//===- GPUOpsLowering.cpp - GPU FuncOp / ReturnOp lowering ----------------===//
//
// 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 "GPUOpsLowering.h"

#include "mlir/Conversion/GPUCommon/GPUCommonPass.h"
#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
#include "mlir/IR/Attributes.h"
#include "mlir/IR/Builders.h"
#include "mlir/IR/BuiltinTypes.h"
#include "llvm/ADT/SmallVectorExtras.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/Support/FormatVariadic.h"

using namespace mlir;

LogicalResult
GPUFuncOpLowering::matchAndRewrite(gpu::GPUFuncOp gpuFuncOp, OpAdaptor adaptor,
                                   ConversionPatternRewriter &rewriter) const {
  Location loc = gpuFuncOp.getLoc();

  SmallVector<LLVM::GlobalOp, 3> workgroupBuffers;
  workgroupBuffers.reserve(gpuFuncOp.getNumWorkgroupAttributions());
  for (const auto &en : llvm::enumerate(gpuFuncOp.getWorkgroupAttributions())) {
    BlockArgument attribution = en.value();

    auto type = dyn_cast<MemRefType>(attribution.getType());
    assert(type && type.hasStaticShape() && "unexpected type in attribution");

    uint64_t numElements = type.getNumElements();

    auto elementType =
        cast<Type>(typeConverter->convertType(type.getElementType()));
    auto arrayType = LLVM::LLVMArrayType::get(elementType, numElements);
    std::string name = std::string(
        llvm::formatv("__wg_{0}_{1}", gpuFuncOp.getName(), en.index()));
    uint64_t alignment = 0;
    if (auto alignAttr =
            dyn_cast_or_null<IntegerAttr>(gpuFuncOp.getWorkgroupAttributionAttr(
                en.index(), LLVM::LLVMDialect::getAlignAttrName())))
      alignment = alignAttr.getInt();
    auto globalOp = rewriter.create<LLVM::GlobalOp>(
        gpuFuncOp.getLoc(), arrayType, /*isConstant=*/false,
        LLVM::Linkage::Internal, name, /*value=*/Attribute(), alignment,
        workgroupAddrSpace);
    workgroupBuffers.push_back(globalOp);
  }

  // Remap proper input types.
  TypeConverter::SignatureConversion signatureConversion(
      gpuFuncOp.front().getNumArguments());

  Type funcType = getTypeConverter()->convertFunctionSignature(
      gpuFuncOp.getFunctionType(), /*isVariadic=*/false,
      getTypeConverter()->getOptions().useBarePtrCallConv, signatureConversion);
  if (!funcType) {
    return rewriter.notifyMatchFailure(gpuFuncOp, [&](Diagnostic &diag) {
      diag << "failed to convert function signature type for: "
           << gpuFuncOp.getFunctionType();
    });
  }

  // Create the new function operation. Only copy those attributes that are
  // not specific to function modeling.
  SmallVector<NamedAttribute, 4> attributes;
  ArrayAttr argAttrs;
  for (const auto &attr : gpuFuncOp->getAttrs()) {
    if (attr.getName() == SymbolTable::getSymbolAttrName() ||
        attr.getName() == gpuFuncOp.getFunctionTypeAttrName() ||
        attr.getName() ==
            gpu::GPUFuncOp::getNumWorkgroupAttributionsAttrName() ||
        attr.getName() == gpuFuncOp.getWorkgroupAttribAttrsAttrName() ||
        attr.getName() == gpuFuncOp.getPrivateAttribAttrsAttrName())
      continue;
    if (attr.getName() == gpuFuncOp.getArgAttrsAttrName()) {
      argAttrs = gpuFuncOp.getArgAttrsAttr();
      continue;
    }
    attributes.push_back(attr);
  }
  // Add a dialect specific kernel attribute in addition to GPU kernel
  // attribute. The former is necessary for further translation while the
  // latter is expected by gpu.launch_func.
  if (gpuFuncOp.isKernel())
    attributes.emplace_back(kernelAttributeName, rewriter.getUnitAttr());
  auto llvmFuncOp = rewriter.create<LLVM::LLVMFuncOp>(
      gpuFuncOp.getLoc(), gpuFuncOp.getName(), funcType,
      LLVM::Linkage::External, /*dsoLocal=*/false, /*cconv=*/LLVM::CConv::C,
      /*comdat=*/nullptr, attributes);

  {
    // Insert operations that correspond to converted workgroup and private
    // memory attributions to the body of the function. This must operate on
    // the original function, before the body region is inlined in the new
    // function to maintain the relation between block arguments and the
    // parent operation that assigns their semantics.
    OpBuilder::InsertionGuard guard(rewriter);

    // Rewrite workgroup memory attributions to addresses of global buffers.
    rewriter.setInsertionPointToStart(&gpuFuncOp.front());
    unsigned numProperArguments = gpuFuncOp.getNumArguments();

    for (const auto &en : llvm::enumerate(workgroupBuffers)) {
      LLVM::GlobalOp global = en.value();
      auto ptrType = LLVM::LLVMPointerType::get(rewriter.getContext(),
                                                global.getAddrSpace());
      Value address = rewriter.create<LLVM::AddressOfOp>(
          loc, ptrType, global.getSymNameAttr());
      Value memory =
          rewriter.create<LLVM::GEPOp>(loc, ptrType, global.getType(), address,
                                       ArrayRef<LLVM::GEPArg>{0, 0});

      // Build a memref descriptor pointing to the buffer to plug with the
      // existing memref infrastructure. This may use more registers than
      // otherwise necessary given that memref sizes are fixed, but we can try
      // and canonicalize that away later.
      Value attribution = gpuFuncOp.getWorkgroupAttributions()[en.index()];
      auto type = cast<MemRefType>(attribution.getType());
      auto descr = MemRefDescriptor::fromStaticShape(
          rewriter, loc, *getTypeConverter(), type, memory);
      signatureConversion.remapInput(numProperArguments + en.index(), descr);
    }

    // Rewrite private memory attributions to alloca'ed buffers.
    unsigned numWorkgroupAttributions = gpuFuncOp.getNumWorkgroupAttributions();
    auto int64Ty = IntegerType::get(rewriter.getContext(), 64);
    for (const auto &en : llvm::enumerate(gpuFuncOp.getPrivateAttributions())) {
      Value attribution = en.value();
      auto type = cast<MemRefType>(attribution.getType());
      assert(type && type.hasStaticShape() && "unexpected type in attribution");

      // Explicitly drop memory space when lowering private memory
      // attributions since NVVM models it as `alloca`s in the default
      // memory space and does not support `alloca`s with addrspace(5).
      Type elementType = typeConverter->convertType(type.getElementType());
      auto ptrType =
          LLVM::LLVMPointerType::get(rewriter.getContext(), allocaAddrSpace);
      Value numElements = rewriter.create<LLVM::ConstantOp>(
          gpuFuncOp.getLoc(), int64Ty, type.getNumElements());
      uint64_t alignment = 0;
      if (auto alignAttr =
              dyn_cast_or_null<IntegerAttr>(gpuFuncOp.getPrivateAttributionAttr(
                  en.index(), LLVM::LLVMDialect::getAlignAttrName())))
        alignment = alignAttr.getInt();
      Value allocated = rewriter.create<LLVM::AllocaOp>(
          gpuFuncOp.getLoc(), ptrType, elementType, numElements, alignment);
      auto descr = MemRefDescriptor::fromStaticShape(
          rewriter, loc, *getTypeConverter(), type, allocated);
      signatureConversion.remapInput(
          numProperArguments + numWorkgroupAttributions + en.index(), descr);
    }
  }

  // Move the region to the new function, update the entry block signature.
  rewriter.inlineRegionBefore(gpuFuncOp.getBody(), llvmFuncOp.getBody(),
                              llvmFuncOp.end());
  if (failed(rewriter.convertRegionTypes(&llvmFuncOp.getBody(), *typeConverter,
                                         &signatureConversion)))
    return failure();

  // If bare memref pointers are being used, remap them back to memref
  // descriptors This must be done after signature conversion to get rid of the
  // unrealized casts.
  if (getTypeConverter()->getOptions().useBarePtrCallConv) {
    OpBuilder::InsertionGuard guard(rewriter);
    rewriter.setInsertionPointToStart(&llvmFuncOp.getBody().front());
    for (const auto &en : llvm::enumerate(gpuFuncOp.getArgumentTypes())) {
      auto memrefTy = dyn_cast<MemRefType>(en.value());
      if (!memrefTy)
        continue;
      assert(memrefTy.hasStaticShape() &&
             "Bare pointer convertion used with dynamically-shaped memrefs");
      // Use a placeholder when replacing uses of the memref argument to prevent
      // circular replacements.
      auto remapping = signatureConversion.getInputMapping(en.index());
      assert(remapping && remapping->size == 1 &&
             "Type converter should produce 1-to-1 mapping for bare memrefs");
      BlockArgument newArg =
          llvmFuncOp.getBody().getArgument(remapping->inputNo);
      auto placeholder = rewriter.create<LLVM::UndefOp>(
          loc, getTypeConverter()->convertType(memrefTy));
      rewriter.replaceUsesOfBlockArgument(newArg, placeholder);
      Value desc = MemRefDescriptor::fromStaticShape(
          rewriter, loc, *getTypeConverter(), memrefTy, newArg);
      rewriter.replaceOp(placeholder, {desc});
    }
  }

  // Get memref type from function arguments and set the noalias to
  // pointer arguments.
  for (const auto &en : llvm::enumerate(gpuFuncOp.getArgumentTypes())) {
    auto memrefTy = en.value().dyn_cast<MemRefType>();
    NamedAttrList argAttr = argAttrs
                                ? argAttrs[en.index()].cast<DictionaryAttr>()
                                : NamedAttrList();

    auto copyPointerAttribute = [&](StringRef attrName) {
      Attribute attr = argAttr.erase(attrName);

      // This is a proxy for the bare pointer calling convention.
      if (!attr)
        return;
      auto remapping = signatureConversion.getInputMapping(en.index());
      if (remapping->size > 1 &&
          attrName == LLVM::LLVMDialect::getNoAliasAttrName()) {
        emitWarning(llvmFuncOp.getLoc(),
                    "Cannot copy noalias with non-bare pointers.\n");
        return;
      }
      for (size_t i = 0, e = remapping->size; i < e; ++i) {
        if (llvmFuncOp.getArgument(remapping->inputNo + i)
                .getType()
                .isa<LLVM::LLVMPointerType>()) {
          llvmFuncOp.setArgAttr(remapping->inputNo + i, attrName, attr);
        }
      }
    };

    if (argAttr.empty())
      continue;

    if (memrefTy) {
      copyPointerAttribute(LLVM::LLVMDialect::getNoAliasAttrName());
      copyPointerAttribute(LLVM::LLVMDialect::getReadonlyAttrName());
      copyPointerAttribute(LLVM::LLVMDialect::getWriteOnlyAttrName());
      copyPointerAttribute(LLVM::LLVMDialect::getNonNullAttrName());
      copyPointerAttribute(LLVM::LLVMDialect::getDereferenceableAttrName());
      copyPointerAttribute(
          LLVM::LLVMDialect::getDereferenceableOrNullAttrName());
    }
  }
  rewriter.eraseOp(gpuFuncOp);
  return success();
}

static SmallString<16> getUniqueFormatGlobalName(gpu::GPUModuleOp moduleOp) {
  const char formatStringPrefix[] = "printfFormat_";
  // Get a unique global name.
  unsigned stringNumber = 0;
  SmallString<16> stringConstName;
  do {
    stringConstName.clear();
    (formatStringPrefix + Twine(stringNumber++)).toStringRef(stringConstName);
  } while (moduleOp.lookupSymbol(stringConstName));
  return stringConstName;
}

template <typename T>
static LLVM::LLVMFuncOp getOrDefineFunction(T &moduleOp, const Location loc,
                                            ConversionPatternRewriter &rewriter,
                                            StringRef name,
                                            LLVM::LLVMFunctionType type) {
  LLVM::LLVMFuncOp ret;
  if (!(ret = moduleOp.template lookupSymbol<LLVM::LLVMFuncOp>(name))) {
    ConversionPatternRewriter::InsertionGuard guard(rewriter);
    rewriter.setInsertionPointToStart(moduleOp.getBody());
    ret = rewriter.create<LLVM::LLVMFuncOp>(loc, name, type,
                                            LLVM::Linkage::External);
  }
  return ret;
}

LogicalResult GPUPrintfOpToHIPLowering::matchAndRewrite(
    gpu::PrintfOp gpuPrintfOp, gpu::PrintfOpAdaptor adaptor,
    ConversionPatternRewriter &rewriter) const {
  Location loc = gpuPrintfOp->getLoc();

  mlir::Type llvmI8 = typeConverter->convertType(rewriter.getI8Type());
  auto ptrType = LLVM::LLVMPointerType::get(rewriter.getContext());
  mlir::Type llvmI32 = typeConverter->convertType(rewriter.getI32Type());
  mlir::Type llvmI64 = typeConverter->convertType(rewriter.getI64Type());
  // Note: this is the GPUModule op, not the ModuleOp that surrounds it
  // This ensures that global constants and declarations are placed within
  // the device code, not the host code
  auto moduleOp = gpuPrintfOp->getParentOfType<gpu::GPUModuleOp>();

  auto ocklBegin =
      getOrDefineFunction(moduleOp, loc, rewriter, "__ockl_printf_begin",
                          LLVM::LLVMFunctionType::get(llvmI64, {llvmI64}));
  LLVM::LLVMFuncOp ocklAppendArgs;
  if (!adaptor.getArgs().empty()) {
    ocklAppendArgs = getOrDefineFunction(
        moduleOp, loc, rewriter, "__ockl_printf_append_args",
        LLVM::LLVMFunctionType::get(
            llvmI64, {llvmI64, /*numArgs*/ llvmI32, llvmI64, llvmI64, llvmI64,
                      llvmI64, llvmI64, llvmI64, llvmI64, /*isLast*/ llvmI32}));
  }
  auto ocklAppendStringN = getOrDefineFunction(
      moduleOp, loc, rewriter, "__ockl_printf_append_string_n",
      LLVM::LLVMFunctionType::get(
          llvmI64,
          {llvmI64, ptrType, /*length (bytes)*/ llvmI64, /*isLast*/ llvmI32}));

  /// Start the printf hostcall
  Value zeroI64 = rewriter.create<LLVM::ConstantOp>(loc, llvmI64, 0);
  auto printfBeginCall = rewriter.create<LLVM::CallOp>(loc, ocklBegin, zeroI64);
  Value printfDesc = printfBeginCall.getResult();

  // Get a unique global name for the format.
  SmallString<16> stringConstName = getUniqueFormatGlobalName(moduleOp);

  llvm::SmallString<20> formatString(adaptor.getFormat());
  formatString.push_back('\0'); // Null terminate for C
  size_t formatStringSize = formatString.size_in_bytes();

  auto globalType = LLVM::LLVMArrayType::get(llvmI8, formatStringSize);
  LLVM::GlobalOp global;
  {
    ConversionPatternRewriter::InsertionGuard guard(rewriter);
    rewriter.setInsertionPointToStart(moduleOp.getBody());
    global = rewriter.create<LLVM::GlobalOp>(
        loc, globalType,
        /*isConstant=*/true, LLVM::Linkage::Internal, stringConstName,
        rewriter.getStringAttr(formatString));
  }

  // Get a pointer to the format string's first element and pass it to printf()
  Value globalPtr = rewriter.create<LLVM::AddressOfOp>(
      loc,
      LLVM::LLVMPointerType::get(rewriter.getContext(), global.getAddrSpace()),
      global.getSymNameAttr());
  Value stringStart = rewriter.create<LLVM::GEPOp>(
      loc, ptrType, globalType, globalPtr, ArrayRef<LLVM::GEPArg>{0, 0});
  Value stringLen =
      rewriter.create<LLVM::ConstantOp>(loc, llvmI64, formatStringSize);

  Value oneI32 = rewriter.create<LLVM::ConstantOp>(loc, llvmI32, 1);
  Value zeroI32 = rewriter.create<LLVM::ConstantOp>(loc, llvmI32, 0);

  auto appendFormatCall = rewriter.create<LLVM::CallOp>(
      loc, ocklAppendStringN,
      ValueRange{printfDesc, stringStart, stringLen,
                 adaptor.getArgs().empty() ? oneI32 : zeroI32});
  printfDesc = appendFormatCall.getResult();

  // __ockl_printf_append_args takes 7 values per append call
  constexpr size_t argsPerAppend = 7;
  size_t nArgs = adaptor.getArgs().size();
  for (size_t group = 0; group < nArgs; group += argsPerAppend) {
    size_t bound = std::min(group + argsPerAppend, nArgs);
    size_t numArgsThisCall = bound - group;

    SmallVector<mlir::Value, 2 + argsPerAppend + 1> arguments;
    arguments.push_back(printfDesc);
    arguments.push_back(
        rewriter.create<LLVM::ConstantOp>(loc, llvmI32, numArgsThisCall));
    for (size_t i = group; i < bound; ++i) {
      Value arg = adaptor.getArgs()[i];
      if (auto floatType = dyn_cast<FloatType>(arg.getType())) {
        if (!floatType.isF64())
          arg = rewriter.create<LLVM::FPExtOp>(
              loc, typeConverter->convertType(rewriter.getF64Type()), arg);
        arg = rewriter.create<LLVM::BitcastOp>(loc, llvmI64, arg);
      }
      if (arg.getType().getIntOrFloatBitWidth() != 64)
        arg = rewriter.create<LLVM::ZExtOp>(loc, llvmI64, arg);

      arguments.push_back(arg);
    }
    // Pad out to 7 arguments since the hostcall always needs 7
    for (size_t extra = numArgsThisCall; extra < argsPerAppend; ++extra) {
      arguments.push_back(zeroI64);
    }

    auto isLast = (bound == nArgs) ? oneI32 : zeroI32;
    arguments.push_back(isLast);
    auto call = rewriter.create<LLVM::CallOp>(loc, ocklAppendArgs, arguments);
    printfDesc = call.getResult();
  }
  rewriter.eraseOp(gpuPrintfOp);
  return success();
}

LogicalResult GPUPrintfOpToLLVMCallLowering::matchAndRewrite(
    gpu::PrintfOp gpuPrintfOp, gpu::PrintfOpAdaptor adaptor,
    ConversionPatternRewriter &rewriter) const {
  Location loc = gpuPrintfOp->getLoc();

  mlir::Type llvmI8 = typeConverter->convertType(rewriter.getIntegerType(8));
  mlir::Type ptrType =
      LLVM::LLVMPointerType::get(rewriter.getContext(), addressSpace);

  // Note: this is the GPUModule op, not the ModuleOp that surrounds it
  // This ensures that global constants and declarations are placed within
  // the device code, not the host code
  auto moduleOp = gpuPrintfOp->getParentOfType<gpu::GPUModuleOp>();

  auto printfType =
      LLVM::LLVMFunctionType::get(rewriter.getI32Type(), {ptrType},
                                  /*isVarArg=*/true);
  LLVM::LLVMFuncOp printfDecl =
      getOrDefineFunction(moduleOp, loc, rewriter, "printf", printfType);

  // Get a unique global name for the format.
  SmallString<16> stringConstName = getUniqueFormatGlobalName(moduleOp);

  llvm::SmallString<20> formatString(adaptor.getFormat());
  formatString.push_back('\0'); // Null terminate for C
  auto globalType =
      LLVM::LLVMArrayType::get(llvmI8, formatString.size_in_bytes());
  LLVM::GlobalOp global;
  {
    ConversionPatternRewriter::InsertionGuard guard(rewriter);
    rewriter.setInsertionPointToStart(moduleOp.getBody());
    global = rewriter.create<LLVM::GlobalOp>(
        loc, globalType,
        /*isConstant=*/true, LLVM::Linkage::Internal, stringConstName,
        rewriter.getStringAttr(formatString), /*allignment=*/0, addressSpace);
  }

  // Get a pointer to the format string's first element
  Value globalPtr = rewriter.create<LLVM::AddressOfOp>(
      loc,
      LLVM::LLVMPointerType::get(rewriter.getContext(), global.getAddrSpace()),
      global.getSymNameAttr());
  Value stringStart = rewriter.create<LLVM::GEPOp>(
      loc, ptrType, globalType, globalPtr, ArrayRef<LLVM::GEPArg>{0, 0});

  // Construct arguments and function call
  auto argsRange = adaptor.getArgs();
  SmallVector<Value, 4> printfArgs;
  printfArgs.reserve(argsRange.size() + 1);
  printfArgs.push_back(stringStart);
  printfArgs.append(argsRange.begin(), argsRange.end());

  rewriter.create<LLVM::CallOp>(loc, printfDecl, printfArgs);
  rewriter.eraseOp(gpuPrintfOp);
  return success();
}

LogicalResult GPUPrintfOpToVPrintfLowering::matchAndRewrite(
    gpu::PrintfOp gpuPrintfOp, gpu::PrintfOpAdaptor adaptor,
    ConversionPatternRewriter &rewriter) const {
  Location loc = gpuPrintfOp->getLoc();

  mlir::Type llvmI8 = typeConverter->convertType(rewriter.getIntegerType(8));
  mlir::Type ptrType = LLVM::LLVMPointerType::get(rewriter.getContext());

  // Note: this is the GPUModule op, not the ModuleOp that surrounds it
  // This ensures that global constants and declarations are placed within
  // the device code, not the host code
  auto moduleOp = gpuPrintfOp->getParentOfType<gpu::GPUModuleOp>();

  auto vprintfType =
      LLVM::LLVMFunctionType::get(rewriter.getI32Type(), {ptrType, ptrType});
  LLVM::LLVMFuncOp vprintfDecl =
      getOrDefineFunction(moduleOp, loc, rewriter, "vprintf", vprintfType);

  // Get a unique global name for the format.
  SmallString<16> stringConstName = getUniqueFormatGlobalName(moduleOp);

  llvm::SmallString<20> formatString(adaptor.getFormat());
  formatString.push_back('\0'); // Null terminate for C
  auto globalType =
      LLVM::LLVMArrayType::get(llvmI8, formatString.size_in_bytes());
  LLVM::GlobalOp global;
  {
    ConversionPatternRewriter::InsertionGuard guard(rewriter);
    rewriter.setInsertionPointToStart(moduleOp.getBody());
    global = rewriter.create<LLVM::GlobalOp>(
        loc, globalType,
        /*isConstant=*/true, LLVM::Linkage::Internal, stringConstName,
        rewriter.getStringAttr(formatString), /*allignment=*/0);
  }

  // Get a pointer to the format string's first element
  Value globalPtr = rewriter.create<LLVM::AddressOfOp>(loc, global);
  Value stringStart = rewriter.create<LLVM::GEPOp>(
      loc, ptrType, globalType, globalPtr, ArrayRef<LLVM::GEPArg>{0, 0});
  SmallVector<Type> types;
  SmallVector<Value> args;
  // Promote and pack the arguments into a stack allocation.
  for (Value arg : adaptor.getArgs()) {
    Type type = arg.getType();
    Value promotedArg = arg;
    assert(type.isIntOrFloat());
    if (isa<FloatType>(type)) {
      type = rewriter.getF64Type();
      promotedArg = rewriter.create<LLVM::FPExtOp>(loc, type, arg);
    }
    types.push_back(type);
    args.push_back(promotedArg);
  }
  Type structType =
      LLVM::LLVMStructType::getLiteral(gpuPrintfOp.getContext(), types);
  Value one = rewriter.create<LLVM::ConstantOp>(loc, rewriter.getI64Type(),
                                                rewriter.getIndexAttr(1));
  Value tempAlloc =
      rewriter.create<LLVM::AllocaOp>(loc, ptrType, structType, one,
                                      /*alignment=*/0);
  for (auto [index, arg] : llvm::enumerate(args)) {
    Value ptr = rewriter.create<LLVM::GEPOp>(
        loc, ptrType, structType, tempAlloc, ArrayRef<LLVM::GEPArg>{0, index});
    rewriter.create<LLVM::StoreOp>(loc, arg, ptr);
  }
  std::array<Value, 2> printfArgs = {stringStart, tempAlloc};

  rewriter.create<LLVM::CallOp>(loc, vprintfDecl, printfArgs);
  rewriter.eraseOp(gpuPrintfOp);
  return success();
}

/// Unrolls op if it's operating on vectors.
LogicalResult impl::scalarizeVectorOp(Operation *op, ValueRange operands,
                                      ConversionPatternRewriter &rewriter,
                                      const LLVMTypeConverter &converter) {
  TypeRange operandTypes(operands);
  if (llvm::none_of(operandTypes,
                    [](Type type) { return isa<VectorType>(type); })) {
    return rewriter.notifyMatchFailure(op, "expected vector operand");
  }
  if (op->getNumRegions() != 0 || op->getNumSuccessors() != 0)
    return rewriter.notifyMatchFailure(op, "expected no region/successor");
  if (op->getNumResults() != 1)
    return rewriter.notifyMatchFailure(op, "expected single result");
  VectorType vectorType = dyn_cast<VectorType>(op->getResult(0).getType());
  if (!vectorType)
    return rewriter.notifyMatchFailure(op, "expected vector result");

  Location loc = op->getLoc();
  Value result = rewriter.create<LLVM::UndefOp>(loc, vectorType);
  Type indexType = converter.convertType(rewriter.getIndexType());
  StringAttr name = op->getName().getIdentifier();
  Type elementType = vectorType.getElementType();

  for (int64_t i = 0; i < vectorType.getNumElements(); ++i) {
    Value index = rewriter.create<LLVM::ConstantOp>(loc, indexType, i);
    auto extractElement = [&](Value operand) -> Value {
      if (!isa<VectorType>(operand.getType()))
        return operand;
      return rewriter.create<LLVM::ExtractElementOp>(loc, operand, index);
    };
    auto scalarOperands = llvm::map_to_vector(operands, extractElement);
    Operation *scalarOp =
        rewriter.create(loc, name, scalarOperands, elementType, op->getAttrs());
    result = rewriter.create<LLVM::InsertElementOp>(
        loc, result, scalarOp->getResult(0), index);
  }

  rewriter.replaceOp(op, result);
  return success();
}

static IntegerAttr wrapNumericMemorySpace(MLIRContext *ctx, unsigned space) {
  return IntegerAttr::get(IntegerType::get(ctx, 64), space);
}

/// Generates a symbol with 0-sized array type for dynamic shared memory usage,
/// or uses existing symbol.
LLVM::GlobalOp
getDynamicSharedMemorySymbol(ConversionPatternRewriter &rewriter,
                             Operation *moduleOp, gpu::DynamicSharedMemoryOp op,
                             const LLVMTypeConverter *typeConverter,
                             MemRefType memrefType, unsigned alignmentBit) {
  uint64_t alignmentByte = alignmentBit / memrefType.getElementTypeBitWidth();

  FailureOr<unsigned> addressSpace =
      typeConverter->getMemRefAddressSpace(memrefType);
  if (failed(addressSpace)) {
    op->emitError() << "conversion of memref memory space "
                    << memrefType.getMemorySpace()
                    << " to integer address space "
                       "failed. Consider adding memory space conversions.";
  }

  // Step 1. Collect symbol names of LLVM::GlobalOp Ops. Also if any of
  // LLVM::GlobalOp is suitable for shared memory, return it.
  llvm::StringSet<> existingGlobalNames;
  for (auto globalOp :
       moduleOp->getRegion(0).front().getOps<LLVM::GlobalOp>()) {
    existingGlobalNames.insert(globalOp.getSymName());
    if (auto arrayType = dyn_cast<LLVM::LLVMArrayType>(globalOp.getType())) {
      if (globalOp.getAddrSpace() == addressSpace.value() &&
          arrayType.getNumElements() == 0 &&
          globalOp.getAlignment().value_or(0) == alignmentByte) {
        return globalOp;
      }
    }
  }

  // Step 2. Find a unique symbol name
  unsigned uniquingCounter = 0;
  SmallString<128> symName = SymbolTable::generateSymbolName<128>(
      "__dynamic_shmem_",
      [&](StringRef candidate) {
        return existingGlobalNames.contains(candidate);
      },
      uniquingCounter);

  // Step 3. Generate a global op
  OpBuilder::InsertionGuard guard(rewriter);
  rewriter.setInsertionPoint(&moduleOp->getRegion(0).front().front());

  auto zeroSizedArrayType = LLVM::LLVMArrayType::get(
      typeConverter->convertType(memrefType.getElementType()), 0);

  return rewriter.create<LLVM::GlobalOp>(
      op->getLoc(), zeroSizedArrayType, /*isConstant=*/false,
      LLVM::Linkage::Internal, symName, /*value=*/Attribute(), alignmentByte,
      addressSpace.value());
}

LogicalResult GPUDynamicSharedMemoryOpLowering::matchAndRewrite(
    gpu::DynamicSharedMemoryOp op, OpAdaptor adaptor,
    ConversionPatternRewriter &rewriter) const {
  Location loc = op.getLoc();
  MemRefType memrefType = op.getResultMemref().getType();
  Type elementType = typeConverter->convertType(memrefType.getElementType());

  // Step 1: Generate a memref<0xi8> type
  MemRefLayoutAttrInterface layout = {};
  auto memrefType0sz =
      MemRefType::get({0}, elementType, layout, memrefType.getMemorySpace());

  // Step 2: Generate a global symbol or existing for the dynamic shared
  // memory with memref<0xi8> type
  LLVM::LLVMFuncOp funcOp = op->getParentOfType<LLVM::LLVMFuncOp>();
  LLVM::GlobalOp shmemOp = {};
  Operation *moduleOp = funcOp->getParentWithTrait<OpTrait::SymbolTable>();
  shmemOp = getDynamicSharedMemorySymbol(
      rewriter, moduleOp, op, getTypeConverter(), memrefType0sz, alignmentBit);

  // Step 3. Get address of the global symbol
  OpBuilder::InsertionGuard guard(rewriter);
  rewriter.setInsertionPoint(op);
  auto basePtr = rewriter.create<LLVM::AddressOfOp>(loc, shmemOp);
  Type baseType = basePtr->getResultTypes().front();

  // Step 4. Generate GEP using offsets
  SmallVector<LLVM::GEPArg> gepArgs = {0};
  Value shmemPtr = rewriter.create<LLVM::GEPOp>(loc, baseType, elementType,
                                                basePtr, gepArgs);
  // Step 5. Create a memref descriptor
  SmallVector<Value> shape, strides;
  Value sizeBytes;
  getMemRefDescriptorSizes(loc, memrefType0sz, {}, rewriter, shape, strides,
                           sizeBytes);
  auto memRefDescriptor = this->createMemRefDescriptor(
      loc, memrefType0sz, shmemPtr, shmemPtr, shape, strides, rewriter);

  // Step 5. Replace the op with memref descriptor
  rewriter.replaceOp(op, {memRefDescriptor});
  return success();
}

void mlir::populateGpuMemorySpaceAttributeConversions(
    TypeConverter &typeConverter, const MemorySpaceMapping &mapping) {
  typeConverter.addTypeAttributeConversion(
      [mapping](BaseMemRefType type, gpu::AddressSpaceAttr memorySpaceAttr) {
        gpu::AddressSpace memorySpace = memorySpaceAttr.getValue();
        unsigned addressSpace = mapping(memorySpace);
        return wrapNumericMemorySpace(memorySpaceAttr.getContext(),
                                      addressSpace);
      });
}