[clang] fix FE crash during CGCoroutine Gro: NRVO var emission didn't result in an AllocaInst

Author: yuxuanchen1997

clang/lib/CodeGen/CGCoroutine.cpp

@@ -707,11 +707,15 @@ struct GetReturnObjectManager {
     Builder.CreateStore(Builder.getFalse(), GroActiveFlag);
 
     GroEmission = CGF.EmitAutoVarAlloca(*GroVarDecl);
-    auto *GroAlloca = dyn_cast_or_null<llvm::AllocaInst>(
-        GroEmission.getOriginalAllocatedAddress().getPointer());
-    assert(GroAlloca && "expected alloca to be emitted");
-    GroAlloca->setMetadata(llvm::LLVMContext::MD_coro_outside_frame,
-                           llvm::MDNode::get(CGF.CGM.getLLVMContext(), {}));
+
+    if (!GroVarDecl->isNRVOVariable()) {
+      // NRVO variables don't have allocas and won't have the same issue.
+      auto *GroAlloca = dyn_cast_or_null<llvm::AllocaInst>(
+          GroEmission.getOriginalAllocatedAddress().getPointer());
+      assert(GroAlloca && "expected alloca to be emitted");
+      GroAlloca->setMetadata(llvm::LLVMContext::MD_coro_outside_frame,
+                             llvm::MDNode::get(CGF.CGM.getLLVMContext(), {}));
+    }
 
     // Remember the top of EHStack before emitting the cleanup.
     auto old_top = CGF.EHStack.stable_begin();

clang/test/CodeGenCoroutines/coro-gro.cpp

@@ -106,4 +106,31 @@ invoker g() {
   // CHECK: call void @_ZN7invoker15invoker_promise17get_return_objectEv({{.*}} %[[AggRes]]
   co_return;
 }
-// CHECK: ![[OutFrameMetadata]] = !{}
+
+namespace gh148953 {
+
+struct Task {
+  struct promise_type {
+    Task get_return_object();
+    std::suspend_always initial_suspend() { return {}; }
+    std::suspend_always final_suspend() noexcept { return {}; }
+    void return_void() {}
+    void unhandled_exception() {}
+  };
+  Task() {}
+  // Different from `invoker`, this Task is copy constructible.
+  Task(const Task&) {};
+};
+
+// NRVO on const qualified return type should work.
+// CHECK: define{{.*}} void @_ZN8gh1489537exampleEv({{.*}} sret(%"struct.gh148953::Task") align 1 %[[NrvoRes:.+]])
+const Task example() {
+  // CHECK: %[[ResultPtr:.+]] = alloca ptr
+  // CHECK: store ptr %[[NrvoRes]], ptr %[[ResultPtr]]
+  // CHECK: coro.init:
+  // CHECK: call void @_ZN8gh1489534Task12promise_type17get_return_objectEv({{.*}} %[[NrvoRes:.+]], {{.*}})
+  co_return;
+}
+
+} // namespace gh148953
+// CHECK: ![[OutFrameMetadata]] = !{}