On Fri, Oct 18, 2013 at 2:17 PM, Jan Hubicka <hubi...@ucw.cz> wrote:
>> Here is the patch updated to use the new parameter from r203830.
>> Passed bootstrap and regression tests.
>>
>> 2013-10-18 Jan Hubicka <j...@suse.cz>
>> Teresa Johnson <tejohn...@google.com>
>>
>> * predict.c (handle_missing_profiles): New function.
>> (counts_to_freqs): Don't overwrite estimated frequencies
>> when function has no profile counts.
>> * predict.h (handle_missing_profiles): Declare.
>> * tree-profile.c (tree_profiling): Invoke handle_missing_profiles.
>>
>> Index: predict.c
>> ===================================================================
>> --- predict.c (revision 203830)
>> +++ predict.c (working copy)
>> @@ -2758,6 +2758,40 @@ estimate_loops (void)
>> BITMAP_FREE (tovisit);
>> }
>>
>
> You need block comment. It should explain the problem of COMDATs and how they
> are handled.
> It is not an obvious thing.
Done.
>
>> +void
>> +handle_missing_profiles (void)
>> +{
>> + struct cgraph_node *node;
>> + int unlikely_count_fraction = PARAM_VALUE (UNLIKELY_BB_COUNT_FRACTION);
> extra line
>> + /* See if 0 count function has non-0 count callers. In this case we
>> + lost some profile. Drop its function profile to PROFILE_GUESSED. */
>> + FOR_EACH_DEFINED_FUNCTION (node)
>> + {
>> + struct cgraph_edge *e;
>> + gcov_type call_count = 0;
>> + struct function *fn = DECL_STRUCT_FUNCTION (node->symbol.decl);
> Extra line
>> + if (node->count)
>> + continue;
>> + for (e = node->callers; e; e = e->next_caller)
>> + call_count += e->count;
> What about checking if the sum is way off even for non-0 counts.
> I.e. for case where function was inlined to some calls but not to others? In
> that case we may want to scale up the counts (with some resonable care for
> capping)
In this patch I am not changing any counts, so I am leaving this one
for follow-on work (even for the routines missing counts completely
like these, we don't apply any counts, just mark them as guessed. I
have a follow-on patch to send once this goes in that does apply
counts to these 0-count routines only when we decide to inline as we
discussed).
>
> Also I think the code really should propagate - i.e. have simple worklist and
> look for functions that are COMDAT and are called by other COMDAT functions
> where we decided to drop the profile. Having non-trivial chains of comdats is
> common thing.
Done.
>
> What about outputting user visible warning/error on the incosnsistency when
> no COMDAT function is involved same way as we do for BB profile?
Done. This one caught the fact that we have this situation for "extern
template" functions as well when I tested on cpu2006. I added in a
check to ignore those when issuing the warning (they are not emitted
thus don't get any profile counts).
Updated patch below.
Bootstrapped and tested on x86-64-unknown-linux-gnu. Also tested on
profiledbootstrap and profile-use build of SPEC cpu2006. Ok for trunk?
Thanks,
Teresa
2013-10-30 Teresa Johnson <tejohn...@google.com>
* predict.c (drop_profile): New function.
(handle_missing_profiles): Ditto.
(counts_to_freqs): Don't overwrite estimated frequencies
when function has no profile counts.
* predict.h (handle_missing_profiles): Declare.
* tree-profile.c (tree_profiling): Invoke handle_missing_profiles.
Index: predict.c
===================================================================
--- predict.c (revision 204213)
+++ predict.c (working copy)
@@ -2765,6 +2765,107 @@ estimate_loops (void)
BITMAP_FREE (tovisit);
}
+/* Drop the profile for NODE to guessed, and update its frequency based on
+ whether it is expected to be HOT. */
+
+static void
+drop_profile (struct cgraph_node *node, bool hot)
+{
+ struct function *fn = DECL_STRUCT_FUNCTION (node->decl);
+
+ if (dump_file)
+ fprintf (dump_file,
+ "Dropping 0 profile for %s/%i. %s based on calls.\n",
+ cgraph_node_name (node), node->order,
+ hot ? "Function is hot" : "Function is normal");
+ /* We only expect to miss profiles for functions that are reached
+ via non-zero call edges in cases where the function may have
+ been linked from another module or library (COMDATs and extern
+ templates). See the comments below for handle_missing_profiles. */
+ if (!DECL_COMDAT (node->decl) && !DECL_EXTERNAL (node->decl))
+ warning (0,
+ "Missing counts for called function %s/%i",
+ cgraph_node_name (node), node->order);
+
+ profile_status_for_function (fn)
+ = (flag_guess_branch_prob ? PROFILE_GUESSED : PROFILE_ABSENT);
+ node->frequency
+ = hot ? NODE_FREQUENCY_HOT : NODE_FREQUENCY_NORMAL;
+}
+
+/* In the case of COMDAT routines, multiple object files will contain the same
+ function and the linker will select one for the binary. In that case
+ all the other copies from the profile instrument binary will be missing
+ profile counts. Look for cases where this happened, due to non-zero
+ call counts going to 0-count functions, and drop the profile to guessed
+ so that we can use the estimated probabilities and avoid optimizing only
+ for size.
+
+ The other case where the profile may be missing is when the routine
+ is not going to be emitted to the object file, e.g. for "extern template"
+ class methods. Those will be marked DECL_EXTERNAL. Emit a warning in
+ all other cases of non-zero calls to 0-count functions. */
+
+void
+handle_missing_profiles (void)
+{
+ struct cgraph_node *node;
+ int unlikely_count_fraction = PARAM_VALUE (UNLIKELY_BB_COUNT_FRACTION);
+ vec<struct cgraph_node *> worklist;
+ worklist.create (64);
+
+ /* See if 0 count function has non-0 count callers. In this case we
+ lost some profile. Drop its function profile to PROFILE_GUESSED. */
+ FOR_EACH_DEFINED_FUNCTION (node)
+ {
+ struct cgraph_edge *e;
+ gcov_type call_count = 0;
+ struct function *fn = DECL_STRUCT_FUNCTION (node->decl);
+
+ if (node->count)
+ continue;
+ for (e = node->callers; e; e = e->next_caller)
+ call_count += e->count;
+ if (call_count
+ && fn && fn->cfg
+ && (call_count * unlikely_count_fraction >= profile_info->runs))
+ {
+ bool maybe_hot = maybe_hot_count_p (NULL, call_count);
+
+ drop_profile (node, maybe_hot);
+ worklist.safe_push (node);
+ }
+ }
+
+ /* Propagate the profile dropping to other 0-count COMDATs that are
+ potentially called by COMDATs we already dropped the profile on. */
+ while (worklist.length () > 0)
+ {
+ struct cgraph_edge *e;
+
+ node = worklist.pop ();
+ for (e = node->callees; e; e = e->next_caller)
+ {
+ struct cgraph_node *callee = e->callee;
+ struct function *fn = DECL_STRUCT_FUNCTION (callee->decl);
+
+ if (callee->count > 0)
+ continue;
+ if (DECL_COMDAT (callee->decl) && fn && fn->cfg
+ && profile_status_for_function (fn) == PROFILE_READ)
+ {
+ /* Since there are no non-0 call counts to this function,
+ we don't know for sure whether it is hot. Indicate to
+ the drop_profile routine that function should be marked
+ normal, rather than hot. */
+ drop_profile (node, false);
+ worklist.safe_push (callee);
+ }
+ }
+ }
+ worklist.release ();
+}
+
/* Convert counts measured by profile driven feedback to frequencies.
Return nonzero iff there was any nonzero execution count. */
@@ -2774,6 +2875,9 @@ counts_to_freqs (void)
gcov_type count_max, true_count_max = 0;
basic_block bb;
+ if (!ENTRY_BLOCK_PTR->count)
+ return 0;
+
FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
true_count_max = MAX (bb->count, true_count_max);
Index: predict.h
===================================================================
--- predict.h (revision 204213)
+++ predict.h (working copy)
@@ -37,6 +37,7 @@ enum prediction
extern void predict_insn_def (rtx, enum br_predictor, enum prediction);
extern int counts_to_freqs (void);
+extern void handle_missing_profiles (void);
extern void estimate_bb_frequencies (bool);
extern const char *predictor_name (enum br_predictor);
extern tree build_predict_expr (enum br_predictor, enum prediction);
Index: tree-profile.c
===================================================================
--- tree-profile.c (revision 204213)
+++ tree-profile.c (working copy)
@@ -612,6 +612,8 @@ tree_profiling (void)
pop_cfun ();
}
+ handle_missing_profiles ();
+
del_node_map ();
return 0;
}
>
> Honza
--
Teresa Johnson | Software Engineer | tejohn...@google.com | 408-460-2413
