[llvm] r230619 - IRCE: only touch loops that have been shown to have a high

[Sanjoy Das]

Thanks for poking me on this. :)

Checked in a test case in rL230680.

On Thu, Feb 26, 2015 at 6:13 AM, Hal Finkel <hfinkel at anl.gov> wrote:
> Test case?
>
>  -Hal
>
> ----- Original Message -----
>> From: "Sanjoy Das" <sanjoy at playingwithpointers.com>
>> To: llvm-commits at cs.uiuc.edu
>> Sent: Thursday, February 26, 2015 2:56:04 AM
>> Subject: [llvm] r230619 - IRCE: only touch loops that have been shown to have a high
>>
>> Author: sanjoy
>> Date: Thu Feb 26 02:56:04 2015
>> New Revision: 230619
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=230619&view=rev
>> Log:
>> IRCE: only touch loops that have been shown to have a high
>> backedge-taken count in profiliing data.
>>
>>
>> Modified:
>>     llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
>>
>> Modified:
>> llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp?rev=230619&r1=230618&r2=230619&view=diff
>> ==============================================================================
>> ---
>> llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
>> (original)
>> +++
>> llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
>> Thu Feb 26 02:56:04 2015
>> @@ -82,6 +82,9 @@ static cl::opt<unsigned> LoopSizeCutoff(
>>  static cl::opt<bool> PrintChangedLoops("irce-print-changed-loops",
>>  cl::Hidden,
>>                                         cl::init(false));
>>
>> +static cl::opt<int>
>> MaxExitProbReciprocal("irce-max-exit-prob-reciprocal",
>> +                                          cl::Hidden, cl::init(10));
>> +
>>  #define DEBUG_TYPE "irce"
>>
>>  namespace {
>> @@ -441,7 +444,9 @@ struct LoopStructure {
>>      return Result;
>>    }
>>
>> -  static Optional<LoopStructure> parseLoopStructure(ScalarEvolution
>> &, Loop &,
>> +  static Optional<LoopStructure> parseLoopStructure(ScalarEvolution
>> &,
>> +
>>                                                    BranchProbabilityInfo
>> &BPI,
>> +                                                    Loop &,
>>                                                      const char *&);
>>  };
>>
>> @@ -615,8 +620,8 @@ static bool CanBeSMin(ScalarEvolution &S
>>  }
>>
>>  Optional<LoopStructure>
>> -LoopStructure::parseLoopStructure(ScalarEvolution &SE, Loop &L,
>> -                                  const char *&FailureReason) {
>> +LoopStructure::parseLoopStructure(ScalarEvolution &SE,
>> BranchProbabilityInfo &BPI,
>> +                                  Loop &L, const char
>> *&FailureReason) {
>>    assert(L.isLoopSimplifyForm() && "should follow from
>>    addRequired<>");
>>
>>    BasicBlock *Latch = L.getLoopLatch();
>> @@ -640,6 +645,14 @@ LoopStructure::parseLoopStructure(Scalar
>>
>>    unsigned LatchBrExitIdx = LatchBr->getSuccessor(0) == Header ? 1 :
>>    0;
>>
>> +  BranchProbability ExitProbability =
>> +    BPI.getEdgeProbability(LatchBr->getParent(), LatchBrExitIdx);
>> +
>> +  if (ExitProbability > BranchProbability(1, MaxExitProbReciprocal))
>> {
>> +    FailureReason = "short running loop, not profitable";
>> +    return None;
>> +  }
>> +
>>    ICmpInst *ICI = dyn_cast<ICmpInst>(LatchBr->getCondition());
>>    if (!ICI || !isa<IntegerType>(ICI->getOperand(0)->getType())) {
>>      FailureReason = "latch terminator branch not conditional on
>>      integral icmp";
>> @@ -1340,7 +1353,7 @@ bool InductiveRangeCheckElimination::run
>>
>>    const char *FailureReason = nullptr;
>>    Optional<LoopStructure> MaybeLoopStructure =
>> -      LoopStructure::parseLoopStructure(SE, *L, FailureReason);
>> +      LoopStructure::parseLoopStructure(SE, BPI, *L, FailureReason);
>>    if (!MaybeLoopStructure.hasValue()) {
>>      DEBUG(dbgs() << "irce: could not parse loop structure: " <<
>>      FailureReason
>>                   << "\n";);
>>
>>
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>>
>
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory