Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -1790,6 +1790,14 @@
   case llvm::Triple::mips64:
   case llvm::Triple::mips64el:
     getMIPSTargetFeatures(D, Triple, Args, Features);
+    if (ForAS) {
+      StringRef CPUName;
+      StringRef ABIName;
+      mips::getMipsCPUAndABI(Args, Triple, CPUName, ABIName);
+    
+      CmdArgs.push_back("-target-abi");
+      CmdArgs.push_back(ABIName.data());
+    }
     break;
 
   case llvm::Triple::arm:
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())