[PATCH] D60297: [COFF] Pack Name in Symbol as is done in ELF

[Reid Kleckner via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL358794: [COFF] Pack Name in Symbol as is done in ELF (authored by rnk, committed by ).

Changed prior to commit:
  https://reviews.llvm.org/D60297?vs=193913&id=195930#toc

Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D60297/new/

https://reviews.llvm.org/D60297

Files:
  lld/trunk/COFF/Symbols.cpp
  lld/trunk/COFF/Symbols.h


Index: lld/trunk/COFF/Symbols.cpp
===================================================================
--- lld/trunk/COFF/Symbols.cpp
+++ lld/trunk/COFF/Symbols.cpp
@@ -20,6 +20,9 @@
 
 using namespace lld::coff;
 
+static_assert(sizeof(SymbolUnion) <= 48,
+              "symbols should be optimized for memory usage");
+
 // Returns a symbol name for an error message.
 std::string lld::toString(coff::Symbol &B) {
   if (Config->Demangle)
@@ -39,11 +42,15 @@
   // name. Object files contain lots of non-external symbols, and creating
   // StringRefs for them (which involves lots of strlen() on the string table)
   // is a waste of time.
-  if (Name.empty()) {
+  if (NameData == nullptr) {
     auto *D = cast<DefinedCOFF>(this);
-    cast<ObjFile>(D->File)->getCOFFObj()->getSymbolName(D->Sym, Name);
+    StringRef NameStr;
+    cast<ObjFile>(D->File)->getCOFFObj()->getSymbolName(D->Sym, NameStr);
+    NameData = NameStr.data();
+    NameSize = NameStr.size();
+    assert(NameSize == NameStr.size() && "name length truncated");
   }
-  return Name;
+  return StringRef(NameData, NameSize);
 }
 
 InputFile *Symbol::getFile() {
@@ -67,9 +74,10 @@
 
 // MinGW specific.
 void Symbol::replaceKeepingName(Symbol *Other, size_t Size) {
-  StringRef OrigName = Name;
+  StringRef OrigName = getName();
   memcpy(this, Other, Size);
-  Name = OrigName;
+  NameData = OrigName.data();
+  NameSize = OrigName.size();
 }
 
 COFFSymbolRef DefinedCOFF::getCOFFSymbol() {
Index: lld/trunk/COFF/Symbols.h
===================================================================
--- lld/trunk/COFF/Symbols.h
+++ lld/trunk/COFF/Symbols.h
@@ -79,7 +79,8 @@
   explicit Symbol(Kind K, StringRef N = "")
       : SymbolKind(K), IsExternal(true), IsCOMDAT(false),
         WrittenToSymtab(false), PendingArchiveLoad(false), IsGCRoot(false),
-        IsRuntimePseudoReloc(false), Name(N) {}
+        IsRuntimePseudoReloc(false), NameSize(N.size()),
+        NameData(N.empty() ? nullptr : N.data()) {}
 
   const unsigned SymbolKind : 8;
   unsigned IsExternal : 1;
@@ -106,7 +107,10 @@
   unsigned IsRuntimePseudoReloc : 1;
 
 protected:
-  StringRef Name;
+  // Symbol name length. Assume symbol lengths fit in a 32-bit integer.
+  uint32_t NameSize;
+
+  const char *NameData;
 };
 
 // The base class for any defined symbols, including absolute symbols,
@@ -129,7 +133,7 @@
 // Symbols defined via a COFF object file or bitcode file.  For COFF files, this
 // stores a coff_symbol_generic*, and names of internal symbols are lazily
 // loaded through that. For bitcode files, Sym is nullptr and the name is stored
-// as a StringRef.
+// as a decomposed StringRef.
 class DefinedCOFF : public Defined {
   friend Symbol;
 


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