Generate error on unexpected intrisics.

src/IceTargetLoweringARM32.cpp

@@ -4972,6 +4972,9 @@ void TargetARM32::lowerIntrinsicCall(const InstIntrinsicCall *Instr) {
   Type DestTy = (Dest != nullptr) ? Dest->getType() : IceType_void;
   Intrinsics::IntrinsicID ID = Instr->getIntrinsicInfo().ID;
   switch (ID) {
+  default:
+    llvm::report_fatal_error("Unexpected intrinsic");
+    return;
   case Intrinsics::AtomicFence:
   case Intrinsics::AtomicFenceAll:
     assert(Dest == nullptr);

src/IceTargetLoweringMIPS32.cpp

@@ -4037,6 +4037,9 @@ void TargetMIPS32::lowerIntrinsicCall(const InstIntrinsicCall *Instr) {
   Variable *Dest = Instr->getDest();
   Type DestTy = (Dest == nullptr) ? IceType_void : Dest->getType();
   switch (Instr->getIntrinsicInfo().ID) {
+  default:
+    llvm::report_fatal_error("Unexpected intrinsic");
+    return;
   case Intrinsics::AtomicCmpxchg: {
     UnimplementedLoweringError(this, Instr);
     return;

src/IceTargetLoweringX86BaseImpl.h

@@ -4004,6 +4004,9 @@ template <typename TraitsType>
 void TargetX86Base<TraitsType>::lowerIntrinsicCall(
     const InstIntrinsicCall *Instr) {
   switch (Intrinsics::IntrinsicID ID = Instr->getIntrinsicInfo().ID) {
+  default:
+    llvm::report_fatal_error("Unexpected intrinsic");
+    return;
   case Intrinsics::AtomicCmpxchg: {
     if (!Intrinsics::isMemoryOrderValid(
             ID, getConstantMemoryOrder(Instr->getArg(3)),