diff --git a/include/llvm/Target/TargetLibraryInfo.h b/include/llvm/Target/TargetLibraryInfo.h
index b11c24bffb5..bdd214b6b74 100644
--- a/include/llvm/Target/TargetLibraryInfo.h
+++ b/include/llvm/Target/TargetLibraryInfo.h
@@ -55,6 +55,10 @@ public:
   void setAvailable(LibFunc::Func F) {
     AvailableArray[F/8] |= 1 << (F&7);
   }
+  
+  /// disableAllFunctions - This disables all builtins, which is used for
+  /// options like -fno-builtin.
+  void disableAllFunctions();
 };
 
 } // end namespace llvm
diff --git a/lib/Target/TargetLibraryInfo.cpp b/lib/Target/TargetLibraryInfo.cpp
index f4a85b0cd62..c8bed18ffab 100644
--- a/lib/Target/TargetLibraryInfo.cpp
+++ b/lib/Target/TargetLibraryInfo.cpp
@@ -47,3 +47,9 @@ TargetLibraryInfo::TargetLibraryInfo(const Triple &T) : ImmutablePass(ID) {
   
   initialize(*this, T);
 }
+
+/// disableAllFunctions - This disables all builtins, which is used for options
+/// like -fno-builtin.
+void TargetLibraryInfo::disableAllFunctions() {
+  memset(AvailableArray, 0, sizeof(AvailableArray));
+}
diff --git a/tools/opt/opt.cpp b/tools/opt/opt.cpp
index 8ccd8e877b9..e55b4b3e2af 100644
--- a/tools/opt/opt.cpp
+++ b/tools/opt/opt.cpp
@@ -532,8 +532,12 @@ int main(int argc, char **argv) {
   PassManager Passes;
 
   // Add an appropriate TargetLibraryInfo pass for the module's triple.
-  if (!M->getTargetTriple().empty())
-    Passes.add(new TargetLibraryInfo(Triple(M->getTargetTriple())));
+  TargetLibraryInfo *TLI = new TargetLibraryInfo(Triple(M->getTargetTriple()));
+  
+  // The -disable-simplify-libcalls flag actually disables all builtin optzns.
+  if (DisableSimplifyLibCalls)
+    TLI->disableAllFunctions();
+  Passes.add(TLI);
   
   // Add an appropriate TargetData instance for this module.
   TargetData *TD = 0;