MC: Change MCAssembler::Symbols to a vector

Instead of an intrusive double-linked linked list, use a
`std::vector<>`.  This saves a pointer per symbol and simplifies
`MCSymbolData`.  Otherwise, no functionality change here.

While I measured a memory drop from around 1047MB to 1040MB (0.6%) --
and this is a decent cleanup in its own right -- it's primarily a
preparation patch for merging `MCSymbol` and `MCSymbolData`.  I'll post
an updated patch for that to the list in a moment.

(I'm looking at `llc` memory usage on `verify-uselistorder.lto.opt.bc`;
see r236629 for details.)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237487 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/MC/MCAssembler.h b/include/llvm/MC/MCAssembler.h
index eb7936834f34f143d97ea716764299983d7c97ca..d83475d208bf26fe3b7dcca8e22f65d51b4e6271 100644 (file)
--- a/include/llvm/MC/MCAssembler.h
+++ b/include/llvm/MC/MCAssembler.h
@@ -17,6 +17,7 @@
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/ilist.h"
 #include "llvm/ADT/ilist_node.h"
+#include "llvm/ADT/iterator.h"
 #include "llvm/MC/MCDirectives.h"
 #include "llvm/MC/MCFixup.h"
 #include "llvm/MC/MCInst.h"
@@ -657,7 +658,7 @@ public:
 };
 
 // FIXME: Same concerns as with SectionData.
-class MCSymbolData : public ilist_node<MCSymbolData> {
+class MCSymbolData {
   const MCSymbol *Symbol;
 
   /// Fragment - The fragment this symbol's value is relative to, if any. Also
@@ -798,13 +799,14 @@ class MCAssembler {
 
 public:
   typedef iplist<MCSectionData> SectionDataListType;
-  typedef iplist<MCSymbolData> SymbolDataListType;
+  typedef std::vector<std::unique_ptr<MCSymbolData>> SymbolDataListType;
 
   typedef SectionDataListType::const_iterator const_iterator;
   typedef SectionDataListType::iterator iterator;
 
-  typedef SymbolDataListType::const_iterator const_symbol_iterator;
-  typedef SymbolDataListType::iterator symbol_iterator;
+  typedef pointee_iterator<SymbolDataListType::const_iterator>
+  const_symbol_iterator;
+  typedef pointee_iterator<SymbolDataListType::iterator> symbol_iterator;
 
   typedef iterator_range<symbol_iterator> symbol_range;
   typedef iterator_range<const_symbol_iterator> const_symbol_range;
@@ -846,7 +848,7 @@ private:
 
   iplist<MCSectionData> Sections;
 
-  iplist<MCSymbolData> Symbols;
+  SymbolDataListType Symbols;
 
   DenseSet<const MCSymbol *> LocalsUsedInReloc;
 
@@ -1181,8 +1183,8 @@ public:
     if (Created)
       *Created = !Entry;
     if (!Entry) {
-      Entry = new MCSymbolData(Symbol, nullptr, 0);
-      Symbols.push_back(Entry);
+      Symbols.emplace_back(new MCSymbolData(Symbol, nullptr, 0));
+      Entry = Symbols.back().get();
     }
 
     return *Entry;