[PATCH] D13755: Pass to compute dynamic instruction count

[Easwaran Raman via llvm-commits]

I essentially want a map from functions to their dynamic instruction counts
with the ability to update the dynamic count of a function as stuff gets
inlined into it. I also want to compute this only when necessary.
Implementing this as an analysis pass seems an easy way to provide this,
but I see that this may be an overkill especially since inliner is the only
consumer of this analysis (for now).

On Thu, Oct 15, 2015 at 12:12 AM, Eric Christopher <echristo at gmail.com>
wrote:

> Drive by question:
>
> Why a pass and not a utility?
>
> (Admittedly not read the code, just the description)
>
> Thanks!
>
> -eric
>
> On Wed, Oct 14, 2015 at 4:01 PM Easwaran Raman via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> eraman created this revision.
>> eraman added reviewers: chandlerc, hfinkel.
>> eraman added a subscriber: llvm-commits.
>> eraman set the repository for this revision to rL LLVM.
>>
>> An analysis pass in the new PM to compute estimated dynamic instruction
>> count of a function based on the static instruction count and block
>> frequency info. The intention is to use this in inline cost analysis to
>> estimate speedup due to inlining (as discussed in the RFC I sent earlier).
>>
>> We want the static instruction counts to be closely tied to the cost
>> model used in inline cost analysis. I have moved the CallAnalyzer interface
>> to the header file. When used on out-of-line function, the code in
>> CallAnalyzer that tries to simplify instructions is mostly irrelevant. In
>> most cases, this works fine based on the fact that the initial map of known
>> values is empty. In some cases, I need an explicit flag to distinguish
>> whether I'm using the analyzer during inlining or not.
>>
>> Repository:
>>   rL LLVM
>>
>> http://reviews.llvm.org/D13755
>>
>> Files:
>>   include/llvm/Analysis/BlockFrequencyInfo.h
>>   include/llvm/Analysis/BranchProbabilityInfo.h
>>   include/llvm/Analysis/DynamicInstructionCount.h
>>   include/llvm/Analysis/InlineCost.h
>>   lib/Analysis/BlockFrequencyInfo.cpp
>>   lib/Analysis/BranchProbabilityInfo.cpp
>>   lib/Analysis/CMakeLists.txt
>>   lib/Analysis/DynamicInstructionCount.cpp
>>   lib/Analysis/InlineCost.cpp
>>   lib/Passes/PassBuilder.cpp
>>   lib/Passes/PassRegistry.def
>>   test/Analysis/DynamicInstructionCount/basic.ll
>>
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>>
>
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