[llvm] r311371 - [InlineCost] Add cl::opt to allow full inline cost to be computed for debugging purposes.

[Davide Italiano via llvm-commits]

On Sat, Aug 26, 2017 at 3:00 PM, Davide Italiano <davide at freebsd.org> wrote:
> On Fri, Aug 25, 2017 at 6:25 PM, Adam Nemet <anemet at apple.com> wrote:
>>
>> On Aug 25, 2017, at 1:11 PM, Davide Italiano <davide at freebsd.org> wrote:
>>
>> On Mon, Aug 21, 2017 at 1:00 PM, Haicheng Wu via llvm-commits
>> <llvm-commits at lists.llvm.org> wrote:
>>
>> Author: haicheng
>> Date: Mon Aug 21 13:00:09 2017
>> New Revision: 311371
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=311371&view=rev
>> Log:
>> [InlineCost] Add cl::opt to allow full inline cost to be computed for
>> debugging purposes.
>>
>> Currently, the inline cost model will bail once the inline cost exceeds the
>> inline threshold in order to avoid unnecessary compile-time. However, when
>> debugging it is useful to compute the full cost, so this command line option
>> is added to override the default behavior.
>>
>> I took over this work from Chad Rosier (mcrosier at codeaurora.org).
>>
>>
>> This causes a non-linear increase in the time spent in the inliner for
>> us, even with optimization remarks disabled.
>> real    0m2.889s
>> vs
>> real    0m30.429s
>>
>> I'm under the impression the issue is that for the legacy pass manager
>> we create an ORE object on-the-fly (as the inliner is a CGSCC pass,
>> and ORE is a FunctionPass analysis), so ORE is always non-null and we
>> compute the inlineCost in every case. For the new PM, we can rely on
>> proxying, but in the current infrastructure I'm not aware of an easy
>> way of obtaining function passes from outer units of IR.
>> Adam/Chandler, thoughts?
>>
>>
>> Hi Davide,
>>
>> Sorry about the delay.  ORE is always set irrespective of whether remarks
>> are enabled or not regardless whether you use old or new PM.
>>
>>
>> If nothing comes up, I'm going to pass null instead of ORE in
>> InlineSimple to recover from the hit (the feature will be still
>> available in the new PM, where we have a much better infrastructure
>> for the purpose).
>>
>>
>> I think that this interface is unfortunate conditionalizing on ORE to emit
>> remarks.
>>
>> Also the solution you used from WholeProgDevirt doesn't unfortunately work,
>> see https://bugs.llvm.org/show_bug.cgi?id=32352 but it’s OK in the short
>> term.
>>
>> Vivek has been working on the actual solution for this to correctly define
>> OptimizationRemarkEmitter::allowExtraAnalysis.  Vivek, do you think you can
>> get to it soonish?  The API is currently very confusing and I’d like to do
>> something about it.
>>
>> Thanks,
>> Adam
>>
>>
>
> Thanks for your reply, Adam.
> I'm going to disable the feature until the API is fleshed out.
>

Nevermind, ignore my previous reply. What I meant is that I'll leave
my workaround in place until the API is fleshed out.

Thanks,

--
Davide