ValueList.h

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//===-- Bitcode/Reader/ValueList.h - Number values --------------*- 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
//
//===----------------------------------------------------------------------===//
//
// This class gives values and types Unique ID's.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_LIB_BITCODE_READER_VALUELIST_H
#define LLVM_LIB_BITCODE_READER_VALUELIST_H
 
#include "llvm/IR/ValueHandle.h"
#include <cassert>
#include <utility>
#include <vector>
 
namespace llvm {
 
class Constant;
class Error;
class LLVMContext;
class Type;
class Value;
 
class BitcodeReaderValueList {
  /// Maps Value ID to pair of Value* and Type ID.
  std::vector<std::pair<WeakTrackingVH, unsigned>> ValuePtrs;
 
  /// As we resolve forward-referenced constants, we add information about them
  /// to this vector.  This allows us to resolve them in bulk instead of
  /// resolving each reference at a time.  See the code in
  /// ResolveConstantForwardRefs for more information about this.
  ///
  /// The key of this vector is the placeholder constant, the value is the slot
  /// number that holds the resolved value.
  using ResolveConstantsTy = std::vector<std::pair<Constant *, unsigned>>;
  ResolveConstantsTy ResolveConstants;
  LLVMContext &Context;
 
  /// Maximum number of valid references. Forward references exceeding the
  /// maximum must be invalid.
  unsigned RefsUpperBound;
 
public:
  BitcodeReaderValueList(LLVMContext &C, size_t RefsUpperBound)
      : Context(C),
        RefsUpperBound(std::min((size_t)std::numeric_limits<unsigned>::max(),
                                RefsUpperBound)) {}
 
  ~BitcodeReaderValueList() {
    assert(ResolveConstants.empty() && "Constants not resolved?");
  }
 
  // vector compatibility methods
  unsigned size() const { return ValuePtrs.size(); }
  void resize(unsigned N) {
    ValuePtrs.resize(N);
  }
  void push_back(Value *V, unsigned TypeID) {
    ValuePtrs.emplace_back(V, TypeID);
  }
 
  void clear() {
    assert(ResolveConstants.empty() && "Constants not resolved?");
    ValuePtrs.clear();
  }
 
  Value *operator[](unsigned i) const {
    assert(i < ValuePtrs.size());
    return ValuePtrs[i].first;
  }
 
  unsigned getTypeID(unsigned ValNo) const {
    assert(ValNo < ValuePtrs.size());
    return ValuePtrs[ValNo].second;
  }
 
  Value *back() const { return ValuePtrs.back().first; }
  void pop_back() {
    ValuePtrs.pop_back();
  }
  bool empty() const { return ValuePtrs.empty(); }
 
  void shrinkTo(unsigned N) {
    assert(N <= size() && "Invalid shrinkTo request!");
    ValuePtrs.resize(N);
  }
 
  Constant *getConstantFwdRef(unsigned Idx, Type *Ty, unsigned TyID);
  Value *getValueFwdRef(unsigned Idx, Type *Ty, unsigned TyID);
 
  Error assignValue(unsigned Idx, Value *V, unsigned TypeID);
 
  /// Once all constants are read, this method bulk resolves any forward
  /// references.
  void resolveConstantForwardRefs();
};
 
} // end namespace llvm
 
#endif // LLVM_LIB_BITCODE_READER_VALUELIST_H