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//===- CodeGen/MachineConstantPool.h - Abstract Constant Pool ---*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
/// @file
/// This file declares the MachineConstantPool class which is an abstract
/// constant pool to keep track of constants referenced by a function.
#include "llvm/ADT/DenseSet.h"
#include "llvm/MC/SectionKind.h"
#include <climits>
#include <vector>
namespace llvm {
class Constant;
class DataLayout;
class FoldingSetNodeID;
class MachineConstantPool;
class raw_ostream;
class Type;
/// Abstract base class for all machine specific constantpool value subclasses.
class MachineConstantPoolValue {
virtual void anchor();
Type *Ty;
explicit MachineConstantPoolValue(Type *ty) : Ty(ty) {}
virtual ~MachineConstantPoolValue() = default;
/// getType - get type of this MachineConstantPoolValue.
Type *getType() const { return Ty; }
virtual int getExistingMachineCPValue(MachineConstantPool *CP,
unsigned Alignment) = 0;
virtual void addSelectionDAGCSEId(FoldingSetNodeID &ID) = 0;
/// print - Implement operator<<
virtual void print(raw_ostream &O) const = 0;
inline raw_ostream &operator<<(raw_ostream &OS,
const MachineConstantPoolValue &V) {
return OS;
/// This class is a data container for one entry in a MachineConstantPool.
/// It contains a pointer to the value and an offset from the start of
/// the constant pool.
/// An entry in a MachineConstantPool
class MachineConstantPoolEntry {
/// The constant itself.
union {
const Constant *ConstVal;
MachineConstantPoolValue *MachineCPVal;
} Val;
/// The required alignment for this entry. The top bit is set when Val is
/// a target specific MachineConstantPoolValue.
unsigned Alignment;
MachineConstantPoolEntry(const Constant *V, unsigned A)
: Alignment(A) {
Val.ConstVal = V;
MachineConstantPoolEntry(MachineConstantPoolValue *V, unsigned A)
: Alignment(A) {
Val.MachineCPVal = V;
Alignment |= 1U << (sizeof(unsigned) * CHAR_BIT - 1);
/// isMachineConstantPoolEntry - Return true if the MachineConstantPoolEntry
/// is indeed a target specific constantpool entry, not a wrapper over a
/// Constant.
bool isMachineConstantPoolEntry() const {
return (int)Alignment < 0;
int getAlignment() const {
return Alignment & ~(1 << (sizeof(unsigned) * CHAR_BIT - 1));
Type *getType() const;
/// This method classifies the entry according to whether or not it may
/// generate a relocation entry. This must be conservative, so if it might
/// codegen to a relocatable entry, it should say so.
bool needsRelocation() const;
SectionKind getSectionKind(const DataLayout *DL) const;
/// The MachineConstantPool class keeps track of constants referenced by a
/// function which must be spilled to memory. This is used for constants which
/// are unable to be used directly as operands to instructions, which typically
/// include floating point and large integer constants.
/// Instructions reference the address of these constant pool constants through
/// the use of MO_ConstantPoolIndex values. When emitting assembly or machine
/// code, these virtual address references are converted to refer to the
/// address of the function constant pool values.
/// The machine constant pool.
class MachineConstantPool {
unsigned PoolAlignment; ///< The alignment for the pool.
std::vector<MachineConstantPoolEntry> Constants; ///< The pool of constants.
/// MachineConstantPoolValues that use an existing MachineConstantPoolEntry.
DenseSet<MachineConstantPoolValue*> MachineCPVsSharingEntries;
const DataLayout &DL;
const DataLayout &getDataLayout() const { return DL; }
/// The only constructor.
explicit MachineConstantPool(const DataLayout &DL)
: PoolAlignment(1), DL(DL) {}
/// getConstantPoolAlignment - Return the alignment required by
/// the whole constant pool, of which the first element must be aligned.
unsigned getConstantPoolAlignment() const { return PoolAlignment; }
/// getConstantPoolIndex - Create a new entry in the constant pool or return
/// an existing one. User must specify the minimum required alignment for
/// the object.
unsigned getConstantPoolIndex(const Constant *C, unsigned Alignment);
unsigned getConstantPoolIndex(MachineConstantPoolValue *V,
unsigned Alignment);
/// isEmpty - Return true if this constant pool contains no constants.
bool isEmpty() const { return Constants.empty(); }
const std::vector<MachineConstantPoolEntry> &getConstants() const {
return Constants;
/// print - Used by the MachineFunction printer to print information about
/// constant pool objects. Implemented in MachineFunction.cpp
void print(raw_ostream &OS) const;
/// dump - Call print(cerr) to be called from the debugger.
void dump() const;
} // end namespace llvm