llvm/lib/Target/DirectX/DXILResourceAccess.cpp

//===- DXILResourceAccess.cpp - Resource access via load/store ------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "DXILResourceAccess.h"
#include "DirectX.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/Analysis/DXILResource.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/Frontend/HLSL/HLSLResource.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/IntrinsicsDirectX.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/User.h"
#include "llvm/InitializePasses.h"
#include "llvm/Support/FormatVariadic.h"
#include "llvm/Transforms/Utils/ValueMapper.h"

#define DEBUG_TYPE "dxil-resource-access"

using namespace llvm;

static void diagnoseNonUniqueResourceAccess(Instruction *I,
                                            ArrayRef<IntrinsicInst *> Handles) {
  LLVMContext &Context = I->getContext();
  std::string InstStr;
  raw_string_ostream InstOS(InstStr);
  I->print(InstOS);
  Context.diagnose(
      DiagnosticInfoGeneric("At resource access:" + Twine(InstStr), DS_Note));

  for (auto *Handle : Handles) {
    std::string HandleStr;
    raw_string_ostream HandleOS(HandleStr);
    Handle->print(HandleOS);
    Context.diagnose(DiagnosticInfoGeneric(
        "Uses resource handle:" + Twine(HandleStr), DS_Note));
  }
  Context.diagnose(DiagnosticInfoGeneric(
      "Resource access is not guaranteed to map to a unique global resource"));
}

static Value *traverseGEPOffsets(const DataLayout &DL, IRBuilder<> &Builder,
                                 Value *Ptr, uint64_t AccessSize) {
  Value *Offset = nullptr;

  while (Ptr) {
    if (auto *II = dyn_cast<IntrinsicInst>(Ptr)) {
      assert(II->getIntrinsicID() == Intrinsic::dx_resource_getpointer &&
             "Resource access through unexpected intrinsic");
      return Offset ? Offset : ConstantInt::get(Builder.getInt32Ty(), 0);
    }

    auto *GEP = dyn_cast<GetElementPtrInst>(Ptr);
    assert(GEP && "Resource access through unexpected instruction");

    unsigned NumIndices = GEP->getNumIndices();
    uint64_t IndexScale = DL.getTypeAllocSize(GEP->getSourceElementType());
    APInt ConstantOffset(DL.getIndexTypeSizeInBits(GEP->getType()), 0);
    Value *GEPOffset;
    if (GEP->accumulateConstantOffset(DL, ConstantOffset)) {
      // We have a constant offset (in bytes).
      GEPOffset =
          ConstantInt::get(DL.getIndexType(GEP->getType()), ConstantOffset);
      IndexScale = 1;
    } else if (NumIndices == 1) {
      // If we have a single index we're indexing into a top level array. This
      // generally only happens with cbuffers.
      GEPOffset = *GEP->idx_begin();
    } else if (NumIndices == 2) {
      // If we have two indices, this should be an access through a pointer.
      auto *IndexIt = GEP->idx_begin();
      assert(cast<ConstantInt>(IndexIt)->getZExtValue() == 0 &&
             "GEP is not indexing through pointer");
      GEPOffset = *(++IndexIt);
    } else
      llvm_unreachable("Unhandled GEP structure for resource access");

    uint64_t ElemSize = AccessSize;
    if (!(IndexScale % ElemSize)) {
      // If our scale is an exact multiple of the access size, adjust the
      // scaling to avoid an unnecessary division.
      IndexScale /= ElemSize;
      ElemSize = 1;
    }
    if (IndexScale != 1)
      GEPOffset = Builder.CreateMul(
          GEPOffset, ConstantInt::get(Builder.getInt32Ty(), IndexScale));
    if (ElemSize != 1)
      GEPOffset = Builder.CreateUDiv(
          GEPOffset, ConstantInt::get(Builder.getInt32Ty(), ElemSize));

    Offset = Offset ? Builder.CreateAdd(Offset, GEPOffset) : GEPOffset;
    Ptr = GEP->getPointerOperand();
  }

  llvm_unreachable("GEP of null pointer?");
}

static void createTypedBufferStore(IntrinsicInst *II, StoreInst *SI,
                                   dxil::ResourceTypeInfo &RTI) {
  const DataLayout &DL = SI->getDataLayout();
  IRBuilder<> Builder(SI);
  Type *ContainedType = RTI.getHandleTy()->getTypeParameter(0);
  Type *ScalarType = ContainedType->getScalarType();
  Type *LoadType = StructType::get(ContainedType, Builder.getInt1Ty());

  Value *V = SI->getValueOperand();
  if (V->getType() == ContainedType) {
    // V is already the right type.
    assert(SI->getPointerOperand() == II &&
           "Store of whole element has mismatched address to store to");
  } else if (V->getType() == ScalarType) {
    // We're storing a scalar, so we need to load the current value and only
    // replace the relevant part.
    auto *Load = Builder.CreateIntrinsic(
        LoadType, Intrinsic::dx_resource_load_typedbuffer,
        {II->getOperand(0), II->getOperand(1)});
    auto *Struct = Builder.CreateExtractValue(Load, {0});

    uint64_t AccessSize = DL.getTypeSizeInBits(ScalarType) / 8;
    Value *Offset =
        traverseGEPOffsets(DL, Builder, SI->getPointerOperand(), AccessSize);
    V = Builder.CreateInsertElement(Struct, V, Offset);
  } else {
    llvm_unreachable("Store to typed resource has invalid type");
  }

  auto *Inst = Builder.CreateIntrinsic(
      Builder.getVoidTy(), Intrinsic::dx_resource_store_typedbuffer,
      {II->getOperand(0), II->getOperand(1), V});
  SI->replaceAllUsesWith(Inst);
}

static void emitRawStore(IRBuilder<> &Builder, Value *Buffer, Value *Index,
                         Value *Offset, Value *V, dxil::ResourceTypeInfo &RTI) {
  // For raw buffer (ie, HLSL's ByteAddressBuffer), we need to fold the access
  // entirely into the index.
  if (!RTI.isStruct()) {
    auto *ConstantOffset = dyn_cast<ConstantInt>(Offset);
    if (!ConstantOffset || !ConstantOffset->isZero())
      Index = Builder.CreateAdd(Index, Offset);
    Offset = llvm::PoisonValue::get(Builder.getInt32Ty());
  }

  Builder.CreateIntrinsic(Builder.getVoidTy(),
                          Intrinsic::dx_resource_store_rawbuffer,
                          {Buffer, Index, Offset, V});
}

static void createRawStores(IntrinsicInst *II, StoreInst *SI,
                            dxil::ResourceTypeInfo &RTI) {
  const DataLayout &DL = SI->getDataLayout();
  IRBuilder<> Builder(SI);

  Value *V = SI->getValueOperand();
  assert(!V->getType()->isAggregateType() &&
         "Resource store should be scalar or vector type");

  Value *Index = II->getOperand(1);
  // The offset for the rawbuffer load and store ops is always in bytes.
  uint64_t AccessSize = 1;
  Value *Offset =
      traverseGEPOffsets(DL, Builder, SI->getPointerOperand(), AccessSize);

  auto *VT = dyn_cast<FixedVectorType>(V->getType());
  if (VT && VT->getNumElements() > 4) {
    // Split into stores of at most 4 elements.
    Type *EltTy = VT->getElementType();
    Value *Stride = ConstantInt::get(Builder.getInt32Ty(),
                                     4 * (DL.getTypeSizeInBits(EltTy) / 8));

    SmallVector<int, 4> Indices;
    for (unsigned int I = 0, N = VT->getNumElements(); I < N; I += 4) {
      if (I > 0)
        Offset = Builder.CreateAdd(Offset, Stride);

      for (unsigned int J = I, E = std::min(N, J + 4); J < E; ++J)
        Indices.push_back(J);
      Value *Part = Builder.CreateShuffleVector(V, Indices);
      emitRawStore(Builder, II->getOperand(0), Index, Offset, Part, RTI);

      Indices.clear();
    }
  } else
    emitRawStore(Builder, II->getOperand(0), Index, Offset, V, RTI);
}

static void createStoreIntrinsic(IntrinsicInst *II, StoreInst *SI,
                                 dxil::ResourceTypeInfo &RTI) {
  switch (RTI.getResourceKind()) {
  case dxil::ResourceKind::TypedBuffer:
    return createTypedBufferStore(II, SI, RTI);
  case dxil::ResourceKind::RawBuffer:
  case dxil::ResourceKind::StructuredBuffer:
    return createRawStores(II, SI, RTI);
  case dxil::ResourceKind::Texture1D:
  case dxil::ResourceKind::Texture2D:
  case dxil::ResourceKind::Texture2DMS:
  case dxil::ResourceKind::Texture3D:
  case dxil::ResourceKind::TextureCube:
  case dxil::ResourceKind::Texture1DArray:
  case dxil::ResourceKind::Texture2DArray:
  case dxil::ResourceKind::Texture2DMSArray:
  case dxil::ResourceKind::TextureCubeArray:
  case dxil::ResourceKind::FeedbackTexture2D:
  case dxil::ResourceKind::FeedbackTexture2DArray:
    reportFatalUsageError("DXIL Store not implemented for texture resources");
    return;
  case dxil::ResourceKind::CBuffer:
  case dxil::ResourceKind::Sampler:
  case dxil::ResourceKind::TBuffer:
  case dxil::ResourceKind::RTAccelerationStructure:
  case dxil::ResourceKind::Invalid:
  case dxil::ResourceKind::NumEntries:
    llvm_unreachable("Invalid resource kind for store");
  }
  llvm_unreachable("Unhandled case in switch");
}

static void createTypedBufferLoad(IntrinsicInst *II, LoadInst *LI,
                                  dxil::ResourceTypeInfo &RTI) {
  const DataLayout &DL = LI->getDataLayout();
  IRBuilder<> Builder(LI);
  Type *ContainedType = RTI.getHandleTy()->getTypeParameter(0);
  Type *LoadType = StructType::get(ContainedType, Builder.getInt1Ty());

  Value *V =
      Builder.CreateIntrinsic(LoadType, Intrinsic::dx_resource_load_typedbuffer,
                              {II->getOperand(0), II->getOperand(1)});
  V = Builder.CreateExtractValue(V, {0});

  Type *ScalarType = ContainedType->getScalarType();
  uint64_t AccessSize = DL.getTypeSizeInBits(ScalarType) / 8;
  Value *Offset =
      traverseGEPOffsets(DL, Builder, LI->getPointerOperand(), AccessSize);
  auto *ConstantOffset = dyn_cast<ConstantInt>(Offset);
  if (!ConstantOffset || !ConstantOffset->isZero())
    V = Builder.CreateExtractElement(V, Offset);

  // If we loaded a <1 x ...> instead of a scalar (presumably to feed a
  // shufflevector), then make sure we're maintaining the resulting type.
  if (auto *VT = dyn_cast<FixedVectorType>(LI->getType()))
    if (VT->getNumElements() == 1 && !isa<FixedVectorType>(V->getType()))
      V = Builder.CreateInsertElement(PoisonValue::get(VT), V,
                                      Builder.getInt32(0));

  LI->replaceAllUsesWith(V);
}

static void createTextureLoad(IntrinsicInst *II, LoadInst *LI,
                              dxil::ResourceTypeInfo &RTI) {
  const DataLayout &DL = LI->getDataLayout();
  IRBuilder<> Builder(LI);
  Type *ContainedType = RTI.getHandleTy()->getTypeParameter(0);

  Value *Handle = II->getOperand(0);
  Value *Coords = II->getOperand(1);

  // For operator[], mip level is 0.
  Value *MipLevel = Builder.getInt32(0);

  // For operator[], offsets are zero.
  Type *CoordTy = Coords->getType();
  Type *OffsetTy;
  if (auto *VecTy = dyn_cast<FixedVectorType>(CoordTy))
    OffsetTy =
        FixedVectorType::get(Builder.getInt32Ty(), VecTy->getNumElements());
  else
    OffsetTy = Builder.getInt32Ty();
  Value *Offsets = Constant::getNullValue(OffsetTy);

  Value *V =
      Builder.CreateIntrinsic(ContainedType, Intrinsic::dx_resource_load_level,
                              {Handle, Coords, MipLevel, Offsets});

  Type *ScalarType = ContainedType->getScalarType();
  uint64_t AccessSize = DL.getTypeSizeInBits(ScalarType) / 8;
  Value *Offset =
      traverseGEPOffsets(DL, Builder, LI->getPointerOperand(), AccessSize);
  auto *ConstantOffset = dyn_cast<ConstantInt>(Offset);
  if (!ConstantOffset || !ConstantOffset->isZero())
    V = Builder.CreateExtractElement(V, Offset);

  // If we loaded a <1 x ...> instead of a scalar (presumably to feed a
  // shufflevector), then make sure we're maintaining the resulting type.
  if (auto *VT = dyn_cast<FixedVectorType>(LI->getType()))
    if (VT->getNumElements() == 1 && !isa<FixedVectorType>(V->getType()))
      V = Builder.CreateInsertElement(PoisonValue::get(VT), V,
                                      Builder.getInt32(0));

  LI->replaceAllUsesWith(V);
}

static Value *emitRawLoad(IRBuilder<> &Builder, Type *Ty, Value *Buffer,
                          Value *Index, Value *Offset,
                          dxil::ResourceTypeInfo &RTI) {
  // For raw buffer (ie, HLSL's ByteAddressBuffer), we need to fold the access
  // entirely into the index.
  if (!RTI.isStruct()) {
    auto *ConstantOffset = dyn_cast<ConstantInt>(Offset);
    if (!ConstantOffset || !ConstantOffset->isZero())
      Index = Builder.CreateAdd(Index, Offset);
    Offset = llvm::PoisonValue::get(Builder.getInt32Ty());
  }

  // The load intrinsic includes the bit for CheckAccessFullyMapped, so we need
  // to add that to the return type.
  Type *TypeWithCheck = StructType::get(Ty, Builder.getInt1Ty());
  Value *V = Builder.CreateIntrinsic(TypeWithCheck,
                                     Intrinsic::dx_resource_load_rawbuffer,
                                     {Buffer, Index, Offset});
  return Builder.CreateExtractValue(V, {0});
}

static void createRawLoads(IntrinsicInst *II, LoadInst *LI,
                           dxil::ResourceTypeInfo &RTI) {
  const DataLayout &DL = LI->getDataLayout();
  IRBuilder<> Builder(LI);

  Value *Index = II->getOperand(1);
  // The offset for the rawbuffer load and store ops is always in bytes.
  uint64_t AccessSize = 1;
  Value *Offset =
      traverseGEPOffsets(DL, Builder, LI->getPointerOperand(), AccessSize);

  // TODO: We could make this handle aggregates by walking the structure and
  // handling each field individually, but we don't ever generate code that
  // would hit that so it seems superfluous.
  assert(!LI->getType()->isAggregateType() &&
         "Resource load should be scalar or vector type");

  Value *V;
  if (auto *VT = dyn_cast<FixedVectorType>(LI->getType())) {
    // Split into loads of at most 4 elements.
    Type *EltTy = VT->getElementType();
    Value *Stride = ConstantInt::get(Builder.getInt32Ty(),
                                     4 * (DL.getTypeSizeInBits(EltTy) / 8));

    SmallVector<Value *> Parts;
    for (unsigned int I = 0, N = VT->getNumElements(); I < N; I += 4) {
      Type *Ty = FixedVectorType::get(EltTy, N - I < 4 ? N - I : 4);
      if (I > 0)
        Offset = Builder.CreateAdd(Offset, Stride);
      Parts.push_back(
          emitRawLoad(Builder, Ty, II->getOperand(0), Index, Offset, RTI));
    }

    V = Parts.size() > 1 ? concatenateVectors(Builder, Parts) : Parts[0];
  } else
    V = emitRawLoad(Builder, LI->getType(), II->getOperand(0), Index, Offset,
                    RTI);

  LI->replaceAllUsesWith(V);
}

namespace {
/// Helper for building a `load.cbufferrow` intrinsic given a simple type.
struct CBufferRowIntrin {
  Intrinsic::ID IID;
  Type *RetTy;
  unsigned int EltSize;
  unsigned int NumElts;

  CBufferRowIntrin(const DataLayout &DL, Type *Ty) {
    assert(Ty == Ty->getScalarType() && "Expected scalar type");

    switch (DL.getTypeSizeInBits(Ty)) {
    case 16:
      IID = Intrinsic::dx_resource_load_cbufferrow_8;
      RetTy = StructType::get(Ty, Ty, Ty, Ty, Ty, Ty, Ty, Ty);
      EltSize = 2;
      NumElts = 8;
      break;
    case 32:
      IID = Intrinsic::dx_resource_load_cbufferrow_4;
      RetTy = StructType::get(Ty, Ty, Ty, Ty);
      EltSize = 4;
      NumElts = 4;
      break;
    case 64:
      IID = Intrinsic::dx_resource_load_cbufferrow_2;
      RetTy = StructType::get(Ty, Ty);
      EltSize = 8;
      NumElts = 2;
      break;
    default:
      llvm_unreachable("Only 16, 32, and 64 bit types supported");
    }
  }
};
} // namespace

static void createCBufferLoad(IntrinsicInst *II, LoadInst *LI,
                              dxil::ResourceTypeInfo &RTI) {
  const DataLayout &DL = LI->getDataLayout();

  Type *Ty = LI->getType();
  assert(!isa<StructType>(Ty) && "Structs not handled yet");
  CBufferRowIntrin Intrin(DL, Ty->getScalarType());

  StringRef Name = LI->getName();
  Value *Handle = II->getOperand(0);

  IRBuilder<> Builder(LI);

  ConstantInt *GlobalOffset = dyn_cast<ConstantInt>(II->getOperand(1));
  assert(GlobalOffset && "CBuffer getpointer index must be constant");

  uint64_t GlobalOffsetVal = GlobalOffset->getZExtValue();
  Value *CurrentRow = ConstantInt::get(
      Builder.getInt32Ty(), GlobalOffsetVal / hlsl::CBufferRowSizeInBytes);
  unsigned int CurrentIndex =
      (GlobalOffsetVal % hlsl::CBufferRowSizeInBytes) / Intrin.EltSize;

  // Every object in a cbuffer either fits in a row or is aligned to a row. This
  // means that only the very last pointer access can point into a row.
  auto *LastGEP = dyn_cast<GEPOperator>(LI->getPointerOperand());
  if (!LastGEP) {
    // If we don't have a GEP at all we're just accessing the resource through
    // the result of getpointer directly.
    assert(LI->getPointerOperand() == II &&
           "Unexpected indirect access to resource without GEP");
  } else {
    Value *GEPOffset = traverseGEPOffsets(
        DL, Builder, LastGEP->getPointerOperand(), hlsl::CBufferRowSizeInBytes);
    CurrentRow = Builder.CreateAdd(GEPOffset, CurrentRow);

    APInt ConstantOffset(DL.getIndexTypeSizeInBits(LastGEP->getType()), 0);
    if (LastGEP->accumulateConstantOffset(DL, ConstantOffset)) {
      APInt Remainder(DL.getIndexTypeSizeInBits(LastGEP->getType()),
                      hlsl::CBufferRowSizeInBytes);
      APInt::udivrem(ConstantOffset, Remainder, ConstantOffset, Remainder);
      CurrentRow = Builder.CreateAdd(
          CurrentRow, ConstantInt::get(Builder.getInt32Ty(), ConstantOffset));
      CurrentIndex += Remainder.udiv(Intrin.EltSize).getZExtValue();
    } else {
      assert(LastGEP->getNumIndices() == 1 &&
             "Last GEP of cbuffer access is not array or struct access");
      // We assume a non-constant access will be row-aligned. This is safe
      // because arrays and structs are always row aligned, and accesses to
      // vector elements will show up as a load of the vector followed by an
      // extractelement.
      CurrentRow = cast<ConstantInt>(CurrentRow)->isZero()
                       ? *LastGEP->idx_begin()
                       : Builder.CreateAdd(CurrentRow, *LastGEP->idx_begin());
      CurrentIndex = 0;
    }
  }

  auto *CBufLoad = Builder.CreateIntrinsic(
      Intrin.RetTy, Intrin.IID, {Handle, CurrentRow}, nullptr, Name + ".load");
  auto *Elt =
      Builder.CreateExtractValue(CBufLoad, {CurrentIndex++}, Name + ".extract");

  // At this point we've loaded the first scalar of our result, but our original
  // type may have been a vector.
  unsigned int Remaining =
      ((DL.getTypeSizeInBits(Ty) / 8) / Intrin.EltSize) - 1;
  if (Remaining == 0) {
    // We only have a single element, so we're done.
    Value *Result = Elt;

    // However, if we loaded a <1 x T>, then we need to adjust the type.
    if (auto *VT = dyn_cast<FixedVectorType>(Ty)) {
      assert(VT->getNumElements() == 1 && "Can't have multiple elements here");
      Result = Builder.CreateInsertElement(PoisonValue::get(VT), Result,
                                           Builder.getInt32(0), Name);
    }
    LI->replaceAllUsesWith(Result);
    return;
  }

  // Walk each element and extract it, wrapping to new rows as needed.
  SmallVector<Value *> Extracts{Elt};
  while (Remaining--) {
    CurrentIndex %= Intrin.NumElts;

    if (CurrentIndex == 0) {
      CurrentRow = Builder.CreateAdd(CurrentRow,
                                     ConstantInt::get(Builder.getInt32Ty(), 1));
      CBufLoad = Builder.CreateIntrinsic(Intrin.RetTy, Intrin.IID,
                                         {Handle, CurrentRow}, nullptr,
                                         Name + ".load");
    }

    Extracts.push_back(Builder.CreateExtractValue(CBufLoad, {CurrentIndex++},
                                                  Name + ".extract"));
  }

  // Finally, we build up the original loaded value.
  Value *Result = PoisonValue::get(Ty);
  for (int I = 0, E = Extracts.size(); I < E; ++I)
    Result = Builder.CreateInsertElement(
        Result, Extracts[I], Builder.getInt32(I), Name + formatv(".upto{}", I));
  LI->replaceAllUsesWith(Result);
}

static void createLoadIntrinsic(IntrinsicInst *II, LoadInst *LI,
                                dxil::ResourceTypeInfo &RTI) {
  switch (RTI.getResourceKind()) {
  case dxil::ResourceKind::TypedBuffer:
    return createTypedBufferLoad(II, LI, RTI);
  case dxil::ResourceKind::RawBuffer:
  case dxil::ResourceKind::StructuredBuffer:
    return createRawLoads(II, LI, RTI);
  case dxil::ResourceKind::CBuffer:
    return createCBufferLoad(II, LI, RTI);
  case dxil::ResourceKind::Texture1D:
  case dxil::ResourceKind::Texture2D:
  case dxil::ResourceKind::Texture2DMS:
  case dxil::ResourceKind::Texture3D:
  case dxil::ResourceKind::TextureCube:
  case dxil::ResourceKind::Texture1DArray:
  case dxil::ResourceKind::Texture2DArray:
  case dxil::ResourceKind::Texture2DMSArray:
  case dxil::ResourceKind::TextureCubeArray:
    return createTextureLoad(II, LI, RTI);
  case dxil::ResourceKind::FeedbackTexture2D:
  case dxil::ResourceKind::FeedbackTexture2DArray:
  case dxil::ResourceKind::TBuffer:
    reportFatalUsageError("Load not yet implemented for resource type");
    return;
  case dxil::ResourceKind::Sampler:
  case dxil::ResourceKind::RTAccelerationStructure:
  case dxil::ResourceKind::Invalid:
  case dxil::ResourceKind::NumEntries:
    llvm_unreachable("Invalid resource kind for load");
  }
  llvm_unreachable("Unhandled case in switch");
}

static Instruction *getStoreLoadPointerOperand(Instruction *AI) {
  if (auto *LI = dyn_cast<LoadInst>(AI))
    return dyn_cast<Instruction>(LI->getPointerOperand());
  if (auto *SI = dyn_cast<StoreInst>(AI))
    return dyn_cast<Instruction>(SI->getPointerOperand());

  return nullptr;
}

static const std::array<Intrinsic::ID, 2> HandleIntrins = {
    Intrinsic::dx_resource_handlefrombinding,
    Intrinsic::dx_resource_handlefromimplicitbinding,
};

static SmallVector<IntrinsicInst *> collectUsedHandles(Value *Ptr) {
  SmallVector<Value *> Worklist = {Ptr};
  SmallVector<IntrinsicInst *> Handles;

  while (!Worklist.empty()) {
    Value *X = Worklist.pop_back_val();

    if (!X->getType()->isPointerTy() && !X->getType()->isTargetExtTy())
      return {}; // Early exit on store/load into non-resource

    if (auto *Phi = dyn_cast<PHINode>(X))
      for (Use &V : Phi->incoming_values())
        Worklist.push_back(V.get());
    else if (auto *Select = dyn_cast<SelectInst>(X))
      for (Value *V : {Select->getTrueValue(), Select->getFalseValue()})
        Worklist.push_back(V);
    else if (auto *II = dyn_cast<IntrinsicInst>(X)) {
      Intrinsic::ID IID = II->getIntrinsicID();

      if (IID == Intrinsic::dx_resource_getpointer)
        Worklist.push_back(II->getArgOperand(/*Handle=*/0));

      if (llvm::is_contained(HandleIntrins, IID))
        Handles.push_back(II);
    }
  }

  return Handles;
}

static hlsl::Binding getHandleIntrinsicBinding(IntrinsicInst *Handle,
                                               DXILResourceTypeMap &DRTM) {
  assert(llvm::is_contained(HandleIntrins, Handle->getIntrinsicID()) &&
         "Only expects a Handle as determined from collectUsedHandles.");

  auto *HandleTy = cast<TargetExtType>(Handle->getType());
  dxil::ResourceClass Class = DRTM[HandleTy].getResourceClass();
  uint32_t Space = cast<ConstantInt>(Handle->getArgOperand(0))->getZExtValue();
  uint32_t LowerBound =
      cast<ConstantInt>(Handle->getArgOperand(1))->getZExtValue();
  uint32_t Size = cast<ConstantInt>(Handle->getArgOperand(2))->getZExtValue();
  uint32_t UpperBound = Size == UINT32_MAX ? UINT32_MAX : LowerBound + Size - 1;

  return hlsl::Binding(Class, Space, LowerBound, UpperBound, nullptr);
}

namespace {
/// Helper for propagating the current handle and ptr indices.
struct AccessIndices {
  Value *GetPtrIdx;
  Value *HandleIdx;

  bool hasGetPtrIdx() { return GetPtrIdx != nullptr; }
  bool hasHandleIdx() { return HandleIdx != nullptr; }
};
} // namespace

// getAccessIndices traverses up the control flow that a ptr came from and
// propagates back the indicies used to access the resource (AccessIndices):
//
//  - GetPtrIdx is the index of dx.resource.getpointer
//  - HandleIdx is the index of dx.resource.handlefrom.*
static AccessIndices
getAccessIndices(Instruction *I, SmallSetVector<Instruction *, 16> &DeadInsts) {
  if (auto *II = dyn_cast<IntrinsicInst>(I)) {
    if (llvm::is_contained(HandleIntrins, II->getIntrinsicID())) {
      DeadInsts.insert(II);
      return {nullptr, II->getArgOperand(/*Index=*/3)};
    }

    if (II->getIntrinsicID() == Intrinsic::dx_resource_getpointer) {
      auto *V = dyn_cast<Instruction>(II->getArgOperand(/*Handle=*/0));
      auto AccessIdx = getAccessIndices(V, DeadInsts);
      assert(!AccessIdx.hasGetPtrIdx() &&
             "Encountered multiple dx.resource.getpointers in ptr chain?");
      AccessIdx.GetPtrIdx = II->getArgOperand(1);

      DeadInsts.insert(II);
      return AccessIdx;
    }
  }

  if (auto *Phi = dyn_cast<PHINode>(I)) {
    unsigned NumEdges = Phi->getNumIncomingValues();
    assert(NumEdges != 0 && "Malformed Phi Node");

    IRBuilder<> Builder(Phi);
    PHINode *GetPtrPhi = PHINode::Create(Builder.getInt32Ty(), NumEdges);
    PHINode *HandlePhi = PHINode::Create(Builder.getInt32Ty(), NumEdges);

    bool HasGetPtr = true;
    for (unsigned Idx = 0; Idx < NumEdges; Idx++) {
      auto *BB = Phi->getIncomingBlock(Idx);
      auto *V = dyn_cast<Instruction>(Phi->getIncomingValue(Idx));
      auto AccessIdx = getAccessIndices(V, DeadInsts);
      HasGetPtr &= AccessIdx.hasGetPtrIdx();
      if (HasGetPtr)
        GetPtrPhi->addIncoming(AccessIdx.GetPtrIdx, BB);
      HandlePhi->addIncoming(AccessIdx.HandleIdx, BB);
    }

    if (HasGetPtr)
      Builder.Insert(GetPtrPhi);
    else
      GetPtrPhi = nullptr;

    Builder.Insert(HandlePhi);

    DeadInsts.insert(Phi);
    return {GetPtrPhi, HandlePhi};
  }

  if (auto *Select = dyn_cast<SelectInst>(I)) {
    auto *TrueV = dyn_cast<Instruction>(Select->getTrueValue());
    auto TrueAccessIdx = getAccessIndices(TrueV, DeadInsts);

    auto *FalseV = dyn_cast<Instruction>(Select->getFalseValue());
    auto FalseAccessIdx = getAccessIndices(FalseV, DeadInsts);

    IRBuilder<> Builder(Select);
    Value *GetPtrSelect = nullptr;

    if (TrueAccessIdx.hasGetPtrIdx() && FalseAccessIdx.hasGetPtrIdx())
      GetPtrSelect =
          Builder.CreateSelect(Select->getCondition(), TrueAccessIdx.GetPtrIdx,
                               FalseAccessIdx.GetPtrIdx);

    auto *HandleSelect =
        Builder.CreateSelect(Select->getCondition(), TrueAccessIdx.HandleIdx,
                             FalseAccessIdx.HandleIdx);
    DeadInsts.insert(Select);
    return {GetPtrSelect, HandleSelect};
  }

  llvm_unreachable("collectUsedHandles should assure this does not occur");
}

static void
replaceHandleWithIndices(Instruction *Ptr, IntrinsicInst *OldHandle,
                         SmallSetVector<Instruction *, 16> &DeadInsts) {
  auto AccessIdx = getAccessIndices(Ptr, DeadInsts);
  assert(AccessIdx.hasGetPtrIdx() && AccessIdx.hasHandleIdx() &&
         "Couldn't retrieve indices. This is guaranteed by getAccessIndices");

  IRBuilder<> Builder(Ptr);
  IntrinsicInst *Handle = cast<IntrinsicInst>(OldHandle->clone());
  Handle->setArgOperand(/*Index=*/3, AccessIdx.HandleIdx);
  Builder.Insert(Handle);

  auto *GetPtr =
      Builder.CreateIntrinsic(Ptr->getType(), Intrinsic::dx_resource_getpointer,
                              {Handle, AccessIdx.GetPtrIdx});

  Ptr->replaceAllUsesWith(GetPtr);
  DeadInsts.insert(Ptr);
}

// Try to legalize dx.resource.handlefrom.*.binding and dx.resource.getpointer
// calls with their respective index values and propagate the index values to
// be used at resource access.
//
// If it can't be transformed to be legal then:
//
// Reports an error if a resource access is not guaranteed into a unique global
// resource.
//
// Returns true if any changes are made.
static bool legalizeResourceHandles(Function &F, DXILResourceTypeMap &DRTM) {
  SmallSetVector<Instruction *, 16> DeadInsts;
  for (BasicBlock &BB : make_early_inc_range(F)) {
    for (Instruction &I : BB) {
      if (auto *PtrOp = getStoreLoadPointerOperand(&I)) {
        SmallVector<IntrinsicInst *> Handles = collectUsedHandles(PtrOp);
        unsigned NumHandles = Handles.size();
        if (NumHandles <= 1)
          continue; // Legal, no-replacement required

        bool SameGlobalBinding = true;
        hlsl::Binding B = getHandleIntrinsicBinding(Handles[0], DRTM);
        for (unsigned Idx = 1; Idx < NumHandles; Idx++)
          SameGlobalBinding &=
              (B == getHandleIntrinsicBinding(Handles[Idx], DRTM));

        if (!SameGlobalBinding) {
          diagnoseNonUniqueResourceAccess(&I, Handles);
          continue;
        }

        replaceHandleWithIndices(PtrOp, Handles[0], DeadInsts);
      }
    }
  }

  bool MadeChanges = false;

  for (auto *I : llvm::reverse(DeadInsts))
    if (I->hasNUses(0)) { // Handle can still be used outside of replaced path
      I->eraseFromParent();
      MadeChanges = true;
    }

  return MadeChanges;
}

static void replaceAccess(IntrinsicInst *II, dxil::ResourceTypeInfo &RTI) {
  SmallVector<User *> Worklist;
  for (User *U : II->users())
    Worklist.push_back(U);

  SmallVector<Instruction *> DeadInsts;
  while (!Worklist.empty()) {
    User *U = Worklist.back();
    Worklist.pop_back();

    if (auto *GEP = dyn_cast<GetElementPtrInst>(U)) {
      for (User *U : GEP->users())
        Worklist.push_back(U);
      DeadInsts.push_back(GEP);

    } else if (auto *SI = dyn_cast<StoreInst>(U)) {
      assert(SI->getValueOperand() != II && "Pointer escaped!");
      createStoreIntrinsic(II, SI, RTI);
      DeadInsts.push_back(SI);

    } else if (auto *LI = dyn_cast<LoadInst>(U)) {
      createLoadIntrinsic(II, LI, RTI);
      DeadInsts.push_back(LI);
    } else
      llvm_unreachable("Unhandled instruction - pointer escaped?");
  }

  // Traverse the now-dead instructions in RPO and remove them.
  for (Instruction *Dead : llvm::reverse(DeadInsts))
    Dead->eraseFromParent();
  II->eraseFromParent();
}

static bool transformResourcePointers(Function &F, DXILResourceTypeMap &DRTM) {
  SmallVector<std::pair<IntrinsicInst *, dxil::ResourceTypeInfo>> Resources;
  for (BasicBlock &BB : make_early_inc_range(F))
    for (Instruction &I : BB)
      if (auto *II = dyn_cast<IntrinsicInst>(&I))
        if (II->getIntrinsicID() == Intrinsic::dx_resource_getpointer) {
          auto *HandleTy = cast<TargetExtType>(II->getArgOperand(0)->getType());
          Resources.emplace_back(II, DRTM[HandleTy]);
        }

  for (auto &[II, RI] : Resources)
    replaceAccess(II, RI);

  return !Resources.empty();
}

PreservedAnalyses DXILResourceAccess::run(Function &F,
                                          FunctionAnalysisManager &FAM) {
  auto &MAMProxy = FAM.getResult<ModuleAnalysisManagerFunctionProxy>(F);
  DXILResourceTypeMap *DRTM =
      MAMProxy.getCachedResult<DXILResourceTypeAnalysis>(*F.getParent());
  assert(DRTM && "DXILResourceTypeAnalysis must be available");

  bool MadeHandleChanges = legalizeResourceHandles(F, *DRTM);
  bool MadeResourceChanges = transformResourcePointers(F, *DRTM);
  if (!(MadeHandleChanges || MadeResourceChanges))
    return PreservedAnalyses::all();

  PreservedAnalyses PA;
  PA.preserve<DXILResourceTypeAnalysis>();
  PA.preserve<DominatorTreeAnalysis>();
  return PA;
}

namespace {
class DXILResourceAccessLegacy : public FunctionPass {
public:
  bool runOnFunction(Function &F) override {
    DXILResourceTypeMap &DRTM =
        getAnalysis<DXILResourceTypeWrapperPass>().getResourceTypeMap();
    bool MadeHandleChanges = legalizeResourceHandles(F, DRTM);
    bool MadeResourceChanges = transformResourcePointers(F, DRTM);
    return MadeHandleChanges || MadeResourceChanges;
  }
  StringRef getPassName() const override { return "DXIL Resource Access"; }
  DXILResourceAccessLegacy() : FunctionPass(ID) {}

  static char ID; // Pass identification.
  void getAnalysisUsage(llvm::AnalysisUsage &AU) const override {
    AU.addRequired<DXILResourceTypeWrapperPass>();
    AU.addPreserved<DominatorTreeWrapperPass>();
  }
};
char DXILResourceAccessLegacy::ID = 0;
} // end anonymous namespace

INITIALIZE_PASS_BEGIN(DXILResourceAccessLegacy, DEBUG_TYPE,
                      "DXIL Resource Access", false, false)
INITIALIZE_PASS_DEPENDENCY(DXILResourceTypeWrapperPass)
INITIALIZE_PASS_END(DXILResourceAccessLegacy, DEBUG_TYPE,
                    "DXIL Resource Access", false, false)

FunctionPass *llvm::createDXILResourceAccessLegacyPass() {
  return new DXILResourceAccessLegacy();
}