SimToSV.cpp

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//===- LowerSimToSV.cpp - Sim to SV 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 transform translates Sim ops to SV.
//
//===----------------------------------------------------------------------===//
 
#include "circt/Conversion/SimToSV.h"
#include "circt/Dialect/Comb/CombOps.h"
#include "circt/Dialect/Emit/EmitOps.h"
#include "circt/Dialect/HW/HWOps.h"
#include "circt/Dialect/SV/SVOps.h"
#include "circt/Dialect/Seq/SeqOps.h"
#include "circt/Dialect/Sim/SimDialect.h"
#include "circt/Dialect/Sim/SimOps.h"
#include "circt/Support/Namespace.h"
#include "mlir/IR/Builders.h"
#include "mlir/IR/DialectImplementation.h"
#include "mlir/IR/ImplicitLocOpBuilder.h"
#include "mlir/IR/Threading.h"
#include "mlir/Pass/Pass.h"
#include "mlir/Transforms/DialectConversion.h"
 
#define DEBUG_TYPE "lower-sim-to-sv"
 
namespace circt {
#define GEN_PASS_DEF_LOWERSIMTOSV
#include "circt/Conversion/Passes.h.inc"
} // namespace circt
 
using namespace circt;
using namespace sim;
 
namespace {
 
struct SimConversionState {
  hw::HWModuleOp module;
  bool usedSynthesisMacro = false;
  SetVector<StringAttr> dpiCallees;
};
 
template <typename T>
struct SimConversionPattern : public OpConversionPattern<T> {
  explicit SimConversionPattern(MLIRContext *context, SimConversionState &state)
      : OpConversionPattern<T>(context), state(state) {}
 
  SimConversionState &state;
};
 
} // namespace
 
// Lower `sim.plusargs.test` to a standard SV implementation.
//
class PlusArgsTestLowering : public SimConversionPattern<PlusArgsTestOp> {
public:
  using SimConversionPattern<PlusArgsTestOp>::SimConversionPattern;
 
  LogicalResult
  matchAndRewrite(PlusArgsTestOp op, OpAdaptor adaptor,
                  ConversionPatternRewriter &rewriter) const final {
    auto loc = op.getLoc();
    auto resultType = rewriter.getIntegerType(1);
    auto str = rewriter.create<sv::ConstantStrOp>(loc, op.getFormatString());
    auto reg = rewriter.create<sv::RegOp>(loc, resultType,
                                          rewriter.getStringAttr("_pargs"));
    rewriter.create<sv::InitialOp>(loc, [&] {
      auto call = rewriter.create<sv::SystemFunctionOp>(
          loc, resultType, "test$plusargs", ArrayRef<Value>{str});
      rewriter.create<sv::BPAssignOp>(loc, reg, call);
    });
 
    rewriter.replaceOpWithNewOp<sv::ReadInOutOp>(op, reg);
    return success();
  }
};
 
// Lower `sim.plusargs.value` to a standard SV implementation.
//
class PlusArgsValueLowering : public SimConversionPattern<PlusArgsValueOp> {
public:
  using SimConversionPattern<PlusArgsValueOp>::SimConversionPattern;
 
  LogicalResult
  matchAndRewrite(PlusArgsValueOp op, OpAdaptor adaptor,
                  ConversionPatternRewriter &rewriter) const final {
    auto loc = op.getLoc();
 
    auto i1ty = rewriter.getIntegerType(1);
    auto type = op.getResult().getType();
 
    auto regv = rewriter.create<sv::RegOp>(loc, type,
                                           rewriter.getStringAttr("_pargs_v_"));
    auto regf = rewriter.create<sv::RegOp>(loc, i1ty,
                                           rewriter.getStringAttr("_pargs_f"));
 
    state.usedSynthesisMacro = true;
    rewriter.create<sv::IfDefOp>(
        loc, "SYNTHESIS",
        [&]() {
          auto cstFalse = rewriter.create<hw::ConstantOp>(loc, APInt(1, 0));
          auto cstZ = rewriter.create<sv::ConstantZOp>(loc, type);
          auto assignZ = rewriter.create<sv::AssignOp>(loc, regv, cstZ);
          circt::sv::setSVAttributes(
              assignZ,
              sv::SVAttributeAttr::get(
                  rewriter.getContext(),
                  "This dummy assignment exists to avoid undriven lint "
                  "warnings (e.g., Verilator UNDRIVEN).",
                  /*emitAsComment=*/true));
          rewriter.create<sv::AssignOp>(loc, regf, cstFalse);
        },
        [&]() {
          rewriter.create<sv::InitialOp>(loc, [&] {
            auto zero32 = rewriter.create<hw::ConstantOp>(loc, APInt(32, 0));
            auto tmpResultType = rewriter.getIntegerType(32);
            auto str =
                rewriter.create<sv::ConstantStrOp>(loc, op.getFormatString());
            auto call = rewriter.create<sv::SystemFunctionOp>(
                loc, tmpResultType, "value$plusargs",
                ArrayRef<Value>{str, regv});
            auto test = rewriter.create<comb::ICmpOp>(
                loc, comb::ICmpPredicate::ne, call, zero32, true);
            rewriter.create<sv::BPAssignOp>(loc, regf, test);
          });
        });
 
    auto readf = rewriter.create<sv::ReadInOutOp>(loc, regf);
    auto readv = rewriter.create<sv::ReadInOutOp>(loc, regv);
    rewriter.replaceOp(op, {readf, readv});
    return success();
  }
};
 
template <typename FromOp, typename ToOp>
class SimulatorStopLowering : public SimConversionPattern<FromOp> {
public:
  using SimConversionPattern<FromOp>::SimConversionPattern;
 
  LogicalResult
  matchAndRewrite(FromOp op, typename FromOp::Adaptor adaptor,
                  ConversionPatternRewriter &rewriter) const final {
    auto loc = op.getLoc();
 
    Value clockCast = rewriter.create<seq::FromClockOp>(loc, adaptor.getClk());
 
    this->state.usedSynthesisMacro = true;
    rewriter.create<sv::IfDefOp>(
        loc, "SYNTHESIS", [&] {},
        [&] {
          rewriter.create<sv::AlwaysOp>(
              loc, sv::EventControl::AtPosEdge, clockCast, [&] {
                rewriter.create<sv::IfOp>(loc, adaptor.getCond(),
                                          [&] { rewriter.create<ToOp>(loc); });
              });
        });
 
    rewriter.eraseOp(op);
 
    return success();
  }
};
 
class DPICallLowering : public SimConversionPattern<DPICallOp> {
public:
  using SimConversionPattern<DPICallOp>::SimConversionPattern;
 
  LogicalResult
  matchAndRewrite(DPICallOp op, OpAdaptor adaptor,
                  ConversionPatternRewriter &rewriter) const final {
    auto loc = op.getLoc();
    // Record the callee.
    state.dpiCallees.insert(op.getCalleeAttr().getAttr());
 
    bool isClockedCall = !!op.getClock();
    bool hasEnable = !!op.getEnable();
 
    SmallVector<sv::RegOp> temporaries;
    SmallVector<Value> reads;
    for (auto [type, result] :
         llvm::zip(op.getResultTypes(), op.getResults())) {
      temporaries.push_back(rewriter.create<sv::RegOp>(op.getLoc(), type));
      reads.push_back(
          rewriter.create<sv::ReadInOutOp>(op.getLoc(), temporaries.back()));
    }
 
    auto emitCall = [&]() {
      auto call = rewriter.create<sv::FuncCallProceduralOp>(
          op.getLoc(), op.getResultTypes(), op.getCalleeAttr(),
          adaptor.getInputs());
      for (auto [lhs, rhs] : llvm::zip(temporaries, call.getResults())) {
        if (isClockedCall)
          rewriter.create<sv::PAssignOp>(op.getLoc(), lhs, rhs);
        else
          rewriter.create<sv::BPAssignOp>(op.getLoc(), lhs, rhs);
      }
    };
    if (isClockedCall) {
      Value clockCast =
          rewriter.create<seq::FromClockOp>(loc, adaptor.getClock());
      rewriter.create<sv::AlwaysOp>(
          loc, ArrayRef<sv::EventControl>{sv::EventControl::AtPosEdge},
          ArrayRef<Value>{clockCast}, [&]() {
            if (!hasEnable)
              return emitCall();
            rewriter.create<sv::IfOp>(op.getLoc(), adaptor.getEnable(),
                                      emitCall);
          });
    } else {
      // Unclocked call is lowered into always_comb.
      // TODO: If there is a return value and no output argument, use an
      // unclocked call op.
      rewriter.create<sv::AlwaysCombOp>(loc, [&]() {
        if (!hasEnable)
          return emitCall();
        auto assignXToResults = [&] {
          for (auto lhs : temporaries) {
            auto xValue = rewriter.create<sv::ConstantXOp>(
                op.getLoc(), lhs.getType().getElementType());
            rewriter.create<sv::BPAssignOp>(op.getLoc(), lhs, xValue);
          }
        };
        rewriter.create<sv::IfOp>(op.getLoc(), adaptor.getEnable(), emitCall,
                                  assignXToResults);
      });
    }
 
    rewriter.replaceOp(op, reads);
    return success();
  }
};
 
// A helper struct to lower DPI function/call.
struct LowerDPIFunc {
  llvm::DenseMap<StringAttr, StringAttr> symbolToFragment;
  circt::Namespace nameSpace;
  LowerDPIFunc(mlir::ModuleOp module) { nameSpace.add(module); }
  void lower(sim::DPIFuncOp func);
  void addFragments(hw::HWModuleOp module,
                    ArrayRef<StringAttr> dpiCallees) const;
};
 
void LowerDPIFunc::lower(sim::DPIFuncOp func) {
  ImplicitLocOpBuilder builder(func.getLoc(), func);
  ArrayAttr inputLocsAttr, outputLocsAttr;
  if (func.getArgumentLocs()) {
    SmallVector<Attribute> inputLocs, outputLocs;
    for (auto [port, loc] :
         llvm::zip(func.getModuleType().getPorts(),
                   func.getArgumentLocsAttr().getAsRange<LocationAttr>())) {
      (port.dir == hw::ModulePort::Output ? outputLocs : inputLocs)
          .push_back(loc);
    }
    inputLocsAttr = builder.getArrayAttr(inputLocs);
    outputLocsAttr = builder.getArrayAttr(outputLocs);
  }
 
  auto svFuncDecl =
      builder.create<sv::FuncOp>(func.getSymNameAttr(), func.getModuleType(),
                                 func.getPerArgumentAttrsAttr(), inputLocsAttr,
                                 outputLocsAttr, func.getVerilogNameAttr());
  // DPI function is a declaration so it must be a private function.
  svFuncDecl.setPrivate();
  auto name = builder.getStringAttr(nameSpace.newName(
      func.getSymNameAttr().getValue(), "dpi_import_fragument"));
 
  builder.create<emit::FragmentOp>(name, [&]() {
    builder.create<sv::FuncDPIImportOp>(func.getSymNameAttr(), StringAttr());
  });
 
  symbolToFragment.insert({func.getSymNameAttr(), name});
  func.erase();
}
 
void LowerDPIFunc::addFragments(hw::HWModuleOp module,
                                ArrayRef<StringAttr> dpiCallees) const {
  llvm::SetVector<Attribute> fragments;
  // Add existing emit fragments.
  if (auto exstingFragments =
          module->getAttrOfType<ArrayAttr>(emit::getFragmentsAttrName()))
    for (auto fragment : exstingFragments.getAsRange<FlatSymbolRefAttr>())
      fragments.insert(fragment);
  for (auto callee : dpiCallees) {
    auto attr = symbolToFragment.at(callee);
    fragments.insert(FlatSymbolRefAttr::get(attr));
  }
  if (!fragments.empty())
    module->setAttr(
        emit::getFragmentsAttrName(),
        ArrayAttr::get(module.getContext(), fragments.takeVector()));
}
 
namespace {
struct SimToSVPass : public circt::impl::LowerSimToSVBase<SimToSVPass> {
  void runOnOperation() override {
    auto circuit = getOperation();
    MLIRContext *context = &getContext();
    LowerDPIFunc lowerDPIFunc(circuit);
 
    // Lower DPI functions.
    for (auto func :
         llvm::make_early_inc_range(circuit.getOps<sim::DPIFuncOp>()))
      lowerDPIFunc.lower(func);
 
    std::atomic<bool> usedSynthesisMacro = false;
    auto lowerModule = [&](hw::HWModuleOp module) {
      SimConversionState state;
      ConversionTarget target(*context);
      target.addIllegalDialect<SimDialect>();
      target.addLegalDialect<sv::SVDialect>();
      target.addLegalDialect<hw::HWDialect>();
      target.addLegalDialect<seq::SeqDialect>();
      target.addLegalDialect<comb::CombDialect>();
 
      RewritePatternSet patterns(context);
      patterns.add<PlusArgsTestLowering>(context, state);
      patterns.add<PlusArgsValueLowering>(context, state);
      patterns.add<SimulatorStopLowering<sim::FinishOp, sv::FinishOp>>(context,
                                                                       state);
      patterns.add<SimulatorStopLowering<sim::FatalOp, sv::FatalOp>>(context,
                                                                     state);
      patterns.add<DPICallLowering>(context, state);
      auto result = applyPartialConversion(module, target, std::move(patterns));
 
      if (failed(result))
        return result;
 
      // Set the emit fragment.
      lowerDPIFunc.addFragments(module, state.dpiCallees.takeVector());
 
      if (state.usedSynthesisMacro)
        usedSynthesisMacro = true;
      return result;
    };
 
    if (failed(mlir::failableParallelForEach(
            context, circuit.getOps<hw::HWModuleOp>(), lowerModule)))
      return signalPassFailure();
 
    if (usedSynthesisMacro) {
      Operation *op = circuit.lookupSymbol("SYNTHESIS");
      if (op) {
        if (!isa<sv::MacroDeclOp>(op)) {
          op->emitOpError("should be a macro declaration");
          return signalPassFailure();
        }
      } else {
        auto builder = ImplicitLocOpBuilder::atBlockBegin(
            UnknownLoc::get(context), circuit.getBody());
        builder.create<sv::MacroDeclOp>("SYNTHESIS");
      }
    }
  }
};
} // anonymous namespace
 
std::unique_ptr<Pass> circt::createLowerSimToSVPass() {
  return std::make_unique<SimToSVPass>();
}