Fix clang -Wcovered-switch-default after stack-id change by D60137

llvm-svn: 363543
diff --git a/llvm/lib/Target/AMDGPU/SIFrameLowering.cpp b/llvm/lib/Target/AMDGPU/SIFrameLowering.cpp
index f6dadb7..ca2fcfa 100644
--- a/llvm/lib/Target/AMDGPU/SIFrameLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/SIFrameLowering.cpp
@@ -545,14 +545,13 @@
 }
 
 bool SIFrameLowering::isSupportedStackID(TargetStackID::Value ID) const {
-    switch (ID) {
-    default:
-      return false;
-    case TargetStackID::Default:
-    case TargetStackID::NoAlloc:
-    case TargetStackID::SGPRSpill:
-      return true;
-    }
+  switch (ID) {
+  case TargetStackID::Default:
+  case TargetStackID::NoAlloc:
+  case TargetStackID::SGPRSpill:
+    return true;
+  }
+  llvm_unreachable("Invalid TargetStackID::Value");
 }
 
 void SIFrameLowering::emitPrologue(MachineFunction &MF,