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      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
    140