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thirdparty/clang/include/llvm/CodeGen/MachineConstantPool.h

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+//===-- CodeGen/MachineConstantPool.h - Abstract Constant Pool --*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+/// @file
+/// This file declares the MachineConstantPool class which is an abstract
+/// constant pool to keep track of constants referenced by a function.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_MACHINECONSTANTPOOL_H
+#define LLVM_CODEGEN_MACHINECONSTANTPOOL_H
+
+#include "llvm/ADT/DenseSet.h"
+#include <cassert>
+#include <climits>
+#include <vector>
+
+namespace llvm {
+
+class Constant;
+class FoldingSetNodeID;
+class DataLayout;
+class TargetMachine;
+class Type;
+class MachineConstantPool;
+class raw_ostream;
+
+/// Abstract base class for all machine specific constantpool value subclasses.
+///
+class MachineConstantPoolValue {
+  virtual void anchor();
+  Type *Ty;
+
+public:
+  explicit MachineConstantPoolValue(Type *ty) : Ty(ty) {}
+  virtual ~MachineConstantPoolValue() {}
+
+  /// getType - get type of this MachineConstantPoolValue.
+  ///
+  Type *getType() const { return Ty; }
+
+  
+  /// getRelocationInfo - 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.  The return values are the same as Constant::getRelocationInfo().
+  virtual unsigned getRelocationInfo() const = 0;
+  
+  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) {
+  V.print(OS);
+  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.
+/// @brief An entry in a MachineConstantPool
+class MachineConstantPoolEntry {
+public:
+  /// 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;
+  
+  /// getRelocationInfo - 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.  The return values are:
+  /// 
+  ///  0: This constant pool entry is guaranteed to never have a relocation
+  ///     applied to it (because it holds a simple constant like '4').
+  ///  1: This entry has relocations, but the entries are guaranteed to be
+  ///     resolvable by the static linker, so the dynamic linker will never see
+  ///     them.
+  ///  2: This entry may have arbitrary relocations. 
+  unsigned getRelocationInfo() 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.
+/// @brief The machine constant pool.
+class MachineConstantPool {
+  const DataLayout *TD;   ///< The machine's DataLayout.
+  unsigned PoolAlignment; ///< The alignment for the pool.
+  std::vector<MachineConstantPoolEntry> Constants; ///< The pool of constants.
+  /// MachineConstantPoolValues that use an existing MachineConstantPoolEntry.
+  DenseSet<MachineConstantPoolValue*> MachineCPVsSharingEntries;
+public:
+  /// @brief The only constructor.
+  explicit MachineConstantPool(const DataLayout *td)
+    : TD(td), PoolAlignment(1) {}
+  ~MachineConstantPool();
+    
+  /// 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 llvm namespace
+
+#endif