[PATCH] D17742: Perform InstructioinCombiningPass before SampleProfile pass.

[Xinliang David Li via llvm-commits]

On Tue, Mar 1, 2016 at 12:03 PM, Diego Novillo <dnovillo at google.com> wrote:

>
>
> On Tue, Mar 1, 2016 at 2:39 PM, Dehao Chen <danielcdh at gmail.com> wrote:
>
>>
>>   call void bitcast (void (%"class.llvm::SmallVectorImpl"*)*
>> @_ZN4llvm15SmallVectorImplIjED2Ev to void
>> (%"class.llvm::SmallVector"*)*)(%"class.llvm::SmallVector"* %3) #7, !dbg
>> !4175
>>
>> I just spent ~2 hours to generate a small C++ file to produce this "call
>> with bitcast" pattern, but whatever I tried, front end will not give me
>> exactly the same pattern. Shall I just keep the record in the commit log
>> about how to reproduce with FoldingSet.bc?
>>
>
> Not really.  Just wanted a motivation for the change.  Adding a pass as a
> pre-requisite for the sampler profiler means adding compile time.  Do you
> think this will trigger a lot in general?  I'm somewhat concerned about
> compile time inflation, but if it's useful in general for the sample
> profiling case, then I don't mind.
>

yeh -- as long as the compile time is spent to serve a good purpose for
SamplePGO :)

David


>
>
> ================
>> Comment at: test/Transforms/SampleProfile/cov-zero-samples.ll:3
>> @@ -2,3 +2,3 @@
>>  ;
>> -; CHECK: remark: cov-zero-samples.cc:9:25: Applied 404065 samples from
>> profile (offset: 2.1)
>> +; CHECK: remark: cov-zero-samples.cc:9:29: Applied 404065 samples from
>> profile (offset: 2.1)
>>  ; CHECK: remark: cov-zero-samples.cc:10:9: Applied 443089 samples from
>> profile (offset: 3)
>> ----------------
>> dnovillo wrote:
>> > Why did the discriminators change here?  Was this because of
>> instcombine?  What did it do?
>> This is not changing discriminator but column number.
>> inst-combine optimized the code to combine some instructions together and
>> used the LOC of one instruction as the new instruction's LOC.
>>
>
> Ah, thanks.
>
>
> Diego.
>
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