Re: [CHKP, PATCH] Fix LTO cgraph merge for instrumented functions

[Ilya Enkovich <enkovich dot gnu at gmail dot com>]

On 10 Apr 03:15, Jan Hubicka wrote:
> > 
> > References are not streamed out for nodes which are referenced in a
> > partition but don't belong to it ('continue' condition in output_refs
> > loop).
> 
> Yeah, but it already special cases aliases (because we now always preserve IPA_REF_ALIAS link
> in the boundary, so I think making IPA_REF_CHKP to be rpeserved should go the same path)
> so we can special case the instrumentation thunks too?

Any cgraph_node having instrumented clone should have it, not only instrumentation thunks.  Surely we can make an exception for IPA_REF_CHKP.

> > 
> > >
> > > I suppose we still need to
> > >  1) write_symbol and lto-symtab should know that transparent aliases are not real
> > >     symbols and ignore them. We have predicate symtab_node::real_symbol_p,
> > >     I suppose it should return true.
> > >
> > >     I think cgraph_merge and varpool_merge in lto-symtab needs to know what to do
> > >     when merging two symbols with transparent aliases.
> > >  2) At some point we need to populate transparent alias links as discussed in the
> > >     other thread.
> > >  3) For safety, I guess we want symbol_table::change_decl_assembler_name to either
> > >     sanity check there are no trasparent alias links pointing to old assembler
> > >     names or update it.
> > 
> > Wouldn't search for possible referring via transparent aliases nodes
> > be too expensive?
> 
> Changing of decl_assembler_name is not very common and if we set up the links
> only after renaming of statics, i think we are safe. But it would be better to
> keep verify it at some point.
> 
> I suppose verify_node check that there is no transparent alias link on symbols
> were it is not supposed to be and that there is link when it is supposed to be (i.e.
> symtab_state is >=EXPANSION and symbol is either weakref on tragets w/o native weakrefs
> or instrumentation cone.
> 
> Would you please mind adding the test and making sure it triggers when things are
> out of sync?
> 

OK, but I suppose it should be a part of transparent alias links rework discussed in another thread.  BTW are you going to intoroduce transparent aliases in cgraph soon?  

> > 
> > >  4) I think we want verify_node to check that transparent alias links and chkp points
> > >     as intended and only on those symbols where they need to be
> > >
> > > There is also logic in lto-partition to always insert alias target
> > >> > OK, so you have the chkp references that links to instrumented_version.
> > >> > You do not stream them for boundary symbols but for some reason they are needed,
> > >> > but when you can end up with wrong CHKP link?
> > >>
> > >> Wrong links may appear when cgraph nodes are merged.
> > >
> > > I see, I think you really want to fix these at merging time as sugested in 1).
> > > In this case even the node->instrumented_version pointer may be out of date and
> > > point to a node that lost in merging?
> > 
> > node->instrumented_version is redirected and never points to lost
> > symbol. But during merge we may have situations when
> > (node->instrumented_version->instrumented_version != node) because of
> > multiple not merged (yet) symbols referencing the same merged target.
> 
> OK, which should not be a problem if we stream the links instead of rebuilding them, right?

IPA_REF_CHKP refs don't affect instrumented_version merging. And I actually don't see here any problems, instrumented_version links always come into consistent state when symbol merging finishes.


Here is a new patch version.  It has no chkp_maybe_fix_chkp_ref function,  IPA_REF_CHKP references are streamed out instead.  Bootstrapped and tested on x86_64-unknown-linux-gnu.  OK for trunk?  I also want to port it to GCC 5 branch after release.

Thanks,
Ilya
--
gcc/

2015-04-14  Ilya Enkovich  <ilya.enkovich@intel.com>

	* ipa.c (symbol_table::remove_unreachable_nodes): Don't
	remove instumentation thunks calling reachable functions.
	* lto-cgraph.c (output_refs): Always output IPA_REF_CHKP.
	* lto/lto-partition.c (privatize_symbol_name_1): New.
	(privatize_symbol_name): Privatize both decl and orig_decl
	names for instrumented functions.

gcc/testsuite/

2015-04-14  Ilya Enkovich  <ilya.enkovich@intel.com>

	* gcc.dg/lto/chkp-privatize-1_0.c: New.
	* gcc.dg/lto/chkp-privatize-1_1.c: New.
	* gcc.dg/lto/chkp-privatize-2_0.c: New.
	* gcc.dg/lto/chkp-privatize-2_1.c: New.


diff --git a/gcc/ipa.c b/gcc/ipa.c
index b3752de..3054afe 100644
--- a/gcc/ipa.c
+++ b/gcc/ipa.c
@@ -492,7 +492,22 @@ symbol_table::remove_unreachable_nodes (FILE *file)
 	    }
 	  else if (cnode->thunk.thunk_p)
 	    enqueue_node (cnode->callees->callee, &first, &reachable);
-	      
+
+	  /* For instrumentation clones we always need original
+	     function node for proper LTO privatization.  */
+	  if (cnode->instrumentation_clone
+	      && reachable.contains (cnode)
+	      && cnode->definition)
+	    {
+	      gcc_assert (cnode->instrumented_version || in_lto_p);
+	      if (cnode->instrumented_version)
+		{
+		  enqueue_node (cnode->instrumented_version, &first,
+				&reachable);
+		  reachable.add (cnode->instrumented_version);
+		}
+	    }
+
 	  /* If any reachable function has simd clones, mark them as
 	     reachable as well.  */
 	  if (cnode->simd_clones)
diff --git a/gcc/lto-cgraph.c b/gcc/lto-cgraph.c
index ac50e4b..ea352f1 100644
--- a/gcc/lto-cgraph.c
+++ b/gcc/lto-cgraph.c
@@ -805,8 +805,33 @@ output_refs (lto_symtab_encoder_t encoder)
     {
       symtab_node *node = lto_symtab_encoder_deref (encoder, i);
 
+      /* IPA_REF_ALIAS and IPA_REF_CHKP references are always preserved
+	 in the boundary.  Alias node can't have other references and
+	 can be always handled as if it's not in the boundary.  */
       if (!node->alias && !lto_symtab_encoder_in_partition_p (encoder, node))
-	continue;
+	{
+	  cgraph_node *cnode = dyn_cast <cgraph_node *> (node);
+	  /* Output IPA_REF_CHKP reference.  */
+	  if (cnode
+	      && cnode->instrumented_version
+	      && !cnode->instrumentation_clone)
+	    {
+	      for (int i = 0; node->iterate_reference (i, ref); i++)
+		if (ref->use == IPA_REF_CHKP)
+		  {
+		    if (lto_symtab_encoder_lookup (encoder, ref->referred)
+			!= LCC_NOT_FOUND)
+		      {
+			int nref = lto_symtab_encoder_lookup (encoder, node);
+			streamer_write_gcov_count_stream (ob->main_stream, 1);
+			streamer_write_uhwi_stream (ob->main_stream, nref);
+			lto_output_ref (ob, ref, encoder);
+		      }
+		    break;
+		  }
+	    }
+	  continue;
+	}
 
       count = node->ref_list.nreferences ();
       if (count)
diff --git a/gcc/lto/lto-partition.c b/gcc/lto/lto-partition.c
index 235b735..7d117e9 100644
--- a/gcc/lto/lto-partition.c
+++ b/gcc/lto/lto-partition.c
@@ -877,27 +877,13 @@ validize_symbol_for_target (symtab_node *node)
     }
 }
 
-/* Mangle NODE symbol name into a local name.  
-   This is necessary to do
-   1) if two or more static vars of same assembler name
-      are merged into single ltrans unit.
-   2) if previously static var was promoted hidden to avoid possible conflict
-      with symbols defined out of the LTO world.  */
+/* Helper for privatize_symbol_name.  Mangle NODE symbol name
+   represented by DECL.  */
 
 static bool
-privatize_symbol_name (symtab_node *node)
+privatize_symbol_name_1 (symtab_node *node, tree decl)
 {
-  tree decl = node->decl;
-  const char *name;
-  cgraph_node *cnode = dyn_cast <cgraph_node *> (node);
-
-  /* If we want to privatize instrumentation clone
-     then we need to change original function name
-     which is used via transparent alias chain.  */
-  if (cnode && cnode->instrumentation_clone)
-    decl = cnode->orig_decl;
-
-  name = IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl));
+  const char *name = IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl));
 
   if (must_not_rename (node, name))
     return false;
@@ -906,31 +892,57 @@ privatize_symbol_name (symtab_node *node)
   symtab->change_decl_assembler_name (decl,
 				      clone_function_name_1 (name,
 							     "lto_priv"));
+
   if (node->lto_file_data)
     lto_record_renamed_decl (node->lto_file_data, name,
 			     IDENTIFIER_POINTER
 			     (DECL_ASSEMBLER_NAME (decl)));
+
+  if (symtab->dump_file)
+    fprintf (symtab->dump_file,
+	     "Privatizing symbol name: %s -> %s\n",
+	     name, IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl)));
+
+  return true;
+}
+
+/* Mangle NODE symbol name into a local name.
+   This is necessary to do
+   1) if two or more static vars of same assembler name
+      are merged into single ltrans unit.
+   2) if previously static var was promoted hidden to avoid possible conflict
+      with symbols defined out of the LTO world.  */
+
+static bool
+privatize_symbol_name (symtab_node *node)
+{
+  if (!privatize_symbol_name_1 (node, node->decl))
+    return false;
+
   /* We could change name which is a target of transparent alias
      chain of instrumented function name.  Fix alias chain if so  .*/
-  if (cnode)
+  if (cgraph_node *cnode = dyn_cast <cgraph_node *> (node))
     {
       tree iname = NULL_TREE;
       if (cnode->instrumentation_clone)
-	iname = DECL_ASSEMBLER_NAME (cnode->decl);
+	{
+	  /* If we want to privatize instrumentation clone
+	     then we also need to privatize original function.  */
+	  if (cnode->instrumented_version)
+	    privatize_symbol_name (cnode->instrumented_version);
+	  else
+	    privatize_symbol_name_1 (cnode, cnode->orig_decl);
+	  iname = DECL_ASSEMBLER_NAME (cnode->decl);
+	  TREE_CHAIN (iname) = DECL_ASSEMBLER_NAME (cnode->orig_decl);
+	}
       else if (cnode->instrumented_version
-	       && cnode->instrumented_version->orig_decl == decl)
-	iname = DECL_ASSEMBLER_NAME (cnode->instrumented_version->decl);
-
-      if (iname)
+	       && cnode->instrumented_version->orig_decl == cnode->decl)
 	{
-	  gcc_assert (IDENTIFIER_TRANSPARENT_ALIAS (iname));
-	  TREE_CHAIN (iname) = DECL_ASSEMBLER_NAME (decl);
+	  iname = DECL_ASSEMBLER_NAME (cnode->instrumented_version->decl);
+	  TREE_CHAIN (iname) = DECL_ASSEMBLER_NAME (cnode->decl);
 	}
     }
-  if (symtab->dump_file)
-    fprintf (symtab->dump_file,
-	    "Privatizing symbol name: %s -> %s\n",
-	    name, IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl)));
+
   return true;
 }
 
diff --git a/gcc/testsuite/gcc.dg/lto/chkp-privatize-1_0.c b/gcc/testsuite/gcc.dg/lto/chkp-privatize-1_0.c
new file mode 100644
index 0000000..2054aa15
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/lto/chkp-privatize-1_0.c
@@ -0,0 +1,17 @@
+/* { dg-lto-do link } */
+/* { dg-require-effective-target mpx } */
+/* { dg-lto-options { { -Ofast -flto -fcheck-pointer-bounds -mmpx } } } */
+
+extern int __attribute__((noinline)) f1 (int i);
+
+static int __attribute__((noinline))
+f2 (int i)
+{
+  return i + 6;
+}
+
+int
+main (int argc, char **argv)
+{
+  return f1 (argc) + f2 (argc);
+}
diff --git a/gcc/testsuite/gcc.dg/lto/chkp-privatize-1_1.c b/gcc/testsuite/gcc.dg/lto/chkp-privatize-1_1.c
new file mode 100644
index 0000000..4fa8656
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/lto/chkp-privatize-1_1.c
@@ -0,0 +1,11 @@
+static int __attribute__((noinline))
+f2 (int i)
+{
+  return 2 * i;
+}
+
+int __attribute__((noinline))
+f1 (int i)
+{
+  return f2 (i) + 10;
+}
diff --git a/gcc/testsuite/gcc.dg/lto/chkp-privatize-2_0.c b/gcc/testsuite/gcc.dg/lto/chkp-privatize-2_0.c
new file mode 100644
index 0000000..be7f601
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/lto/chkp-privatize-2_0.c
@@ -0,0 +1,18 @@
+/* { dg-lto-do link } */
+/* { dg-require-effective-target mpx } */
+/* { dg-lto-options { { -Ofast -flto -fcheck-pointer-bounds -mmpx } } } */
+
+static int
+__attribute__ ((noinline))
+func1 (int i)
+{
+  return i + 2;
+}
+
+extern int func2 (int i);
+
+int
+main (int argc, char **argv)
+{
+  return func1 (argc) + func2 (argc) + 1;
+}
diff --git a/gcc/testsuite/gcc.dg/lto/chkp-privatize-2_1.c b/gcc/testsuite/gcc.dg/lto/chkp-privatize-2_1.c
new file mode 100644
index 0000000..db39e7f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/lto/chkp-privatize-2_1.c
@@ -0,0 +1,8 @@
+int func1 = 10;
+
+int
+func2 (int i)
+{
+  func1++;
+  return i + func1;
+}