Re: [Google] Refine hot caller heuristic

[Easwaran Raman <eraman at google dot com>]

On Tue, Aug 20, 2013 at 9:35 PM, Xinliang David Li <davidxl@google.com> wrote:
> Do you need to guard the jump function access with check if
> (ipa_node_params_vector.exists ())?
I believe it is not necessary since, for example, ipa_analyze_node
calls ipa_check_create_node_params that calls create. But I see it is
used in ipa-inline-analysis.c everywhere. So I have added a check and
conservatively return false.

>
> Ideally, useful_cold_callee should be folded into the inline hints
> estimation.  Question about the heuristic: why filtering out
> PASS_THROUGH parameter cases completely? Passing 'this' parameter in
> many cases can result in good PRE opportunities.  Why not skip the
> unknown type?

The rationale is it is useful to inline bar into foo in the snippet below:

void foo ()
{
  A a;
  bar(&a);
  ...
}

Capturing this requires UNKNOWN and KNOWN_TYPE jump functions. I have
changed the check accordingly. I have attached the new patch.

- Easwaran

> David
>
> On Tue, Aug 20, 2013 at 12:26 PM, Easwaran Raman <eraman@google.com> wrote:
>> The current hot caller heuristic simply promotes edges whose caller is
>> hot. This patch does the following:
>> * Turn it off for applications with large footprint since the size
>> increase hurts them
>> * Be more selective by considering arguments to callee when the
>> heuristic is enabled.
>>
>> This performs well on internal benchmarks. Ok for google/4_8 branch if
>> all tests pass?
>>
>> - Easwaran

Attachment: hot_caller.patch
Description: Binary data