Index: llvm/lib/Target/AVR/MCTargetDesc/AVRMCCodeEmitter.cpp
===================================================================
--- llvm/lib/Target/AVR/MCTargetDesc/AVRMCCodeEmitter.cpp
+++ llvm/lib/Target/AVR/MCTargetDesc/AVRMCCodeEmitter.cpp
@@ -146,7 +146,8 @@
 
   switch (RegOp.getReg()) {
   default:
-    llvm_unreachable("Expected either Y or Z register");
+    Ctx.reportError(MI.getLoc(), "expected either Y or Z register");
+    return 0;
   case AVR::R31R30:
     RegBit = 0;
     break; // Z register
Index: llvm/test/CodeGen/AVR/inline-asm/inline-asm-invalid.ll
===================================================================
--- llvm/test/CodeGen/AVR/inline-asm/inline-asm-invalid.ll
+++ llvm/test/CodeGen/AVR/inline-asm/inline-asm-invalid.ll
@@ -1,4 +1,5 @@
-; RUN: not llc < %s -march=avr -no-integrated-as 2>&1 | FileCheck %s
+; RUN: not llc < %s -march=avr -mcpu=avr6 -filetype=obj -no-integrated-as 2>&1 \
+; RUN:     | FileCheck %s
 
 define void @foo(i16 %a) {
   ; CHECK: error: invalid operand in inline asm: 'jl ${0:l}'
@@ -13,3 +14,9 @@
   call i16 asm sideeffect ";; ${0:C}", "=d"()
   ret void
 }
+
+define void @foo2() {
+  ; CHECK: error: expected either Y or Z register
+  call void asm sideeffect "ldd r24, X+2", ""()
+  ret void
+}