[GOOGLE] Fix AutoFDO size issue

[Xinliang David Li]

After inline summary is recomputed, the large code growth problem will
also be better controlled, right?

David

On Thu, Nov 13, 2014 at 2:48 PM, Xinliang David Li <davidxl@google.com> wrote:
> Is there a need to have 10 iterations of early inline for autofdo?
>
> David
>
> On Thu, Nov 13, 2014 at 2:25 PM, Dehao Chen <dehao@google.com> wrote:
>> In AutoFDO, we increase einline iterations. This could lead to
>> extensive code bloat if we have recursive calls like:
>>
>> dtor() {
>>   destroy(node);
>> }
>>
>> destroy(node) {
>>   destroy(left)
>>   destroy(right)
>> }
>>
>> In this case, the size growth will be around 8 which is smaller than
>> threshold (11). However, if we allow this to happen for 2 iterations,
>> it will expand the size by 1024X. To fix this problem, we want to set
>> a much smaller threshold in the AutoFDO case. This is because AutoFDO
>> do not not rely on aggressive einline to gain more profile context.
>>
>> And also, in AutoFDO pass, after we processed a function, we need to
>> recompute inline parameters because rebuild_cgraph_edges will zero out
>> all inline parameters.
>>
>> The patch is attached below, bootstrapped and perf test on-going. OK
>> for google-4_9?
>>
>> Thanks,
>> Dehao
>>
>> Index: gcc/auto-profile.c
>> ===================================================================
>> --- gcc/auto-profile.c (revision 217523)
>> +++ gcc/auto-profile.c (working copy)
>> @@ -1771,6 +1771,7 @@ auto_profile (void)
>>        free_dominance_info (CDI_DOMINATORS);
>>        free_dominance_info (CDI_POST_DOMINATORS);
>>        rebuild_cgraph_edges ();
>> +      compute_inline_parameters (cgraph_get_node
>> (current_function_decl), true);
>>        pop_cfun ();
>>      }
>>
>> Index: gcc/opts.c
>> ===================================================================
>> --- gcc/opts.c (revision 217523)
>> +++ gcc/opts.c (working copy)
>> @@ -1853,6 +1853,12 @@ common_handle_option (struct gcc_options *opts,
>>        maybe_set_param_value (
>>   PARAM_EARLY_INLINER_MAX_ITERATIONS, 10,
>>   opts->x_param_values, opts_set->x_param_values);
>> +      maybe_set_param_value (
>> +        PARAM_EARLY_INLINING_INSNS, 4,
>> +        opts->x_param_values, opts_set->x_param_values);
>> +      maybe_set_param_value (
>> +        PARAM_EARLY_INLINING_INSNS_COMDAT, 4,
>> +        opts->x_param_values, opts_set->x_param_values);
>>        value = true;
>>      /* No break here - do -fauto-profile processing. */
>>      case OPT_fauto_profile: