[lld] r231552 - Resolver: optimize fallback atoms.

[Rui Ueyama]

Author: ruiu
Date: Fri Mar  6 22:23:46 2015
New Revision: 231552

URL: http://llvm.org/viewvc/llvm-project?rev=231552&view=rev
Log:
Resolver: optimize fallback atoms.

Atoms with fallback atoms are never be added to the symbol table.
However, we added such atoms to _undefines array. We had to call
isCoalescedAway to identify and skip them. We should just stop
adding them in the first place.

This seems to make the linker ~1% faster in my test case.

Modified:
    lld/trunk/lib/Core/Resolver.cpp

Modified: lld/trunk/lib/Core/Resolver.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/Core/Resolver.cpp?rev=231552&r1=231551&r2=231552&view=diff
==============================================================================
--- lld/trunk/lib/Core/Resolver.cpp (original)
+++ lld/trunk/lib/Core/Resolver.cpp Fri Mar  6 22:23:46 2015
@@ -54,8 +54,7 @@ void Resolver::forEachUndefines(File &fi
       StringRef undefName = _undefines[i];
       if (undefName.empty())
         continue;
-      const Atom *atom = _symbolTable.findByName(undefName);
-      if (!isa<UndefinedAtom>(atom) || _symbolTable.isCoalescedAway(atom)) {
+      if (_symbolTable.isDefined(undefName)) {
         // The symbol was resolved by some other file. Cache the result.
         _undefines[i] = "";
         continue;
@@ -119,18 +118,18 @@ bool Resolver::doUndefinedAtom(const Und
 
   // tell symbol table
   bool newUndefAdded = _symbolTable.add(atom);
-  if (newUndefAdded)
-    _undefines.push_back(atom.name());
 
   // If the undefined symbol has an alternative name, try to resolve the
   // symbol with the name to give it a second chance. This feature is used
   // for COFF "weak external" symbol.
   if (newUndefAdded || !_symbolTable.isDefined(atom.name())) {
     if (const UndefinedAtom *fallbackAtom = atom.fallback()) {
-      doUndefinedAtom(*fallbackAtom);
       _symbolTable.addReplacement(&atom, fallbackAtom);
+      return doUndefinedAtom(*fallbackAtom);
     }
   }
+  if (newUndefAdded)
+    _undefines.push_back(atom.name());
   return newUndefAdded;
 }