1//===- ConstantPool.h - Keep track of assembler-generated  ------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file declares the ConstantPool and AssemblerConstantPools classes.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_MC_CONSTANTPOOLS_H
15#define LLVM_MC_CONSTANTPOOLS_H
16
17#include "llvm/ADT/DenseMap.h"
18#include "llvm/ADT/MapVector.h"
19#include "llvm/ADT/SmallVector.h"
20#include "llvm/Support/SMLoc.h"
21#include <cstdint>
22#include <map>
23
24namespace llvm {
25
26class MCContext;
27class MCExpr;
28class MCSection;
29class MCStreamer;
30class MCSymbol;
31class MCSymbolRefExpr;
32
33struct ConstantPoolEntry {
34  ConstantPoolEntry(MCSymbol *L, const MCExpr *Val, unsigned Sz, SMLoc Loc_)
35    : Label(L), Value(Val), Size(Sz), Loc(Loc_) {}
36
37  MCSymbol *Label;
38  const MCExpr *Value;
39  unsigned Size;
40  SMLoc Loc;
41};
42
43// A class to keep track of assembler-generated constant pools that are use to
44// implement the ldr-pseudo.
45class ConstantPool {
46  using EntryVecTy = SmallVector<ConstantPoolEntry, 4>;
47  EntryVecTy Entries;
48  std::map<int64_t, const MCSymbolRefExpr *> CachedEntries;
49
50public:
51  // Initialize a new empty constant pool
52  ConstantPool() = default;
53
54  // Add a new entry to the constant pool in the next slot.
55  // \param Value is the new entry to put in the constant pool.
56  // \param Size is the size in bytes of the entry
57  //
58  // \returns a MCExpr that references the newly inserted value
59  const MCExpr *addEntry(const MCExpr *Value, MCContext &Context,
60                         unsigned Size, SMLoc Loc);
61
62  // Emit the contents of the constant pool using the provided streamer.
63  void emitEntries(MCStreamer &Streamer);
64
65  // Return true if the constant pool is empty
66  bool empty();
67
68  void clearCache();
69};
70
71class AssemblerConstantPools {
72  // Map type used to keep track of per-Section constant pools used by the
73  // ldr-pseudo opcode. The map associates a section to its constant pool. The
74  // constant pool is a vector of (label, value) pairs. When the ldr
75  // pseudo is parsed we insert a new (label, value) pair into the constant pool
76  // for the current section and add MCSymbolRefExpr to the new label as
77  // an opcode to the ldr. After we have parsed all the user input we
78  // output the (label, value) pairs in each constant pool at the end of the
79  // section.
80  //
81  // We use the MapVector for the map type to ensure stable iteration of
82  // the sections at the end of the parse. We need to iterate over the
83  // sections in a stable order to ensure that we have print the
84  // constant pools in a deterministic order when printing an assembly
85  // file.
86  using ConstantPoolMapTy = MapVector<MCSection *, ConstantPool>;
87  ConstantPoolMapTy ConstantPools;
88
89public:
90  void emitAll(MCStreamer &Streamer);
91  void emitForCurrentSection(MCStreamer &Streamer);
92  void clearCacheForCurrentSection(MCStreamer &Streamer);
93  const MCExpr *addEntry(MCStreamer &Streamer, const MCExpr *Expr,
94                         unsigned Size, SMLoc Loc);
95
96private:
97  ConstantPool *getConstantPool(MCSection *Section);
98  ConstantPool &getOrCreateConstantPool(MCSection *Section);
99};
100
101} // end namespace llvm
102
103#endif // LLVM_MC_CONSTANTPOOLS_H
104