[CIR][CIRGen] Bring getAddressOfBaseClass a bit closer to OG

Author: bcardosolopes

clang/lib/CIR/CodeGen/CIRGenClass.cpp

@@ -1572,10 +1572,12 @@ CIRGenFunction::getAddressOfBaseClass(Address Value,
 
   // If there is no virtual base, use cir.base_class_addr.  It takes care of
   // the adjustment and the null pointer check.
-  if (!VBase) {
+  if (NonVirtualOffset.isZero() && !VBase) {
     if (sanitizePerformTypeCheck()) {
       llvm_unreachable("NYI: sanitizePerformTypeCheck");
     }
+    return builder.createBaseClassAddr(getLoc(Loc), Value, BaseValueTy, 0,
+                                       /*assumeNotNull=*/true);
   }
 
   if (sanitizePerformTypeCheck()) {

clang/test/CIR/CodeGen/derived-cast.cpp

@@ -26,7 +26,7 @@ A *B::getAsA() {
 // CIR: %[[VAL_2:.*]] = cir.alloca !cir.ptr<!ty_A>, !cir.ptr<!cir.ptr<!ty_A>>, ["__retval"] {alignment = 8 : i64}
 // CIR: %[[VAL_3:.*]] = cir.load %[[VAL_1]] : !cir.ptr<!cir.ptr<!ty_B>>, !cir.ptr<!ty_B>
 // CIR: %[[VAL_4:.*]] = cir.derived_class_addr(%[[VAL_3]] : !cir.ptr<!ty_B> nonnull) [4] -> !cir.ptr<!ty_X>
-// CIR: %[[VAL_5:.*]] = cir.base_class_addr(%[[VAL_4]] : !cir.ptr<!ty_X>) [0] -> !cir.ptr<!ty_A>
+// CIR: %[[VAL_5:.*]] = cir.base_class_addr(%[[VAL_4]] : !cir.ptr<!ty_X> nonnull) [0] -> !cir.ptr<!ty_A>
 // CIR: cir.store %[[VAL_5]], %[[VAL_2]] : !cir.ptr<!ty_A>, !cir.ptr<!cir.ptr<!ty_A>>
 // CIR: %[[VAL_6:.*]] = cir.load %[[VAL_2]] : !cir.ptr<!cir.ptr<!ty_A>>, !cir.ptr<!ty_A>
 // CIR: cir.return %[[VAL_6]] : !cir.ptr<!ty_A>