Index: lib/Basic/Targets.cpp
===================================================================
--- lib/Basic/Targets.cpp
+++ lib/Basic/Targets.cpp
@@ -6625,6 +6625,19 @@
   NumAliases = 0;
 }
 
+// We attempt to use PNaCl (le32) frontend and Mips32EL backend.
+class NaClMips32ELTargetInfo : public Mips32ELTargetInfo {
+public:
+  NaClMips32ELTargetInfo(const llvm::Triple &Triple) :
+    Mips32ELTargetInfo(Triple)  {
+      MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 0;
+  }
+
+  BuiltinVaListKind getBuiltinVaListKind() const override {
+    return TargetInfo::PNaClABIBuiltinVaList;
+  }
+};
+
 class Le64TargetInfo : public TargetInfo {
   static const Builtin::Info BuiltinInfo[];
 
@@ -6995,7 +7008,7 @@
     case llvm::Triple::NetBSD:
       return new NetBSDTargetInfo<Mips32ELTargetInfo>(Triple);
     case llvm::Triple::NaCl:
-      return new NaClTargetInfo<Mips32ELTargetInfo>(Triple);
+      return new NaClTargetInfo<NaClMips32ELTargetInfo>(Triple);
     default:
       return new Mips32ELTargetInfo(Triple);
     }
Index: lib/CodeGen/TargetInfo.cpp
===================================================================
--- lib/CodeGen/TargetInfo.cpp
+++ lib/CodeGen/TargetInfo.cpp
@@ -7125,6 +7125,8 @@
     return *(TheTargetCodeGenInfo = new PNaClTargetCodeGenInfo(Types));
   case llvm::Triple::mips:
   case llvm::Triple::mipsel:
+    if (Triple.getOS() == llvm::Triple::NaCl)
+      return *(TheTargetCodeGenInfo = new PNaClTargetCodeGenInfo(Types));
     return *(TheTargetCodeGenInfo = new MIPSTargetCodeGenInfo(Types, true));
 
   case llvm::Triple::mips64:
Index: lib/Driver/ToolChains.h
===================================================================
--- lib/Driver/ToolChains.h
+++ lib/Driver/ToolChains.h
@@ -743,7 +743,9 @@
                       llvm::opt::ArgStringList &CmdArgs) const override;
 
   bool
-  IsIntegratedAssemblerDefault() const override { return false; }
+  IsIntegratedAssemblerDefault() const override {
+    return getTriple().getArch() == llvm::Triple::mipsel;
+  }
 
   // Get the path to the file containing NaCl's ARM macros. It lives in NaCl_TC
   // because the AssembleARM tool needs a const char * that it can pass around
Index: lib/Driver/ToolChains.cpp
===================================================================
--- lib/Driver/ToolChains.cpp
+++ lib/Driver/ToolChains.cpp
@@ -2385,6 +2385,13 @@
       file_paths.push_back(ToolPath + "arm-nacl");
       break;
     }
+    case llvm::Triple::mipsel: {
+      file_paths.push_back(FilePath + "mipsel-nacl/lib");
+      file_paths.push_back(FilePath + "mipsel-nacl/usr/lib");
+      prog_paths.push_back(ProgPath + "bin");
+      file_paths.push_back(ToolPath + "mipsel-nacl");
+      break;
+    }
     default:
       break;
   }
@@ -2420,6 +2427,9 @@
   case llvm::Triple::x86_64:
     llvm::sys::path::append(P, "x86_64-nacl/usr/include");
     break;
+  case llvm::Triple::mipsel:
+    llvm::sys::path::append(P, "mipsel-nacl/usr/include");
+    break;
   default:
     return;
   }
@@ -2464,6 +2474,10 @@
     llvm::sys::path::append(P, "x86_64-nacl/include/c++/v1");
     addSystemInclude(DriverArgs, CC1Args, P.str());
     break;
+  case llvm::Triple::mipsel:
+    llvm::sys::path::append(P, "mipsel-nacl/include/c++/v1");
+    addSystemInclude(DriverArgs, CC1Args, P.str());
+    break;
   default:
     break;
   }
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -8252,6 +8252,8 @@
     CmdArgs.push_back("armelf_nacl");
   else if (Arch == llvm::Triple::x86_64)
     CmdArgs.push_back("elf_x86_64_nacl");
+  else if (Arch == llvm::Triple::mipsel)
+    CmdArgs.push_back("mipselelf_nacl");
   else
     D.Diag(diag::err_target_unsupported_arch) << ToolChain.getArchName()
                                               << "Native Client";
@@ -8315,6 +8317,13 @@
       if (Args.hasArg(options::OPT_pthread) ||
           Args.hasArg(options::OPT_pthreads) ||
           D.CCCIsCXX()) {
+        // Gold, used by Mips, handles nested groups differently than ld, and
+        // without '-lnacl' it prefers symbols from libpthread.a over libnacl.a,
+        // which is not a desired behaviour here.
+        // See https://sourceware.org/ml/binutils/2015-03/msg00034.html
+        if (getToolChain().getArch() == llvm::Triple::mipsel)
+          CmdArgs.push_back("-lnacl");
+
         CmdArgs.push_back("-lpthread");
       }
 
@@ -8325,6 +8334,13 @@
       else
         CmdArgs.push_back("-lgcc_s");
       CmdArgs.push_back("--no-as-needed");
+
+      // Mips needs to create and use pnacl_legacy library that contains
+      // definitions from bitcode/pnaclmm.c and definitions for
+      // __nacl_tp_tls_offset() and __nacl_tp_tdb_offset().
+      if (getToolChain().getArch() == llvm::Triple::mipsel)
+        CmdArgs.push_back("-lpnacl_legacy");
+
       CmdArgs.push_back("--end-group");
     }