LowerExtmemToHW.cpp

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//===- LowerExtmemToHW.cpp - lock functions pass ----------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Contains the definitions of the lower extmem pass.
//
//===----------------------------------------------------------------------===//
 
#include "PassDetails.h"
#include "circt/Conversion/HandshakeToHW.h"
#include "circt/Dialect/ESI/ESIOps.h"
#include "circt/Dialect/HW/HWOps.h"
#include "circt/Dialect/HW/HWTypes.h"
#include "circt/Dialect/Handshake/HandshakeOps.h"
#include "circt/Dialect/Handshake/HandshakePasses.h"
#include "circt/Support/BackedgeBuilder.h"
#include "mlir/Dialect/Arith/IR/Arith.h"
#include "mlir/IR/PatternMatch.h"
#include "mlir/Rewrite/FrozenRewritePatternSet.h"
#include "mlir/Transforms/DialectConversion.h"
#include "llvm/Support/Debug.h"
 
using namespace circt;
using namespace handshake;
using namespace mlir;
namespace {
using NamedType = std::pair<StringAttr, Type>;
struct HandshakeMemType {
  llvm::SmallVector<NamedType> inputTypes, outputTypes;
  MemRefType memRefType;
  unsigned loadPorts, storePorts;
};
 
struct LoadName {
  StringAttr dataIn;
  StringAttr addrOut;
 
  static LoadName get(MLIRContext *ctx, unsigned idx) {
    return {StringAttr::get(ctx, "ld" + std::to_string(idx) + ".data"),
            StringAttr::get(ctx, "ld" + std::to_string(idx) + ".addr")};
  }
};
 
struct StoreNames {
  StringAttr doneIn;
  StringAttr out;
 
  static StoreNames get(MLIRContext *ctx, unsigned idx) {
    return {StringAttr::get(ctx, "st" + std::to_string(idx) + ".done"),
            StringAttr::get(ctx, "st" + std::to_string(idx))};
  }
};
 
} // namespace
 
static Type indexToMemAddr(Type t, MemRefType memRef) {
  assert(t.isa<IndexType>() && "Expected index type");
  auto shape = memRef.getShape();
  assert(shape.size() == 1 && "Expected 1D memref");
  unsigned addrWidth = llvm::Log2_64_Ceil(shape[0]);
  return IntegerType::get(t.getContext(), addrWidth);
}
 
static HandshakeMemType getMemTypeForExtmem(Value v) {
  auto *ctx = v.getContext();
  assert(v.getType().isa<mlir::MemRefType>() && "Value is not a memref type");
  auto extmemOp = cast<handshake::ExternalMemoryOp>(*v.getUsers().begin());
  HandshakeMemType memType;
  llvm::SmallVector<hw::detail::FieldInfo> inFields, outFields;
 
  // Add memory type.
  memType.memRefType = v.getType().cast<MemRefType>();
  memType.loadPorts = extmemOp.getLdCount();
  memType.storePorts = extmemOp.getStCount();
 
  // Add load ports.
  for (auto [i, ldif] : llvm::enumerate(extmemOp.getLoadPorts())) {
    auto names = LoadName::get(ctx, i);
    memType.inputTypes.push_back({names.dataIn, ldif.dataOut.getType()});
    memType.outputTypes.push_back(
        {names.addrOut,
         indexToMemAddr(ldif.addressIn.getType(), memType.memRefType)});
  }
 
  // Add store ports.
  for (auto [i, stif] : llvm::enumerate(extmemOp.getStorePorts())) {
    auto names = StoreNames::get(ctx, i);
 
    // Incoming store data and address
    llvm::SmallVector<hw::StructType::FieldInfo> storeOutFields;
    storeOutFields.push_back(
        {StringAttr::get(ctx, "address"),
         indexToMemAddr(stif.addressIn.getType(), memType.memRefType)});
    storeOutFields.push_back(
        {StringAttr::get(ctx, "data"), stif.dataIn.getType()});
    auto inType = hw::StructType::get(ctx, storeOutFields);
    memType.outputTypes.push_back({names.out, inType});
    memType.inputTypes.push_back({names.doneIn, stif.doneOut.getType()});
  }
 
  return memType;
}
 
namespace {
struct HandshakeLowerExtmemToHWPass
    : public HandshakeLowerExtmemToHWBase<HandshakeLowerExtmemToHWPass> {
 
  HandshakeLowerExtmemToHWPass(std::optional<bool> createESIWrapper) {
    if (createESIWrapper)
      this->createESIWrapper = *createESIWrapper;
  }
 
  void runOnOperation() override {
    auto op = getOperation();
    for (auto func : op.getOps<handshake::FuncOp>()) {
      if (failed(lowerExtmemToHW(func))) {
        signalPassFailure();
        return;
      }
    }
  };
 
  LogicalResult lowerExtmemToHW(handshake::FuncOp func);
  LogicalResult
  wrapESI(handshake::FuncOp func, hw::ModulePortInfo origPorts,
          const std::map<unsigned, HandshakeMemType> &argReplacements);
};
 
LogicalResult HandshakeLowerExtmemToHWPass::wrapESI(
    handshake::FuncOp func, hw::ModulePortInfo origPorts,
    const std::map<unsigned, HandshakeMemType> &argReplacements) {
  auto *ctx = func.getContext();
  OpBuilder b(func);
  auto loc = func.getLoc();
 
  // Create external module which will match the interface of 'func' after it's
  // been lowered to HW.
  b.setInsertionPoint(func);
  auto newPortInfo = handshake::getPortInfoForOpTypes(
      func, func.getArgumentTypes(), func.getResultTypes());
  auto extMod = b.create<hw::HWModuleExternOp>(
      loc, StringAttr::get(ctx, "__" + func.getName() + "_hw"), newPortInfo);
 
  // Add an attribute to the original handshake function to indicate that it
  // needs to resolve to extMod in a later pass.
  func->setAttr(kPredeclarationAttr,
                FlatSymbolRefAttr::get(ctx, extMod.getName()));
 
  // Create wrapper module. This will have the same ports as the original
  // module, sans the replaced arguments.
  auto wrapperModPortInfo = origPorts;
  llvm::SmallVector<unsigned> argReplacementsIdxs;
  llvm::transform(argReplacements, std::back_inserter(argReplacementsIdxs),
                  [](auto &pair) { return pair.first; });
  for (auto i : llvm::reverse(argReplacementsIdxs))
    wrapperModPortInfo.eraseInput(i);
  auto wrapperMod = b.create<hw::HWModuleOp>(
      loc, StringAttr::get(ctx, func.getName() + "_esi_wrapper"),
      wrapperModPortInfo);
  Value clk = wrapperMod.getBodyBlock()->getArgument(
      wrapperMod.getBodyBlock()->getNumArguments() - 2);
  Value rst = wrapperMod.getBodyBlock()->getArgument(
      wrapperMod.getBodyBlock()->getNumArguments() - 1);
  SmallVector<Value> clkRes = {clk, rst};
 
  b.setInsertionPointToStart(wrapperMod.getBodyBlock());
  BackedgeBuilder bb(b, loc);
 
  // Create backedges for the results of the external module. These will be
  // replaced by the service instance requests if associated with a memory.
  llvm::SmallVector<Backedge> backedges;
  for (auto resType : extMod.getOutputTypes())
    backedges.push_back(bb.get(resType));
 
  // Maintain which index we're currently at in the lowered handshake module's
  // return.
  unsigned resIdx = origPorts.sizeOutputs();
 
  // Maintain the arguments which each memory will add to the inner module
  // instance.
  llvm::SmallVector<llvm::OwningArrayRef<Value>> instanceArgsForMem;
 
  for (auto [i, memType] : argReplacements) {
 
    b.setInsertionPoint(wrapperMod);
    // Create a memory service declaration for each memref argument that was
    // served.
    auto origPortInfo = origPorts.atInput(i);
    auto memrefShape = memType.memRefType.getShape();
    auto dataType = memType.memRefType.getElementType();
    assert(memrefShape.size() == 1 && "Only 1D memrefs are supported");
    unsigned memrefSize = memrefShape[0];
    auto memServiceDecl = b.create<esi::RandomAccessMemoryDeclOp>(
        loc, origPortInfo.name, TypeAttr::get(dataType),
        b.getI64IntegerAttr(memrefSize));
    esi::ServicePortInfo writePortInfo = memServiceDecl.writePortInfo();
    esi::ServicePortInfo readPortInfo = memServiceDecl.readPortInfo();
 
    SmallVector<Value> instanceArgsFromThisMem;
 
    // Create service requests. This MUST follow the order of which ports were
    // added in other parts of this pass (load ports first, then store ports).
    b.setInsertionPointToStart(wrapperMod.getBodyBlock());
 
    // Load ports:
    for (unsigned i = 0; i < memType.loadPorts; ++i) {
      auto req = b.create<esi::RequestConnectionOp>(
          loc, readPortInfo.type, readPortInfo.port,
          esi::AppIDAttr::get(ctx, b.getStringAttr("load"), {}));
      auto reqUnpack = b.create<esi::UnpackBundleOp>(
          loc, req.getToClient(), ValueRange{backedges[resIdx]});
      instanceArgsFromThisMem.push_back(
          reqUnpack.getToChannels()
              [esi::RandomAccessMemoryDeclOp::RespDirChannelIdx]);
      ++resIdx;
    }
 
    // Store ports:
    for (unsigned i = 0; i < memType.storePorts; ++i) {
      auto req = b.create<esi::RequestConnectionOp>(
          loc, writePortInfo.type, writePortInfo.port,
          esi::AppIDAttr::get(ctx, b.getStringAttr("store"), {}));
      auto reqUnpack = b.create<esi::UnpackBundleOp>(
          loc, req.getToClient(), ValueRange{backedges[resIdx]});
      instanceArgsFromThisMem.push_back(
          reqUnpack.getToChannels()
              [esi::RandomAccessMemoryDeclOp::RespDirChannelIdx]);
      ++resIdx;
    }
 
    instanceArgsForMem.emplace_back(instanceArgsFromThisMem);
  }
 
  // Stitch together arguments from the top-level ESI wrapper and the instance
  // arguments generated from the service requests.
  llvm::SmallVector<Value> instanceArgs;
 
  // Iterate over the arguments of the original handshake.func and determine
  // whether to grab operands from the arg replacements or the wrapper module.
  unsigned wrapperArgIdx = 0;
 
  for (unsigned i = 0, e = func.getNumArguments(); i < e; i++) {
    // Arg replacement indices refer to the original handshake.func argument
    // index.
    if (argReplacements.count(i)) {
      // This index was originally a memref - pop the instance arguments for the
      // next-in-line memory and add them.
      auto &memArgs = instanceArgsForMem.front();
      instanceArgs.append(memArgs.begin(), memArgs.end());
      instanceArgsForMem.erase(instanceArgsForMem.begin());
    } else {
      // Add the argument from the wrapper mod. This is maintained by its own
      // counter (memref arguments are removed, so if there was an argument at
      // this point, it needs to come from the wrapper module).
      instanceArgs.push_back(
          wrapperMod.getBodyBlock()->getArgument(wrapperArgIdx++));
    }
  }
 
  // Add any missing arguments from the wrapper module (this will be clock and
  // reset)
  for (; wrapperArgIdx < wrapperMod.getBodyBlock()->getNumArguments();
       ++wrapperArgIdx)
    instanceArgs.push_back(
        wrapperMod.getBodyBlock()->getArgument(wrapperArgIdx));
 
  // Instantiate the inner module.
  auto instance =
      b.create<hw::InstanceOp>(loc, extMod, func.getName(), instanceArgs);
 
  // And resolve the backedges.
  for (auto [res, be] : llvm::zip(instance.getResults(), backedges))
    be.setValue(res);
 
  // Finally, grab the (non-memory) outputs from the inner module and return
  // them through the wrapper.
  auto outputOp =
      cast<hw::OutputOp>(wrapperMod.getBodyBlock()->getTerminator());
  b.setInsertionPoint(outputOp);
  b.create<hw::OutputOp>(
      outputOp.getLoc(),
      instance.getResults().take_front(wrapperMod.getNumOutputPorts()));
  outputOp.erase();
 
  return success();
}
 
// Truncates the index-typed 'v' into an integer-type of the same width as the
// 'memref' argument.
// Uses arith operations since these are supported in the HandshakeToHW
// lowering.
static Value truncateToMemoryWidth(Location loc, OpBuilder &b, Value v,
                                   MemRefType memRefType) {
  assert(v.getType().isa<IndexType>() && "Expected an index-typed value");
  auto addrWidth = llvm::Log2_64_Ceil(memRefType.getShape().front());
  return b.create<arith::IndexCastOp>(loc, b.getIntegerType(addrWidth), v);
}
 
static Value plumbLoadPort(Location loc, OpBuilder &b,
                           handshake::MemLoadInterface &ldif, Value loadData,
                           MemRefType memrefType) {
  // We need to feed both the load data and the load done outputs.
  // Fork the extracted load data into two, and 'join' the second one to
  // generate a none-typed output to drive the load done.
  auto dataFork = b.create<ForkOp>(loc, loadData, 2);
 
  auto dataOut = dataFork.getResult()[0];
  llvm::SmallVector<Value> joinArgs = {dataFork.getResult()[1]};
  auto dataDone = b.create<JoinOp>(loc, joinArgs);
 
  ldif.dataOut.replaceAllUsesWith(dataOut);
  ldif.doneOut.replaceAllUsesWith(dataDone);
 
  // Return load address, to be fed to the top-level output, truncated to the
  // width of the memory that is accessed.
  return truncateToMemoryWidth(loc, b, ldif.addressIn, memrefType);
}
 
static Value plumbStorePort(Location loc, OpBuilder &b,
                            handshake::MemStoreInterface &stif, Value done,
                            Type outType, MemRefType memrefType) {
  stif.doneOut.replaceAllUsesWith(done);
  // Return the store address and data to be fed to the top-level output.
  // Address is truncated to the width of the memory that is accessed.
  llvm::SmallVector<Value> structArgs = {
      truncateToMemoryWidth(loc, b, stif.addressIn, memrefType), stif.dataIn};
 
  return b
      .create<hw::StructCreateOp>(loc, outType.cast<hw::StructType>(),
                                  structArgs)
      .getResult();
}
 
static void appendToStringArrayAttr(Operation *op, StringRef attrName,
                                    StringRef attrVal) {
  auto *ctx = op->getContext();
  llvm::SmallVector<Attribute> newArr;
  llvm::copy(op->getAttrOfType<ArrayAttr>(attrName).getValue(),
             std::back_inserter(newArr));
  newArr.push_back(StringAttr::get(ctx, attrVal));
  op->setAttr(attrName, ArrayAttr::get(ctx, newArr));
}
 
static void insertInStringArrayAttr(Operation *op, StringRef attrName,
                                    StringRef attrVal, unsigned idx) {
  auto *ctx = op->getContext();
  llvm::SmallVector<Attribute> newArr;
  llvm::copy(op->getAttrOfType<ArrayAttr>(attrName).getValue(),
             std::back_inserter(newArr));
  newArr.insert(newArr.begin() + idx, StringAttr::get(ctx, attrVal));
  op->setAttr(attrName, ArrayAttr::get(ctx, newArr));
}
 
static void eraseFromArrayAttr(Operation *op, StringRef attrName,
                               unsigned idx) {
  auto *ctx = op->getContext();
  llvm::SmallVector<Attribute> newArr;
  llvm::copy(op->getAttrOfType<ArrayAttr>(attrName).getValue(),
             std::back_inserter(newArr));
  newArr.erase(newArr.begin() + idx);
  op->setAttr(attrName, ArrayAttr::get(ctx, newArr));
}
 
struct ArgTypeReplacement {
  unsigned index;
  TypeRange ins;
  TypeRange outs;
};
 
LogicalResult
HandshakeLowerExtmemToHWPass::lowerExtmemToHW(handshake::FuncOp func) {
  // Gather memref ports to be converted. This is an ordered map, and will be
  // iterated from lo to hi indices.
  std::map<unsigned, Value> memrefArgs;
  for (auto [i, arg] : llvm::enumerate(func.getArguments()))
    if (arg.getType().isa<MemRefType>())
      memrefArgs[i] = arg;
 
  if (memrefArgs.empty())
    return success(); // nothing to do.
 
  // Record which arg indices were replaces with handshake memory ports.
  // This is an ordered map, and will be iterated from lo to hi indices.
  std::map<unsigned, HandshakeMemType> argReplacements;
 
  // Record the hw.module i/o of the original func (used for ESI wrapper).
  auto origPortInfo = handshake::getPortInfoForOpTypes(
      func, func.getArgumentTypes(), func.getResultTypes());
 
  OpBuilder b(func);
  for (auto it : memrefArgs) {
    // Do not use structured bindings for 'it' - cannot reference inside lambda.
    unsigned i = it.first;
    auto arg = it.second;
    auto loc = arg.getLoc();
    // Get the attached extmemory external module.
    auto extmemOp = cast<handshake::ExternalMemoryOp>(*arg.getUsers().begin());
    b.setInsertionPoint(extmemOp);
 
    // Add memory input - this is the output of the extmemory op.
    auto memIOTypes = getMemTypeForExtmem(arg);
    MemRefType memrefType = arg.getType().cast<MemRefType>();
 
    auto oldReturnOp =
        cast<handshake::ReturnOp>(func.getBody().front().getTerminator());
    llvm::SmallVector<Value> newReturnOperands = oldReturnOp.getOperands();
    unsigned addedInPorts = 0;
    auto memName = func.getArgName(i);
    auto addArgRes = [&](unsigned id, NamedType &argType, NamedType &resType) {
      // Function argument
      unsigned newArgIdx = i + addedInPorts;
      func.insertArgument(newArgIdx, argType.second, {}, arg.getLoc());
      insertInStringArrayAttr(func, "argNames",
                              memName.str() + "_" + argType.first.str(),
                              newArgIdx);
      auto newInPort = func.getArgument(newArgIdx);
      ++addedInPorts;
 
      // Function result.
      func.insertResult(func.getNumResults(), resType.second, {});
      appendToStringArrayAttr(func, "resNames",
                              memName.str() + "_" + resType.first.str());
      return newInPort;
    };
 
    // Plumb load ports.
    unsigned portIdx = 0;
    for (auto loadPort : extmemOp.getLoadPorts()) {
      auto newInPort = addArgRes(loadPort.index, memIOTypes.inputTypes[portIdx],
                                 memIOTypes.outputTypes[portIdx]);
      newReturnOperands.push_back(
          plumbLoadPort(loc, b, loadPort, newInPort, memrefType));
      ++portIdx;
    }
 
    // Plumb store ports.
    for (auto storePort : extmemOp.getStorePorts()) {
      auto newInPort =
          addArgRes(storePort.index, memIOTypes.inputTypes[portIdx],
                    memIOTypes.outputTypes[portIdx]);
      newReturnOperands.push_back(
          plumbStorePort(loc, b, storePort, newInPort,
                         memIOTypes.outputTypes[portIdx].second, memrefType));
      ++portIdx;
    }
 
    // Replace the return op of the function with a new one that returns the
    // memory output struct.
    b.setInsertionPoint(oldReturnOp);
    b.create<ReturnOp>(arg.getLoc(), newReturnOperands);
    oldReturnOp.erase();
 
    // Erase the extmemory operation since I/O plumbing has replaced all of its
    // results.
    extmemOp.erase();
 
    // Erase the original memref argument of the top-level i/o now that it's
    // use has been removed.
    func.eraseArgument(i + addedInPorts);
    eraseFromArrayAttr(func, "argNames", i + addedInPorts);
 
    argReplacements[i] = memIOTypes;
  }
 
  if (createESIWrapper)
    if (failed(wrapESI(func, origPortInfo, argReplacements)))
      return failure();
 
  return success();
}
 
} // namespace
 
std::unique_ptr<mlir::Pass>
circt::handshake::createHandshakeLowerExtmemToHWPass(
    std::optional<bool> createESIWrapper) {
  return std::make_unique<HandshakeLowerExtmemToHWPass>(createESIWrapper);
}