LLVM  6.0.0svn
ConstantPools.h
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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 
24 namespace llvm {
25 
26 class MCContext;
27 class MCExpr;
28 class MCSection;
29 class MCStreamer;
30 class MCSymbol;
31 class MCSymbolRefExpr;
32 
34  ConstantPoolEntry(MCSymbol *L, const MCExpr *Val, unsigned Sz, SMLoc Loc_)
35  : Label(L), Value(Val), Size(Sz), Loc(Loc_) {}
36 
38  const MCExpr *Value;
39  unsigned Size;
41 };
42 
43 // A class to keep track of assembler-generated constant pools that are use to
44 // implement the ldr-pseudo.
45 class ConstantPool {
47  EntryVecTy Entries;
48  std::map<int64_t, const MCSymbolRefExpr *> CachedEntries;
49 
50 public:
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 
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.
87  ConstantPoolMapTy ConstantPools;
88 
89 public:
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 
96 private:
97  ConstantPool *getConstantPool(MCSection *Section);
98  ConstantPool &getOrCreateConstantPool(MCSection *Section);
99 };
100 
101 } // end namespace llvm
102 
103 #endif // LLVM_MC_CONSTANTPOOLS_H
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:39
const MCExpr * Value
Definition: ConstantPools.h:38
LLVMContext & Context
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:42
Base class for the full range of assembler expressions which are needed for parsing.
Definition: MCExpr.h:36
ConstantPoolEntry(MCSymbol *L, const MCExpr *Val, unsigned Sz, SMLoc Loc_)
Definition: ConstantPools.h:34
Context object for machine code objects.
Definition: MCContext.h:59
Streaming machine code generation interface.
Definition: MCStreamer.h:169
LLVM Value Representation.
Definition: Value.h:73
Represents a location in source code.
Definition: SMLoc.h:24