SystemCLowerInstanceInterop.cpp

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//===- SystemCLowerInstanceInterop.cpp - Instance-side interop 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
//
//===----------------------------------------------------------------------===//
//
// This is the main SystemC instance-side interp lowering pass implementation.
//
//===----------------------------------------------------------------------===//
 
#include "PassDetails.h"
#include "circt/Dialect/Interop/InteropOps.h"
#include "circt/Dialect/SystemC/SystemCOps.h"
#include "circt/Dialect/SystemC/SystemCPasses.h"
#include "mlir/Pass/Pass.h"
#include "mlir/Transforms/DialectConversion.h"
 
using namespace mlir;
using namespace circt;
using namespace circt::systemc;
 
//===----------------------------------------------------------------------===//
// Interop lowering patterns
//===----------------------------------------------------------------------===//
 
namespace {
/// Lower the systemc::InteropVerilatedOp operation.
class InteropVerilatedOpConversion
    : public OpConversionPattern<InteropVerilatedOp> {
public:
  using OpConversionPattern<InteropVerilatedOp>::OpConversionPattern;
 
  LogicalResult
  matchAndRewrite(InteropVerilatedOp op, OpAdaptor adaptor,
                  ConversionPatternRewriter &rewriter) const override {
    // TODO: instead of hardcoding the verilated module's class name, it should
    // be derived from a configs attribute as this can be specified via the CLI
    // arguments of verilator
    // stateType ::= VModuleName*
    SmallString<128> verilatedModuleName("V");
    verilatedModuleName += op.getModuleName();
    auto stateType = emitc::PointerType::get(
        emitc::OpaqueType::get(op->getContext(), verilatedModuleName));
    Location loc = op.getLoc();
 
    // Include the C++ header produced by Verilator at the location of the HW
    // module.
    auto *hwModule =
        SymbolTable::lookupNearestSymbolFrom(op, op.getModuleNameAttr());
    OpBuilder includeBuilder(hwModule);
    includeBuilder.create<emitc::IncludeOp>(
        loc, (verilatedModuleName + ".h").str(), false);
 
    // Request a pointer to the verilated module as persistent state.
    Value state = rewriter
                      .create<interop::ProceduralAllocOp>(loc, stateType,
                                                          InteropMechanism::CPP)
                      .getStates()[0];
 
    insertStateInitialization(rewriter, loc, state);
 
    ValueRange results = insertUpdateLogic(
        rewriter, loc, state, adaptor.getInputs(), op.getResults(),
        adaptor.getInputNames(), adaptor.getResultNames());
 
    insertStateDeallocation(rewriter, loc, state);
 
    // Replace the return values of the instance with the result values of the
    // interop update operation.
    rewriter.replaceOp(op, results);
    return success();
  }
 
private:
  /// Insert a interop init operation to allocate an instance of the verilated
  /// module on the heap and let the above requested pointer point to it.
  void insertStateInitialization(PatternRewriter &rewriter, Location loc,
                                 Value state) const {
    auto initOp = rewriter.create<interop::ProceduralInitOp>(
        loc, state, InteropMechanism::CPP);
 
    OpBuilder initBuilder = OpBuilder::atBlockBegin(initOp.getBody());
    Value newState =
        initBuilder.create<NewOp>(loc, state.getType(), ValueRange());
    initBuilder.create<interop::ReturnOp>(loc, newState);
  }
 
  /// Create an update interop operation to assign the input values to the input
  /// ports of the verilated module, call 'eval', and read the output ports of
  /// the verilated module.
  ValueRange insertUpdateLogic(PatternRewriter &rewriter, Location loc,
                               Value stateValue, ValueRange inputValues,
                               ValueRange resultValues, ArrayAttr inputNames,
                               ArrayAttr resultNames) const {
    auto updateOp = rewriter.create<interop::ProceduralUpdateOp>(
        loc, resultValues.getTypes(), inputValues, stateValue,
        InteropMechanism::CPP);
 
    OpBuilder updateBuilder = OpBuilder::atBlockBegin(updateOp.getBody());
 
    // Write to the verilated module's input ports.
    Value state = updateOp.getBody()->getArguments().front();
    for (size_t i = 0; i < inputValues.size(); ++i) {
      Value member = updateBuilder.create<MemberAccessOp>(
          loc, inputValues[i].getType(), state, cast<StringAttr>(inputNames[i]),
          MemberAccessKind::Arrow);
      updateBuilder.create<AssignOp>(loc, member,
                                     updateOp.getBody()->getArgument(i + 1));
    }
 
    // Call 'eval'.
    auto evalFunc = updateBuilder.create<MemberAccessOp>(
        loc, FunctionType::get(updateBuilder.getContext(), {}, {}), state,
        "eval", MemberAccessKind::Arrow);
 
    // TODO: this has to be changed to a systemc::CallIndirectOp once the PR is
    // merged, also remove the dependency to the func dialect from the cmake,
    // header include, pass dependent dialects
    updateBuilder.create<func::CallIndirectOp>(loc, evalFunc.getResult());
 
    // Read the verilated module's output ports.
    SmallVector<Value> results;
    for (size_t i = 0; i < resultValues.size(); ++i) {
      results.push_back(updateBuilder.create<MemberAccessOp>(
          loc, resultValues[i].getType(), state,
          cast<StringAttr>(resultNames[i]).getValue(),
          MemberAccessKind::Arrow));
    }
 
    updateBuilder.create<interop::ReturnOp>(loc, results);
 
    return updateOp->getResults();
  }
 
  /// Deallocate the memory allocated in the interop init operation.
  void insertStateDeallocation(PatternRewriter &rewriter, Location loc,
                               Value state) const {
    auto deallocOp = rewriter.create<interop::ProceduralDeallocOp>(
        loc, state, InteropMechanism::CPP);
 
    OpBuilder deallocBuilder = OpBuilder::atBlockBegin(deallocOp.getBody());
    deallocBuilder.create<DeleteOp>(loc, deallocOp.getBody()->getArgument(0));
  }
};
} // namespace
 
//===----------------------------------------------------------------------===//
// Pass initialization
//===----------------------------------------------------------------------===//
 
namespace {
struct SystemCLowerInstanceInteropPass
    : SystemCLowerInstanceInteropBase<SystemCLowerInstanceInteropPass> {
  void runOnOperation() override;
};
} // namespace
 
void circt::systemc::populateSystemCLowerInstanceInteropPatterns(
    RewritePatternSet &patterns, MLIRContext *ctx) {
  patterns.add<InteropVerilatedOpConversion>(ctx);
}
 
void SystemCLowerInstanceInteropPass::runOnOperation() {
  RewritePatternSet patterns(&getContext());
 
  ConversionTarget target(getContext());
  target.addLegalDialect<interop::InteropDialect>();
  target.addLegalDialect<emitc::EmitCDialect>();
  target.addLegalDialect<SystemCDialect>();
  target.addLegalOp<func::CallIndirectOp>();
  target.addIllegalOp<InteropVerilatedOp>();
 
  // Setup the conversion.
  populateSystemCLowerInstanceInteropPatterns(patterns, &getContext());
 
  // Apply the partial conversion.
  if (failed(
          applyPartialConversion(getOperation(), target, std::move(patterns))))
    signalPassFailure();
}
 
/// Create the SystemC Lower Interop pass.
std::unique_ptr<Pass> circt::systemc::createSystemCLowerInstanceInteropPass() {
  return std::make_unique<SystemCLowerInstanceInteropPass>();
}