Revert "[ MC ] Match labels to existing fragments even when switching sections."

This reverts commit 4272372c571cd33edc77a8844b0a224ad7339138.

Caused an MSan buildbot failure. More information available in the patch
that introduced the bug: https://reviews.llvm.org/D71368

1 files changed, 13 insertions, 59 deletions

diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
index fc7fe4cb76c..6c85f2296cf 100644
--- a/llvm/lib/MC/MCObjectStreamer.cpp
+++ b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -42,64 +42,20 @@ MCAssembler *MCObjectStreamer::getAssemblerPtr() {
   return nullptr;
 }
 
-void MCObjectStreamer::addPendingLabel(MCSymbol* S) {
-  MCSection *CurSection = getCurrentSectionOnly();
-  if (CurSection) {
-    // Register labels that have not yet been assigned to a Section.
-    if (!PendingLabels.empty()) {
-      for (MCSymbol* Sym : PendingLabels)
-        CurSection->addPendingLabel(Sym);
-      PendingLabels.clear();
-    }
-
-    // Add this label to the current Section / Subsection.
-    CurSection->addPendingLabel(S, CurSubsectionIdx);
-
-    // Add this Section to the list of PendingLabelSections.
-    auto SecIt = std::find(PendingLabelSections.begin(),
-                           PendingLabelSections.end(), CurSection);
-    if (SecIt == PendingLabelSections.end())
-      PendingLabelSections.push_back(CurSection);
-  }
-  else
-    // There is no Section / Subsection for this label yet.
-    PendingLabels.push_back(S);
-}
-
 void MCObjectStreamer::flushPendingLabels(MCFragment *F, uint64_t FOffset) {
-  MCSection *CurSection = getCurrentSectionOnly();
-  if (!CurSection) {
-    assert(PendingLabels.empty());
+  if (PendingLabels.empty())
     return;
-  }
-  // Register labels that have not yet been assigned to a Section.
-  if (!PendingLabels.empty()) {
-    for (MCSymbol* Sym : PendingLabels)
-      CurSection->addPendingLabel(Sym, CurSubsectionIdx);
-    PendingLabels.clear();
-  }
-
-  // Associate a fragment with this label, either the supplied fragment
-  // or an empty data fragment.
-  if (F)
-    CurSection->flushPendingLabels(F, FOffset, CurSubsectionIdx);
-  else
-    CurSection->flushPendingLabels(nullptr, 0, CurSubsectionIdx);
-}
-
-void MCObjectStreamer::flushPendingLabels() {
-  // Register labels that have not yet been assigned to a Section.
-  if (!PendingLabels.empty()) {
+  if (!F) {
+    F = new MCDataFragment();
     MCSection *CurSection = getCurrentSectionOnly();
-    assert(CurSection);
-    for (MCSymbol* Sym : PendingLabels)
-      CurSection->addPendingLabel(Sym, CurSubsectionIdx);
-    PendingLabels.clear();
+    CurSection->getFragmentList().insert(CurInsertionPoint, F);
+    F->setParent(CurSection);
   }
-
-  // Assign an empty data fragment to all remaining pending labels.
-  for (MCSection* Section : PendingLabelSections)
-    Section->flushPendingLabels();
+  for (MCSymbol *Sym : PendingLabels) {
+    Sym->setFragment(F);
+    Sym->setOffset(FOffset);
+  }
+  PendingLabels.clear();
 }
 
 // When fixup's offset is a forward declared label, e.g.:
@@ -164,7 +120,6 @@ void MCObjectStreamer::reset() {
   EmitEHFrame = true;
   EmitDebugFrame = false;
   PendingLabels.clear();
-  PendingLabelSections.clear();
   MCStreamer::reset();
 }
 
@@ -282,7 +237,7 @@ void MCObjectStreamer::EmitLabel(MCSymbol *Symbol, SMLoc Loc) {
     // fragment. (They will all be reassigned to a real fragment in
     // flushPendingLabels())
     Symbol->setOffset(0);
-    addPendingLabel(Symbol);
+    PendingLabels.push_back(Symbol);
   }
 }
 
@@ -302,7 +257,7 @@ void MCObjectStreamer::EmitLabelAtPos(MCSymbol *Symbol, SMLoc Loc,
     assert(isa<MCDummyFragment>(F) &&
            "F must either be an MCDataFragment or the pending MCDummyFragment");
     assert(Offset == 0);
-    addPendingLabel(Symbol);
+    PendingLabels.push_back(Symbol);
   }
 }
 
@@ -337,6 +292,7 @@ void MCObjectStreamer::ChangeSection(MCSection *Section,
 bool MCObjectStreamer::changeSectionImpl(MCSection *Section,
                                          const MCExpr *Subsection) {
   assert(Section && "Cannot switch to a null section!");
+  flushPendingLabels(nullptr);
   getContext().clearDwarfLocSeen();
 
   bool Created = getAssembler().registerSection(*Section);
@@ -756,9 +712,7 @@ void MCObjectStreamer::FinishImpl() {
   // Dump out the dwarf file & directory tables and line tables.
   MCDwarfLineTable::Emit(this, getAssembler().getDWARFLinetableParams());
 
-  // Update any remaining pending labels with empty data fragments.
   flushPendingLabels();
-
   resolvePendingFixups();
   getAssembler().Finish();
 }