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

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

Ping

2015-05-05 11:06 GMT+03:00 Ilya Enkovich <enkovich.gnu@gmail.com>:
> Ping
>
> 2015-04-14 12:14 GMT+03:00 Ilya Enkovich <enkovich.gnu@gmail.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;
>> +}