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
22namespace llvm {
23
24class MCContext;
25class MCExpr;
26class MCSection;
27class MCStreamer;
28class MCSymbol;
29class MCSymbolRefExpr;
30
31struct ConstantPoolEntry {
32 ConstantPoolEntry(MCSymbol *L, const MCExpr *Val, unsigned Sz, SMLoc Loc_)
33 : Label(L), Value(Val), Size(Sz), Loc(Loc_) {}
34
35 MCSymbol *Label;
36 const MCExpr *Value;
37 unsigned Size;
38 SMLoc Loc;
39};
40
41// A class to keep track of assembler-generated constant pools that are use to
42// implement the ldr-pseudo.
43class ConstantPool {
44 using EntryVecTy = SmallVector<ConstantPoolEntry, 4>;
45 EntryVecTy Entries;
46
47 // Caches of entries that already exist, indexed by their contents
48 // and also the size of the constant.
49 std::map<std::pair<int64_t, unsigned>, const MCSymbolRefExpr *>
50 CachedConstantEntries;
51 DenseMap<std::pair<const MCSymbol *, unsigned>, const MCSymbolRefExpr *>
52 CachedSymbolEntries;
53
54public:
55 // Initialize a new empty constant pool
56 ConstantPool() = default;
57
58 // Add a new entry to the constant pool in the next slot.
59 // \param Value is the new entry to put in the constant pool.
60 // \param Size is the size in bytes of the entry
61 //
62 // \returns a MCExpr that references the newly inserted value
63 const MCExpr *addEntry(const MCExpr *Value, MCContext &Context,
64 unsigned Size, SMLoc Loc);
65
66 // Emit the contents of the constant pool using the provided streamer.
67 void emitEntries(MCStreamer &Streamer);
68
69 // Return true if the constant pool is empty
70 bool empty();
71
72 void clearCache();
73};
74
75class AssemblerConstantPools {
76 // Map type used to keep track of per-Section constant pools used by the
77 // ldr-pseudo opcode. The map associates a section to its constant pool. The
78 // constant pool is a vector of (label, value) pairs. When the ldr
79 // pseudo is parsed we insert a new (label, value) pair into the constant pool
80 // for the current section and add MCSymbolRefExpr to the new label as
81 // an opcode to the ldr. After we have parsed all the user input we
82 // output the (label, value) pairs in each constant pool at the end of the
83 // section.
84 //
85 // We use the MapVector for the map type to ensure stable iteration of
86 // the sections at the end of the parse. We need to iterate over the
87 // sections in a stable order to ensure that we have print the
88 // constant pools in a deterministic order when printing an assembly
89 // file.
90 using ConstantPoolMapTy = MapVector<MCSection *, ConstantPool>;
91 ConstantPoolMapTy ConstantPools;
92
93public:
94 void emitAll(MCStreamer &Streamer);
95 void emitForCurrentSection(MCStreamer &Streamer);
96 void clearCacheForCurrentSection(MCStreamer &Streamer);
97 const MCExpr *addEntry(MCStreamer &Streamer, const MCExpr *Expr,
98 unsigned Size, SMLoc Loc);
99
100private:
101 ConstantPool *getConstantPool(MCSection *Section);
102 ConstantPool &getOrCreateConstantPool(MCSection *Section);
103};
104
105} // end namespace llvm
106
107#endif // LLVM_MC_CONSTANTPOOLS_H
108

source code of llvm/include/llvm/MC/ConstantPools.h