ImportLiberty.cpp

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//===----------------------------------------------------------------------===//
//
// 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 file implements the Liberty file import functionality.
//
//===----------------------------------------------------------------------===//
 
#include "circt/Conversion/ImportLiberty.h"
#include "circt/Dialect/Comb/CombDialect.h"
#include "circt/Dialect/Comb/CombOps.h"
#include "circt/Dialect/HW/HWOps.h"
#include "mlir/IR/Attributes.h"
#include "mlir/IR/Builders.h"
#include "mlir/IR/BuiltinAttributes.h"
#include "mlir/IR/BuiltinOps.h"
#include "mlir/IR/BuiltinTypes.h"
#include "mlir/IR/Diagnostics.h"
#include "mlir/IR/Location.h"
#include "mlir/IR/MLIRContext.h"
#include "mlir/IR/Value.h"
#include "mlir/Support/FileUtilities.h"
#include "mlir/Support/LogicalResult.h"
#include "mlir/Tools/mlir-translate/Translation.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/LogicalResult.h"
#include "llvm/Support/SourceMgr.h"
 
#define DEBUG_TYPE "import-liberty"
 
using namespace mlir;
using namespace circt;
using namespace circt::hw;
using namespace circt::comb;
 
namespace {
 
/// Liberty token types for lexical analysis
enum class LibertyTokenKind {
  // Literals
  Identifier,
  String,
  Number,
 
  // Punctuation
  LBrace, // {
  RBrace, // }
  LParen, // (
  RParen, // )
  Colon,  // :
  Semi,   // ;
  Comma,  // ,
 
  // Special
  EndOfFile,
  Error
};
 
StringRef stringifyTokenKind(LibertyTokenKind kind) {
  switch (kind) {
  case LibertyTokenKind::Identifier:
    return "identifier";
  case LibertyTokenKind::String:
    return "string";
  case LibertyTokenKind::Number:
    return "number";
  case LibertyTokenKind::LBrace:
    return "'{'";
  case LibertyTokenKind::RBrace:
    return "'}'";
  case LibertyTokenKind::LParen:
    return "'('";
  case LibertyTokenKind::RParen:
    return "')'";
  case LibertyTokenKind::Colon:
    return "':'";
  case LibertyTokenKind::Semi:
    return "';'";
  case LibertyTokenKind::Comma:
    return "','";
 
  case LibertyTokenKind::EndOfFile:
    return "end of file";
  case LibertyTokenKind::Error:
    return "error";
  }
  return "unknown";
}
 
struct LibertyToken {
  LibertyTokenKind kind;
  StringRef spelling;
  SMLoc location;
 
  LibertyToken(LibertyTokenKind kind, StringRef spelling, SMLoc location)
      : kind(kind), spelling(spelling), location(location) {}
 
  bool is(LibertyTokenKind k) const { return kind == k; }
};
 
class LibertyLexer {
public:
  LibertyLexer(const llvm::SourceMgr &sourceMgr, MLIRContext *context)
      : sourceMgr(sourceMgr), context(context),
        curBuffer(
            sourceMgr.getMemoryBuffer(sourceMgr.getMainFileID())->getBuffer()),
        curPtr(curBuffer.begin()) {}
 
  LibertyToken nextToken();
  LibertyToken peekToken();
 
  SMLoc getCurrentLoc() const { return SMLoc::getFromPointer(curPtr); }
 
  Location translateLocation(llvm::SMLoc loc) const {
    unsigned mainFileID = sourceMgr.getMainFileID();
    auto lineAndColumn = sourceMgr.getLineAndColumn(loc, mainFileID);
    return FileLineColLoc::get(
        StringAttr::get(
            context,
            sourceMgr.getMemoryBuffer(mainFileID)->getBufferIdentifier()),
        lineAndColumn.first, lineAndColumn.second);
  }
 
  bool isAtEnd() const { return curPtr >= curBuffer.end(); }
 
private:
  const llvm::SourceMgr &sourceMgr;
  MLIRContext *context;
  StringRef curBuffer;
  const char *curPtr;
 
  void skipWhitespaceAndComments();
  LibertyToken lexIdentifier();
  LibertyToken lexString();
  LibertyToken lexNumber();
  LibertyToken makeToken(LibertyTokenKind kind, const char *start);
};
 
/// Helper class to parse boolean expressions from Liberty function attributes.
///
/// This parser implements a recursive-descent parser for Liberty boolean
/// expressions with the following operator precedence (highest to lowest):
///   1. NOT (!, ')      - Unary negation (prefix or postfix)
///   2. AND (*, &)      - Conjunction
///   3. XOR (^)         - Exclusive OR
///   4. OR  (+, |)      - Disjunction
///
/// Parentheses can be used to override precedence. The grammar is:
///   OrExpr    -> XorExpr { ('+'|'|') XorExpr }
///   XorExpr   -> AndExpr { '^' AndExpr }
///   AndExpr   -> UnaryExpr { ('*'|'&') UnaryExpr }
///   UnaryExpr -> '!' UnaryExpr | '(' OrExpr ')' ['\''] | ID ['\']
class ExpressionParser {
public:
  ExpressionParser(LibertyLexer &lexer, OpBuilder &builder, StringRef expr,
                   const llvm::StringMap<Value> &values, SMLoc baseLoc);
 
  ParseResult parse(Value &result);
 
private:
  enum class TokenKind {
    ID,
    AND,
    OR,
    XOR,
    PREFIX_NOT,  // !
    POSTFIX_NOT, // '
    LPAREN,
    RPAREN,
    END
  };
 
  struct Token {
    TokenKind kind;
    StringRef spelling;
    SMLoc loc;
  };
 
  LibertyLexer &lexer;
  OpBuilder &builder;
  const llvm::StringMap<Value> &values;
  SMLoc baseLoc;
  const char *exprStart;
  SmallVector<Token> tokens;
  size_t pos = 0;
  Value trueVal = nullptr;
 
  SMLoc getLoc(const char *ptr);
  void tokenize(StringRef expr);
  Token peek() const;
  Token consume();
  Value createNot(Value val, SMLoc loc);
 
  ParseResult parseOrExpr(Value &result);
  ParseResult parseXorExpr(Value &result);
  ParseResult parseAndExpr(Value &result);
  ParseResult parseUnaryExpr(Value &result);
 
  InFlightDiagnostic emitError(llvm::SMLoc loc, const Twine &message) const;
  InFlightDiagnostic emitWarning(llvm::SMLoc loc, const Twine &message) const;
};
 
//===----------------------------------------------------------------------===//
// ExpressionParser Implementation
//===----------------------------------------------------------------------===//
 
ExpressionParser::ExpressionParser(LibertyLexer &lexer, OpBuilder &builder,
                                   StringRef expr,
                                   const llvm::StringMap<Value> &values,
                                   SMLoc baseLoc)
    : lexer(lexer), builder(builder), values(values), baseLoc(baseLoc),
      exprStart(expr.begin()) {
  tokenize(expr);
}
 
ParseResult ExpressionParser::parse(Value &result) {
  return parseOrExpr(result);
}
 
SMLoc ExpressionParser::getLoc(const char *ptr) {
  size_t offset = ptr - exprStart;
  return SMLoc::getFromPointer(baseLoc.getPointer() + 1 + offset);
}
 
void ExpressionParser::tokenize(StringRef expr) {
  const char *ptr = expr.begin();
  const char *end = expr.end();
 
  while (ptr < end) {
    // Skip whitespace
    if (isspace(*ptr)) {
      ++ptr;
      continue;
    }
 
    SMLoc loc = getLoc(ptr);
 
    // Identifier
    if (isalnum(*ptr) || *ptr == '_') {
      const char *start = ptr;
      while (ptr < end && (isalnum(*ptr) || *ptr == '_'))
        ++ptr;
      tokens.push_back({TokenKind::ID, StringRef(start, ptr - start), loc});
      continue;
    }
 
    // Operators and punctuation
    switch (*ptr) {
    case '*':
    case '&':
      tokens.push_back({TokenKind::AND, StringRef(ptr, 1), loc});
      break;
    case '+':
    case '|':
      tokens.push_back({TokenKind::OR, StringRef(ptr, 1), loc});
      break;
    case '^':
      tokens.push_back({TokenKind::XOR, StringRef(ptr, 1), loc});
      break;
    case '!':
      tokens.push_back({TokenKind::PREFIX_NOT, StringRef(ptr, 1), loc});
      break;
    case '\'':
      tokens.push_back({TokenKind::POSTFIX_NOT, StringRef(ptr, 1), loc});
      break;
    case '(':
      tokens.push_back({TokenKind::LPAREN, StringRef(ptr, 1), loc});
      break;
    case ')':
      tokens.push_back({TokenKind::RPAREN, StringRef(ptr, 1), loc});
      break;
    }
    ++ptr;
  }
 
  tokens.push_back({TokenKind::END, "", getLoc(ptr)});
}
 
ExpressionParser::Token ExpressionParser::peek() const { return tokens[pos]; }
 
ExpressionParser::Token ExpressionParser::consume() { return tokens[pos++]; }
 
Value ExpressionParser::createNot(Value val, SMLoc loc) {
  if (!trueVal)
    trueVal = hw::ConstantOp::create(builder, lexer.translateLocation(loc),
                                     builder.getI1Type(), 1);
  return comb::XorOp::create(builder, lexer.translateLocation(loc), val,
                             trueVal);
}
 
/// Parse OR expressions with lowest precedence.
/// OrExpr -> XorExpr { ('+'|'|') XorExpr }
/// This implements left-associative parsing: A + B + C becomes (A + B) + C
ParseResult ExpressionParser::parseOrExpr(Value &result) {
  Value lhs;
  if (parseXorExpr(lhs))
    return failure();
  while (peek().kind == TokenKind::OR) {
    auto loc = consume().loc;
    Value rhs;
    if (parseXorExpr(rhs))
      return failure();
    lhs = comb::OrOp::create(builder, lexer.translateLocation(loc), lhs, rhs);
  }
  result = lhs;
  return success();
}
 
/// Parse XOR expressions with medium precedence.
/// XorExpr -> AndExpr { '^' AndExpr }
/// This implements left-associative parsing: A ^ B ^ C becomes (A ^ B) ^ C
ParseResult ExpressionParser::parseXorExpr(Value &result) {
  Value lhs;
  if (parseAndExpr(lhs))
    return failure();
  while (peek().kind == TokenKind::XOR) {
    auto loc = consume().loc;
    Value rhs;
    if (parseAndExpr(rhs))
      return failure();
    lhs = comb::XorOp::create(builder, lexer.translateLocation(loc), lhs, rhs);
  }
  result = lhs;
  return success();
}
 
/// Parse AND expressions with highest precedence.
/// AndExpr -> UnaryExpr { ('*'|'&'|implicit) UnaryExpr }
/// This implements left-associative parsing: A * B * C becomes (A * B) * C
/// Space between expressions is treated as implicit AND.
ParseResult ExpressionParser::parseAndExpr(Value &result) {
  Value lhs;
  if (parseUnaryExpr(lhs))
    return failure();
  while (peek().kind == TokenKind::AND ||
         (peek().kind == TokenKind::ID || peek().kind == TokenKind::LPAREN ||
          peek().kind == TokenKind::PREFIX_NOT)) {
    auto loc = peek().loc;
    if (peek().kind == TokenKind::AND)
      consume();
    Value rhs;
    if (parseUnaryExpr(rhs))
      return failure();
    lhs = comb::AndOp::create(builder, lexer.translateLocation(loc), lhs, rhs);
  }
  result = lhs;
  return success();
}
 
/// Parse unary expressions and primary expressions.
/// UnaryExpr -> '!' UnaryExpr | '(' OrExpr ')' ['\''] | ID ['\']
/// Handles prefix NOT (!), parenthesized expressions, and identifiers.
/// Postfix NOT (') is only allowed after expressions and identifiers.
ParseResult ExpressionParser::parseUnaryExpr(Value &result) {
  // Prefix NOT (!)
  if (peek().kind == TokenKind::PREFIX_NOT) {
    auto loc = consume().loc;
    Value val;
    if (parseUnaryExpr(val))
      return failure();
    result = createNot(val, loc);
    return success();
  }
 
  // Parenthesized expression
  if (peek().kind == TokenKind::LPAREN) {
    consume();
    Value val;
    if (parseOrExpr(val))
      return failure();
    if (peek().kind != TokenKind::RPAREN)
      return failure();
    consume();
    // Postfix NOT (')
    if (peek().kind == TokenKind::POSTFIX_NOT) {
      auto loc = consume().loc;
      val = createNot(val, loc);
    }
    result = val;
    return success();
  }
 
  // Identifier
  if (peek().kind == TokenKind::ID) {
    auto tok = consume();
    StringRef name = tok.spelling;
    auto it = values.find(name);
    if (it == values.end())
      return emitError(tok.loc, "variable not found");
    Value val = it->second;
    // Postfix NOT (')
    if (peek().kind == TokenKind::POSTFIX_NOT) {
      auto loc = consume().loc;
      val = createNot(val, loc);
    }
    result = val;
    return success();
  }
 
  return emitError(peek().loc, "expected expression");
}
 
InFlightDiagnostic ExpressionParser::emitError(llvm::SMLoc loc,
                                               const Twine &message) const {
  return mlir::emitError(lexer.translateLocation(loc), message);
}
 
InFlightDiagnostic ExpressionParser::emitWarning(llvm::SMLoc loc,
                                                 const Twine &message) const {
  return mlir::emitWarning(lexer.translateLocation(loc), message);
}
 
// Parsed result of a Liberty group
struct LibertyGroup {
  StringRef name;
  SMLoc loc;
  SmallVector<Attribute> args;
  struct AttrEntry {
    StringRef name;
    Attribute value;
    SMLoc loc;
    AttrEntry(StringRef name, Attribute value, SMLoc loc)
        : name(name), value(value), loc(loc) {}
  };
  SmallVector<AttrEntry> attrs;
  SmallVector<std::unique_ptr<LibertyGroup>> subGroups;
 
  // Helper to find an attribute by name
  std::pair<Attribute, SMLoc> getAttribute(StringRef name) const {
    for (const auto &attr : attrs)
      if (attr.name == name)
        return {attr.value, attr.loc};
    return {};
  }
 
  void eraseSubGroup(llvm::function_ref<bool(const LibertyGroup &)> pred) {
    subGroups.erase(
        std::remove_if(subGroups.begin(), subGroups.end(),
                       [pred](const auto &group) { return pred(*group); }),
        subGroups.end());
  }
 
  LogicalResult checkArgs(
      size_t n,
      llvm::function_ref<LogicalResult(size_t idx, Attribute)> pred) const {
    if (args.size() != n)
      return failure();
    for (size_t i = 0; i < n; ++i)
      if (failed(pred(i, args[i])))
        return failure();
    return success();
  }
};
 
class LibertyParser {
public:
  LibertyParser(const llvm::SourceMgr &sourceMgr, MLIRContext *context,
                ModuleOp module)
      : lexer(sourceMgr, context), module(module),
        builder(module.getBodyRegion()) {}
 
  ParseResult parse();
 
private:
  LibertyLexer lexer;
  ModuleOp module;
  OpBuilder builder;
 
  // Specific group parsers
  ParseResult parseLibrary();
  ParseResult parseGroupBody(LibertyGroup &group);
  ParseResult parseStatement(LibertyGroup &parent);
 
  // Lowering methods
  ParseResult lowerCell(const LibertyGroup &group, StringAttr &cellNameAttr);
 
  //===--------------------------------------------------------------------===//
  // Parser for Subgroup of "cell" group.
  //===--------------------------------------------------------------------===//
 
  Attribute convertGroupToAttr(const LibertyGroup &group);
 
  // Attribute parsing
  ParseResult parseAttribute(Attribute &result);
  static ParseResult parseAttribute(Attribute &result, OpBuilder &builder,
                                    StringRef attr);
 
  // Expression parsing
  ParseResult parseExpression(Value &result, StringRef expr,
                              const llvm::StringMap<Value> &values, SMLoc loc);
 
  InFlightDiagnostic emitError(llvm::SMLoc loc, const Twine &message) const {
    return mlir::emitError(lexer.translateLocation(loc), message);
  }
 
  InFlightDiagnostic emitWarning(llvm::SMLoc loc, const Twine &message) const {
    return mlir::emitWarning(lexer.translateLocation(loc), message);
  }
 
  ParseResult consume(LibertyTokenKind kind, const Twine &msg) {
    if (lexer.nextToken().is(kind))
      return success();
    return emitError(lexer.getCurrentLoc(), msg);
  }
 
  ParseResult consumeUntil(LibertyTokenKind kind) {
    while (!lexer.peekToken().is(kind) &&
           lexer.peekToken().kind != LibertyTokenKind::EndOfFile)
      lexer.nextToken();
    if (lexer.peekToken().is(kind))
      return success();
    return emitError(lexer.getCurrentLoc(),
                     " expected " + stringifyTokenKind(kind));
  }
 
  ParseResult consume(LibertyTokenKind kind) {
    if (lexer.nextToken().is(kind))
      return success();
    return emitError(lexer.getCurrentLoc(),
                     " expected " + stringifyTokenKind(kind));
  }
 
  ParseResult expect(LibertyTokenKind kind) {
    if (!lexer.peekToken().is(kind))
      return emitError(lexer.getCurrentLoc(),
                       " expected " + stringifyTokenKind(kind));
 
    return success();
  }
 
  StringRef getTokenSpelling(const LibertyToken &token) {
    StringRef str = token.spelling;
    if (token.kind == LibertyTokenKind::String)
      str = str.drop_front().drop_back();
    return str;
  }
};
 
//===----------------------------------------------------------------------===//
// LibertyLexer Implementation
//===----------------------------------------------------------------------===//
 
void LibertyLexer::skipWhitespaceAndComments() {
  while (curPtr < curBuffer.end()) {
    if (isspace(*curPtr)) {
      ++curPtr;
      continue;
    }
 
    // Comments
    if (*curPtr == '/' && curPtr + 1 < curBuffer.end()) {
      if (*(curPtr + 1) == '*') { // /* ... */
        curPtr += 2;
        while (curPtr + 1 < curBuffer.end() &&
               (*curPtr != '*' || *(curPtr + 1) != '/'))
          ++curPtr;
        if (curPtr + 1 < curBuffer.end())
          curPtr += 2;
        continue;
      }
      if (*(curPtr + 1) == '/') { // // ...
        while (curPtr < curBuffer.end() && *curPtr != '\n')
          ++curPtr;
        continue;
      }
    }
 
    // Backslash newline continuation
    if (*curPtr == '\\' && curPtr + 1 < curBuffer.end() &&
        *(curPtr + 1) == '\n') {
      curPtr += 2;
      continue;
    }
 
    break;
  }
}
 
LibertyToken LibertyLexer::lexIdentifier() {
  const char *start = curPtr;
  while (curPtr < curBuffer.end() &&
         (isalnum(*curPtr) || *curPtr == '_' || *curPtr == '.'))
    ++curPtr;
  return makeToken(LibertyTokenKind::Identifier, start);
}
 
LibertyToken LibertyLexer::lexString() {
  const char *start = curPtr;
  ++curPtr; // skip opening quote
  while (curPtr < curBuffer.end() && *curPtr != '"') {
    if (*curPtr == '\\' && curPtr + 1 < curBuffer.end())
      ++curPtr; // skip escaped char
    ++curPtr;
  }
  if (curPtr < curBuffer.end())
    ++curPtr; // skip closing quote
  return makeToken(LibertyTokenKind::String, start);
}
 
LibertyToken LibertyLexer::lexNumber() {
  const char *start = curPtr;
  bool seenDot = false;
  while (curPtr < curBuffer.end()) {
    if (isdigit(*curPtr)) {
      ++curPtr;
    } else if (*curPtr == '.') {
      if (seenDot) {
        mlir::emitError(translateLocation(SMLoc::getFromPointer(curPtr)),
                        "multiple decimal points in number");
        return makeToken(LibertyTokenKind::Error, start);
      }
      seenDot = true;
      ++curPtr;
    } else {
      break;
    }
  }
  return makeToken(LibertyTokenKind::Number, start);
}
 
LibertyToken LibertyLexer::makeToken(LibertyTokenKind kind, const char *start) {
  return LibertyToken(kind, StringRef(start, curPtr - start),
                      SMLoc::getFromPointer(start));
}
 
LibertyToken LibertyLexer::nextToken() {
  skipWhitespaceAndComments();
 
  if (curPtr >= curBuffer.end())
    return makeToken(LibertyTokenKind::EndOfFile, curPtr);
 
  const char *start = curPtr;
  char c = *curPtr;
 
  if (isalpha(c) || c == '_')
    return lexIdentifier();
 
  if (isdigit(c) ||
      (c == '.' && curPtr + 1 < curBuffer.end() && isdigit(*(curPtr + 1))))
    return lexNumber();
 
  if (c == '"')
    return lexString();
 
  ++curPtr;
  switch (c) {
  case '{':
    return makeToken(LibertyTokenKind::LBrace, start);
  case '}':
    return makeToken(LibertyTokenKind::RBrace, start);
  case '(':
    return makeToken(LibertyTokenKind::LParen, start);
  case ')':
    return makeToken(LibertyTokenKind::RParen, start);
  case ':':
    return makeToken(LibertyTokenKind::Colon, start);
  case ';':
    return makeToken(LibertyTokenKind::Semi, start);
  case ',':
    return makeToken(LibertyTokenKind::Comma, start);
 
  default:
    return makeToken(LibertyTokenKind::Error, start);
  }
}
 
LibertyToken LibertyLexer::peekToken() {
  const char *savedPtr = curPtr;
  LibertyToken token = nextToken();
  curPtr = savedPtr;
  return token;
}
 
//===----------------------------------------------------------------------===//
// LibertyParser Implementation
//===----------------------------------------------------------------------===//
 
ParseResult LibertyParser::parse() {
  while (lexer.peekToken().kind != LibertyTokenKind::EndOfFile) {
    auto token = lexer.peekToken();
    // Skip any stray tokens that aren't valid group starts
    if (token.kind != LibertyTokenKind::Identifier ||
        token.spelling != "library") {
      return emitError(token.location, "expected `library` keyword");
    }
    lexer.nextToken();
    if (parseLibrary())
      return failure();
  }
  return success();
}
 
ParseResult LibertyParser::parseLibrary() {
  LibertyGroup libertyLib;
  if (parseGroupBody(libertyLib))
    return failure();
 
  DenseSet<StringAttr> seenCells;
  for (auto &stmt : libertyLib.subGroups) {
    // TODO: Support more group types
    if (stmt->name == "cell") {
      StringAttr cellNameAttr;
      if (lowerCell(*stmt, cellNameAttr))
        return failure();
      if (!seenCells.insert(cellNameAttr).second)
        return emitError(stmt->loc, "redefinition of cell '" +
                                        cellNameAttr.getValue() + "'");
      continue;
    }
  }
 
  libertyLib.eraseSubGroup(
      [](const LibertyGroup &group) { return group.name == "cell"; });
  auto attr = convertGroupToAttr(libertyLib);
  module->setAttr("synth.liberty.library", attr);
  return success();
}
 
// Parse a template like: lu_table_template (delay_template_6x6) { variable_1:
// total_output_net_capacitance; variable_2: input_net_transition; }
Attribute LibertyParser::convertGroupToAttr(const LibertyGroup &group) {
  SmallVector<NamedAttribute> attrs;
  if (!group.args.empty())
    attrs.push_back(
        builder.getNamedAttr("args", builder.getArrayAttr(group.args)));
 
  for (const auto &attr : group.attrs)
    attrs.push_back(builder.getNamedAttr(attr.name, attr.value));
 
  llvm::StringMap<SmallVector<Attribute>> subGroups;
  for (const auto &sub : group.subGroups)
    subGroups[sub->name].push_back(convertGroupToAttr(*sub));
 
  for (auto &it : subGroups)
    attrs.push_back(
        builder.getNamedAttr(it.getKey(), builder.getArrayAttr(it.getValue())));
 
  return builder.getDictionaryAttr(attrs);
}
 
ParseResult LibertyParser::lowerCell(const LibertyGroup &group,
                                     StringAttr &cellNameAttr) {
  if (group.args.empty())
    return emitError(group.loc, "cell missing name");
 
  cellNameAttr = dyn_cast<StringAttr>(group.args[0]);
  if (!cellNameAttr)
    return emitError(group.loc, "cell name must be a string");
 
  SmallVector<hw::PortInfo> ports;
  SmallVector<const LibertyGroup *> pinGroups;
  llvm::DenseSet<StringAttr> seenPins;
 
  // First pass: gather ports
  for (const auto &sub : group.subGroups) {
    if (sub->name != "pin")
      continue;
 
    pinGroups.push_back(sub.get());
    if (sub->args.empty())
      return emitError(sub->loc, "pin missing name");
 
    StringAttr pinName = dyn_cast<StringAttr>(sub->args[0]);
    if (!seenPins.insert(pinName).second)
      return emitError(sub->loc,
                       "redefinition of pin '" + pinName.getValue() + "'");
 
    std::optional<hw::ModulePort::Direction> dir;
    SmallVector<NamedAttribute> pinAttrs;
 
    for (const auto &attr : sub->attrs) {
      if (attr.name == "direction") {
        if (auto val = dyn_cast<StringAttr>(attr.value)) {
          if (val.getValue() == "input")
            dir = hw::ModulePort::Direction::Input;
          else if (val.getValue() == "output")
            dir = hw::ModulePort::Direction::Output;
          else if (val.getValue() == "inout")
            dir = hw::ModulePort::Direction::InOut;
          else
            return emitError(sub->loc,
                             "pin direction must be input, output, or inout");
        } else {
          return emitError(sub->loc,
                           "pin direction must be a string attribute");
        }
        continue;
      }
      pinAttrs.push_back(builder.getNamedAttr(attr.name, attr.value));
    }
 
    if (!dir)
      return emitError(sub->loc, "pin direction must be specified");
 
    llvm::StringMap<SmallVector<Attribute>> subGroups;
    for (const auto &child : sub->subGroups) {
      // TODO: Properly handle timing subgroups etc.
      subGroups[child->name].push_back(convertGroupToAttr(*child));
    }
 
    for (auto &it : subGroups)
      pinAttrs.push_back(builder.getNamedAttr(
          it.getKey(), builder.getArrayAttr(it.getValue())));
 
    auto libertyAttrs = builder.getDictionaryAttr(pinAttrs);
    auto attrs = builder.getDictionaryAttr(
        builder.getNamedAttr("synth.liberty.pin", libertyAttrs));
 
    hw::PortInfo port;
    port.name = pinName;
    port.type = builder.getI1Type();
    port.dir = *dir;
    port.attrs = attrs;
    ports.push_back(port);
  }
 
  // Fix up argNum for inputs
  int inputIdx = 0;
  for (auto &p : ports) {
    if (p.dir == hw::ModulePort::Direction::Input)
      p.argNum = inputIdx++;
    else
      p.argNum = 0;
  }
 
  auto loc = lexer.translateLocation(group.loc);
  auto moduleOp = hw::HWModuleOp::create(builder, loc, cellNameAttr, ports);
 
  OpBuilder::InsertionGuard guard(builder);
  builder.setInsertionPointToStart(moduleOp.getBodyBlock());
 
  llvm::StringMap<Value> portValues;
  for (const auto &port : ports)
    if (port.dir == hw::ModulePort::Direction::Input)
      portValues[port.name.getValue()] =
          moduleOp.getBodyBlock()->getArgument(port.argNum);
 
  SmallVector<Value> outputs;
  for (const auto &port : ports) {
    if (port.dir != hw::ModulePort::Direction::Output)
      continue;
 
    auto *it = llvm::find_if(pinGroups, [&](const LibertyGroup *g) {
      assert(g->name == "pin" && "expected pin group");
      // First arg is the pin name
      return cast<StringAttr>(g->args[0]) == port.name;
    });
 
    if (!it)
      continue;
    const LibertyGroup *pg = *it;
    auto attrPair = pg->getAttribute("function");
    if (!attrPair.first)
      return emitError(pg->loc, "expected function attribute");
    Value val;
    if (parseExpression(val, cast<StringAttr>(attrPair.first).getValue(),
                        portValues, attrPair.second))
      return failure();
    outputs.push_back(val);
  }
 
  auto *block = moduleOp.getBodyBlock();
  block->getTerminator()->setOperands(outputs);
  return success();
}
 
ParseResult LibertyParser::parseGroupBody(LibertyGroup &group) {
  // Parse args: ( arg1, arg2 )
  if (lexer.peekToken().kind == LibertyTokenKind::LParen) {
    lexer.nextToken(); // (
    while (lexer.peekToken().kind != LibertyTokenKind::RParen) {
      Attribute arg;
      if (parseAttribute(arg))
        return failure();
      group.args.push_back(arg);
      if (lexer.peekToken().kind == LibertyTokenKind::Comma)
        lexer.nextToken();
    }
    if (consume(LibertyTokenKind::RParen, "expected ')'"))
      return failure();
  }
 
  // Parse body: { ... }
  if (lexer.peekToken().kind == LibertyTokenKind::LBrace) {
    lexer.nextToken(); // {
    while (lexer.peekToken().kind != LibertyTokenKind::RBrace &&
           lexer.peekToken().kind != LibertyTokenKind::EndOfFile) {
      if (parseStatement(group))
        return failure();
    }
    if (consume(LibertyTokenKind::RBrace, "expected '}'"))
      return failure();
  } else {
    // Optional semicolon if no body
    if (lexer.peekToken().kind == LibertyTokenKind::Semi)
      lexer.nextToken();
  }
  return success();
}
 
// Parse group, attribute, or define statements
ParseResult LibertyParser::parseStatement(LibertyGroup &parent) {
  auto nameTok = lexer.nextToken();
  if (nameTok.kind != LibertyTokenKind::Identifier)
    return emitError(nameTok.location, "expected identifier");
  StringRef name = nameTok.spelling;
 
  // Attribute statement.
  if (lexer.peekToken().kind == LibertyTokenKind::Colon) {
    lexer.nextToken(); // :
    Attribute val;
    auto loc = lexer.peekToken().location;
    if (parseAttribute(val))
      return failure();
    parent.attrs.emplace_back(name, val, loc);
    return consume(LibertyTokenKind::Semi, "expected ';'");
  }
 
  // Group statement.
  if (lexer.peekToken().kind == LibertyTokenKind::LParen) {
    auto subGroup = std::make_unique<LibertyGroup>();
    subGroup->name = name;
    subGroup->loc = nameTok.location;
    if (parseGroupBody(*subGroup))
      return failure();
    parent.subGroups.push_back(std::move(subGroup));
    return success();
  }
 
  // TODO: Support define.
 
  return emitError(nameTok.location, "expected ':' or '('");
}
 
ParseResult LibertyParser::parseAttribute(Attribute &result, OpBuilder &builder,
                                          StringRef attr) {
  double val;
  if (!attr.getAsDouble(val)) {
    result = builder.getF64FloatAttr(val);
  } else {
    // Keep as string if not a valid number
    result = builder.getStringAttr(attr);
  }
  return success();
}
// Parse an attribute value, which can be:
// - A string: "value"
// - A number: 1.23
// - An identifier: value
ParseResult LibertyParser::parseAttribute(Attribute &result) {
  auto token = lexer.peekToken();
  // Number token
  if (token.is(LibertyTokenKind::Number)) {
    lexer.nextToken();
    StringRef numStr = token.spelling;
    double val;
    if (!numStr.getAsDouble(val)) {
      result = builder.getF64FloatAttr(val);
      return success();
    }
    return emitError(token.location, "expected number value");
  }
 
  // Identifier token
  if (token.is(LibertyTokenKind::Identifier)) {
    lexer.nextToken();
    result = builder.getStringAttr(token.spelling);
    return success();
  }
 
  if (token.is(LibertyTokenKind::String)) {
    lexer.nextToken();
    StringRef str = getTokenSpelling(token);
    result = builder.getStringAttr(str);
    return success();
  }
 
  // TODO: Add array for timing attributes
  return emitError(token.location, "expected attribute value");
}
 
// Parse boolean expressions from Liberty function attributes
// Supports: *, +, ^, !, (), and identifiers
ParseResult LibertyParser::parseExpression(Value &result, StringRef expr,
                                           const llvm::StringMap<Value> &values,
                                           SMLoc loc) {
  ExpressionParser parser(lexer, builder, expr, values, loc);
  return parser.parse(result);
}
 
} // namespace
 
namespace circt::liberty {
void registerImportLibertyTranslation() {
  TranslateToMLIRRegistration reg(
      "import-liberty", "Import Liberty file",
      [](llvm::SourceMgr &sourceMgr, MLIRContext *context) {
        ModuleOp module = ModuleOp::create(UnknownLoc::get(context));
        LibertyParser parser(sourceMgr, context, module);
        // Load required dialects
        context->loadDialect<hw::HWDialect>();
        context->loadDialect<comb::CombDialect>();
        if (failed(parser.parse()))
          return OwningOpRef<ModuleOp>();
        return OwningOpRef<ModuleOp>(module);
      },
      [](DialectRegistry &registry) {
        registry.insert<HWDialect>();
        registry.insert<comb::CombDialect>();
      });
}
} // namespace circt::liberty