LowerGpuOpsToROCDLOps.cpp

Go to the documentation of this file.

//===- LowerGpuOpsToROCDLOps.cpp - MLIR GPU to ROCDL lowering passes ------===//
//
// 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 file implements a pass to generate ROCDLIR operations for higher-level
// GPU operations.
//
//===----------------------------------------------------------------------===//
 
#include "mlir/Conversion/GPUToROCDL/GPUToROCDLPass.h"
#include "mlir/Dialect/Arith/Transforms/Passes.h"
#include "mlir/Pass/Pass.h"
#include "mlir/Pass/PassManager.h"
 
#include "mlir/Conversion/AMDGPUToROCDL/AMDGPUToROCDL.h"
#include "mlir/Conversion/ConvertToLLVM/ToLLVMInterface.h"
#include "mlir/Conversion/ConvertToLLVM/ToLLVMPass.h"
#include "mlir/Conversion/GPUCommon/GPUCommonPass.h"
#include "mlir/Conversion/LLVMCommon/ConversionTarget.h"
#include "mlir/Conversion/LLVMCommon/LoweringOptions.h"
#include "mlir/Conversion/LLVMCommon/Pattern.h"
#include "mlir/Conversion/LLVMCommon/TypeConverter.h"
#include "mlir/Conversion/MathToLLVM/MathToLLVM.h"
#include "mlir/Conversion/MathToROCDL/MathToROCDL.h"
#include "mlir/Dialect/AMDGPU/IR/AMDGPUDialect.h"
#include "mlir/Dialect/ControlFlow/IR/ControlFlow.h"
#include "mlir/Dialect/Func/IR/FuncOps.h"
#include "mlir/Dialect/GPU/IR/GPUDialect.h"
#include "mlir/Dialect/GPU/Transforms/Passes.h"
#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
#include "mlir/Dialect/LLVMIR/ROCDLDialect.h"
#include "mlir/Dialect/MemRef/IR/MemRef.h"
#include "mlir/Dialect/Vector/IR/VectorOps.h"
#include "mlir/IR/BuiltinAttributes.h"
#include "mlir/Transforms/DialectConversion.h"
#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
 
#include "../GPUCommon/GPUOpsLowering.h"
#include "../GPUCommon/IndexIntrinsicsOpLowering.h"
 
namespace mlir {
#define GEN_PASS_DEF_CONVERTGPUOPSTOROCDLOPS
#include "mlir/Conversion/Passes.h.inc"
} // namespace mlir
 
using namespace mlir;
 
// Truncate or extend the result depending on the index bitwidth specified
// by the LLVMTypeConverter options.
static Value truncOrExtToLLVMType(ConversionPatternRewriter &rewriter,
                                  Location loc, Value value,
                                  const LLVMTypeConverter &converter) {
  int64_t intWidth = cast<IntegerType>(value.getType()).getWidth();
  int64_t indexBitwidth = converter.getIndexTypeBitwidth();
  auto indexBitwidthType =
      IntegerType::get(rewriter.getContext(), converter.getIndexTypeBitwidth());
  // TODO: use <=> in C++20.
  if (indexBitwidth > intWidth) {
    return LLVM::SExtOp::create(rewriter, loc, indexBitwidthType, value);
  }
  if (indexBitwidth < intWidth) {
    return LLVM::TruncOp::create(rewriter, loc, indexBitwidthType, value);
  }
  return value;
}
 
/// Returns true if the given `gpu.func` can be safely called using the bare
/// pointer calling convention.
static bool canBeCalledWithBarePointers(gpu::GPUFuncOp func) {
  bool canBeBare = true;
  for (Type type : func.getArgumentTypes())
    if (auto memrefTy = dyn_cast<BaseMemRefType>(type))
      canBeBare &= LLVMTypeConverter::canConvertToBarePtr(memrefTy);
  return canBeBare;
}
 
static Value getLaneId(RewriterBase &rewriter, Location loc) {
  auto int32Type = IntegerType::get(rewriter.getContext(), 32);
  Value zero = arith::ConstantIntOp::create(rewriter, loc, 0, 32);
  Value minus1 = arith::ConstantIntOp::create(rewriter, loc, -1, 32);
  NamedAttribute noundef = rewriter.getNamedAttr(
      LLVM::LLVMDialect::getNoUndefAttrName(), rewriter.getUnitAttr());
  NamedAttribute lowRange = rewriter.getNamedAttr(
      LLVM::LLVMDialect::getRangeAttrName(),
      LLVM::ConstantRangeAttr::get(rewriter.getContext(), APInt::getZero(32),
                                   APInt(32, 32)));
  NamedAttribute highRange = rewriter.getNamedAttr(
      LLVM::LLVMDialect::getRangeAttrName(),
      LLVM::ConstantRangeAttr::get(rewriter.getContext(), APInt::getZero(32),
                                   APInt(32, 64)));
  Value mbcntLo = ROCDL::MbcntLoOp::create(
      rewriter, loc, int32Type, minus1, zero, /*arg_attrs=*/{},
      /*res_attrs=*/
      rewriter.getArrayAttr(rewriter.getDictionaryAttr({noundef, lowRange})));
  Value laneId = ROCDL::MbcntHiOp::create(
      rewriter, loc, int32Type, minus1, mbcntLo, /*arg_attrs=*/{},
      rewriter.getArrayAttr(rewriter.getDictionaryAttr({noundef, highRange})));
  return laneId;
}
 
static constexpr StringLiteral amdgcnDataLayout =
    "e-p:64:64-p1:64:64-p2:32:32-p3:32:32-p4:64:64-p5:32:32-p6:32:32"
    "-p7:160:256:256:32-p8:128:128:128:48-p9:192:256:256:32-i64:64-v16:16-v24:"
    "32-v32:"
    "32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-v2048:2048-n32:"
    "64-S32-A5-G1-ni:7:8:9";
 
namespace {
struct GPULaneIdOpToROCDL : ConvertOpToLLVMPattern<gpu::LaneIdOp> {
  using ConvertOpToLLVMPattern<gpu::LaneIdOp>::ConvertOpToLLVMPattern;
 
  LogicalResult
  matchAndRewrite(gpu::LaneIdOp op, gpu::LaneIdOp::Adaptor adaptor,
                  ConversionPatternRewriter &rewriter) const override {
    Location loc = op.getLoc();
    MLIRContext *context = rewriter.getContext();
    // convert to:
    //   %mlo = call noundef range(i32 0, 32)
    //     @llvm.amdgcn.mbcnt.lo(-1, 0)
    // followed by:
    //   %lid = call noundef range(i32 0, 64)
    //     @llvm.amdgcn.mbcnt.hi(-1, %mlo)
 
    Value laneId = getLaneId(rewriter, loc);
    // Truncate or extend the result depending on the index bitwidth specified
    // by the LLVMTypeConverter options.
    const unsigned indexBitwidth = getTypeConverter()->getIndexTypeBitwidth();
    if (indexBitwidth > 32) {
      laneId = LLVM::SExtOp::create(
          rewriter, loc, IntegerType::get(context, indexBitwidth), laneId);
    } else if (indexBitwidth < 32) {
      laneId = LLVM::TruncOp::create(
          rewriter, loc, IntegerType::get(context, indexBitwidth), laneId);
    }
    rewriter.replaceOp(op, {laneId});
    return success();
  }
};
 
struct GPUSubgroupSizeOpToROCDL : ConvertOpToLLVMPattern<gpu::SubgroupSizeOp> {
  using ConvertOpToLLVMPattern::ConvertOpToLLVMPattern;
 
  GPUSubgroupSizeOpToROCDL(const LLVMTypeConverter &converter,
                           amdgpu::Chipset chipset)
      : ConvertOpToLLVMPattern<gpu::SubgroupSizeOp>(converter),
        chipset(chipset) {}
 
  LogicalResult
  matchAndRewrite(gpu::SubgroupSizeOp op, gpu::SubgroupSizeOp::Adaptor adaptor,
                  ConversionPatternRewriter &rewriter) const override {
    LLVM::ConstantRangeAttr bounds = nullptr;
    bool isBeforeGfx10 = chipset.majorVersion < 10;
    if (auto upperBoundAttr = op.getUpperBoundAttr()) {
      bounds = rewriter.getAttr<LLVM::ConstantRangeAttr>(
          /*bitWidth=*/32, /*lower=*/isBeforeGfx10 ? 64 : 32,
          /*upper=*/op.getUpperBoundAttr().getInt() + 1);
    }
    Value wavefrontOp = ROCDL::WavefrontSizeOp::create(
        rewriter, op.getLoc(), rewriter.getI32Type(), bounds);
    wavefrontOp = truncOrExtToLLVMType(rewriter, op.getLoc(), wavefrontOp,
                                       *getTypeConverter());
    rewriter.replaceOp(op, {wavefrontOp});
    return success();
  }
 
  const amdgpu::Chipset chipset;
};
 
static bool isSupportedReadLaneType(Type type) {
  // read(first)lane also supports some vector types, but limit it for scalars
  // for now.
  return type.isInteger(16) || type.isInteger(32) || type.isInteger(64) ||
         isa<Float16Type, BFloat16Type, Float32Type, Float64Type,
             LLVM::LLVMPointerType>(type);
}
 
struct GPUSubgroupBroadcastOpToROCDL
    : public ConvertOpToLLVMPattern<gpu::SubgroupBroadcastOp> {
  using ConvertOpToLLVMPattern::ConvertOpToLLVMPattern;
 
  LogicalResult
  matchAndRewrite(gpu::SubgroupBroadcastOp op, OpAdaptor adaptor,
                  ConversionPatternRewriter &rewriter) const override {
    Value src = adaptor.getSrc();
    if (!isSupportedReadLaneType(src.getType()))
      return rewriter.notifyMatchFailure(op, "unsupported readlane type");
 
    if (adaptor.getBroadcastType() == gpu::BroadcastType::specific_lane) {
      rewriter.replaceOpWithNewOp<ROCDL::ReadlaneOp>(op, src.getType(), src,
                                                     adaptor.getLane());
    } else { // first_active_lane
      rewriter.replaceOpWithNewOp<ROCDL::ReadfirstlaneOp>(op, src.getType(),
                                                          src);
    }
    return success();
  }
};
 
struct GPUShuffleOpLowering : public ConvertOpToLLVMPattern<gpu::ShuffleOp> {
  using ConvertOpToLLVMPattern<gpu::ShuffleOp>::ConvertOpToLLVMPattern;
 
  /// Lowers a shuffle to the corresponding ROCDL ops.
  ///
  /// Use the `width` argument to see if src lane is participating.
  /// If not the dstLane would be itself.
  ///
  ///  Shuffle with DS Bpermute:
  ///   let shflMode = [xor, up, down, idx]
  ///   let width = 32(usually warpsize), step = [1, 2, 4, 8, 16, ... , width].
  ///   1. curLaneId = using mbcnt.lo + mbcnt.hi
  ///   2. widthOrZeroIfOutside = (curLaneId + width) & -width
  ///   3. dstLane = shflMode(curLaneId, step)
  ///   4. isActiveSrcLane = dstLane < isActiveSrcLane
  ///   5. dstLane = isActiveSrcLane ? dstLane : curLaneId
  ///   6. dwordAlignedDstLane = dstLane * 4 or dstLane << 2.
  ///   7. bpermute(dwordAlignedDstLane, shfl_value).
  ///
  LogicalResult
  matchAndRewrite(gpu::ShuffleOp op, OpAdaptor adaptor,
                  ConversionPatternRewriter &rewriter) const override {
    Location loc = op->getLoc();
    Value initShflValue = adaptor.getValue();
 
    Value srcLaneId = getLaneId(rewriter, loc);
 
    auto int32Type = IntegerType::get(rewriter.getContext(), 32);
    Value width = adaptor.getWidth();
    Value zero = LLVM::ConstantOp::create(rewriter, loc, int32Type, 0);
    Value negwidth = LLVM::SubOp::create(rewriter, loc, int32Type, zero, width);
    Value add = LLVM::AddOp::create(rewriter, loc, int32Type, srcLaneId, width);
    Value widthOrZeroIfOutside =
        LLVM::AndOp::create(rewriter, loc, int32Type, add, negwidth);
    Value dstLane;
 
    switch (op.getMode()) {
    case gpu::ShuffleMode::UP:
      dstLane = LLVM::SubOp::create(rewriter, loc, int32Type, srcLaneId,
                                    adaptor.getOffset());
      break;
    case gpu::ShuffleMode::DOWN:
      dstLane = LLVM::AddOp::create(rewriter, loc, int32Type, srcLaneId,
                                    adaptor.getOffset());
      break;
    case gpu::ShuffleMode::XOR:
      dstLane = LLVM::XOrOp::create(rewriter, loc, int32Type, srcLaneId,
                                    adaptor.getOffset());
      break;
    case gpu::ShuffleMode::IDX:
      dstLane = adaptor.getOffset();
      break;
    }
    Value isActiveSrcLane = LLVM::ICmpOp::create(
        rewriter, loc, LLVM::ICmpPredicate::slt, dstLane, widthOrZeroIfOutside);
    Value selectDstLane = LLVM::SelectOp::create(rewriter, loc, isActiveSrcLane,
                                                 dstLane, srcLaneId);
    Value two = LLVM::ConstantOp::create(rewriter, loc, int32Type, 2);
    Value dwordAlignedDstLane =
        LLVM::ShlOp::create(rewriter, loc, int32Type, selectDstLane, two);
 
    SmallVector<Value> decomposed =
        LLVM::decomposeValue(rewriter, loc, initShflValue, int32Type);
    SmallVector<Value> swizzled;
    for (Value v : decomposed) {
      Value res = ROCDL::DsBpermuteOp::create(rewriter, loc, int32Type,
                                              dwordAlignedDstLane, v);
      swizzled.emplace_back(res);
    }
    Value shflValue =
        LLVM::composeValue(rewriter, loc, swizzled, initShflValue.getType());
    rewriter.replaceOp(op, {shflValue, isActiveSrcLane});
    return success();
  }
};
 
/// Import the GPU Ops to ROCDL Patterns.
#include "GPUToROCDL.cpp.inc"
 
// A pass that replaces all occurrences of GPU device operations with their
// corresponding ROCDL equivalent.
//
// This pass only handles device code and is not meant to be run on GPU host
// code.
struct LowerGpuOpsToROCDLOpsPass final
    : public impl::ConvertGpuOpsToROCDLOpsBase<LowerGpuOpsToROCDLOpsPass> {
  using Base::Base;
 
  void getDependentDialects(DialectRegistry &registry) const override {
    Base::getDependentDialects(registry);
    registerConvertToLLVMDependentDialectLoading(registry);
  }
 
  void runOnOperation() override {
    gpu::GPUModuleOp m = getOperation();
    MLIRContext *ctx = m.getContext();
 
    auto llvmDataLayout = m->getAttrOfType<StringAttr>(
        LLVM::LLVMDialect::getDataLayoutAttrName());
    if (!llvmDataLayout) {
      llvmDataLayout = StringAttr::get(ctx, amdgcnDataLayout);
      m->setAttr(LLVM::LLVMDialect::getDataLayoutAttrName(), llvmDataLayout);
    }
    // Request C wrapper emission.
    for (auto func : m.getOps<func::FuncOp>()) {
      func->setAttr(LLVM::LLVMDialect::getEmitCWrapperAttrName(),
                    UnitAttr::get(ctx));
    }
 
    FailureOr<amdgpu::Chipset> maybeChipset = amdgpu::Chipset::parse(chipset);
    if (failed(maybeChipset)) {
      emitError(UnknownLoc::get(ctx), "Invalid chipset name: " + chipset);
      return signalPassFailure();
    }
 
    /// Customize the bitwidth used for the device side index computations.
    LowerToLLVMOptions options(
        ctx, DataLayout(cast<DataLayoutOpInterface>(m.getOperation())));
    options.dataLayout = llvm::DataLayout(llvmDataLayout.getValue());
    if (indexBitwidth != kDeriveIndexBitwidthFromDataLayout)
      options.overrideIndexBitwidth(indexBitwidth);
 
    if (useBarePtrCallConv) {
      options.useBarePtrCallConv = true;
      WalkResult canUseBarePointers =
          m.walk([](gpu::GPUFuncOp func) -> WalkResult {
            if (canBeCalledWithBarePointers(func))
              return WalkResult::advance();
            return WalkResult::interrupt();
          });
      if (canUseBarePointers.wasInterrupted()) {
        emitError(UnknownLoc::get(ctx),
                  "bare pointer calling convention requires all memrefs to "
                  "have static shape and use the identity map");
        return signalPassFailure();
      }
    }
 
    // Apply in-dialect lowering. In-dialect lowering will replace
    // ops which need to be lowered further, which is not supported by a
    // single conversion pass.
    {
      RewritePatternSet patterns(ctx);
      populateGpuRewritePatterns(patterns);
      populateGpuPromoteShuffleToAMDGPUPatterns(patterns, maybeChipset);
      (void)applyPatternsGreedily(m, std::move(patterns));
    }
 
    LLVMTypeConverter converter(ctx, options);
    populateGpuMemorySpaceAttributeConversions(
        converter, [](gpu::AddressSpace space) {
          switch (space) {
          case gpu::AddressSpace::Global:
            return 1;
          case gpu::AddressSpace::Workgroup:
            return 3;
          case gpu::AddressSpace::Private:
            return 5;
          }
          llvm_unreachable("unknown address space enum value");
          return 0;
        });
 
    RewritePatternSet llvmPatterns(ctx);
    LLVMConversionTarget target(getContext());
 
    llvm::SmallDenseSet<StringRef> allowedDialectsSet(allowedDialects.begin(),
                                                      allowedDialects.end());
    for (Dialect *dialect : ctx->getLoadedDialects()) {
      bool allowed = allowedDialectsSet.contains(dialect->getNamespace());
      // Empty `allowedDialectsSet` means all dialects are allowed.
      if (!allowedDialectsSet.empty() && !allowed)
        continue;
 
      auto *iface = dyn_cast<ConvertToLLVMPatternInterface>(dialect);
      if (!iface) {
        // Error out if dialect was explicily specified but doesn't implement
        // conversion interface.
        if (allowed) {
          m.emitError()
              << "dialect does not implement ConvertToLLVMPatternInterface: "
              << dialect->getNamespace();
          return signalPassFailure();
        }
        continue;
      }
 
      iface->populateConvertToLLVMConversionPatterns(target, converter,
                                                     llvmPatterns);
    }
 
    populateAMDGPUToROCDLConversionPatterns(converter, llvmPatterns,
                                            *maybeChipset);
    populateGpuToROCDLConversionPatterns(converter, llvmPatterns, runtime,
                                         *maybeChipset);
    configureGpuToROCDLConversionLegality(target);
    if (failed(applyPartialConversion(m, target, std::move(llvmPatterns))))
      signalPassFailure();
    auto *rocdlDialect = getContext().getLoadedDialect<ROCDL::ROCDLDialect>();
    auto reqdWorkGroupSizeAttrHelper =
        rocdlDialect->getReqdWorkGroupSizeAttrHelper();
    auto flatWorkGroupSizeAttrHelper =
        rocdlDialect->getFlatWorkGroupSizeAttrHelper();
    // Manually rewrite known block size attributes so the LLVMIR translation
    // infrastructure can pick them up.
    m.walk([&](LLVM::LLVMFuncOp op) {
      if (reqdWorkGroupSizeAttrHelper.isAttrPresent(op)) {
        auto blockSizes = reqdWorkGroupSizeAttrHelper.getAttr(op);
        // Also set up the rocdl.flat_work_group_size attribute to prevent
        // conflicting metadata.
        uint32_t flatSize = 1;
        for (uint32_t size : blockSizes.asArrayRef()) {
          flatSize *= size;
        }
        StringAttr flatSizeAttr =
            StringAttr::get(ctx, Twine(flatSize) + "," + Twine(flatSize));
        flatWorkGroupSizeAttrHelper.setAttr(op, flatSizeAttr);
      }
    });
  }
};
 
} // namespace
 
void mlir::configureGpuToROCDLConversionLegality(ConversionTarget &target) {
  target.addIllegalOp<func::FuncOp>();
  target.addLegalDialect<::mlir::LLVM::LLVMDialect>();
  target.addLegalDialect<ROCDL::ROCDLDialect>();
  target.addIllegalDialect<gpu::GPUDialect>();
  target.addIllegalOp<LLVM::CosOp, LLVM::ExpOp, LLVM::Exp2Op, LLVM::FCeilOp,
                      LLVM::FFloorOp, LLVM::FRemOp, LLVM::LogOp, LLVM::Log10Op,
                      LLVM::Log2Op, LLVM::PowOp, LLVM::SinOp>();
  // These ops are legal for f32 type.
  target.addDynamicallyLegalOp<LLVM::ExpOp, LLVM::LogOp>([](Operation *op) {
    return any_of(op->getOperandTypes(), llvm::IsaPred<Float32Type>);
  });
  // TODO: Remove once we support replacing non-root ops.
  target.addLegalOp<gpu::YieldOp, gpu::GPUModuleOp>();
}
 
void mlir::populateGpuToROCDLConversionPatterns(
    const LLVMTypeConverter &converter, RewritePatternSet &patterns,
    mlir::gpu::amd::Runtime runtime, amdgpu::Chipset chipset) {
  using gpu::index_lowering::IndexKind;
  using gpu::index_lowering::IntrType;
  using mlir::gpu::amd::Runtime;
  auto *rocdlDialect =
      converter.getContext().getLoadedDialect<ROCDL::ROCDLDialect>();
  populateWithGenerated(patterns);
  patterns.add<
      gpu::index_lowering::OpLowering<gpu::ThreadIdOp, ROCDL::ThreadIdXOp,
                                      ROCDL::ThreadIdYOp, ROCDL::ThreadIdZOp>>(
      converter, IndexKind::Block, IntrType::Id);
  patterns.add<gpu::index_lowering::OpLowering<
      gpu::BlockIdOp, ROCDL::BlockIdXOp, ROCDL::BlockIdYOp, ROCDL::BlockIdZOp>>(
      converter, IndexKind::Grid, IntrType::Id);
  patterns.add<
      gpu::index_lowering::OpLowering<gpu::BlockDimOp, ROCDL::BlockDimXOp,
                                      ROCDL::BlockDimYOp, ROCDL::BlockDimZOp>>(
      converter, IndexKind::Block, IntrType::Dim);
  patterns.add<gpu::index_lowering::OpLowering<
      gpu::GridDimOp, ROCDL::GridDimXOp, ROCDL::GridDimYOp, ROCDL::GridDimZOp>>(
      converter, IndexKind::Grid, IntrType::Dim);
  patterns.add<GPUReturnOpLowering>(converter);
  patterns.add<GPUFuncOpLowering>(
      converter,
      GPUFuncOpLoweringOptions{
          /*allocaAddrSpace=*/ROCDL::ROCDLDialect::kPrivateMemoryAddressSpace,
          /*workgroupAddrSpace=*/ROCDL::ROCDLDialect::kSharedMemoryAddressSpace,
          rocdlDialect->getKernelAttrHelper().getName(),
          rocdlDialect->getReqdWorkGroupSizeAttrHelper().getName()});
  if (Runtime::HIP == runtime) {
    patterns.add<GPUPrintfOpToHIPLowering>(converter);
  } else if (Runtime::OpenCL == runtime) {
    // Use address space = 4 to match the OpenCL definition of printf()
    patterns.add<GPUPrintfOpToLLVMCallLowering>(converter, /*addressSpace=*/4);
  }
  // TODO: Add alignment for workgroup memory
  patterns.add<GPUDynamicSharedMemoryOpLowering>(converter);
 
  patterns.add<GPUShuffleOpLowering, GPULaneIdOpToROCDL,
               GPUSubgroupBroadcastOpToROCDL>(converter);
  patterns.add<GPUSubgroupSizeOpToROCDL>(converter, chipset);
 
  populateMathToROCDLConversionPatterns(converter, patterns);
}