[llvm] r259915 - CallAnalyzer::analyzeCall: change the condition back to "Cost < Threshold"

[Hans Wennborg via llvm-commits]

If Cost = 0 doesn't mean inlining the function has zero cost, that seems broken.

I think eraman knows this code. Maybe he wants to take a look?

On Mon, Feb 22, 2016 at 9:11 PM, Akira Hatanaka via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Hi Hans,
>
> This commit (or r252595) causes the inliner to inline functions you don't
> want to inline (large functions) in some cases. For example, if you compile
> the attached test case with "opt -inline", function "callee" will always get
> inlined even after replicating the inline-asm instruction in the last basic
> block a large number of times. This happens because the loop in
> CallAnalyzer::analyzeCall that visits the basic blocks of "callee" breaks
> out when Cost exceeds Threshold, and when that happens Cost happens to be 0.
> In this case Cost doesn't represent the true cost of the function (Cost<=0
> doesn't mean "inlining is free").
>
> Could you take a look?
>
> On Fri, Feb 5, 2016 at 12:32 PM, Hans Wennborg via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
>>
>> Author: hans
>> Date: Fri Feb  5 14:32:42 2016
>> New Revision: 259915
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=259915&view=rev
>> Log:
>> CallAnalyzer::analyzeCall: change the condition back to "Cost < Threshold"
>>
>> In r252595, I inadvertently changed the condition to "Cost <= Threshold",
>> which caused a significant size regression in Chrome. This commit
>> rectifies
>> that.
>>
>> Modified:
>>     llvm/trunk/lib/Analysis/InlineCost.cpp
>>
>> Modified: llvm/trunk/lib/Analysis/InlineCost.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InlineCost.cpp?rev=259915&r1=259914&r2=259915&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Analysis/InlineCost.cpp (original)
>> +++ llvm/trunk/lib/Analysis/InlineCost.cpp Fri Feb  5 14:32:42 2016
>> @@ -1392,7 +1392,7 @@ bool CallAnalyzer::analyzeCall(CallSite
>>    else if (NumVectorInstructions <= NumInstructions / 2)
>>      Threshold -= (FiftyPercentVectorBonus - TenPercentVectorBonus);
>>
>> -  return Cost <= std::max(0, Threshold);
>> +  return Cost < std::max(1, Threshold);
>>  }
>>
>>  #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
>>
>>
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