[llvm-commits] [llvm] r167759 - in /llvm/trunk: include/llvm/PassManagers.h lib/VMCore/PassManager.cpp

[Chandler Carruth]

On Mon, Nov 12, 2012 at 2:01 PM, Benjamin Kramer <benny.kra at gmail.com> wrote:
>
> On 12.11.2012, at 22:42, Evan Cheng <evan.cheng at apple.com> wrote:
>
>> Author: evancheng
>> Date: Mon Nov 12 15:42:53 2012
>> New Revision: 167759
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=167759&view=rev
>> Log:
>> Cache size of PassVector to speed up getNumContainedPasses().
>> getNumContainedPasses() used to compute the size of the vector on demand. It is
>> called repeated in loops (such as runOnFunction()) and it can be updated while
>> inside the loop.
>
> Do you have some numbers to back this change? Getting the size of a small vector is loading two pointers, a sub and a shift. That shouldn't be expensive enough to justify adding more code.
>
> OTOH, the call to size() is inside a virtual function, and I don't think that any of the calls to it can be devirtualized. I'd expect the lack of inlining and the indirect call to be a lot slower than the arithmetic in size(). However, it looks like getNumContainedPasses() isn't overridden anywhere so maybe we should just make it non-virtual if it's popping up in profiles?

As I've also been looking at both compile time and the pass managers,
I'd also love to know the rough scenario which causes this to show up
in profiles so I have a better idea of what might be important to
profile in making any changes here.

>
> - Ben
>
>>
>> Modified:
>>    llvm/trunk/include/llvm/PassManagers.h
>>    llvm/trunk/lib/VMCore/PassManager.cpp
>>
>> Modified: llvm/trunk/include/llvm/PassManagers.h
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/PassManagers.h?rev=167759&r1=167758&r2=167759&view=diff
>> ==============================================================================
>> --- llvm/trunk/include/llvm/PassManagers.h (original)
>> +++ llvm/trunk/include/llvm/PassManagers.h Mon Nov 12 15:42:53 2012
>> @@ -263,7 +263,7 @@
>> class PMDataManager {
>> public:
>>
>> -  explicit PMDataManager() : TPM(NULL), Depth(0) {
>> +  explicit PMDataManager() : TPM(NULL), PassVectorSize(0), Depth(0) {
>>     initializeAnalysisInfo();
>>   }
>>
>> @@ -344,7 +344,7 @@
>>   void dumpPreservedSet(const Pass *P) const;
>>
>>   virtual unsigned getNumContainedPasses() const {
>> -    return (unsigned)PassVector.size();
>> +    return PassVectorSize;
>>   }
>>
>>   virtual PassManagerType getPassManagerType() const {
>> @@ -369,14 +369,16 @@
>>   // Top level manager.
>>   PMTopLevelManager *TPM;
>>
>> -  // Collection of pass that are managed by this manager
>> -  SmallVector<Pass *, 16> PassVector;
>> -
>>   // Collection of Analysis provided by Parent pass manager and
>>   // used by current pass manager. At at time there can not be more
>>   // then PMT_Last active pass mangers.
>>   std::map<AnalysisID, Pass *> *InheritedAnalysis[PMT_Last];
>>
>> +  // Collection of pass that are managed by this manager
>> +  SmallVector<Pass *, 16> PassVector;
>> +
>> +  // Cache the size of PassVector
>> +  unsigned PassVectorSize;
>>
>>   /// isPassDebuggingExecutionsOrMore - Return true if -debug-pass=Executions
>>   /// or higher is specified.
>> @@ -444,7 +446,7 @@
>>   }
>>
>>   FunctionPass *getContainedPass(unsigned N) {
>> -    assert ( N < PassVector.size() && "Pass number out of range!");
>> +    assert ( N < PassVectorSize && "Pass number out of range!");
>>     FunctionPass *FP = static_cast<FunctionPass *>(PassVector[N]);
>>     return FP;
>>   }
>>
>> Modified: llvm/trunk/lib/VMCore/PassManager.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/VMCore/PassManager.cpp?rev=167759&r1=167758&r2=167759&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/VMCore/PassManager.cpp (original)
>> +++ llvm/trunk/lib/VMCore/PassManager.cpp Mon Nov 12 15:42:53 2012
>> @@ -195,7 +195,7 @@
>>   }
>>
>>   BasicBlockPass *getContainedPass(unsigned N) {
>> -    assert(N < PassVector.size() && "Pass number out of range!");
>> +    assert(N < PassVectorSize && "Pass number out of range!");
>>     BasicBlockPass *BP = static_cast<BasicBlockPass *>(PassVector[N]);
>>     return BP;
>>   }
>> @@ -346,7 +346,7 @@
>>   }
>>
>>   ModulePass *getContainedPass(unsigned N) {
>> -    assert(N < PassVector.size() && "Pass number out of range!");
>> +    assert(N < PassVectorSize && "Pass number out of range!");
>>     return static_cast<ModulePass *>(PassVector[N]);
>>   }
>>
>> @@ -963,6 +963,7 @@
>>   if (!ProcessAnalysis) {
>>     // Add pass
>>     PassVector.push_back(P);
>> +    ++PassVectorSize;
>>     return;
>>   }
>>
>> @@ -1024,6 +1025,7 @@
>>
>>   // Add pass
>>   PassVector.push_back(P);
>> +  ++PassVectorSize;
>> }
>>
>>
>>
>>
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