diff --git a/clang/include/clang/Driver/ToolChain.h b/clang/include/clang/Driver/ToolChain.h
index a578778aff16..a5d51ca9d7c9 100644
--- a/clang/include/clang/Driver/ToolChain.h
+++ b/clang/include/clang/Driver/ToolChain.h
@@ -171,14 +171,16 @@ public:
 
   /// ComputeLLVMTriple - Return the LLVM target triple to use, after taking
   /// command line arguments into account.
-  virtual std::string ComputeLLVMTriple(const ArgList &Args) const;
+  virtual std::string ComputeLLVMTriple(const ArgList &Args,
+                                 types::ID InputType = types::TY_INVALID) const;
 
   /// ComputeEffectiveClangTriple - Return the Clang triple to use for this
   /// target, which may take into account the command line arguments. For
   /// example, on Darwin the -mmacosx-version-min= command line argument (which
   /// sets the deployment target) determines the version in the triple passed to
   /// Clang.
-  virtual std::string ComputeEffectiveClangTriple(const ArgList &Args) const;
+  virtual std::string ComputeEffectiveClangTriple(const ArgList &Args,
+                                 types::ID InputType = types::TY_INVALID) const;
 
   /// configureObjCRuntime - Configure the known properties of the
   /// Objective-C runtime for this platform.
diff --git a/clang/lib/Driver/ToolChain.cpp b/clang/lib/Driver/ToolChain.cpp
index d83fd9af258e..074f1a348132 100644
--- a/clang/lib/Driver/ToolChain.cpp
+++ b/clang/lib/Driver/ToolChain.cpp
@@ -169,7 +169,8 @@ static const char *getLLVMArchSuffixForARM(StringRef CPU) {
   return "";
 }
 
-std::string ToolChain::ComputeLLVMTriple(const ArgList &Args) const {
+std::string ToolChain::ComputeLLVMTriple(const ArgList &Args, 
+                                         types::ID InputType) const {
   switch (getTriple().getArch()) {
   default:
     return getTripleString();
@@ -187,7 +188,10 @@ std::string ToolChain::ComputeLLVMTriple(const ArgList &Args) const {
     bool ThumbDefault =
       (Suffix == "v7" && getTriple().getOS() == llvm::Triple::Darwin);
     std::string ArchName = "arm";
-    if (Args.hasFlag(options::OPT_mthumb, options::OPT_mno_thumb, ThumbDefault))
+
+    // Assembly files should start in ARM mode.
+    if (InputType != types::TY_PP_Asm &&
+        Args.hasFlag(options::OPT_mthumb, options::OPT_mno_thumb, ThumbDefault))
       ArchName = "thumb";
     Triple.setArchName(ArchName + Suffix.str());
 
@@ -196,7 +200,8 @@ std::string ToolChain::ComputeLLVMTriple(const ArgList &Args) const {
   }
 }
 
-std::string ToolChain::ComputeEffectiveClangTriple(const ArgList &Args) const {
+std::string ToolChain::ComputeEffectiveClangTriple(const ArgList &Args, 
+                                                   types::ID InputType) const {
   // Diagnose use of Darwin OS deployment target arguments on non-Darwin.
   if (Arg *A = Args.getLastArg(options::OPT_mmacosx_version_min_EQ,
                                options::OPT_miphoneos_version_min_EQ,
@@ -204,7 +209,7 @@ std::string ToolChain::ComputeEffectiveClangTriple(const ArgList &Args) const {
     getDriver().Diag(diag::err_drv_clang_unsupported)
       << A->getAsString(Args);
 
-  return ComputeLLVMTriple(Args);
+  return ComputeLLVMTriple(Args, InputType);
 }
 
 ToolChain::CXXStdlibType ToolChain::GetCXXStdlibType(const ArgList &Args) const{
diff --git a/clang/lib/Driver/ToolChains.cpp b/clang/lib/Driver/ToolChains.cpp
index 5e0378525bff..5ed9dc897032 100644
--- a/clang/lib/Driver/ToolChains.cpp
+++ b/clang/lib/Driver/ToolChains.cpp
@@ -189,8 +189,9 @@ Darwin::~Darwin() {
     delete it->second;
 }
 
-std::string Darwin::ComputeEffectiveClangTriple(const ArgList &Args) const {
-  llvm::Triple Triple(ComputeLLVMTriple(Args));
+std::string Darwin::ComputeEffectiveClangTriple(const ArgList &Args,
+                                                types::ID InputType) const {
+  llvm::Triple Triple(ComputeLLVMTriple(Args, InputType));
 
   // If the target isn't initialized (e.g., an unknown Darwin platform, return
   // the default triple).
@@ -958,8 +959,9 @@ bool Darwin::SupportsObjCGC() const {
 }
 
 std::string
-Darwin_Generic_GCC::ComputeEffectiveClangTriple(const ArgList &Args) const {
-  return ComputeLLVMTriple(Args);
+Darwin_Generic_GCC::ComputeEffectiveClangTriple(const ArgList &Args,
+                                                types::ID InputType) const {
+  return ComputeLLVMTriple(Args, InputType);
 }
 
 /// Generic_GCC - A tool chain using the 'gcc' command to perform
diff --git a/clang/lib/Driver/ToolChains.h b/clang/lib/Driver/ToolChains.h
index 10c416a5fb9f..c7771170b838 100644
--- a/clang/lib/Driver/ToolChains.h
+++ b/clang/lib/Driver/ToolChains.h
@@ -89,7 +89,8 @@ public:
   Darwin(const HostInfo &Host, const llvm::Triple& Triple);
   ~Darwin();
 
-  std::string ComputeEffectiveClangTriple(const ArgList &Args) const;
+  std::string ComputeEffectiveClangTriple(const ArgList &Args,
+                                          types::ID InputType) const;
 
   /// @name Darwin Specific Toolchain API
   /// {
@@ -292,7 +293,8 @@ public:
   Darwin_Generic_GCC(const HostInfo &Host, const llvm::Triple& Triple)
     : Generic_GCC(Host, Triple) {}
 
-  std::string ComputeEffectiveClangTriple(const ArgList &Args) const;
+  std::string ComputeEffectiveClangTriple(const ArgList &Args,
+                                          types::ID InputType) const;
 
   virtual const char *GetDefaultRelocationModel() const { return "pic"; }
 };
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 4d4abff6399b..cd86f16744e0 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -2230,7 +2230,8 @@ void ClangAs::ConstructJob(Compilation &C, const JobAction &JA,
 
   // Add the "effective" target triple.
   CmdArgs.push_back("-triple");
-  std::string TripleStr = getToolChain().ComputeEffectiveClangTriple(Args);
+  std::string TripleStr = 
+    getToolChain().ComputeEffectiveClangTriple(Args, Input.getType());
   CmdArgs.push_back(Args.MakeArgString(TripleStr));
 
   // Set the output mode, we currently only expect to be used as a real