llvm/lib/MC/MCSection.cpp

   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
  21 using namespace llvm;
  22
  23 MCSection::MCSection(SectionVariant V, StringRef Name, SectionKind K,
  24                      MCSymbol *Begin)
  25     : Begin(Begin), BundleGroupBeforeFirstInst(false), HasInstructions(false),
  26       IsRegistered(false), DummyFragment(this), Name(Name), Variant(V),
  27       Kind(K) {}
  28
  29 MCSymbol *MCSection::getEndSymbol(MCContext &Ctx) {
  30   if (!End)
  31     End = Ctx.createTempSymbol("sec_end");
  32   return End;
  33 }
  34
  35 bool MCSection::hasEnded() const { return End && End->isInSection(); }
  36
  37 MCSection::~MCSection() = default;
  38
  39 void MCSection::setBundleLockState(BundleLockStateType NewState) {
  40   if (NewState == NotBundleLocked) {
  41     if (BundleLockNestingDepth == 0) {
  42       report_fatal_error("Mismatched bundle_lock/unlock directives");
  43     }
  44     if (--BundleLockNestingDepth == 0) {
  45       BundleLockState = NotBundleLocked;
  46     }
  47     return;
  48   }
  49
  50   // If any of the directives is an align_to_end directive, the whole nested
  51   // group is align_to_end. So don't downgrade from align_to_end to just locked.
  52   if (BundleLockState != BundleLockedAlignToEnd) {
  53     BundleLockState = NewState;
  54   }
  55   ++BundleLockNestingDepth;
  56 }
  57
  58 MCSection::iterator
  59 MCSection::getSubsectionInsertionPoint(unsigned Subsection) {
  60   if (Subsection == 0 && SubsectionFragmentMap.empty())
  61     return end();
  62
  63   SmallVectorImpl<std::pair<unsigned, MCFragment *>>::iterator MI = lower_bound(
  64       SubsectionFragmentMap, 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     F->setSubsectionNumber(Subsection);
  84   }
  85
  86   return IP;
  87 }
  88
  89 StringRef MCSection::getVirtualSectionKind() const { return "virtual"; }
  90
  91 void MCSection::addPendingLabel(MCSymbol *label, unsigned Subsection) {
  92   PendingLabels.push_back(PendingLabel(label, Subsection));
  93 }
  94
  95 void MCSection::flushPendingLabels(MCFragment *F, uint64_t FOffset,
  96                                    unsigned Subsection) {
  97   if (PendingLabels.empty())
  98     return;
  99
 100   // Set the fragment and fragment offset for all pending symbols in the
 101   // specified Subsection, and remove those symbols from the pending list.
 102   for (auto It = PendingLabels.begin(); It != PendingLabels.end(); ++It) {
 103     PendingLabel& Label = *It;
 104     if (Label.Subsection == Subsection) {
 105       Label.Sym->setFragment(F);
 106       Label.Sym->setOffset(FOffset);
 107       PendingLabels.erase(It--);
 108     }
 109   }
 110 }
 111
 112 void MCSection::flushPendingLabels() {
 113   // Make sure all remaining pending labels point to data fragments, by
 114   // creating new empty data fragments for each Subsection with labels pending.
 115   while (!PendingLabels.empty()) {
 116     PendingLabel& Label = PendingLabels[0];
 117     iterator CurInsertionPoint =
 118       this->getSubsectionInsertionPoint(Label.Subsection);
 119     MCFragment *F = new MCDataFragment();
 120     getFragmentList().insert(CurInsertionPoint, F);
 121     F->setParent(this);
 122     flushPendingLabels(F, 0, Label.Subsection);
 123   }
 124 }
 125
 126 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 127 LLVM_DUMP_METHOD void MCSection::dump() const {
 128   raw_ostream &OS = errs();
 129
 130   OS << "<MCSection";
 131   OS << " Fragments:[\n      ";
 132   for (auto it = begin(), ie = end(); it != ie; ++it) {
 133     if (it != begin())
 134       OS << ",\n      ";
 135     it->dump();
 136   }
 137   OS << "]>";
 138 }
 139 #endif