LLVM  10.0.0svn
ConstantPools.h
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1 //===- ConstantPools.h - Keep track of assembler-generated ------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file declares the ConstantPool and AssemblerConstantPools classes.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_MC_CONSTANTPOOLS_H
14 #define LLVM_MC_CONSTANTPOOLS_H
15 
16 #include "llvm/ADT/DenseMap.h"
17 #include "llvm/ADT/MapVector.h"
18 #include "llvm/ADT/SmallVector.h"
19 #include "llvm/Support/SMLoc.h"
20 #include <cstdint>
21 #include <map>
22 
23 namespace llvm {
24 
25 class MCContext;
26 class MCExpr;
27 class MCSection;
28 class MCStreamer;
29 class MCSymbol;
30 class MCSymbolRefExpr;
31 
33  ConstantPoolEntry(MCSymbol *L, const MCExpr *Val, unsigned Sz, SMLoc Loc_)
34  : Label(L), Value(Val), Size(Sz), Loc(Loc_) {}
35 
37  const MCExpr *Value;
38  unsigned Size;
40 };
41 
42 // A class to keep track of assembler-generated constant pools that are use to
43 // implement the ldr-pseudo.
44 class ConstantPool {
46  EntryVecTy Entries;
47  std::map<int64_t, const MCSymbolRefExpr *> CachedEntries;
48 
49 public:
50  // Initialize a new empty constant pool
51  ConstantPool() = default;
52 
53  // Add a new entry to the constant pool in the next slot.
54  // \param Value is the new entry to put in the constant pool.
55  // \param Size is the size in bytes of the entry
56  //
57  // \returns a MCExpr that references the newly inserted value
58  const MCExpr *addEntry(const MCExpr *Value, MCContext &Context,
59  unsigned Size, SMLoc Loc);
60 
61  // Emit the contents of the constant pool using the provided streamer.
62  void emitEntries(MCStreamer &Streamer);
63 
64  // Return true if the constant pool is empty
65  bool empty();
66 
67  void clearCache();
68 };
69 
71  // Map type used to keep track of per-Section constant pools used by the
72  // ldr-pseudo opcode. The map associates a section to its constant pool. The
73  // constant pool is a vector of (label, value) pairs. When the ldr
74  // pseudo is parsed we insert a new (label, value) pair into the constant pool
75  // for the current section and add MCSymbolRefExpr to the new label as
76  // an opcode to the ldr. After we have parsed all the user input we
77  // output the (label, value) pairs in each constant pool at the end of the
78  // section.
79  //
80  // We use the MapVector for the map type to ensure stable iteration of
81  // the sections at the end of the parse. We need to iterate over the
82  // sections in a stable order to ensure that we have print the
83  // constant pools in a deterministic order when printing an assembly
84  // file.
86  ConstantPoolMapTy ConstantPools;
87 
88 public:
89  void emitAll(MCStreamer &Streamer);
90  void emitForCurrentSection(MCStreamer &Streamer);
91  void clearCacheForCurrentSection(MCStreamer &Streamer);
92  const MCExpr *addEntry(MCStreamer &Streamer, const MCExpr *Expr,
93  unsigned Size, SMLoc Loc);
94 
95 private:
96  ConstantPool *getConstantPool(MCSection *Section);
97  ConstantPool &getOrCreateConstantPool(MCSection *Section);
98 };
99 
100 } // end namespace llvm
101 
102 #endif // LLVM_MC_CONSTANTPOOLS_H
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:38
const MCExpr * Value
Definition: ConstantPools.h:37
LLVMContext & Context
This class represents lattice values for constants.
Definition: AllocatorList.h:23
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:41
C::iterator addEntry(C &Container, StringRef InstallName)
Base class for the full range of assembler expressions which are needed for parsing.
Definition: MCExpr.h:35
ConstantPoolEntry(MCSymbol *L, const MCExpr *Val, unsigned Sz, SMLoc Loc_)
Definition: ConstantPools.h:33
Context object for machine code objects.
Definition: MCContext.h:64
Streaming machine code generation interface.
Definition: MCStreamer.h:188
constexpr bool empty(const T &RangeOrContainer)
Test whether RangeOrContainer is empty. Similar to C++17 std::empty.
Definition: STLExtras.h:209
LLVM Value Representation.
Definition: Value.h:72
Represents a location in source code.
Definition: SMLoc.h:23