diff --git a/llvm/lib/Target/Mips/MipsFastISel.cpp b/llvm/lib/Target/Mips/MipsFastISel.cpp
index 605f78d..265f6de 100644
--- a/llvm/lib/Target/Mips/MipsFastISel.cpp
+++ b/llvm/lib/Target/Mips/MipsFastISel.cpp
@@ -1394,6 +1394,13 @@
 
 bool MipsFastISel::emitIntExt(MVT SrcVT, unsigned SrcReg, MVT DestVT,
                               unsigned DestReg, bool IsZExt) {
+  // FastISel does not have plumbing to deal with extensions where the SrcVT or
+  // DestVT are odd things, so test to make sure that they are both types we can
+  // handle (i1/i8/i16/i32 for SrcVT and i8/i16/i32/i64 for DestVT), otherwise
+  // bail out to SelectionDAG.
+  if (((DestVT != MVT::i8) && (DestVT != MVT::i16) && (DestVT != MVT::i32)) ||
+      ((SrcVT != MVT::i1) && (SrcVT != MVT::i8) && (SrcVT != MVT::i16)))
+    return false;
   if (IsZExt)
     return emitIntZExt(SrcVT, SrcReg, DestVT, DestReg);
   return emitIntSExt(SrcVT, SrcReg, DestVT, DestReg);