inh and
	get_relevant_ref_binfo_multi_inh and use
	gimple_fold_obj_type_ref_known_binfo.
	* gimple.h (gimple_fold_obj_type_ref): Declare.
	(gimple_fold_obj_type_ref_known_binfo): Declare.
	* tree-ssa-ccp.c (fold_gimple_call): Simplify condition for
	folding virtual calls and call gimple_fold_obj_type_ref.


Index: icln/gcc/gimple.c
===================================================================
--- icln.orig/gcc/gimple.c
+++ icln/gcc/gimple.c
@@ -4628,27 +4628,167 @@ gimple_decl_printable_name (tree decl, i
   return IDENTIFIER_POINTER (DECL_NAME (decl));
 }
 
+/* Search for a base binfo of BINFO that corresponds to TYPE and return it if
+   it is found or NULL_TREE if it is not. */
+
+static tree
+get_base_binfo_for_type (tree binfo, tree type)
+{
+  int i;
+  tree base_binfo;
+  tree res = NULL_TREE;
+
+  for (i = 0; BINFO_BASE_ITERATE (binfo, i, base_binfo); i++)
+    if (TREE_TYPE (base_binfo) == type)
+      {
+	gcc_assert (!res);
+	res = base_binfo;
+      }
+
+  return res;
+}
+
+/* Return a binfo describing the true type of object referenced by expression
+   REF if all component references access first ancestors.  REF can consist of
+   a series of COMPONENT_REFs of with a declaration or an INDIREC_REF.  It can
+   also be just a simple declaration, indirect reference or an SSA_NAME.  If
+   the function discoveres an INIDRECT_REF or an SSA_NAME, it will assume that
+   the encapsulating type is described by KNOWN_BINFO or return NULL_TREE if
+   KNOWN_BINFO is NULL_TREE.  Otherwise the first nonartifical field declaration
+   or the base declaration will be examined to get the encapsulating type.  If
+   a COMPONENT_REF referencing an ancestor which is not the first one, this
+   function returns NULL_TREE and sets *try_multi to true.  */
+
+static tree
+get_relevant_ref_binfo_single_inh (tree ref, tree known_binfo, bool *try_multi)
+{
+  while (true)
+    {
+      if (TREE_CODE (ref) == COMPONENT_REF)
+	{
+	  tree par_type;
+	  tree binfo, base_binfo;
+	  tree field = TREE_OPERAND (ref, 1);
+
+	  if (!DECL_ARTIFICIAL (field))
+	    {
+	      tree type = TREE_TYPE (field);
+	      if (TREE_CODE (type) == RECORD_TYPE)
+		return TYPE_BINFO (type);
+	      else
+		return NULL_TREE;
+	    }
+
+	  par_type = TREE_TYPE (TREE_OPERAND (ref, 0));
+	  binfo = TYPE_BINFO (par_type);
+	  if (!binfo
+	      || BINFO_N_BASE_BINFOS (binfo) == 0)
+	    {
+	      if (try_multi)
+		*try_multi = 1;
+	      return NULL_TREE;
+	    }
+	  base_binfo = BINFO_BASE_BINFO (binfo, 0);
+	  if (TREE_TYPE (base_binfo) != TREE_TYPE (field))
+	    {
+	      if (try_multi)
+		*try_multi = 1;
+	      return NULL_TREE;
+	    }
+
+	  ref = TREE_OPERAND (ref, 0);
+	}
+      else if (DECL_P (ref) && TREE_CODE (TREE_TYPE (ref)) == RECORD_TYPE)
+	return TYPE_BINFO (TREE_TYPE (ref));
+      else if (known_binfo
+	       && (TREE_CODE (ref) == SSA_NAME
+		   || TREE_CODE (ref) == INDIRECT_REF))
+	return known_binfo;
+      else
+	return NULL_TREE;
+    }
+}
 
-/* Fold a OBJ_TYPE_REF expression to the address of a function.
-   KNOWN_TYPE carries the true type of OBJ_TYPE_REF_OBJECT(REF).  Adapted
-   from cp_fold_obj_type_ref, but it tolerates types with no binfo
-   data.  */
+
+/* Return a binfo describing the part of object referenced by expression REF.
+   This can and often is a base_binfo of a descendatn binfo. REF can consist of
+   a series of COMPONENT_REFs of with a declaration or an INDIREC_REF.  It can
+   also be just a simple declaration, indirect reference or an SSA_NAME.  If
+   the function discoveres an INIDRECT_REF or an SSA_NAME, it will assume that
+   the encapsulating type is described by KNOWN_BINFO or return NULL_TREE if
+   KNOWN_BINFO is NULL_TREE.  Otherwise the first nonartifical field
+   declaration or the base declaration will be examined to get the
+   encapsulating type.  */
+
+static tree
+get_relevant_ref_binfo_multi_inh (tree ref, tree known_binfo)
+{
+  if (DECL_P (ref) && TREE_CODE (TREE_TYPE (ref)) == RECORD_TYPE)
+    return TYPE_BINFO (TREE_TYPE (ref));
+  else if (TREE_CODE (ref) == COMPONENT_REF)
+    {
+      tree desc_binfo;
+      tree field = TREE_OPERAND (ref, 1);
+
+      if (!DECL_ARTIFICIAL (field))
+	{
+	  tree type = TREE_TYPE (field);
+	  if (TREE_CODE (type) == RECORD_TYPE)
+	    return TYPE_BINFO (type);
+	  else
+	    return NULL_TREE;
+	}
+
+      desc_binfo = get_relevant_ref_binfo_multi_inh (TREE_OPERAND (ref, 0),
+						     known_binfo);
+      if (!desc_binfo)
+	return NULL_TREE;
+      return get_base_binfo_for_type (desc_binfo, TREE_TYPE (field));
+    }
+  else if (known_binfo
+	   && (TREE_CODE (ref) == SSA_NAME
+	       || TREE_CODE (ref) == INDIRECT_REF))
+    return known_binfo;
+  else
+    return NULL_TREE;
+}
+
+/* Return a binfo describing the part of object referenced by expression REF
+   using both get_relevant_ref_binfo_single_inh and
+   get_relevant_ref_binfo_multi_inh in this particular order.  */
 
 tree
-gimple_fold_obj_type_ref (tree ref, tree known_type)
+gimple_get_relevant_ref_binfo (tree ref, tree known_binfo)
+{
+  bool try_multi = false;
+  tree binfo;
+
+  binfo = get_relevant_ref_binfo_single_inh (ref, known_binfo, &try_multi);
+  if (!binfo && try_multi)
+    binfo = get_relevant_ref_binfo_multi_inh (ref, known_binfo);
+  return binfo;
+}
+
+
+/* Fold a OBJ_TYPE_REF expression to the address of a function. TOKEN is
+   integer form of OBJ_TYPE_REF_TOKEN of the reference expression.  KNOWN_BINFO
+   carries the binfo describing the true type of OBJ_TYPE_REF_OBJECT(REF).  */
+
+tree
+gimple_fold_obj_type_ref_known_binfo (HOST_WIDE_INT token, tree known_binfo)
 {
-  HOST_WIDE_INT index;
   HOST_WIDE_INT i;
-  tree v;
-  tree fndecl;
+  tree v, fndecl;
 
-  if (TYPE_BINFO (known_type) == NULL_TREE)
+  /* If binfo flag 2 is not set, this binfo does not "have its own virtual
+     table" (according to cp/cp-tree.h) and cannot be safely used for
+     devirtualization.  Purely empirical experience also shows that we can also
+     bail out if flag 5 is set.  This test also probably works in lto.  */
+  if (BINFO_FLAG_5 (known_binfo))
     return NULL_TREE;
-
-  v = BINFO_VIRTUALS (TYPE_BINFO (known_type));
-  index = tree_low_cst (OBJ_TYPE_REF_TOKEN (ref), 1);
+  v = BINFO_VIRTUALS (known_binfo);
   i = 0;
-  while (i != index)
+  while (i != token)
     {
       i += (TARGET_VTABLE_USES_DESCRIPTORS
 	    ? TARGET_VTABLE_USES_DESCRIPTORS : 1);
@@ -4656,15 +4796,34 @@ gimple_fold_obj_type_ref (tree ref, tree
     }
 
   fndecl = TREE_VALUE (v);
+  return build_fold_addr_expr (fndecl);
+}
 
-#ifdef ENABLE_CHECKING
-  gcc_assert (tree_int_cst_equal (OBJ_TYPE_REF_TOKEN (ref),
-				  DECL_VINDEX (fndecl)));
-#endif
 
-  cgraph_node (fndecl)->local.vtable_method = true;
+/* Fold a OBJ_TYPE_REF expression to the address of a function.  If KNOWN_TYPE
+   is not NULL_TREE, it is the true type of the outmost encapsulating object if
+   that comes from a pointer SSA_NAME.  If the true outmost encapsulating type
+   can be determined from a declaration OBJ_TYPE_REF_OBJECT(REF), it is used
+   regardless of KNOWN_TYPE (which thuc can be NULL_TREE).  */
 
-  return build_fold_addr_expr (fndecl);
+tree
+gimple_fold_obj_type_ref (tree ref, tree known_type)
+{
+  tree obj = OBJ_TYPE_REF_OBJECT (ref);
+  tree known_binfo = known_type ? TYPE_BINFO (known_type) : NULL_TREE;
+  tree binfo;
+
+  if (TREE_CODE (obj) == ADDR_EXPR)
+    obj = TREE_OPERAND (obj, 0);
+
+  binfo = gimple_get_relevant_ref_binfo (obj, known_binfo);
+  if (binfo)
+    {
+      HOST_WIDE_INT token = tree_low_cst (OBJ_TYPE_REF_TOKEN (ref), 1);
+      return gimple_fold_obj_type_ref_known_binfo (token, binfo);
+    }
+  else
+    return NULL_TREE;
 }
 
 #include "gt-gimple.h"
Index: icln/gcc/tree-ssa-ccp.c
===================================================================
--- icln.orig/gcc/tree-ssa-ccp.c
+++ icln/gcc/tree-ssa-ccp.c
@@ -2924,9 +2924,6 @@ fold_gimple_call (gimple_stmt_iterator *
     }
   else
     {
-      /* Check for resolvable OBJ_TYPE_REF.  The only sorts we can resolve
-         here are when we've propagated the address of a decl into the
-         object slot.  */
       /* ??? Should perhaps do this in fold proper.  However, doing it
          there requires that we create a new CALL_EXPR, and that requires
          copying EH region info to the new node.  Easier to just do it
@@ -2934,19 +2931,11 @@ fold_gimple_call (gimple_stmt_iterator *
       /* ??? Is there a good reason not to do this in fold_stmt_inplace?  */
       callee = gimple_call_fn (stmt);
       if (TREE_CODE (callee) == OBJ_TYPE_REF
-          && lang_hooks.fold_obj_type_ref
-          && TREE_CODE (OBJ_TYPE_REF_OBJECT (callee)) == ADDR_EXPR
-          && DECL_P (TREE_OPERAND
-                     (OBJ_TYPE_REF_OBJECT (callee), 0)))
+          && TREE_CODE (OBJ_TYPE_REF_OBJECT (callee)) == ADDR_EXPR)
         {
           tree t;
 
-          /* ??? Caution: Broken ADDR_EXPR semantics means that
-             looking at the type of the operand of the addr_expr
-             can yield an array type.  See silly exception in
-             check_pointer_types_r.  */
-          t = TREE_TYPE (TREE_TYPE (OBJ_TYPE_REF_OBJECT (callee)));
-          t = lang_hooks.fold_obj_type_ref (callee, t);
+          t = gimple_fold_obj_type_ref (callee, NULL_TREE);
           if (t)
             {
               gimple_call_set_fn (stmt, t);
Index: icln/gcc/gimple.h
===================================================================
--- icln.orig/gcc/gimple.h
+++ icln/gcc/gimple.h
@@ -864,7 +864,9 @@ unsigned get_gimple_rhs_num_ops (enum tr
 #define gimple_alloc(c, n) gimple_alloc_stat (c, n MEM_STAT_INFO)
 gimple gimple_alloc_stat (enum gimple_code, unsigned MEM_STAT_DECL);
 const char *gimple_decl_printable_name (tree, int);
+tree gimple_get_relevant_ref_binfo (tree ref, tree known_binfo);
 tree gimple_fold_obj_type_ref (tree, tree);
+tree gimple_fold_obj_type_ref_known_binfo (HOST_WIDE_INT, tree);
 
 /* Returns true iff T is a valid GIMPLE statement.  */
 extern bool is_gimple_stmt (tree);
Index: icln/gcc/testsuite/g++.dg/otr-fold-1.C
===================================================================
--- /dev/null
+++ icln/gcc/testsuite/g++.dg/otr-fold-1.C
@@ -0,0 +1,77 @@
+/* Verify that simple virtual calls are inlined even without early
+   inlining, even when a typecast to an ancestor is involved along the
+   way.  */
+/* { dg-do run } */
+/* { dg-options "-O -fdump-tree-optimized-slim"  } */
+
+extern "C" void abort (void);
+
+class Distraction
+{
+public:
+  float f;
+  double d;
+  Distraction ()
+  {
+    f = 8.3;
+    d = 10.2;
+  }
+  virtual float bar (float z);
+};
+
+class A
+{
+public:
+  int data;
+  virtual int foo (int i);
+};
+
+
+class B : public Distraction, public A
+{
+public:
+  virtual int foo (int i);
+};
+
+float Distraction::bar (float z)
+{
+  f += z;
+  return f/2;
+}
+
+int A::foo (int i)
+{
+  return i + 1;
+}
+
+int B::foo (int i)
+{
+  return i + 2;
+}
+
+int __attribute__ ((noinline,noclone)) get_input(void)
+{
+  return 1;
+}
+
+static int middleman_1 (class A *obj, int i)
+{
+  return obj->foo (i);
+}
+
+static int middleman_2 (class B *obj, int i)
+{
+  return middleman_1 (obj, i);
+}
+
+int main (int argc, char *argv[])
+{
+  class B b;
+
+  if (middleman_2 (&b, get_input ()) != 3)
+    abort ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump "= B::foo"  "optimized"  } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */