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 std::map<int64_t, const MCSymbolRefExpr *> CachedConstantEntries;
47 DenseMap<const MCSymbol *, const MCSymbolRefExpr *> CachedSymbolEntries;
48
49public:
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
70class AssemblerConstantPools {
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.
85 using ConstantPoolMapTy = MapVector<MCSection *, ConstantPool>;
86 ConstantPoolMapTy ConstantPools;
87
88public:
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
95private:
96 ConstantPool *getConstantPool(MCSection *Section);
97 ConstantPool &getOrCreateConstantPool(MCSection *Section);
98};
99
100} // end namespace llvm
101
102#endif // LLVM_MC_CONSTANTPOOLS_H
103

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