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Re: [PATCH] Indirect-call topn targets profiler (instrumentation)


> On Mon, Oct 6, 2014 at 11:22 AM, Jan Hubicka <hubicka@ucw.cz> wrote:
> > Rong,
> > Would be possible to use topn profiler to get resonale histograms for switch
> > expansion, too?  In that case it may make sense to have value version of it as well.
> 
> The underlying topn_profiler can be used the same way as the current
> one_value profiler for different scenarios. However, I wonder if it is
> useful for switch value profiling -- the arc profiling can do the
> same.

Well, for switch expansion one really wants a histogram of values across the switch
values for the decision tree balancing.  But I guess this profiler does not fit
that very well.

Consider cases like

switch (a)
{
   case 3:
   case 5:
   case 7:
	prime();
   case 2:
   case 4:
   case 6:
	even();
  default:
	bogus ();
}

Arc profiling does tell you how often a is prime or even, but it does not help you
to balance the tree, because the value ranges are iinterlacing
> 
> David
> 
> >
> > Otherwise the patch seems OK.  I would implement it myself by introducing separate
> > variables holding the topn profiler declaration, but can not think of downsides of
> > doing it your way.
> >
> > The topn profiler should be better on determining the dominating target, so perhaps
> > you could look into hooking it into ipa-profile.c.  Extending speculative edges for
> > multiple targets ought to be also quite easy - we need to update speculative_call_info
> > to collect edges annotated to a given call stmt into a vector instead of taking the
> > two references it does now.
> >
> > It would be also very nice to update it to handle case where all the edges are direct
> > so we can use it tospeculatively inlinine functions that can be interposed at runtime.
> >
> > Thanks,
> > Honza
> >
> > Index: gcc/tree-profile.c
> > ===================================================================
> > --- gcc/tree-profile.c  (revision 215886)
> > +++ gcc/tree-profile.c  (working copy)
> > @@ -56,6 +56,7 @@ along with GCC; see the file COPYING3.  If not see
> >  #include "target.h"
> >  #include "tree-cfgcleanup.h"
> >  #include "tree-nested.h"
> > +#include "params.h"
> >
> >  static GTY(()) tree gcov_type_node;
> >  static GTY(()) tree tree_interval_profiler_fn;
> > @@ -101,7 +102,10 @@ init_ic_make_global_vars (void)
> >      {
> >        ic_void_ptr_var
> >         = build_decl (UNKNOWN_LOCATION, VAR_DECL,
> > -                     get_identifier ("__gcov_indirect_call_callee"),
> > +                     get_identifier (
> > +                             (PARAM_VALUE (PARAM_INDIR_CALL_TOPN_PROFILE) ?
> > +                              "__gcov_indirect_call_topn_callee" :
> > +                              "__gcov_indirect_call_callee")),
> >                       ptr_void);
> >        TREE_PUBLIC (ic_void_ptr_var) = 1;
> >        DECL_EXTERNAL (ic_void_ptr_var) = 1;
> > @@ -131,7 +135,10 @@ init_ic_make_global_vars (void)
> >      {
> >        ic_gcov_type_ptr_var
> >         = build_decl (UNKNOWN_LOCATION, VAR_DECL,
> > -                     get_identifier ("__gcov_indirect_call_counters"),
> > +                     get_identifier (
> > +                             (PARAM_VALUE (PARAM_INDIR_CALL_TOPN_PROFILE) ?
> > +                              "__gcov_indirect_call_topn_counters" :
> > +                              "__gcov_indirect_call_counters")),
> >                       gcov_type_ptr);
> >        TREE_PUBLIC (ic_gcov_type_ptr_var) = 1;
> >        DECL_EXTERNAL (ic_gcov_type_ptr_var) = 1;
> > @@ -226,8 +233,10 @@ gimple_init_edge_profiler (void)
> >                                               ptr_void,
> >                                               NULL_TREE);
> >           tree_indirect_call_profiler_fn
> > -                 = build_fn_decl ("__gcov_indirect_call_profiler_v2",
> > -                                        ic_profiler_fn_type);
> > +                 = build_fn_decl ( (PARAM_VALUE (PARAM_INDIR_CALL_TOPN_PROFILE) ?
> > +                                    "__gcov_indirect_call_topn_profiler":
> > +                                    "__gcov_indirect_call_profiler_v2"),
> > +                                  ic_profiler_fn_type);
> >          }
> >        TREE_NOTHROW (tree_indirect_call_profiler_fn) = 1;
> >        DECL_ATTRIBUTES (tree_indirect_call_profiler_fn)
> > @@ -398,6 +407,12 @@ gimple_gen_ic_profiler (histogram_value value, uns
> >    gimple_stmt_iterator gsi = gsi_for_stmt (stmt);
> >    tree ref_ptr = tree_coverage_counter_addr (tag, base);
> >
> > +  if ( (PARAM_VALUE (PARAM_INDIR_CALL_TOPN_PROFILE) &&
> > +        tag == GCOV_COUNTER_V_INDIR) ||
> > +       (!PARAM_VALUE (PARAM_INDIR_CALL_TOPN_PROFILE) &&
> > +        tag == GCOV_COUNTER_ICALL_TOPNV))
> > +    return;
> > +
> >    ref_ptr = force_gimple_operand_gsi (&gsi, ref_ptr,
> >                                       true, NULL_TREE, true, GSI_SAME_STMT);
> >
> > @@ -442,8 +457,7 @@ gimple_gen_ic_func_profiler (void)
> >      stmt1: __gcov_indirect_call_profiler_v2 (profile_id,
> >                                              &current_function_decl)
> >     */
> > -  gsi =
> > -                                            gsi_after_labels (split_edge (single_succ_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun))));
> > +  gsi = gsi_after_labels (split_edge (single_succ_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun))));
> >
> >    cur_func = force_gimple_operand_gsi (&gsi,
> >                                        build_addr (current_function_decl,
> > Index: gcc/value-prof.c
> > ===================================================================
> > --- gcc/value-prof.c    (revision 215886)
> > +++ gcc/value-prof.c    (working copy)
> > @@ -60,6 +60,7 @@ along with GCC; see the file COPYING3.  If not see
> >  #include "builtins.h"
> >  #include "tree-nested.h"
> >  #include "hash-set.h"
> > +#include "params.h"
> >
> >  /* In this file value profile based optimizations are placed.  Currently the
> >     following optimizations are implemented (for more detailed descriptions
> > @@ -359,6 +360,22 @@ dump_histogram_value (FILE *dump_file, histogram_v
> >        }
> >        fprintf (dump_file, ".\n");
> >        break;
> > +    case HIST_TYPE_INDIR_CALL_TOPN:
> > +      fprintf (dump_file, "Indirect call topn ");
> > +      if (hist->hvalue.counters)
> > +       {
> > +           int i;
> > +
> > +           fprintf (dump_file, "accu:%"PRId64, hist->hvalue.counters[0]);
> > +           for (i = 1; i < (GCOV_ICALL_TOPN_VAL << 2); i += 2)
> > +             {
> > +               fprintf (dump_file, " target:%"PRId64 " value:%"PRId64,
> > +                       (int64_t) hist->hvalue.counters[i],
> > +                       (int64_t) hist->hvalue.counters[i+1]);
> > +             }
> > +        }
> > +      fprintf (dump_file, ".\n");
> > +      break;
> >      case HIST_TYPE_MAX:
> >        gcc_unreachable ();
> >     }
> > @@ -432,9 +449,14 @@ stream_in_histogram_value (struct lto_input_block
> >           break;
> >
> >         case HIST_TYPE_IOR:
> > -  case HIST_TYPE_TIME_PROFILE:
> > +        case HIST_TYPE_TIME_PROFILE:
> >           ncounters = 1;
> >           break;
> > +
> > +        case HIST_TYPE_INDIR_CALL_TOPN:
> > +          ncounters = (GCOV_ICALL_TOPN_VAL << 2) + 1;
> > +          break;
> > +
> >         case HIST_TYPE_MAX:
> >           gcc_unreachable ();
> >         }
> > @@ -1920,8 +1942,12 @@ gimple_indirect_call_to_profile (gimple stmt, hist
> >
> >    values->reserve (3);
> >
> > -  values->quick_push (gimple_alloc_histogram_value (cfun, HIST_TYPE_INDIR_CALL,
> > -                                                   stmt, callee));
> > +  values->quick_push (gimple_alloc_histogram_value (
> > +                        cfun,
> > +                        PARAM_VALUE (PARAM_INDIR_CALL_TOPN_PROFILE) ?
> > +                          HIST_TYPE_INDIR_CALL_TOPN :
> > +                          HIST_TYPE_INDIR_CALL,
> > +                       stmt, callee));
> >
> >    return;
> >  }
> > @@ -2011,9 +2037,9 @@ gimple_find_values_to_profile (histogram_values *v
> >           hist->n_counters = 3;
> >           break;
> >
> > -  case HIST_TYPE_TIME_PROFILE:
> > -    hist->n_counters = 1;
> > -    break;
> > +        case HIST_TYPE_TIME_PROFILE:
> > +          hist->n_counters = 1;
> > +          break;
> >
> >         case HIST_TYPE_AVERAGE:
> >           hist->n_counters = 2;
> > @@ -2023,6 +2049,10 @@ gimple_find_values_to_profile (histogram_values *v
> >           hist->n_counters = 1;
> >           break;
> >
> > +        case HIST_TYPE_INDIR_CALL_TOPN:
> > +          hist->n_counters = GCOV_ICALL_TOPN_NCOUNTS;
> > +          break;
> > +
> >         default:
> >           gcc_unreachable ();
> >         }
> > Index: gcc/value-prof.h
> > ===================================================================
> > --- gcc/value-prof.h    (revision 215886)
> > +++ gcc/value-prof.h    (working copy)
> > @@ -35,6 +35,8 @@ enum hist_type
> >    HIST_TYPE_AVERAGE,   /* Compute average value (sum of all values).  */
> >    HIST_TYPE_IOR,       /* Used to compute expected alignment.  */
> >    HIST_TYPE_TIME_PROFILE, /* Used for time profile */
> > +  HIST_TYPE_INDIR_CALL_TOPN, /* Tries to identify the top N most frequently
> > +                                called functions in indirect call.  */
> >    HIST_TYPE_MAX
> >  };
> >
> > Index: gcc/profile.c
> > ===================================================================
> > --- gcc/profile.c       (revision 215886)
> > +++ gcc/profile.c       (working copy)
> > @@ -183,6 +183,7 @@ instrument_values (histogram_values values)
> >           break;
> >
> >         case HIST_TYPE_INDIR_CALL:
> > +       case HIST_TYPE_INDIR_CALL_TOPN:
> >           gimple_gen_ic_profiler (hist, t, 0);
> >           break;
> >


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