diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index e3fe925b7f138..777e376d3c4ff 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -23647,19 +23647,18 @@ SDValue X86TargetLowering::LowerVAARG(SDValue Op, SelectionDAG &DAG) const {
   EVT ArgVT = Op.getNode()->getValueType(0);
   Type *ArgTy = ArgVT.getTypeForEVT(*DAG.getContext());
   uint32_t ArgSize = DAG.getDataLayout().getTypeAllocSize(ArgTy);
-  uint8_t ArgMode = 0;
+  uint8_t ArgMode;
 
   // Decide which area this value should be read from.
   // TODO: Implement the AMD64 ABI in its entirety. This simple
   // selection mechanism works only for the basic types.
-  if (ArgVT == MVT::f80) {
-    llvm_unreachable("va_arg for f80 not yet implemented");
-  } else if (ArgVT.isFloatingPoint() && ArgSize <= 16 /*bytes*/) {
+  assert(ArgVT != MVT::f80 && "va_arg for f80 not yet implemented");
+  if (ArgVT.isFloatingPoint() && ArgSize <= 16 /*bytes*/) {
     ArgMode = 2;  // Argument passed in XMM register. Use fp_offset.
-  } else if (ArgVT.isInteger() && ArgSize <= 32 /*bytes*/) {
-    ArgMode = 1;  // Argument passed in GPR64 register(s). Use gp_offset.
   } else {
-    llvm_unreachable("Unhandled argument type in LowerVAARG");
+    assert(ArgVT.isInteger() && ArgSize <= 32 /*bytes*/ &&
+           "Unhandled argument type in LowerVAARG");
+    ArgMode = 1;  // Argument passed in GPR64 register(s). Use gp_offset.
   }
 
   if (ArgMode == 2) {