Index: lib/Driver/Tools.h
===================================================================
--- lib/Driver/Tools.h
+++ lib/Driver/Tools.h
@@ -108,7 +108,8 @@
     ClangAs(const ToolChain &TC) : Tool("clang::as",
                                         "clang integrated assembler", TC,
                                         RF_Full) {}
-
+    void AddMIPSTargetArgs(const llvm::opt::ArgList &Args,
+                           llvm::opt::ArgStringList &CmdArgs) const;
     bool hasGoodDiagnostics() const override { return true; }
     bool hasIntegratedAssembler() const override { return false; }
     bool hasIntegratedCPP() const override { return false; }
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -4827,6 +4827,17 @@
   return CLFallback.get();
 }
 
+void ClangAs::AddMIPSTargetArgs(const ArgList &Args,
+                              ArgStringList &CmdArgs) const {
+  StringRef CPUName;
+  StringRef ABIName;
+  const llvm::Triple &Triple = getToolChain().getTriple();
+  mips::getMipsCPUAndABI(Args, Triple, CPUName, ABIName);
+
+  CmdArgs.push_back("-target-abi");
+  CmdArgs.push_back(ABIName.data());
+}
+
 void ClangAs::ConstructJob(Compilation &C, const JobAction &JA,
                            const InputInfo &Output,
                            const InputInfoList &Inputs,
@@ -4964,6 +4975,19 @@
       getToolChain().getTriple().isOSLinux())
     SplitDebugInfo(getToolChain(), C, *this, JA, Args, Output,
                    SplitDebugName(Args, Inputs));
+
+    // Add target specific flags.
+  switch(getToolChain().getArch()) {
+  default:
+    break;
+
+  case llvm::Triple::mips:
+  case llvm::Triple::mipsel:
+  case llvm::Triple::mips64:
+  case llvm::Triple::mips64el:
+    AddMIPSTargetArgs(Args, CmdArgs);
+    break;
+  }
 }
 
 void GnuTool::anchor() {}
Index: tools/driver/cc1as_main.cpp
===================================================================
--- tools/driver/cc1as_main.cpp
+++ tools/driver/cc1as_main.cpp
@@ -78,6 +78,9 @@
   /// be a list of strings starting with '+' or '-'.
   std::vector<std::string> Features;
 
+  /// If given, the name of the target ABI to use.
+  std::string ABI;
+
   /// @}
   /// @name Language Options
   /// @{
@@ -185,6 +188,7 @@
   Opts.Triple = llvm::Triple::normalize(Args->getLastArgValue(OPT_triple));
   Opts.CPU = Args->getLastArgValue(OPT_target_cpu);
   Opts.Features = Args->getAllArgValues(OPT_target_feature);
+  Opts.ABI = Args->getLastArgValue(OPT_target_abi);
 
   // Use the default target triple if unspecified.
   if (Opts.Triple.empty())