Re: [GOOGLE] Don't update the callee count if caller is not resolved node

[Dehao Chen <dehao at google dot com>]

On Mon, Oct 28, 2013 at 9:49 PM, Xinliang David Li <davidxl@google.com> wrote:
> Is it sufficient to check if the final caller is defined in primary module?

This might not be sufficient because the final caller may come from
comdat of aux-modules (not defined in the primary module).

>
> Note that in some cases, doing profile update 'speculatively' (without
> your fix) can be more precise (assuming the inlining gets materialized
> in a different compilation), but in general it might be better to be
> conservative in profile update (as in your patch) -- the downside is
> you may end up with less aggressive size optimization.

This is actually no speculatively update profile, but double update.

E.g. comdat_foo()-->bar() with count 100

and comdat_foo() has been defined in 2 aux-modules. Then there will be
two edges from comdat_foo()-->bar(), each of which has the count 100.
But bar()'s entry count is only 100 (assume comdat_foo is the only
caller). Then if we update bar() twice when inline these two edges,
the second update will be wrong.

Dehao

>
> David
>
> On Mon, Oct 28, 2013 at 3:51 PM, Dehao Chen <dehao@google.com> wrote:
>> This patch changes to no update callee count if caller count is not a
>> resolved node (in LIPO mode) during AutoFDO compilation. This is
>> because AutoFDO will have the same edge counts for all unresolved
>> nodes. Original update method will lead to multi-update of the callee.
>>
>> Bootstrapped and testing on going.
>>
>> OK for google-4_8 if test is OK?
>>
>> Thanks,
>> Dehao
>>
>> Index: gcc/ipa-inline-transform.c
>> ===================================================================
>> --- gcc/ipa-inline-transform.c (revision 204131)
>> +++ gcc/ipa-inline-transform.c (working copy)
>> @@ -169,6 +169,15 @@ clone_inlined_nodes (struct cgraph_edge *e, bool d
>>        else
>>   {
>>    struct cgraph_node *n;
>> +  if (flag_auto_profile && L_IPO_COMP_MODE
>> +      && cgraph_pre_profiling_inlining_done)
>> +    {
>> +      struct cgraph_node *caller = e->caller;
>> +      if (caller->global.inlined_to)
>> + caller = caller->global.inlined_to;
>> +      if (cgraph_lipo_get_resolved_node (caller->symbol.decl) != caller)
>> + update_original = false;
>> +    }
>>    n = cgraph_clone_node (e->callee, e->callee->symbol.decl,
>>   e->count, e->frequency,
>>   update_original, vNULL, true);