LLVM  3.7.0
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 
15 #ifndef LLVM_MC_CONSTANTPOOLS_H
16 #define LLVM_MC_CONSTANTPOOLS_H
17 
18 #include "llvm/ADT/MapVector.h"
19 #include "llvm/ADT/SmallVector.h"
20 
21 namespace llvm {
22 class MCContext;
23 class MCExpr;
24 class MCSection;
25 class MCStreamer;
26 class MCSymbol;
27 
29  ConstantPoolEntry(MCSymbol *L, const MCExpr *Val, unsigned Sz)
30  : Label(L), Value(Val), Size(Sz) {}
32  const MCExpr *Value;
33  unsigned Size;
34 };
35 
36 // A class to keep track of assembler-generated constant pools that are use to
37 // implement the ldr-pseudo.
38 class ConstantPool {
40  EntryVecTy Entries;
41 
42 public:
43  // Initialize a new empty constant pool
45 
46  // Add a new entry to the constant pool in the next slot.
47  // \param Value is the new entry to put in the constant pool.
48  // \param Size is the size in bytes of the entry
49  //
50  // \returns a MCExpr that references the newly inserted value
51  const MCExpr *addEntry(const MCExpr *Value, MCContext &Context,
52  unsigned Size);
53 
54  // Emit the contents of the constant pool using the provided streamer.
55  void emitEntries(MCStreamer &Streamer);
56 
57  // Return true if the constant pool is empty
58  bool empty();
59 };
60 
62  // Map type used to keep track of per-Section constant pools used by the
63  // ldr-pseudo opcode. The map associates a section to its constant pool. The
64  // constant pool is a vector of (label, value) pairs. When the ldr
65  // pseudo is parsed we insert a new (label, value) pair into the constant pool
66  // for the current section and add MCSymbolRefExpr to the new label as
67  // an opcode to the ldr. After we have parsed all the user input we
68  // output the (label, value) pairs in each constant pool at the end of the
69  // section.
70  //
71  // We use the MapVector for the map type to ensure stable iteration of
72  // the sections at the end of the parse. We need to iterate over the
73  // sections in a stable order to ensure that we have print the
74  // constant pools in a deterministic order when printing an assembly
75  // file.
77  ConstantPoolMapTy ConstantPools;
78 
79 public:
80  void emitAll(MCStreamer &Streamer);
81  void emitForCurrentSection(MCStreamer &Streamer);
82  const MCExpr *addEntry(MCStreamer &Streamer, const MCExpr *Expr,
83  unsigned Size);
84 
85 private:
86  ConstantPool *getConstantPool(MCSection *Section);
87  ConstantPool &getOrCreateConstantPool(MCSection *Section);
88 };
89 } // end namespace llvm
90 
91 #endif
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:48
const MCExpr * Value
Definition: ConstantPools.h:32
const MCExpr * addEntry(MCStreamer &Streamer, const MCExpr *Expr, unsigned Size)
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:39
Base class for the full range of assembler expressions which are needed for parsing.
Definition: MCExpr.h:33
Context object for machine code objects.
Definition: MCContext.h:48
const MCExpr * addEntry(const MCExpr *Value, MCContext &Context, unsigned Size)
Streaming machine code generation interface.
Definition: MCStreamer.h:157
void emitForCurrentSection(MCStreamer &Streamer)
void emitAll(MCStreamer &Streamer)
void emitEntries(MCStreamer &Streamer)
ConstantPoolEntry(MCSymbol *L, const MCExpr *Val, unsigned Sz)
Definition: ConstantPools.h:29
LLVM Value Representation.
Definition: Value.h:69