[Clang] Add __builtin_stack_address

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

@@ -3692,6 +3692,10 @@ bool SelectionDAGLegalize::ExpandNode(SDNode *Node) {
     } else {
       Results.push_back(DAG.getUNDEF(Node->getValueType(0)));
       Results.push_back(Node->getOperand(0));
+
+      DAG.getContext()->diagnose(DiagnosticInfoLegalizationFailure(
+          Node->getOperationName(&DAG) + " is not supported on this target.",
+          DAG.getMachineFunction().getFunction(), dl.getDebugLoc()));
     }
     break;
   case ISD::STACKRESTORE:

llvm/test/CodeGen/NVPTX/stackaddress.ll

@@ -0,0 +1,9 @@
+; RUN: not llc < %s -mtriple nvptx 2>&1 | FileCheck %s
+
+declare ptr @llvm.stackaddress.p0()
+
+define ptr @test() {
+; CHECK: STACKADDRESS is not supported on this target.
+  %sp = call ptr @llvm.stackaddress.p0()
+  ret ptr %sp
+}