Commit ca134c39 authored by Johannes Doerfert's avatar Johannes Doerfert
Browse files

[OpenMP] Group side-effects to improve guarding efficiency 

When we guard side-effects as part of SPMDzation we do it for
consecutive instructions that need guarding. This patch will try to
reorder guarded side-effects in a block to decrease the number of
guarded regions we need. It does not use any smarts, e.g., alias
analysis, to move side-effects over non-interfering reads. Instead,
it only moves side-effects downwards to the next guarded side-effect
if there was nothing in between that could have possibly be affected.

Reviewed By: ggeorgakoudis

Differential Revision: https://reviews.llvm.org/D109070
parent deefeffb

llvm/lib/Transforms/IPO/OpenMPOpt.cpp

+28 −1
Original line number Diff line number Diff line
@@ -3188,6 +3188,34 @@ struct AAKernelInfoFunction : AAKernelInfo { 
            ->setDebugLoc(DL);

    };



    auto &AllocSharedRFI = OMPInfoCache.RFIs[OMPRTL___kmpc_alloc_shared];

    SmallPtrSet<BasicBlock *, 8> Visited;

    for (Instruction *GuardedI : SPMDCompatibilityTracker) {

      BasicBlock *BB = GuardedI->getParent();

      if (!Visited.insert(BB).second)

        continue;



      SmallVector<std::pair<Instruction *, Instruction *>> Reorders;

      Instruction *LastEffect = nullptr;

      BasicBlock::reverse_iterator IP = BB->rbegin(), IPEnd = BB->rend();

      while (++IP != IPEnd) {

        if (!IP->mayHaveSideEffects() && !IP->mayReadFromMemory())

          continue;

        Instruction *I = &*IP;

        if (OpenMPOpt::getCallIfRegularCall(*I, &AllocSharedRFI))

          continue;

        if (!I->user_empty() || !SPMDCompatibilityTracker.contains(I)) {

          LastEffect = nullptr;

          continue;

        }

        if (LastEffect)

          Reorders.push_back({I, LastEffect});

        LastEffect = &*IP;

      }

      for (auto &Reorder : Reorders)

        Reorder.first->moveBefore(Reorder.second);

    }



    SmallVector<std::pair<Instruction *, Instruction *>, 4> GuardedRegions;



    for (Instruction *GuardedI : SPMDCompatibilityTracker) {
@@ -4242,7 +4270,6 @@ void OpenMPOpt::registerAAs(bool IsModulePass) { 
          DepClassTy::NONE, /* ForceUpdate */ false,

          /* UpdateAfterInit */ false);





    registerFoldRuntimeCall(OMPRTL___kmpc_is_generic_main_thread_id);

    registerFoldRuntimeCall(OMPRTL___kmpc_is_spmd_exec_mode);

    registerFoldRuntimeCall(OMPRTL___kmpc_parallel_level);

llvm/test/Transforms/OpenMP/spmdization_guarding.ll

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+359 −0

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