Index: lib/Target/AMDGPU/AMDGPUInstrInfo.cpp
===================================================================
--- lib/Target/AMDGPU/AMDGPUInstrInfo.cpp
+++ lib/Target/AMDGPU/AMDGPUInstrInfo.cpp
@@ -144,6 +144,9 @@
 
 static SIEncodingFamily subtargetEncodingFamily(const AMDGPUSubtarget &ST) {
   switch (ST.getGeneration()) {
+  default:
+    llvm_unreachable("invalid generation");
+  // fall through
   case AMDGPUSubtarget::SOUTHERN_ISLANDS:
   case AMDGPUSubtarget::SEA_ISLANDS:
     return SIEncodingFamily::SI;