FreezePaths.cpp

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//===- FreezePaths.cpp - Freeze Paths 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 OM freeze paths pass.
//
//===----------------------------------------------------------------------===//
 
#include "circt/Dialect/HW/HWInstanceGraph.h"
#include "circt/Dialect/HW/HWOps.h"
#include "circt/Dialect/HW/InnerSymbolTable.h"
#include "circt/Dialect/OM/OMAttributes.h"
#include "circt/Dialect/OM/OMOps.h"
#include "circt/Dialect/OM/OMPasses.h"
#include "mlir/Pass/Pass.h"
 
namespace circt {
namespace om {
#define GEN_PASS_DEF_FREEZEPATHS
#include "circt/Dialect/OM/OMPasses.h.inc"
} // namespace om
} // namespace circt
 
using namespace circt;
using namespace om;
 
namespace {
struct PathVisitor {
  PathVisitor(hw::InstanceGraph &instanceGraph, hw::InnerRefNamespace &irn,
              std::function<StringAttr(Operation *)> &getOpName)
      : instanceGraph(instanceGraph), irn(irn), getOpNameFallback(getOpName) {}
 
  StringAttr field;
  LogicalResult processPath(Location loc, hw::HierPathOp hierPathOp,
                            PathAttr &targetPath, StringAttr &bottomModule,
                            StringAttr &component, StringAttr &field);
  LogicalResult process(BasePathCreateOp pathOp);
  LogicalResult process(PathCreateOp pathOp);
  LogicalResult process(EmptyPathOp pathOp);
  LogicalResult processListCreator(Operation *listCreateOp);
  LogicalResult process(ObjectFieldOp objectFieldOp);
  LogicalResult run(ModuleOp module);
  hw::InstanceGraph &instanceGraph;
  hw::InnerRefNamespace &irn;
  std::function<StringAttr(Operation *)> getOpNameFallback;
};
} // namespace
 
static LogicalResult getAccessPath(Location loc, Type type, size_t fieldId,
                                   StringAttr &result) {
  SmallString<64> field;
  while (fieldId) {
    if (auto aliasType = dyn_cast<hw::TypeAliasType>(type))
      type = aliasType.getCanonicalType();
    if (auto structType = dyn_cast<hw::StructType>(type)) {
      auto index = structType.getIndexForFieldID(fieldId);
      auto &element = structType.getElements()[index];
      field.push_back('.');
      llvm::append_range(field, element.name.getValue());
      type = element.type;
      fieldId -= structType.getFieldID(index);
    } else if (auto arrayType = dyn_cast<hw::ArrayType>(type)) {
      auto index = arrayType.getIndexForFieldID(fieldId);
      field.push_back('[');
      Twine(index).toVector(field);
      field.push_back(']');
      type = arrayType.getElementType();
      fieldId -= arrayType.getFieldID(index);
    } else {
      return emitError(loc) << "can't create access path with fieldID "
                            << fieldId << " in type " << type;
    }
  }
  result = StringAttr::get(loc->getContext(), field);
  return success();
}
 
// Check if the element type of a potentially nested list includes path types.
static bool hasPathType(Type type) {
  bool isPathType = false;
  type.walk([&](Type innerType) {
    if (isa<BasePathType, PathType>(innerType))
      isPathType = true;
  });
 
  return isPathType;
}
 
mlir::AttrTypeReplacer makeReplacer() {
  mlir::AttrTypeReplacer replacer;
  replacer.addReplacement([](BasePathType innerType) {
    return FrozenBasePathType::get(innerType.getContext());
  });
  replacer.addReplacement([](PathType innerType) {
    return FrozenPathType::get(innerType.getContext());
  });
  return replacer;
}
 
// Convert potentially nested lists of PathType or BasePathType to frozen lists.
static Type processType(Type type) {
  mlir::AttrTypeReplacer replacer = makeReplacer();
  return replacer.replace(type);
}
 
LogicalResult PathVisitor::processPath(Location loc, hw::HierPathOp hierPathOp,
                                       PathAttr &targetPath,
                                       StringAttr &bottomModule,
                                       StringAttr &component,
                                       StringAttr &field) {
  auto *context = hierPathOp->getContext();
  // Look up the associated HierPathOp.
  auto namepath = hierPathOp.getNamepathAttr().getValue();
  SmallVector<PathElement> modules;
 
  // Process the of the hierarchical path.
  for (auto attr : namepath.drop_back()) {
    auto innerRef = cast<hw::InnerRefAttr>(attr);
    auto target = irn.lookup(innerRef);
    assert(target.isOpOnly() && "can't target a port the middle of a namepath");
    auto *op = target.getOp();
    // Get the verilog name of the target.
    auto verilogName = op->getAttrOfType<StringAttr>("hw.verilogName");
    if (!verilogName && getOpNameFallback)
      verilogName = getOpNameFallback(op);
    if (!verilogName) {
      auto diag = emitError(loc, "component does not have verilog name");
      diag.attachNote(op->getLoc()) << "component here";
      return diag;
    }
    modules.emplace_back(innerRef.getModule(), verilogName);
  }
 
  // Process the final target.
  auto &end = namepath.back();
  if (auto innerRef = dyn_cast<hw::InnerRefAttr>(end)) {
    auto target = irn.lookup(innerRef);
    if (target.isPort()) {
      // We are targeting the port of a module.
      auto module = cast<hw::HWModuleLike>(target.getOp());
      auto index = target.getPort();
      bottomModule = module.getModuleNameAttr();
      component = StringAttr::get(context, module.getPortName(index));
      auto loc = module.getPortLoc(index);
      auto type = module.getPortTypes()[index];
      if (failed(getAccessPath(loc, type, target.getField(), field)))
        return failure();
    } else {
      auto *op = target.getOp();
      assert(op && "innerRef should be targeting something");
      // Get the current module.
      auto currentModule = innerRef.getModule();
      // Get the verilog name of the target.
      auto verilogName = op->getAttrOfType<StringAttr>("hw.verilogName");
      if (!verilogName && getOpNameFallback)
        verilogName = getOpNameFallback(op);
      if (!verilogName) {
        auto diag = emitError(loc, "component does not have verilog name");
        diag.attachNote(op->getLoc()) << "component here";
        return diag;
      }
      // If this is our inner ref pair: [Foo::bar]
      // if "bar" is an instance, modules = [Foo::bar], bottomModule = Bar.
      // if "bar" is a wire, modules = [], bottomModule = Foo, component = bar.
      if (auto inst = dyn_cast<hw::HWInstanceLike>(op)) {
        // TODO: add support for instance choices.
        auto mods = inst.getReferencedModuleNamesAttr();
        if (mods.size() > 1)
          return op->emitError("unsupported instance operation");
        // We are targeting an instance.
        modules.emplace_back(currentModule, verilogName);
        bottomModule = cast<StringAttr>(mods[0]);
        component = StringAttr::get(context, "");
        field = StringAttr::get(context, "");
      } else {
        // We are targeting a regular component.
        bottomModule = currentModule;
        component = verilogName;
        auto innerSym = cast<hw::InnerSymbolOpInterface>(op);
        auto value = innerSym.getTargetResult();
        if (failed(getAccessPath(value.getLoc(), value.getType(),
                                 target.getField(), field)))
          return failure();
      }
    }
  } else {
    // We are targeting a module.
    auto symbolRef = cast<FlatSymbolRefAttr>(end);
    bottomModule = symbolRef.getAttr();
    component = StringAttr::get(context, "");
    field = StringAttr::get(context, "");
  }
 
  // Create the target path.
  targetPath = PathAttr::get(context, modules);
  return success();
}
 
LogicalResult PathVisitor::process(PathCreateOp path) {
  auto hierPathOp =
      irn.symTable.lookup<hw::HierPathOp>(path.getTargetAttr().getAttr());
  PathAttr targetPath;
  StringAttr bottomModule;
  StringAttr ref;
  StringAttr field;
  if (failed(processPath(path.getLoc(), hierPathOp, targetPath, bottomModule,
                         ref, field)))
    return failure();
 
  // Replace the old path operation.
  OpBuilder builder(path);
  auto frozenPath = builder.create<FrozenPathCreateOp>(
      path.getLoc(), path.getTargetKindAttr(), path->getOperand(0), targetPath,
      bottomModule, ref, field);
  path.replaceAllUsesWith(frozenPath.getResult());
  path->erase();
 
  return success();
}
 
LogicalResult PathVisitor::process(BasePathCreateOp path) {
  auto hierPathOp =
      irn.symTable.lookup<hw::HierPathOp>(path.getTargetAttr().getAttr());
  PathAttr targetPath;
  StringAttr bottomModule;
  StringAttr ref;
  StringAttr field;
  if (failed(processPath(path.getLoc(), hierPathOp, targetPath, bottomModule,
                         ref, field)))
    return failure();
 
  if (!ref.empty())
    return path->emitError("basepath must target an instance");
  if (!field.empty())
    return path->emitError("basepath must not target a field");
 
  // Replace the old path operation.
  OpBuilder builder(path);
  auto frozenPath = builder.create<FrozenBasePathCreateOp>(
      path.getLoc(), path->getOperand(0), targetPath);
  path.replaceAllUsesWith(frozenPath.getResult());
  path->erase();
 
  return success();
}
 
LogicalResult PathVisitor::process(EmptyPathOp path) {
  OpBuilder builder(path);
  auto frozenPath = builder.create<FrozenEmptyPathOp>(path.getLoc());
  path.replaceAllUsesWith(frozenPath.getResult());
  path->erase();
  return success();
}
 
/// Replace a ListCreateOp of path types with frozen path types.
LogicalResult PathVisitor::processListCreator(Operation *listCreateOp) {
  ListType listType = cast<ListType>(listCreateOp->getResult(0).getType());
 
  // Check if there are any path types in the list(s).
  if (!hasPathType(listType))
    return success();
 
  // Create a new ListType with frozen path types.
  auto newListType = processType(listType);
 
  // Create a new op with the result type updated to replace path types.
  OpBuilder builder(listCreateOp);
  auto *newListCreateOp = builder.create(
      listCreateOp->getLoc(), listCreateOp->getName().getIdentifier(),
      listCreateOp->getOperands(), {newListType});
  listCreateOp->getResult(0).replaceAllUsesWith(newListCreateOp->getResult(0));
  listCreateOp->erase();
  return success();
}
 
/// Replace an ObjectFieldOp of path types with frozen path types.
LogicalResult PathVisitor::process(ObjectFieldOp objectFieldOp) {
  Type resultType = objectFieldOp.getResult().getType();
 
  // Check if there are any path types in the field.
  if (!hasPathType(resultType))
    return success();
 
  // Create a new result Type with frozen path types.
  auto newResultType = processType(resultType);
 
  // Create a new op with the result type updated to replace path types.
  OpBuilder builder(objectFieldOp);
  auto newObjectFieldOp = builder.create<ObjectFieldOp>(
      objectFieldOp.getLoc(), newResultType, objectFieldOp.getObject(),
      objectFieldOp.getFieldPath());
  objectFieldOp.replaceAllUsesWith(newObjectFieldOp.getResult());
  objectFieldOp->erase();
  return success();
}
 
LogicalResult PathVisitor::run(ModuleOp module) {
  auto updatePathType = [&](Value value) {
    if (hasPathType(value.getType()))
      value.setType(processType(value.getType()));
  };
  for (auto classLike : module.getOps<ClassLike>()) {
    // Transform PathType block argument to FrozenPathType.
    for (auto arg : classLike.getBodyBlock()->getArguments())
      updatePathType(arg);
    auto result = classLike->walk([&](Operation *op) -> WalkResult {
      if (auto basePath = dyn_cast<BasePathCreateOp>(op)) {
        if (failed(process(basePath)))
          return WalkResult::interrupt();
      } else if (auto path = dyn_cast<PathCreateOp>(op)) {
        if (failed(process(path)))
          return WalkResult::interrupt();
      } else if (auto path = dyn_cast<EmptyPathOp>(op)) {
        if (failed(process(path)))
          return WalkResult::interrupt();
      } else if (isa<ListCreateOp, ListConcatOp>(op)) {
        if (failed(processListCreator(op)))
          return WalkResult::interrupt();
      } else if (auto objectField = dyn_cast<ObjectFieldOp>(op)) {
        if (failed(process(objectField)))
          return WalkResult::interrupt();
      }
      return WalkResult::advance();
    });
    if (result.wasInterrupted())
      return failure();
 
    // Transform field types
    classLike.replaceFieldTypes(makeReplacer());
  }
  return success();
}
 
namespace {
struct FreezePathsPass
    : public circt::om::impl::FreezePathsBase<FreezePathsPass> {
  FreezePathsPass(std::function<StringAttr(Operation *)> getOpName)
      : getOpName(std::move(getOpName)) {}
  void runOnOperation() override;
 
  std::function<StringAttr(Operation *)> getOpName;
};
} // namespace
 
void FreezePathsPass::runOnOperation() {
  auto module = getOperation();
  auto &instanceGraph = getAnalysis<hw::InstanceGraph>();
  mlir::SymbolTableCollection symbolTableCollection;
  auto &symbolTable = getAnalysis<SymbolTable>();
  hw::InnerSymbolTableCollection collection(module);
  hw::InnerRefNamespace irn{symbolTable, collection};
  if (failed(PathVisitor(instanceGraph, irn, getOpName).run(module)))
    signalPassFailure();
}
 
std::unique_ptr<mlir::Pass> circt::om::createFreezePathsPass(
    std::function<StringAttr(Operation *)> getOpName) {
  return std::make_unique<FreezePathsPass>(getOpName);
}