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 | |
31 | struct 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. |
43 | class 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 | |
54 | public: |
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 | |
75 | class 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 | |
93 | public: |
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 | |
100 | private: |
101 | ConstantPool *getConstantPool(MCSection *Section); |
102 | ConstantPool &getOrCreateConstantPool(MCSection *Section); |
103 | }; |
104 | |
105 | } // end namespace llvm |
106 | |
107 | #endif // LLVM_MC_CONSTANTPOOLS_H |
108 | |