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

[Adam Nemet via llvm-commits]

> On Aug 26, 2017, at 3:20 PM, Davide Italiano <davide at freebsd.org> wrote:
> 
> On Sat, Aug 26, 2017 at 3:00 PM, Davide Italiano <davide at freebsd.org <mailto: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.

OK :).

> 
> Thanks,
> 
> --
> Davide

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