- Adapt the -mfix-loongson2f-btb workaround from as(1) to LLVM/clang.
- Add retguard for octeon/mips64.

Index: lib/Target/Mips/CMakeLists.txt
--- lib/Target/Mips/CMakeLists.txt.orig
+++ lib/Target/Mips/CMakeLists.txt
@@ -41,6 +41,7 @@ add_llvm_target(MipsCodeGen
   MipsISelLowering.cpp
   MipsFrameLowering.cpp
   MipsLegalizerInfo.cpp
+  MipsLoongson2FBTBFix.cpp
   MipsBranchExpansion.cpp
   MipsMCInstLower.cpp
   MipsMachineFunction.cpp
@@ -50,6 +51,7 @@ add_llvm_target(MipsCodeGen
   MipsPreLegalizerCombiner.cpp
   MipsRegisterBankInfo.cpp
   MipsRegisterInfo.cpp
+  MipsReturnProtectorLowering.cpp
   MipsSEFrameLowering.cpp
   MipsSEInstrInfo.cpp
   MipsSEISelDAGToDAG.cpp
