HWStubExternalModules.cpp

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//===- HWStubExternalModules.cpp - HW Module Stubbing Pass ----------------===//
//
// 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 transformation pass converts external modules to empty normal modules.
//
//===----------------------------------------------------------------------===//
 
#include "PassDetail.h"
#include "circt/Dialect/HW/HWOps.h"
#include "circt/Dialect/SV/SVPasses.h"
#include "mlir/IR/Builders.h"
 
using namespace circt;
 
//===----------------------------------------------------------------------===//
// HWStubExternalModules Pass
//===----------------------------------------------------------------------===//
 
namespace {
struct HWStubExternalModulesPass
    : public sv::HWStubExternalModulesBase<HWStubExternalModulesPass> {
  void runOnOperation() override;
};
} // end anonymous namespace
 
void HWStubExternalModulesPass::runOnOperation() {
  auto topModule = getOperation().getBody();
  OpBuilder builder(topModule->getParentOp()->getContext());
  builder.setInsertionPointToEnd(topModule);
 
  for (auto &op : llvm::make_early_inc_range(*topModule))
    if (auto module = dyn_cast<hw::HWModuleExternOp>(op)) {
      hw::ModulePortInfo ports(module.getPortList());
      auto nameAttr = module.getNameAttr();
      auto newModule = builder.create<hw::HWModuleOp>(
          module.getLoc(), nameAttr, ports, module.getParameters());
      auto outputOp = newModule.getBodyBlock()->getTerminator();
      OpBuilder innerBuilder(outputOp);
      SmallVector<Value, 8> outputs;
      // All output ports need values, use x
      for (auto &p : ports.getOutputs()) {
        outputs.push_back(
            innerBuilder.create<sv::ConstantXOp>(outputOp->getLoc(), p.type));
      }
      outputOp->setOperands(outputs);
 
      // Done with the old module.
      module.erase();
    }
}
 
std::unique_ptr<Pass> circt::sv::createHWStubExternalModulesPass() {
  return std::make_unique<HWStubExternalModulesPass>();
}