LLVM  12.0.0git
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/MapVector.h"
17 #include "llvm/ADT/SmallVector.h"
18 #include "llvm/Support/SMLoc.h"
19 #include <cstdint>
20 #include <map>
21 
22 namespace llvm {
23 
24 class MCContext;
25 class MCExpr;
26 class MCSection;
27 class MCStreamer;
28 class MCSymbol;
29 class MCSymbolRefExpr;
30 
32  ConstantPoolEntry(MCSymbol *L, const MCExpr *Val, unsigned Sz, SMLoc Loc_)
33  : Label(L), Value(Val), Size(Sz), Loc(Loc_) {}
34 
36  const MCExpr *Value;
37  unsigned Size;
39 };
40 
41 // A class to keep track of assembler-generated constant pools that are use to
42 // implement the ldr-pseudo.
43 class ConstantPool {
45  EntryVecTy Entries;
46  std::map<int64_t, const MCSymbolRefExpr *> CachedEntries;
47 
48 public:
49  // Initialize a new empty constant pool
50  ConstantPool() = default;
51 
52  // Add a new entry to the constant pool in the next slot.
53  // \param Value is the new entry to put in the constant pool.
54  // \param Size is the size in bytes of the entry
55  //
56  // \returns a MCExpr that references the newly inserted value
57  const MCExpr *addEntry(const MCExpr *Value, MCContext &Context,
58  unsigned Size, SMLoc Loc);
59 
60  // Emit the contents of the constant pool using the provided streamer.
61  void emitEntries(MCStreamer &Streamer);
62 
63  // Return true if the constant pool is empty
64  bool empty();
65 
66  void clearCache();
67 };
68 
70  // Map type used to keep track of per-Section constant pools used by the
71  // ldr-pseudo opcode. The map associates a section to its constant pool. The
72  // constant pool is a vector of (label, value) pairs. When the ldr
73  // pseudo is parsed we insert a new (label, value) pair into the constant pool
74  // for the current section and add MCSymbolRefExpr to the new label as
75  // an opcode to the ldr. After we have parsed all the user input we
76  // output the (label, value) pairs in each constant pool at the end of the
77  // section.
78  //
79  // We use the MapVector for the map type to ensure stable iteration of
80  // the sections at the end of the parse. We need to iterate over the
81  // sections in a stable order to ensure that we have print the
82  // constant pools in a deterministic order when printing an assembly
83  // file.
85  ConstantPoolMapTy ConstantPools;
86 
87 public:
88  void emitAll(MCStreamer &Streamer);
89  void emitForCurrentSection(MCStreamer &Streamer);
90  void clearCacheForCurrentSection(MCStreamer &Streamer);
91  const MCExpr *addEntry(MCStreamer &Streamer, const MCExpr *Expr,
92  unsigned Size, SMLoc Loc);
93 
94 private:
95  ConstantPool *getConstantPool(MCSection *Section);
96  ConstantPool &getOrCreateConstantPool(MCSection *Section);
97 };
98 
99 } // end namespace llvm
100 
101 #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:36
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
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:32
Context object for machine code objects.
Definition: MCContext.h:67
Streaming machine code generation interface.
Definition: MCStreamer.h:196
constexpr bool empty(const T &RangeOrContainer)
Test whether RangeOrContainer is empty. Similar to C++17 std::empty.
Definition: STLExtras.h:266
LLVM Value Representation.
Definition: Value.h:74
Represents a location in source code.
Definition: SMLoc.h:23