diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index bd7d0e5..50a5075 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -310,6 +310,13 @@
     OutStreamer.EmitZerofill(TheSection, GVSym, Size, 1 << AlignLog);
     return;
   }
+  
+  // Handle the tbss directive on darwin which is a thread local bss directive
+  // like zerofill.
+  if (GVKind.isThreadBSS() && MAI->hasMachoTBSSDirective()) {
+    OutStreamer.EmitTBSSSymbol(TheSection, GVSym, Size, 1 << AlignLog);
+    return;
+  }
 
   OutStreamer.SwitchSection(TheSection);
 
diff --git a/lib/MC/MCAsmInfo.cpp b/lib/MC/MCAsmInfo.cpp
index 2b23994..a275be2 100644
--- a/lib/MC/MCAsmInfo.cpp
+++ b/lib/MC/MCAsmInfo.cpp
@@ -21,6 +21,7 @@
 MCAsmInfo::MCAsmInfo() {
   HasSubsectionsViaSymbols = false;
   HasMachoZeroFillDirective = false;
+  HasMachoTBSSDirective = false;
   HasStaticCtorDtorReferenceInStaticMode = false;
   MaxInstLength = 4;
   PCSymbol = "$";
diff --git a/lib/MC/MCAsmInfoDarwin.cpp b/lib/MC/MCAsmInfoDarwin.cpp
index 3c31caa..0bd3b2d 100644
--- a/lib/MC/MCAsmInfoDarwin.cpp
+++ b/lib/MC/MCAsmInfoDarwin.cpp
@@ -35,6 +35,7 @@
   WeakRefDirective = "\t.weak_reference ";
   ZeroDirective = "\t.space\t";  // ".space N" emits N zeros.
   HasMachoZeroFillDirective = true;  // Uses .zerofill
+  HasMachoTBSSDirective = true; // Uses .tbss
   HasStaticCtorDtorReferenceInStaticMode = true;
   
   HiddenVisibilityAttr = MCSA_PrivateExtern;