Re: [GOOGLE] Fix a bug when profile propagation handles infinite loop.

[Xinliang David Li <davidxl at google dot com>]

Ok with the change.

David

On Fri, Oct 25, 2013 at 6:17 PM, Dehao Chen <dehao@google.com> wrote:
> Most are within 10. The largest one I see is 17 across all benchmark.
>
> Dehao
>
> On Fri, Oct 25, 2013 at 4:21 PM, Xinliang David Li <davidxl@google.com> wrote:
>> What is the usual number of iterations?
>>
>> David
>>
>> On Fri, Oct 25, 2013 at 4:10 PM, Dehao Chen <dehao@google.com> wrote:
>>> If the propagation finds an infinite look, if the in-edge count is
>>> non-zero, then it will cause compiler go into infinite loop when
>>> building with AutoFDO.
>>>
>>> Bootstrapped and regression test on-going.
>>>
>>> OK for google-4_8 branch?
>>>
>>> Thanks,
>>> Dehao
>>>
>>> Index: gcc/auto-profile.c
>>> ===================================================================
>>> --- gcc/auto-profile.c (revision 204027)
>>> +++ gcc/auto-profile.c (working copy)
>>> @@ -1287,6 +1287,7 @@ afdo_propagate (void)
>>>  {
>>>    basic_block bb;
>>>    bool changed = true;
>>> +  int i = 0;
>>>
>>>    FOR_ALL_BB (bb)
>>>      {
>>> @@ -1295,7 +1296,7 @@ afdo_propagate (void)
>>>   bb->flags |= BB_ANNOTATED;
>>>      }
>>>
>>> -  while (changed)
>>> +  while (changed && i++ < PARAM_VALUE (PARAM_AUTOFDO_MAX_PROPAGATE_ITERATIONS))
>>>      {
>>>        changed = false;
>>>
>>> Index: gcc/params.def
>>> ===================================================================
>>> --- gcc/params.def (revision 204027)
>>> +++ gcc/params.def (working copy)
>>> @@ -460,6 +460,14 @@ DEFPARAM(PARAM_MAX_PREDICTED_ITERATIONS,
>>>   "The maximum number of loop iterations we predict statically",
>>>   100, 0, 0)
>>>
>>> +/* This parameter controls the maximum iterations that AutoFDO profile
>>> +   prpagation algorithm will run for a specific CFG.  */
>>> +
>>> +DEFPARAM(PARAM_AUTOFDO_MAX_PROPAGATE_ITERATIONS,
>>> +         "max-autofdo-max-propagate-iterations",
>>> +         "The maximum number of AutoFDO profile propagation iterations",
>>> +         1000, 0, 0)
>>> +
>>>  /* This parameter controls the probability of builtin_expect. The default
>>>     value is 90%. This empirical value is obtained through the weighted
>>>     probability of FDO counters (with the FDO count value as the weight)