llvm-project/clang/lib/CodeGen/CGHLSLRuntime.cpp

//===----- CGHLSLRuntime.cpp - Interface to HLSL Runtimes -----------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This provides an abstract class for HLSL code generation.  Concrete
// subclasses of this implement code generation for specific HLSL
// runtime libraries.
//
//===----------------------------------------------------------------------===//

#include "CGHLSLRuntime.h"
#include "CGDebugInfo.h"
#include "CodeGenFunction.h"
#include "CodeGenModule.h"
#include "TargetInfo.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Decl.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/AST/Type.h"
#include "clang/Basic/TargetOptions.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Frontend/HLSL/HLSLRootSignatureUtils.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Alignment.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FormatVariadic.h"

using namespace clang;
using namespace CodeGen;
using namespace clang::hlsl;
using namespace llvm;

using llvm::hlsl::CBufferRowSizeInBytes;

namespace {

void addDxilValVersion(StringRef ValVersionStr, llvm::Module &M) {
  // The validation of ValVersionStr is done at HLSLToolChain::TranslateArgs.
  // Assume ValVersionStr is legal here.
  VersionTuple Version;
  if (Version.tryParse(ValVersionStr) || Version.getBuild() ||
      Version.getSubminor() || !Version.getMinor()) {
    return;
  }

  uint64_t Major = Version.getMajor();
  uint64_t Minor = *Version.getMinor();

  auto &Ctx = M.getContext();
  IRBuilder<> B(M.getContext());
  MDNode *Val = MDNode::get(Ctx, {ConstantAsMetadata::get(B.getInt32(Major)),
                                  ConstantAsMetadata::get(B.getInt32(Minor))});
  StringRef DXILValKey = "dx.valver";
  auto *DXILValMD = M.getOrInsertNamedMetadata(DXILValKey);
  DXILValMD->addOperand(Val);
}

void addRootSignature(ArrayRef<llvm::hlsl::rootsig::RootElement> Elements,
                      llvm::Function *Fn, llvm::Module &M) {
  auto &Ctx = M.getContext();

  llvm::hlsl::rootsig::MetadataBuilder Builder(Ctx, Elements);
  MDNode *RootSignature = Builder.BuildRootSignature();
  MDNode *FnPairing =
      MDNode::get(Ctx, {ValueAsMetadata::get(Fn), RootSignature});

  StringRef RootSignatureValKey = "dx.rootsignatures";
  auto *RootSignatureValMD = M.getOrInsertNamedMetadata(RootSignatureValKey);
  RootSignatureValMD->addOperand(FnPairing);
}

} // namespace

llvm::Type *
CGHLSLRuntime::convertHLSLSpecificType(const Type *T,
                                       SmallVector<int32_t> *Packoffsets) {
  assert(T->isHLSLSpecificType() && "Not an HLSL specific type!");

  // Check if the target has a specific translation for this type first.
  if (llvm::Type *TargetTy =
          CGM.getTargetCodeGenInfo().getHLSLType(CGM, T, Packoffsets))
    return TargetTy;

  llvm_unreachable("Generic handling of HLSL types is not supported.");
}

llvm::Triple::ArchType CGHLSLRuntime::getArch() {
  return CGM.getTarget().getTriple().getArch();
}

// Returns true if the type is an HLSL resource class or an array of them
static bool isResourceRecordTypeOrArrayOf(const clang::Type *Ty) {
  while (const ConstantArrayType *CAT = dyn_cast<ConstantArrayType>(Ty))
    Ty = CAT->getArrayElementTypeNoTypeQual();
  return Ty->isHLSLResourceRecord();
}

// Emits constant global variables for buffer constants declarations
// and creates metadata linking the constant globals with the buffer global.
void CGHLSLRuntime::emitBufferGlobalsAndMetadata(const HLSLBufferDecl *BufDecl,
                                                 llvm::GlobalVariable *BufGV) {
  LLVMContext &Ctx = CGM.getLLVMContext();

  // get the layout struct from constant buffer target type
  llvm::Type *BufType = BufGV->getValueType();
  llvm::Type *BufLayoutType =
      cast<llvm::TargetExtType>(BufType)->getTypeParameter(0);
  llvm::StructType *LayoutStruct = cast<llvm::StructType>(
      cast<llvm::TargetExtType>(BufLayoutType)->getTypeParameter(0));

  // Start metadata list associating the buffer global variable with its
  // constatns
  SmallVector<llvm::Metadata *> BufGlobals;
  BufGlobals.push_back(ValueAsMetadata::get(BufGV));

  const auto *ElemIt = LayoutStruct->element_begin();
  for (Decl *D : BufDecl->buffer_decls()) {
    if (isa<CXXRecordDecl, EmptyDecl>(D))
      // Nothing to do for this declaration.
      continue;
    if (isa<FunctionDecl>(D)) {
      // A function within an cbuffer is effectively a top-level function.
      CGM.EmitTopLevelDecl(D);
      continue;
    }
    VarDecl *VD = dyn_cast<VarDecl>(D);
    if (!VD)
      continue;

    QualType VDTy = VD->getType();
    if (VDTy.getAddressSpace() != LangAS::hlsl_constant) {
      if (VD->getStorageClass() == SC_Static ||
          VDTy.getAddressSpace() == LangAS::hlsl_groupshared ||
          isResourceRecordTypeOrArrayOf(VDTy.getTypePtr())) {
        // Emit static and groupshared variables and resource classes inside
        // cbuffer as regular globals
        CGM.EmitGlobal(VD);
      } else {
        // Anything else that is not in the hlsl_constant address space must be
        // an empty struct or a zero-sized array and can be ignored
        assert(BufDecl->getASTContext().getTypeSize(VDTy) == 0 &&
               "constant buffer decl with non-zero sized type outside of "
               "hlsl_constant address space");
      }
      continue;
    }

    assert(ElemIt != LayoutStruct->element_end() &&
           "number of elements in layout struct does not match");
    llvm::Type *LayoutType = *ElemIt++;

    // FIXME: handle resources inside user defined structs
    // (llvm/wg-hlsl#175)

    // create global variable for the constant and to metadata list
    GlobalVariable *ElemGV =
        cast<GlobalVariable>(CGM.GetAddrOfGlobalVar(VD, LayoutType));
    BufGlobals.push_back(ValueAsMetadata::get(ElemGV));
  }
  assert(ElemIt == LayoutStruct->element_end() &&
         "number of elements in layout struct does not match");

  // add buffer metadata to the module
  CGM.getModule()
      .getOrInsertNamedMetadata("hlsl.cbs")
      ->addOperand(MDNode::get(Ctx, BufGlobals));
}

// Creates resource handle type for the HLSL buffer declaration
static const clang::HLSLAttributedResourceType *
createBufferHandleType(const HLSLBufferDecl *BufDecl) {
  ASTContext &AST = BufDecl->getASTContext();
  QualType QT = AST.getHLSLAttributedResourceType(
      AST.HLSLResourceTy,
      QualType(BufDecl->getLayoutStruct()->getTypeForDecl(), 0),
      HLSLAttributedResourceType::Attributes(ResourceClass::CBuffer));
  return cast<HLSLAttributedResourceType>(QT.getTypePtr());
}

// Iterates over all declarations in the HLSL buffer and based on the
// packoffset or register(c#) annotations it fills outs the Layout
// vector with the user-specified layout offsets.
// The buffer offsets can be specified 2 ways:
// 1. declarations in cbuffer {} block can have a packoffset annotation
//    (translates to HLSLPackOffsetAttr)
// 2. default constant buffer declarations at global scope can have
//    register(c#) annotations (translates to HLSLResourceBindingAttr with
//    RegisterType::C)
// It is not guaranteed that all declarations in a buffer have an annotation.
// For those where it is not specified a -1 value is added to the Layout
// vector. In the final layout these declarations will be placed at the end
// of the HLSL buffer after all of the elements with specified offset.
static void fillPackoffsetLayout(const HLSLBufferDecl *BufDecl,
                                 SmallVector<int32_t> &Layout) {
  assert(Layout.empty() && "expected empty vector for layout");
  assert(BufDecl->hasValidPackoffset());

  for (Decl *D : BufDecl->buffer_decls()) {
    if (isa<CXXRecordDecl, EmptyDecl>(D) || isa<FunctionDecl>(D)) {
      continue;
    }
    VarDecl *VD = dyn_cast<VarDecl>(D);
    if (!VD || VD->getType().getAddressSpace() != LangAS::hlsl_constant)
      continue;

    if (!VD->hasAttrs()) {
      Layout.push_back(-1);
      continue;
    }

    int32_t Offset = -1;
    for (auto *Attr : VD->getAttrs()) {
      if (auto *POA = dyn_cast<HLSLPackOffsetAttr>(Attr)) {
        Offset = POA->getOffsetInBytes();
        break;
      }
      auto *RBA = dyn_cast<HLSLResourceBindingAttr>(Attr);
      if (RBA &&
          RBA->getRegisterType() == HLSLResourceBindingAttr::RegisterType::C) {
        Offset = RBA->getSlotNumber() * CBufferRowSizeInBytes;
        break;
      }
    }
    Layout.push_back(Offset);
  }
}

// Codegen for HLSLBufferDecl
void CGHLSLRuntime::addBuffer(const HLSLBufferDecl *BufDecl) {

  assert(BufDecl->isCBuffer() && "tbuffer codegen is not supported yet");

  // create resource handle type for the buffer
  const clang::HLSLAttributedResourceType *ResHandleTy =
      createBufferHandleType(BufDecl);

  // empty constant buffer is ignored
  if (ResHandleTy->getContainedType()->getAsCXXRecordDecl()->isEmpty())
    return;

  // create global variable for the constant buffer
  SmallVector<int32_t> Layout;
  if (BufDecl->hasValidPackoffset())
    fillPackoffsetLayout(BufDecl, Layout);

  llvm::TargetExtType *TargetTy =
      cast<llvm::TargetExtType>(convertHLSLSpecificType(
          ResHandleTy, BufDecl->hasValidPackoffset() ? &Layout : nullptr));
  llvm::GlobalVariable *BufGV = new GlobalVariable(
      TargetTy, /*isConstant*/ false,
      GlobalValue::LinkageTypes::ExternalLinkage, PoisonValue::get(TargetTy),
      llvm::formatv("{0}{1}", BufDecl->getName(),
                    BufDecl->isCBuffer() ? ".cb" : ".tb"),
      GlobalValue::NotThreadLocal);
  CGM.getModule().insertGlobalVariable(BufGV);

  // Add globals for constant buffer elements and create metadata nodes
  emitBufferGlobalsAndMetadata(BufDecl, BufGV);

  // Initialize cbuffer from binding (implicit or explicit)
  HLSLResourceBindingAttr *RBA = BufDecl->getAttr<HLSLResourceBindingAttr>();
  assert(RBA &&
         "cbuffer/tbuffer should always have resource binding attribute");
  initializeBufferFromBinding(BufDecl, BufGV, RBA);
}

llvm::TargetExtType *
CGHLSLRuntime::getHLSLBufferLayoutType(const RecordType *StructType) {
  const auto Entry = LayoutTypes.find(StructType);
  if (Entry != LayoutTypes.end())
    return Entry->getSecond();
  return nullptr;
}

void CGHLSLRuntime::addHLSLBufferLayoutType(const RecordType *StructType,
                                            llvm::TargetExtType *LayoutTy) {
  assert(getHLSLBufferLayoutType(StructType) == nullptr &&
         "layout type for this struct already exist");
  LayoutTypes[StructType] = LayoutTy;
}

void CGHLSLRuntime::finishCodeGen() {
  auto &TargetOpts = CGM.getTarget().getTargetOpts();
  auto &CodeGenOpts = CGM.getCodeGenOpts();
  auto &LangOpts = CGM.getLangOpts();
  llvm::Module &M = CGM.getModule();
  Triple T(M.getTargetTriple());
  if (T.getArch() == Triple::ArchType::dxil)
    addDxilValVersion(TargetOpts.DxilValidatorVersion, M);
  if (CodeGenOpts.ResMayAlias)
    M.setModuleFlag(llvm::Module::ModFlagBehavior::Error, "dx.resmayalias", 1);

  // NativeHalfType corresponds to the -fnative-half-type clang option which is
  // aliased by clang-dxc's -enable-16bit-types option. This option is used to
  // set the UseNativeLowPrecision DXIL module flag in the DirectX backend
  if (LangOpts.NativeHalfType)
    M.setModuleFlag(llvm::Module::ModFlagBehavior::Error, "dx.nativelowprec",
                    1);

  generateGlobalCtorDtorCalls();
}

void clang::CodeGen::CGHLSLRuntime::setHLSLEntryAttributes(
    const FunctionDecl *FD, llvm::Function *Fn) {
  const auto *ShaderAttr = FD->getAttr<HLSLShaderAttr>();
  assert(ShaderAttr && "All entry functions must have a HLSLShaderAttr");
  const StringRef ShaderAttrKindStr = "hlsl.shader";
  Fn->addFnAttr(ShaderAttrKindStr,
                llvm::Triple::getEnvironmentTypeName(ShaderAttr->getType()));
  if (HLSLNumThreadsAttr *NumThreadsAttr = FD->getAttr<HLSLNumThreadsAttr>()) {
    const StringRef NumThreadsKindStr = "hlsl.numthreads";
    std::string NumThreadsStr =
        formatv("{0},{1},{2}", NumThreadsAttr->getX(), NumThreadsAttr->getY(),
                NumThreadsAttr->getZ());
    Fn->addFnAttr(NumThreadsKindStr, NumThreadsStr);
  }
  if (HLSLWaveSizeAttr *WaveSizeAttr = FD->getAttr<HLSLWaveSizeAttr>()) {
    const StringRef WaveSizeKindStr = "hlsl.wavesize";
    std::string WaveSizeStr =
        formatv("{0},{1},{2}", WaveSizeAttr->getMin(), WaveSizeAttr->getMax(),
                WaveSizeAttr->getPreferred());
    Fn->addFnAttr(WaveSizeKindStr, WaveSizeStr);
  }
  // HLSL entry functions are materialized for module functions with
  // HLSLShaderAttr attribute. SetLLVMFunctionAttributesForDefinition called
  // later in the compiler-flow for such module functions is not aware of and
  // hence not able to set attributes of the newly materialized entry functions.
  // So, set attributes of entry function here, as appropriate.
  if (CGM.getCodeGenOpts().OptimizationLevel == 0)
    Fn->addFnAttr(llvm::Attribute::OptimizeNone);
  Fn->addFnAttr(llvm::Attribute::NoInline);
}

static Value *buildVectorInput(IRBuilder<> &B, Function *F, llvm::Type *Ty) {
  if (const auto *VT = dyn_cast<FixedVectorType>(Ty)) {
    Value *Result = PoisonValue::get(Ty);
    for (unsigned I = 0; I < VT->getNumElements(); ++I) {
      Value *Elt = B.CreateCall(F, {B.getInt32(I)});
      Result = B.CreateInsertElement(Result, Elt, I);
    }
    return Result;
  }
  return B.CreateCall(F, {B.getInt32(0)});
}

static void addSPIRVBuiltinDecoration(llvm::GlobalVariable *GV,
                                      unsigned BuiltIn) {
  LLVMContext &Ctx = GV->getContext();
  IRBuilder<> B(GV->getContext());
  MDNode *Operands = MDNode::get(
      Ctx,
      {ConstantAsMetadata::get(B.getInt32(/* Spirv::Decoration::BuiltIn */ 11)),
       ConstantAsMetadata::get(B.getInt32(BuiltIn))});
  MDNode *Decoration = MDNode::get(Ctx, {Operands});
  GV->addMetadata("spirv.Decorations", *Decoration);
}

static llvm::Value *createSPIRVBuiltinLoad(IRBuilder<> &B, llvm::Module &M,
                                           llvm::Type *Ty, const Twine &Name,
                                           unsigned BuiltInID) {
  auto *GV = new llvm::GlobalVariable(
      M, Ty, /* isConstant= */ true, llvm::GlobalValue::ExternalLinkage,
      /* Initializer= */ nullptr, Name, /* insertBefore= */ nullptr,
      llvm::GlobalVariable::GeneralDynamicTLSModel,
      /* AddressSpace */ 7, /* isExternallyInitialized= */ true);
  addSPIRVBuiltinDecoration(GV, BuiltInID);
  return B.CreateLoad(Ty, GV);
}

llvm::Value *CGHLSLRuntime::emitInputSemantic(IRBuilder<> &B,
                                              const ParmVarDecl &D,
                                              llvm::Type *Ty) {
  assert(D.hasAttrs() && "Entry parameter missing annotation attribute!");
  if (D.hasAttr<HLSLSV_GroupIndexAttr>()) {
    llvm::Function *GroupIndex =
        CGM.getIntrinsic(getFlattenedThreadIdInGroupIntrinsic());
    return B.CreateCall(FunctionCallee(GroupIndex));
  }
  if (D.hasAttr<HLSLSV_DispatchThreadIDAttr>()) {
    llvm::Function *ThreadIDIntrinsic =
        CGM.getIntrinsic(getThreadIdIntrinsic());
    return buildVectorInput(B, ThreadIDIntrinsic, Ty);
  }
  if (D.hasAttr<HLSLSV_GroupThreadIDAttr>()) {
    llvm::Function *GroupThreadIDIntrinsic =
        CGM.getIntrinsic(getGroupThreadIdIntrinsic());
    return buildVectorInput(B, GroupThreadIDIntrinsic, Ty);
  }
  if (D.hasAttr<HLSLSV_GroupIDAttr>()) {
    llvm::Function *GroupIDIntrinsic = CGM.getIntrinsic(getGroupIdIntrinsic());
    return buildVectorInput(B, GroupIDIntrinsic, Ty);
  }
  if (D.hasAttr<HLSLSV_PositionAttr>()) {
    if (getArch() == llvm::Triple::spirv)
      return createSPIRVBuiltinLoad(B, CGM.getModule(), Ty, "sv_position",
                                    /* BuiltIn::Position */ 0);
    llvm_unreachable("SV_Position semantic not implemented for this target.");
  }
  assert(false && "Unhandled parameter attribute");
  return nullptr;
}

void CGHLSLRuntime::emitEntryFunction(const FunctionDecl *FD,
                                      llvm::Function *Fn) {
  llvm::Module &M = CGM.getModule();
  llvm::LLVMContext &Ctx = M.getContext();
  auto *EntryTy = llvm::FunctionType::get(llvm::Type::getVoidTy(Ctx), false);
  Function *EntryFn =
      Function::Create(EntryTy, Function::ExternalLinkage, FD->getName(), &M);

  // Copy function attributes over, we have no argument or return attributes
  // that can be valid on the real entry.
  AttributeList NewAttrs = AttributeList::get(Ctx, AttributeList::FunctionIndex,
                                              Fn->getAttributes().getFnAttrs());
  EntryFn->setAttributes(NewAttrs);
  setHLSLEntryAttributes(FD, EntryFn);

  // Set the called function as internal linkage.
  Fn->setLinkage(GlobalValue::InternalLinkage);

  BasicBlock *BB = BasicBlock::Create(Ctx, "entry", EntryFn);
  IRBuilder<> B(BB);
  llvm::SmallVector<Value *> Args;

  SmallVector<OperandBundleDef, 1> OB;
  if (CGM.shouldEmitConvergenceTokens()) {
    assert(EntryFn->isConvergent());
    llvm::Value *I =
        B.CreateIntrinsic(llvm::Intrinsic::experimental_convergence_entry, {});
    llvm::Value *bundleArgs[] = {I};
    OB.emplace_back("convergencectrl", bundleArgs);
  }

  // FIXME: support struct parameters where semantics are on members.
  // See: https://github.com/llvm/llvm-project/issues/57874
  unsigned SRetOffset = 0;
  for (const auto &Param : Fn->args()) {
    if (Param.hasStructRetAttr()) {
      // FIXME: support output.
      // See: https://github.com/llvm/llvm-project/issues/57874
      SRetOffset = 1;
      Args.emplace_back(PoisonValue::get(Param.getType()));
      continue;
    }
    const ParmVarDecl *PD = FD->getParamDecl(Param.getArgNo() - SRetOffset);
    Args.push_back(emitInputSemantic(B, *PD, Param.getType()));
  }

  CallInst *CI = B.CreateCall(FunctionCallee(Fn), Args, OB);
  CI->setCallingConv(Fn->getCallingConv());
  // FIXME: Handle codegen for return type semantics.
  // See: https://github.com/llvm/llvm-project/issues/57875
  B.CreateRetVoid();

  // Add and identify root signature to function, if applicable
  for (const Attr *Attr : FD->getAttrs()) {
    if (const auto *RSAttr = dyn_cast<RootSignatureAttr>(Attr))
      addRootSignature(RSAttr->getSignatureDecl()->getRootElements(), EntryFn,
                       M);
  }
}

static void gatherFunctions(SmallVectorImpl<Function *> &Fns, llvm::Module &M,
                            bool CtorOrDtor) {
  const auto *GV =
      M.getNamedGlobal(CtorOrDtor ? "llvm.global_ctors" : "llvm.global_dtors");
  if (!GV)
    return;
  const auto *CA = dyn_cast<ConstantArray>(GV->getInitializer());
  if (!CA)
    return;
  // The global_ctor array elements are a struct [Priority, Fn *, COMDat].
  // HLSL neither supports priorities or COMDat values, so we will check those
  // in an assert but not handle them.

  for (const auto &Ctor : CA->operands()) {
    if (isa<ConstantAggregateZero>(Ctor))
      continue;
    ConstantStruct *CS = cast<ConstantStruct>(Ctor);

    assert(cast<ConstantInt>(CS->getOperand(0))->getValue() == 65535 &&
           "HLSL doesn't support setting priority for global ctors.");
    assert(isa<ConstantPointerNull>(CS->getOperand(2)) &&
           "HLSL doesn't support COMDat for global ctors.");
    Fns.push_back(cast<Function>(CS->getOperand(1)));
  }
}

void CGHLSLRuntime::generateGlobalCtorDtorCalls() {
  llvm::Module &M = CGM.getModule();
  SmallVector<Function *> CtorFns;
  SmallVector<Function *> DtorFns;
  gatherFunctions(CtorFns, M, true);
  gatherFunctions(DtorFns, M, false);

  // Insert a call to the global constructor at the beginning of the entry block
  // to externally exported functions. This is a bit of a hack, but HLSL allows
  // global constructors, but doesn't support driver initialization of globals.
  for (auto &F : M.functions()) {
    if (!F.hasFnAttribute("hlsl.shader"))
      continue;
    auto *Token = getConvergenceToken(F.getEntryBlock());
    Instruction *IP = &*F.getEntryBlock().begin();
    SmallVector<OperandBundleDef, 1> OB;
    if (Token) {
      llvm::Value *bundleArgs[] = {Token};
      OB.emplace_back("convergencectrl", bundleArgs);
      IP = Token->getNextNode();
    }
    IRBuilder<> B(IP);
    for (auto *Fn : CtorFns) {
      auto CI = B.CreateCall(FunctionCallee(Fn), {}, OB);
      CI->setCallingConv(Fn->getCallingConv());
    }

    // Insert global dtors before the terminator of the last instruction
    B.SetInsertPoint(F.back().getTerminator());
    for (auto *Fn : DtorFns) {
      auto CI = B.CreateCall(FunctionCallee(Fn), {}, OB);
      CI->setCallingConv(Fn->getCallingConv());
    }
  }

  // No need to keep global ctors/dtors for non-lib profile after call to
  // ctors/dtors added for entry.
  Triple T(M.getTargetTriple());
  if (T.getEnvironment() != Triple::EnvironmentType::Library) {
    if (auto *GV = M.getNamedGlobal("llvm.global_ctors"))
      GV->eraseFromParent();
    if (auto *GV = M.getNamedGlobal("llvm.global_dtors"))
      GV->eraseFromParent();
  }
}

static void initializeBuffer(CodeGenModule &CGM, llvm::GlobalVariable *GV,
                             Intrinsic::ID IntrID,
                             ArrayRef<llvm::Value *> Args) {

  LLVMContext &Ctx = CGM.getLLVMContext();
  llvm::Function *InitResFunc = llvm::Function::Create(
      llvm::FunctionType::get(CGM.VoidTy, false),
      llvm::GlobalValue::InternalLinkage,
      ("_init_buffer_" + GV->getName()).str(), CGM.getModule());
  InitResFunc->addFnAttr(llvm::Attribute::AlwaysInline);

  llvm::BasicBlock *EntryBB =
      llvm::BasicBlock::Create(Ctx, "entry", InitResFunc);
  CGBuilderTy Builder(CGM, Ctx);
  const DataLayout &DL = CGM.getModule().getDataLayout();
  Builder.SetInsertPoint(EntryBB);

  // Make sure the global variable is buffer resource handle
  llvm::Type *HandleTy = GV->getValueType();
  assert(HandleTy->isTargetExtTy() && "unexpected type of the buffer global");

  llvm::Value *CreateHandle = Builder.CreateIntrinsic(
      /*ReturnType=*/HandleTy, IntrID, Args, nullptr,
      Twine(GV->getName()).concat("_h"));

  llvm::Value *HandleRef = Builder.CreateStructGEP(GV->getValueType(), GV, 0);
  Builder.CreateAlignedStore(CreateHandle, HandleRef,
                             HandleRef->getPointerAlignment(DL));
  Builder.CreateRetVoid();

  CGM.AddCXXGlobalInit(InitResFunc);
}

void CGHLSLRuntime::initializeBufferFromBinding(const HLSLBufferDecl *BufDecl,
                                                llvm::GlobalVariable *GV,
                                                HLSLResourceBindingAttr *RBA) {
  llvm::Type *Int1Ty = llvm::Type::getInt1Ty(CGM.getLLVMContext());
  auto *NonUniform = llvm::ConstantInt::get(Int1Ty, false);
  auto *Index = llvm::ConstantInt::get(CGM.IntTy, 0);
  auto *RangeSize = llvm::ConstantInt::get(CGM.IntTy, 1);
  auto *Space =
      llvm::ConstantInt::get(CGM.IntTy, RBA ? RBA->getSpaceNumber() : 0);
  Value *Name = nullptr;

  llvm::Intrinsic::ID IntrinsicID =
      RBA->hasRegisterSlot()
          ? CGM.getHLSLRuntime().getCreateHandleFromBindingIntrinsic()
          : CGM.getHLSLRuntime().getCreateHandleFromImplicitBindingIntrinsic();

  std::string Str(BufDecl->getName());
  std::string GlobalName(Str + ".str");
  Name = CGM.GetAddrOfConstantCString(Str, GlobalName.c_str()).getPointer();

  // buffer with explicit binding
  if (RBA->hasRegisterSlot()) {
    auto *RegSlot = llvm::ConstantInt::get(CGM.IntTy, RBA->getSlotNumber());
    SmallVector<Value *> Args{Space, RegSlot,    RangeSize,
                              Index, NonUniform, Name};
    initializeBuffer(CGM, GV, IntrinsicID, Args);
  } else {
    // buffer with implicit binding
    auto *OrderID =
        llvm::ConstantInt::get(CGM.IntTy, RBA->getImplicitBindingOrderID());
    SmallVector<Value *> Args{OrderID, Space,      RangeSize,
                              Index,   NonUniform, Name};
    initializeBuffer(CGM, GV, IntrinsicID, Args);
  }
}

void CGHLSLRuntime::handleGlobalVarDefinition(const VarDecl *VD,
                                              llvm::GlobalVariable *GV) {
  if (auto Attr = VD->getAttr<HLSLVkExtBuiltinInputAttr>())
    addSPIRVBuiltinDecoration(GV, Attr->getBuiltIn());
}

llvm::Instruction *CGHLSLRuntime::getConvergenceToken(BasicBlock &BB) {
  if (!CGM.shouldEmitConvergenceTokens())
    return nullptr;

  auto E = BB.end();
  for (auto I = BB.begin(); I != E; ++I) {
    auto *II = dyn_cast<llvm::IntrinsicInst>(&*I);
    if (II && llvm::isConvergenceControlIntrinsic(II->getIntrinsicID())) {
      return II;
    }
  }
  llvm_unreachable("Convergence token should have been emitted.");
  return nullptr;
}

class OpaqueValueVisitor : public RecursiveASTVisitor<OpaqueValueVisitor> {
public:
  llvm::SmallPtrSet<OpaqueValueExpr *, 8> OVEs;
  OpaqueValueVisitor() {}

  bool VisitOpaqueValueExpr(OpaqueValueExpr *E) {
    OVEs.insert(E);
    return true;
  }
};

void CGHLSLRuntime::emitInitListOpaqueValues(CodeGenFunction &CGF,
                                             InitListExpr *E) {

  typedef CodeGenFunction::OpaqueValueMappingData OpaqueValueMappingData;
  OpaqueValueVisitor Visitor;
  Visitor.TraverseStmt(E);
  for (auto *OVE : Visitor.OVEs) {
    if (CGF.isOpaqueValueEmitted(OVE))
      continue;
    if (OpaqueValueMappingData::shouldBindAsLValue(OVE)) {
      LValue LV = CGF.EmitLValue(OVE->getSourceExpr());
      OpaqueValueMappingData::bind(CGF, OVE, LV);
    } else {
      RValue RV = CGF.EmitAnyExpr(OVE->getSourceExpr());
      OpaqueValueMappingData::bind(CGF, OVE, RV);
    }
  }
}