1//===- lib/MC/MCSection.cpp - Machine Code Section Representation ---------===//
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#include "llvm/MC/MCSection.h"
10#include "llvm/ADT/SmallVector.h"
11#include "llvm/Config/llvm-config.h"
12#include "llvm/MC/MCContext.h"
13#include "llvm/MC/MCFragment.h"
14#include "llvm/MC/MCSymbol.h"
15#include "llvm/Support/Compiler.h"
16#include "llvm/Support/ErrorHandling.h"
17#include "llvm/Support/raw_ostream.h"
18#include <algorithm>
19#include <utility>
20
21using namespace llvm;
22
23MCSection::MCSection(SectionVariant V, SectionKind K, MCSymbol *Begin)
24    : Begin(Begin), BundleGroupBeforeFirstInst(false), HasInstructions(false),
25      IsRegistered(false), DummyFragment(this), Variant(V), Kind(K) {}
26
27MCSymbol *MCSection::getEndSymbol(MCContext &Ctx) {
28  if (!End)
29    End = Ctx.createTempSymbol("sec_end", true);
30  return End;
31}
32
33bool MCSection::hasEnded() const { return End && End->isInSection(); }
34
35MCSection::~MCSection() = default;
36
37void MCSection::setBundleLockState(BundleLockStateType NewState) {
38  if (NewState == NotBundleLocked) {
39    if (BundleLockNestingDepth == 0) {
40      report_fatal_error("Mismatched bundle_lock/unlock directives");
41    }
42    if (--BundleLockNestingDepth == 0) {
43      BundleLockState = NotBundleLocked;
44    }
45    return;
46  }
47
48  // If any of the directives is an align_to_end directive, the whole nested
49  // group is align_to_end. So don't downgrade from align_to_end to just locked.
50  if (BundleLockState != BundleLockedAlignToEnd) {
51    BundleLockState = NewState;
52  }
53  ++BundleLockNestingDepth;
54}
55
56MCSection::iterator
57MCSection::getSubsectionInsertionPoint(unsigned Subsection) {
58  if (Subsection == 0 && SubsectionFragmentMap.empty())
59    return end();
60
61  SmallVectorImpl<std::pair<unsigned, MCFragment *>>::iterator MI =
62      std::lower_bound(SubsectionFragmentMap.begin(),
63                       SubsectionFragmentMap.end(),
64                       std::make_pair(Subsection, (MCFragment *)nullptr));
65  bool ExactMatch = false;
66  if (MI != SubsectionFragmentMap.end()) {
67    ExactMatch = MI->first == Subsection;
68    if (ExactMatch)
69      ++MI;
70  }
71  iterator IP;
72  if (MI == SubsectionFragmentMap.end())
73    IP = end();
74  else
75    IP = MI->second->getIterator();
76  if (!ExactMatch && Subsection != 0) {
77    // The GNU as documentation claims that subsections have an alignment of 4,
78    // although this appears not to be the case.
79    MCFragment *F = new MCDataFragment();
80    SubsectionFragmentMap.insert(MI, std::make_pair(Subsection, F));
81    getFragmentList().insert(IP, F);
82    F->setParent(this);
83  }
84
85  return IP;
86}
87
88void MCSection::addPendingLabel(MCSymbol* label, unsigned Subsection) {
89  PendingLabels.push_back(PendingLabel(label, Subsection));
90}
91
92void MCSection::flushPendingLabels(MCFragment *F, uint64_t FOffset,
93				   unsigned Subsection) {
94  if (PendingLabels.empty())
95    return;
96
97  // Set the fragment and fragment offset for all pending symbols in the
98  // specified Subsection, and remove those symbols from the pending list.
99  for (auto It = PendingLabels.begin(); It != PendingLabels.end(); ++It) {
100    PendingLabel& Label = *It;
101    if (Label.Subsection == Subsection) {
102      Label.Sym->setFragment(F);
103      Label.Sym->setOffset(FOffset);
104      PendingLabels.erase(It--);
105    }
106  }
107}
108
109void MCSection::flushPendingLabels() {
110  // Make sure all remaining pending labels point to data fragments, by
111  // creating new empty data fragments for each Subsection with labels pending.
112  while (!PendingLabels.empty()) {
113    PendingLabel& Label = PendingLabels[0];
114    iterator CurInsertionPoint =
115      this->getSubsectionInsertionPoint(Label.Subsection);
116    MCFragment *F = new MCDataFragment();
117    getFragmentList().insert(CurInsertionPoint, F);
118    F->setParent(this);
119    flushPendingLabels(F, 0, Label.Subsection);
120  }
121}
122
123#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
124LLVM_DUMP_METHOD void MCSection::dump() const {
125  raw_ostream &OS = errs();
126
127  OS << "<MCSection";
128  OS << " Fragments:[\n      ";
129  for (auto it = begin(), ie = end(); it != ie; ++it) {
130    if (it != begin())
131      OS << ",\n      ";
132    it->dump();
133  }
134  OS << "]>";
135}
136#endif
137