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 
28 struct ConstantPoolEntry {
ConstantPoolEntryConstantPoolEntry29   ConstantPoolEntry(MCSymbol *L, const MCExpr *Val, unsigned Sz)
30     : Label(L), Value(Val), Size(Sz) {}
31   MCSymbol *Label;
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 {
39   typedef SmallVector<ConstantPoolEntry, 4> EntryVecTy;
40   EntryVecTy Entries;
41 
42 public:
43   // Initialize a new empty constant pool
ConstantPool()44   ConstantPool() {}
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 
61 class AssemblerConstantPools {
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.
76   typedef MapVector<const MCSection *, ConstantPool> ConstantPoolMapTy;
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(const MCSection *Section);
87   ConstantPool &getOrCreateConstantPool(const MCSection *Section);
88 };
89 } // end namespace llvm
90 
91 #endif
92