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
15#ifndef LLVM_MC_CONSTANTPOOL_H
16#define LLVM_MC_CONSTANTPOOL_H
17
18#include "llvm/ADT/SmallVector.h"
19namespace llvm {
20class MCContext;
21class MCExpr;
22class MCSection;
23class MCStreamer;
24class MCSymbol;
25// A class to keep track of assembler-generated constant pools that are use to
26// implement the ldr-pseudo.
27class ConstantPool {
28  typedef SmallVector<std::pair<MCSymbol *, const MCExpr *>, 4> EntryVecTy;
29  EntryVecTy Entries;
30
31public:
32  // Initialize a new empty constant pool
33  ConstantPool() {}
34
35  // Add a new entry to the constant pool in the next slot.
36  // \param Value is the new entry to put in the constant pool.
37  //
38  // \returns a MCExpr that references the newly inserted value
39  const MCExpr *addEntry(const MCExpr *Value, MCContext &Context);
40
41  // Emit the contents of the constant pool using the provided streamer.
42  void emitEntries(MCStreamer &Streamer);
43
44  // Return true if the constant pool is empty
45  bool empty();
46};
47
48class AssemblerConstantPools {
49  // Map type used to keep track of per-Section constant pools used by the
50  // ldr-pseudo opcode. The map associates a section to its constant pool. The
51  // constant pool is a vector of (label, value) pairs. When the ldr
52  // pseudo is parsed we insert a new (label, value) pair into the constant pool
53  // for the current section and add MCSymbolRefExpr to the new label as
54  // an opcode to the ldr. After we have parsed all the user input we
55  // output the (label, value) pairs in each constant pool at the end of the
56  // section.
57  //
58  // We use the MapVector for the map type to ensure stable iteration of
59  // the sections at the end of the parse. We need to iterate over the
60  // sections in a stable order to ensure that we have print the
61  // constant pools in a deterministic order when printing an assembly
62  // file.
63  typedef MapVector<const MCSection *, ConstantPool> ConstantPoolMapTy;
64  ConstantPoolMapTy ConstantPools;
65
66public:
67  AssemblerConstantPools() {}
68  ~AssemblerConstantPools() {}
69
70  void emitAll(MCStreamer &Streamer);
71  void emitForCurrentSection(MCStreamer &Streamer);
72  const MCExpr *addEntry(MCStreamer &Streamer, const MCExpr *Expr);
73
74private:
75  ConstantPool *getConstantPool(const MCSection *Section);
76  ConstantPool &getOrCreateConstantPool(const MCSection *Section);
77};
78} // end namespace llvm
79
80#endif
81