Preprocessor: Allocate MacroInfo objects using a BumpPtrAllocator instead using new/delete.  This speeds up -Eonly on Cocoa.h using the regular lexer by 1.8% and the PTHLexer by 3%.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@61042 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/Preprocessor.cpp b/lib/Lex/Preprocessor.cpp
index 00d3d56..3fa76fa 100644
--- a/lib/Lex/Preprocessor.cpp
+++ b/lib/Lex/Preprocessor.cpp
@@ -95,9 +95,9 @@
   // Free any macro definitions.
   for (llvm::DenseMap<IdentifierInfo*, MacroInfo*>::iterator I =
        Macros.begin(), E = Macros.end(); I != E; ++I) {
-    // Free the macro definition.
-    delete I->second;
-    I->second = 0;
+    // We don't need to free the MacroInfo objects directly.  These
+    // will be released when the BumpPtrAllocator 'BP' object gets
+    // destroyed.
     I->first->setHasMacroDefinition(false);
   }