[CIR] Unblock destructor alias handling (#150497)

This change removes a stale errorNYI message to allow destructor alias
handling. The error message was an artifact of the order in which
various parts of the implementation were upstreamed. Now that all the
parts are in place, all this needed was to remove the diagnostic and add
a test.

Author: andykaylor

clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp

@@ -113,8 +113,6 @@ static StructorCIRGen getCIRGenToUse(CIRGenModule &cgm,
 
   GlobalDecl aliasDecl;
   if (const auto *dd = dyn_cast<CXXDestructorDecl>(md)) {
-    // The assignment is correct here, but other support for this is NYI.
-    cgm.errorNYI(md->getSourceRange(), "getCIRGenToUse: dtor");
     aliasDecl = GlobalDecl(dd, Dtor_Complete);
   } else {
     const auto *cd = cast<CXXConstructorDecl>(md);

clang/test/CIR/CodeGen/dtor-alias.cpp

@@ -0,0 +1,75 @@
+// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-linux-gnu -mconstructor-aliases -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck --input-file=%t.cir %s
+// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-linux-gnu -mconstructor-aliases -fclangir -emit-llvm %s -o %t-cir.ll
+// RUN: FileCheck --check-prefix=LLVM --input-file=%t-cir.ll %s
+// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-linux-gnu -mconstructor-aliases -emit-llvm %s -o %t.ll
+// RUN: FileCheck --check-prefix=OGCG --input-file=%t.ll %s
+
+struct B {
+  ~B();
+};
+B::~B() {
+}
+
+// OGCG: @_ZN1BD1Ev = unnamed_addr alias void (ptr), ptr @_ZN1BD2Ev
+
+// CHECK: cir.func{{.*}} @_ZN1BD2Ev(%arg0: !cir.ptr<!rec_B>
+// CHECK:   %[[THIS_ADDR:.*]] = cir.alloca !cir.ptr<!rec_B>, !cir.ptr<!cir.ptr<!rec_B>>, ["this", init]
+// CHECK:   cir.store %arg0, %[[THIS_ADDR]]
+// CHECK:   %[[THIS:.*]] = cir.load %[[THIS_ADDR]] : !cir.ptr<!cir.ptr<!rec_B>>, !cir.ptr<!rec_B>
+
+// CHECK: cir.func{{.*}} private dso_local @_ZN1BD1Ev(!cir.ptr<!rec_B>) alias(@_ZN1BD2Ev)
+
+// LLVM: define{{.*}} @_ZN1BD2Ev(ptr %[[THIS_ARG:.*]])
+// LLVM:   %[[THIS_ADDR:.*]] = alloca ptr
+// LLVM:   store ptr %[[THIS_ARG]], ptr %[[THIS_ADDR]]
+// LLVM:   %[[THIS:.*]] = load ptr, ptr %[[THIS_ADDR]]
+
+// This should be an alias, like the similar OGCG alias above, but that's not
+// implemented yet.
+// LLVM: declare dso_local void @_ZN1BD1Ev(ptr)
+
+// OGCG: define{{.*}} @_ZN1BD2Ev(ptr{{.*}} %[[THIS_ARG:.*]])
+// OGCG:   %[[THIS_ADDR:.*]] = alloca ptr
+// OGCG:   store ptr %[[THIS_ARG]], ptr %[[THIS_ADDR]]
+// OGCG:   %[[THIS:.*]] = load ptr, ptr %[[THIS_ADDR]]
+
+// The destructor in this case is handled by RAUW rather than aliasing.
+struct Struk {
+  ~Struk() {}
+};
+
+void baz() {
+  Struk s;
+}
+
+// CHECK:   cir.func{{.*}} @_ZN5StrukD2Ev(%arg0: !cir.ptr<!rec_Struk>
+// CHECK:     %[[THIS_ADDR:.*]] = cir.alloca !cir.ptr<!rec_Struk>, !cir.ptr<!cir.ptr<!rec_Struk>>, ["this", init]
+// CHECK:     cir.store %arg0, %[[THIS_ADDR]] : !cir.ptr<!rec_Struk>, !cir.ptr<!cir.ptr<!rec_Struk>>
+// CHECK:     %[[THIS:.*]] = cir.load %[[THIS_ADDR]] : !cir.ptr<!cir.ptr<!rec_Struk>>, !cir.ptr<!rec_Struk>
+// CHECK:     cir.return
+
+// CHECK-NOT:   cir.func{{.*}} @_ZN5StrukD1Ev
+
+// CHECK:   cir.func{{.*}} @_Z3bazv()
+// CHECK:     %[[S_ADDR:.*]] = cir.alloca !rec_Struk, !cir.ptr<!rec_Struk>, ["s"]
+// CHECK:     cir.call @_ZN5StrukD2Ev(%[[S_ADDR]]) nothrow : (!cir.ptr<!rec_Struk>) -> ()
+
+// LLVM: define linkonce_odr void @_ZN5StrukD2Ev(ptr %[[THIS_ARG]])
+// LLVM:   %[[THIS_ADDR:.*]] = alloca ptr
+// LLVM:   store ptr %[[THIS_ARG]], ptr %[[THIS_ADDR]]
+// LLVM:   %[[THIS:.*]] = load ptr, ptr %[[THIS_ADDR]]
+
+// LLVM: define{{.*}} void @_Z3bazv()
+// LLVM:   %[[S_ADDR:.*]] = alloca %struct.Struk
+// LLVM:   call void @_ZN5StrukD2Ev(ptr{{.*}} %[[S_ADDR]])
+
+// This function gets emitted before the destructor in OGCG.
+// OGCG: define{{.*}} void @_Z3bazv()
+// OGCG:   %[[S_ADDR:.*]] = alloca %struct.Struk
+// OGCG:   call void @_ZN5StrukD2Ev(ptr{{.*}} %[[S_ADDR]])
+
+// OGCG: define linkonce_odr void @_ZN5StrukD2Ev(ptr{{.*}} %[[THIS_ARG]])
+// OGCG:   %[[THIS_ADDR:.*]] = alloca ptr
+// OGCG:   store ptr %[[THIS_ARG]], ptr %[[THIS_ADDR]]
+// OGCG:   %[[THIS:.*]] = load ptr, ptr %[[THIS_ADDR]]