1//===- MCSection.h - Machine Code Sections ----------------------*- 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 MCSection class.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_MC_MCSECTION_H
14#define LLVM_MC_MCSECTION_H
15
16#include "llvm/ADT/SmallVector.h"
17#include "llvm/ADT/ilist.h"
18#include "llvm/MC/MCFragment.h"
19#include "llvm/MC/SectionKind.h"
20#include "llvm/Support/Alignment.h"
21#include <cassert>
22#include <utility>
23
24namespace llvm {
25
26class MCAsmInfo;
27class MCContext;
28class MCExpr;
29class MCSymbol;
30class raw_ostream;
31class Triple;
32
33template <> struct ilist_alloc_traits<MCFragment> {
34  static void deleteNode(MCFragment *V);
35};
36
37/// Instances of this class represent a uniqued identifier for a section in the
38/// current translation unit.  The MCContext class uniques and creates these.
39class MCSection {
40public:
41  enum SectionVariant { SV_COFF = 0, SV_ELF, SV_MachO, SV_Wasm, SV_XCOFF };
42
43  /// Express the state of bundle locked groups while emitting code.
44  enum BundleLockStateType {
45    NotBundleLocked,
46    BundleLocked,
47    BundleLockedAlignToEnd
48  };
49
50  using FragmentListType = iplist<MCFragment>;
51
52  using const_iterator = FragmentListType::const_iterator;
53  using iterator = FragmentListType::iterator;
54
55  using const_reverse_iterator = FragmentListType::const_reverse_iterator;
56  using reverse_iterator = FragmentListType::reverse_iterator;
57
58private:
59  MCSymbol *Begin;
60  MCSymbol *End = nullptr;
61  /// The alignment requirement of this section.
62  Align Alignment;
63  /// The section index in the assemblers section list.
64  unsigned Ordinal = 0;
65  /// The index of this section in the layout order.
66  unsigned LayoutOrder;
67
68  /// Keeping track of bundle-locked state.
69  BundleLockStateType BundleLockState = NotBundleLocked;
70
71  /// Current nesting depth of bundle_lock directives.
72  unsigned BundleLockNestingDepth = 0;
73
74  /// We've seen a bundle_lock directive but not its first instruction
75  /// yet.
76  bool BundleGroupBeforeFirstInst : 1;
77
78  /// Whether this section has had instructions emitted into it.
79  bool HasInstructions : 1;
80
81  bool IsRegistered : 1;
82
83  MCDummyFragment DummyFragment;
84
85  FragmentListType Fragments;
86
87  /// Mapping from subsection number to insertion point for subsection numbers
88  /// below that number.
89  SmallVector<std::pair<unsigned, MCFragment *>, 1> SubsectionFragmentMap;
90
91  /// State for tracking labels that don't yet have Fragments
92  struct PendingLabel {
93    MCSymbol* Sym;
94    unsigned Subsection;
95    PendingLabel(MCSymbol* Sym, unsigned Subsection = 0)
96      : Sym(Sym), Subsection(Subsection) {}
97  };
98  SmallVector<PendingLabel, 2> PendingLabels;
99
100protected:
101  SectionVariant Variant;
102  SectionKind Kind;
103
104  MCSection(SectionVariant V, SectionKind K, MCSymbol *Begin);
105  ~MCSection();
106
107public:
108  MCSection(const MCSection &) = delete;
109  MCSection &operator=(const MCSection &) = delete;
110
111  SectionKind getKind() const { return Kind; }
112
113  SectionVariant getVariant() const { return Variant; }
114
115  MCSymbol *getBeginSymbol() { return Begin; }
116  const MCSymbol *getBeginSymbol() const {
117    return const_cast<MCSection *>(this)->getBeginSymbol();
118  }
119  void setBeginSymbol(MCSymbol *Sym) {
120    assert(!Begin);
121    Begin = Sym;
122  }
123  MCSymbol *getEndSymbol(MCContext &Ctx);
124  bool hasEnded() const;
125
126  unsigned getAlignment() const { return Alignment.value(); }
127  void setAlignment(Align Value) { Alignment = Value; }
128
129  unsigned getOrdinal() const { return Ordinal; }
130  void setOrdinal(unsigned Value) { Ordinal = Value; }
131
132  unsigned getLayoutOrder() const { return LayoutOrder; }
133  void setLayoutOrder(unsigned Value) { LayoutOrder = Value; }
134
135  BundleLockStateType getBundleLockState() const { return BundleLockState; }
136  void setBundleLockState(BundleLockStateType NewState);
137  bool isBundleLocked() const { return BundleLockState != NotBundleLocked; }
138
139  bool isBundleGroupBeforeFirstInst() const {
140    return BundleGroupBeforeFirstInst;
141  }
142  void setBundleGroupBeforeFirstInst(bool IsFirst) {
143    BundleGroupBeforeFirstInst = IsFirst;
144  }
145
146  bool hasInstructions() const { return HasInstructions; }
147  void setHasInstructions(bool Value) { HasInstructions = Value; }
148
149  bool isRegistered() const { return IsRegistered; }
150  void setIsRegistered(bool Value) { IsRegistered = Value; }
151
152  MCSection::FragmentListType &getFragmentList() { return Fragments; }
153  const MCSection::FragmentListType &getFragmentList() const {
154    return const_cast<MCSection *>(this)->getFragmentList();
155  }
156
157  /// Support for MCFragment::getNextNode().
158  static FragmentListType MCSection::*getSublistAccess(MCFragment *) {
159    return &MCSection::Fragments;
160  }
161
162  const MCDummyFragment &getDummyFragment() const { return DummyFragment; }
163  MCDummyFragment &getDummyFragment() { return DummyFragment; }
164
165  iterator begin() { return Fragments.begin(); }
166  const_iterator begin() const { return Fragments.begin(); }
167
168  iterator end() { return Fragments.end(); }
169  const_iterator end() const { return Fragments.end(); }
170
171  MCSection::iterator getSubsectionInsertionPoint(unsigned Subsection);
172
173  void dump() const;
174
175  virtual void PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
176                                    raw_ostream &OS,
177                                    const MCExpr *Subsection) const = 0;
178
179  /// Return true if a .align directive should use "optimized nops" to fill
180  /// instead of 0s.
181  virtual bool UseCodeAlign() const = 0;
182
183  /// Check whether this section is "virtual", that is has no actual object
184  /// file contents.
185  virtual bool isVirtualSection() const = 0;
186
187  /// Add a pending label for the requested subsection. This label will be
188  /// associated with a fragment in flushPendingLabels()
189  void addPendingLabel(MCSymbol* label, unsigned Subsection = 0);
190
191  /// Associate all pending labels in a subsection with a fragment.
192  void flushPendingLabels(MCFragment *F, uint64_t FOffset = 0,
193			  unsigned Subsection = 0);
194
195  /// Associate all pending labels with empty data fragments. One fragment
196  /// will be created for each subsection as necessary.
197  void flushPendingLabels();
198};
199
200} // end namespace llvm
201
202#endif // LLVM_MC_MCSECTION_H
203