Unverified Commit 01aefba7 authored by Florian Hahn's avatar Florian Hahn Committed by GitHub
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[VPlan] Get GEP wrap flags from VPInstructions (NFCI). (#195730) 

Add helper to retrieve GEP no-wrap flags from VPInstructions, looking
through zero-index GEPs and pointer casts, like
Value::stripPointerCasts. Removes an access to underlying IR.
parent 9792c778

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

+6 −10
Original line number Diff line number Diff line
@@ -6423,25 +6423,21 @@ VPRecipeBase *VPRecipeBuilder::tryToWidenMemory(VPInstruction *VPI, 
  VPValue *Ptr = VPI->getOpcode() == Instruction::Load ? VPI->getOperand(0)

                                                       : VPI->getOperand(1);

  if (Consecutive) {

    auto *GEP = dyn_cast<GetElementPtrInst>(

        Ptr->getUnderlyingValue()->stripPointerCasts());

    GEPNoWrapFlags Flags = vputils::getGEPFlagsForPtr(Ptr);

    VPSingleDefRecipe *VectorPtr;

    if (Reverse) {

      // When folding the tail, we may compute an address that we don't in the

      // original scalar loop: drop the GEP no-wrap flags in this case.

      // Otherwise preserve existing flags without no-unsigned-wrap, as we will

      // emit negative indices.

      GEPNoWrapFlags Flags =

          CM.foldTailByMasking() || !GEP

      GEPNoWrapFlags ReverseFlags = CM.foldTailByMasking()

                                        ? GEPNoWrapFlags::none()

              : GEP->getNoWrapFlags().withoutNoUnsignedWrap();

                                        : Flags.withoutNoUnsignedWrap();

      VectorPtr = new VPVectorEndPointerRecipe(

          Ptr, &Plan.getVF(), getLoadStoreType(I),

          /*Stride*/ -1, Flags, VPI->getDebugLoc());

          /*Stride*/ -1, ReverseFlags, VPI->getDebugLoc());

    } else {

      VectorPtr = new VPVectorPointerRecipe(Ptr, getLoadStoreType(I),

                                            GEP ? GEP->getNoWrapFlags()

                                                : GEPNoWrapFlags::none(),

      VectorPtr = new VPVectorPointerRecipe(Ptr, getLoadStoreType(I), Flags,

                                            VPI->getDebugLoc());

    }

    Builder.setInsertPoint(VPI);

llvm/lib/Transforms/Vectorize/VPlanUtils.cpp

+19 −0
Original line number Diff line number Diff line
@@ -138,6 +138,25 @@ static bool poisonGuaranteesUB(const VPValue *V) { 
  return false;

}



GEPNoWrapFlags vputils::getGEPFlagsForPtr(VPValue *Ptr) {

  // Like IR stripPointerCasts, look through GEPs with all-zero indices and

  // casts to find a root GEP VPInstruction.

  while (auto *PtrVPI = dyn_cast<VPInstruction>(Ptr)) {

    unsigned Opcode = PtrVPI->getOpcode();

    if (Opcode == Instruction::GetElementPtr) {

      if (any_of(drop_begin(PtrVPI->operands()),

                 [](VPValue *Op) { return !match(Op, m_ZeroInt()); }))

        return PtrVPI->getGEPNoWrapFlags();

      Ptr = PtrVPI->getOperand(0);

      continue;

    }

    if (Opcode != Instruction::BitCast && Opcode != Instruction::AddrSpaceCast)

      break;

    Ptr = PtrVPI->getOperand(0);

  }

  return GEPNoWrapFlags::none();

}



const SCEV *vputils::getSCEVExprForVPValue(const VPValue *V,

                                           PredicatedScalarEvolution &PSE,

                                           const Loop *L) {

llvm/lib/Transforms/Vectorize/VPlanUtils.h

+4 −0
Original line number Diff line number Diff line
@@ -155,6 +155,10 @@ template <typename RecipeTy> static RecipeTy *findUserOf(VPValue *V) { 
/// nullptr if not found.

VPInstruction *findCanonicalIVIncrement(VPlan &Plan);



/// Returns the GEP nowrap flags for \p Ptr, looking through pointer casts

/// mirroring Value::stripPointerCasts.

GEPNoWrapFlags getGEPFlagsForPtr(VPValue *Ptr);



/// Find the ComputeReductionResult recipe for \p PhiR, looking through selects

/// inserted for predicated reductions or tail folding.

VPInstruction *findComputeReductionResult(VPReductionPHIRecipe *PhiR);