[PATCH] D13188: [MachO] Stop generating *coal* sections.

[Rafael Espíndola via llvm-commits]

> But you would still want to call the destructors (either explicitly or implicitly) of MCSection subclasses, right? If we don't run the destructors, we'll be leaking MCSection::SubsectionFragmentMap, even if we make changes to use BumpPtrAllocator for MCSection::Fragments.

You are right, sorry about that.

> If you are worried about the overhead of using shared_ptr, I think we can continue using raw pointers and add checks that prevent the destructor from being run twice, although I'm not sure that would be a good idea.

It is just that changes like this really shouldn't need to worry about
memory management. If destructors must be called, we should probably
just use SpecificBumpPtrAllocator. What do you think of the attached
patch?

Cheers,
Rafael
-------------- next part --------------
diff --git a/include/llvm/MC/MCContext.h b/include/llvm/MC/MCContext.h
index e33b802..6380af6 100644
--- a/include/llvm/MC/MCContext.h
+++ b/include/llvm/MC/MCContext.h
@@ -71,6 +71,10 @@ namespace llvm {
     /// objects.
     BumpPtrAllocator Allocator;
 
+    SpecificBumpPtrAllocator<MCSectionCOFF> COFFAllocator;
+    SpecificBumpPtrAllocator<MCSectionELF> ELFAllocator;
+    SpecificBumpPtrAllocator<MCSectionMachO> MachOAllocator;
+
     /// Bindings of names to symbols.
     SymbolTable Symbols;
 
diff --git a/lib/MC/MCContext.cpp b/lib/MC/MCContext.cpp
index 9149f89..ff195d0 100644
--- a/lib/MC/MCContext.cpp
+++ b/lib/MC/MCContext.cpp
@@ -74,12 +74,9 @@ MCContext::~MCContext() {
 
 void MCContext::reset() {
   // Call the destructors so the fragments are freed
-  for (auto &I : ELFUniquingMap)
-    I.second->~MCSectionELF();
-  for (auto &I : COFFUniquingMap)
-    I.second->~MCSectionCOFF();
-  for (auto &I : MachOUniquingMap)
-    I.second->~MCSectionMachO();
+  COFFAllocator.DestroyAll();
+  ELFAllocator.DestroyAll();
+  MachOAllocator.DestroyAll();
 
   UsedNames.clear();
   Symbols.clear();
@@ -294,8 +291,8 @@ MCSectionMachO *MCContext::getMachOSection(StringRef Segment, StringRef Section,
     Begin = createTempSymbol(BeginSymName, false);
 
   // Otherwise, return a new section.
-  return Entry = new (*this) MCSectionMachO(Segment, Section, TypeAndAttributes,
-                                            Reserved2, Kind, Begin);
+  return Entry = new (MachOAllocator.Allocate()) MCSectionMachO(
+             Segment, Section, TypeAndAttributes, Reserved2, Kind, Begin);
 }
 
 void MCContext::renameELFSection(MCSectionELF *Section, StringRef Name) {
@@ -322,7 +319,7 @@ MCSectionELF *MCContext::createELFRelSection(StringRef Name, unsigned Type,
   bool Inserted;
   std::tie(I, Inserted) = ELFRelSecNames.insert(std::make_pair(Name, true));
 
-  return new (*this)
+  return new (ELFAllocator.Allocate())
       MCSectionELF(I->getKey(), Type, Flags, SectionKind::getReadOnly(),
                    EntrySize, Group, true, nullptr, Associated);
 }
@@ -367,15 +364,15 @@ MCSectionELF *MCContext::getELFSection(StringRef Section, unsigned Type,
   if (BeginSymName)
     Begin = createTempSymbol(BeginSymName, false);
 
-  MCSectionELF *Result =
-      new (*this) MCSectionELF(CachedName, Type, Flags, Kind, EntrySize,
-                               GroupSym, UniqueID, Begin, Associated);
+  MCSectionELF *Result = new (ELFAllocator.Allocate())
+      MCSectionELF(CachedName, Type, Flags, Kind, EntrySize, GroupSym, UniqueID,
+                   Begin, Associated);
   Entry.second = Result;
   return Result;
 }
 
 MCSectionELF *MCContext::createELFGroupSection(const MCSymbolELF *Group) {
-  MCSectionELF *Result = new (*this)
+  MCSectionELF *Result = new (ELFAllocator.Allocate())
       MCSectionELF(".group", ELF::SHT_GROUP, 0, SectionKind::getReadOnly(), 4,
                    Group, ~0, nullptr, nullptr);
   return Result;
@@ -404,7 +401,7 @@ MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
     Begin = createTempSymbol(BeginSymName, false);
 
   StringRef CachedName = Iter->first.SectionName;
-  MCSectionCOFF *Result = new (*this) MCSectionCOFF(
+  MCSectionCOFF *Result = new (COFFAllocator.Allocate()) MCSectionCOFF(
       CachedName, Characteristics, COMDATSymbol, Selection, Kind, Begin);
 
   Iter->second = Result;