Index: cfe/trunk/lib/Driver/Tools.cpp
===================================================================
--- cfe/trunk/lib/Driver/Tools.cpp
+++ cfe/trunk/lib/Driver/Tools.cpp
@@ -4145,7 +4145,8 @@
                     options::OPT_fno_lax_vector_conversions))
     CmdArgs.push_back("-fno-lax-vector-conversions");
 
-  if (Args.getLastArg(options::OPT_fapple_kext))
+  if (Args.getLastArg(options::OPT_fapple_kext) ||
+      (Args.hasArg(options::OPT_mkernel) && types::isCXX(InputType)))
     CmdArgs.push_back("-fapple-kext");
 
   Args.AddLastArg(CmdArgs, options::OPT_fobjc_sender_dependent_dispatch);
@@ -4279,15 +4280,9 @@
       A->render(Args, CmdArgs);
   }
 
-  if (Args.hasArg(options::OPT_mkernel)) {
-    if (!Args.hasArg(options::OPT_fapple_kext) && types::isCXX(InputType))
-      CmdArgs.push_back("-fapple-kext");
-    if (!Args.hasArg(options::OPT_fbuiltin))
-      CmdArgs.push_back("-fno-builtin");
-    Args.ClaimAllArgs(options::OPT_fno_builtin);
-  }
-  // -fbuiltin is default.
-  else if (!Args.hasFlag(options::OPT_fbuiltin, options::OPT_fno_builtin))
+  // -fbuiltin is default unless -mkernel is used
+  if (!Args.hasFlag(options::OPT_fbuiltin, options::OPT_fno_builtin,
+                    !Args.hasArg(options::OPT_mkernel)))
     CmdArgs.push_back("-fno-builtin");
 
   if (!Args.hasFlag(options::OPT_fassume_sane_operator_new,
@@ -4687,14 +4682,11 @@
     }
   }
 
-  if (KernelOrKext || isNoCommonDefault(getToolChain().getTriple())) {
-    if (!Args.hasArg(options::OPT_fcommon))
-      CmdArgs.push_back("-fno-common");
-    Args.ClaimAllArgs(options::OPT_fno_common);
-  }
-
-  // -fcommon is default, only pass non-default.
-  else if (!Args.hasFlag(options::OPT_fcommon, options::OPT_fno_common))
+  // -fcommon is the default unless compiling kernel code or the target says so
+  bool NoCommonDefault =
+      KernelOrKext || isNoCommonDefault(getToolChain().getTriple());
+  if (!Args.hasFlag(options::OPT_fcommon, options::OPT_fno_common,
+                    !NoCommonDefault))
     CmdArgs.push_back("-fno-common");
 
   // -fsigned-bitfields is default, and clang doesn't yet support
Index: cfe/trunk/test/Driver/apple-kext-mkernel.c
===================================================================
--- cfe/trunk/test/Driver/apple-kext-mkernel.c
+++ cfe/trunk/test/Driver/apple-kext-mkernel.c
@@ -1,15 +1,20 @@
-// RUN: %clang -target x86_64-apple-darwin10 \
-// RUN:   -mkernel -### -fsyntax-only %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-X86 < %t %s
+// RUN: %clang -target x86_64-apple-darwin10 -mkernel -### -fsyntax-only %s 2>&1 | FileCheck --check-prefix=CHECK-X86 %s
+// RUN: %clang -target x86_64-apple-darwin10 -mkernel -### -fsyntax-only -fbuiltin -fno-builtin -fcommon -fno-common %s 2>&1 | FileCheck --check-prefix=CHECK-X86 %s
 
 // CHECK-X86: "-disable-red-zone"
 // CHECK-X86: "-fno-builtin"
 // CHECK-X86: "-fno-rtti"
 // CHECK-X86: "-fno-common"
 
-// RUN: %clang -target x86_64-apple-darwin10 \
-// RUN:   -arch armv7 -mkernel -mstrict-align -### -fsyntax-only %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-ARM < %t %s
+// RUN: %clang -target x86_64-apple-darwin10 -mkernel -### -fsyntax-only -fbuiltin -fcommon %s 2>&1 | FileCheck --check-prefix=CHECK-X86-2 %s
+
+// CHECK-X86-2: "-disable-red-zone"
+// CHECK-X86-2-NOT: "-fno-builtin"
+// CHECK-X86-2: "-fno-rtti"
+// CHECK-X86-2-NOT: "-fno-common"
+
+// RUN: %clang -target x86_64-apple-darwin10 -arch armv7 -mkernel -mstrict-align -### -fsyntax-only %s 2>&1 | FileCheck --check-prefix=CHECK-ARM %s
+// RUN: %clang -target x86_64-apple-darwin10 -arch armv7 -mkernel -mstrict-align -### -fsyntax-only -fbuiltin -fno-builtin -fcommon -fno-common %s 2>&1 | FileCheck --check-prefix=CHECK-ARM %s
 
 // CHECK-ARM: "-target-feature" "+long-calls"
 // CHECK-ARM: "-target-feature" "+strict-align"