[Clang][CodeGen] Handle parens

Author: dtcxzyw

clang/lib/CodeGen/CGExpr.cpp

@@ -4781,9 +4781,9 @@ LValue CodeGenFunction::EmitMemberExpr(const MemberExpr *E) {
   // Check whether the underlying base pointer is a constant null.
   // If so, we do not set inbounds flag for GEP to avoid breaking some old-style
   // offsetof idioms.
-  Expr *UnderlyingBaseExpr = BaseExpr;
+  Expr *UnderlyingBaseExpr = BaseExpr->IgnoreParens();
   while (auto *BaseMemberExpr = dyn_cast<MemberExpr>(UnderlyingBaseExpr))
-    UnderlyingBaseExpr = BaseMemberExpr->getBase();
+    UnderlyingBaseExpr = BaseMemberExpr->getBase()->IgnoreParens();
   bool IsBaseConstantNull = getContext().isSentinelNullExpr(UnderlyingBaseExpr);
   // If this is s.x, emit s as an lvalue.  If it is s->x, emit s as a scalar.
   LValue BaseLV;

clang/test/CodeGenCXX/catch-nullptr-and-nonzero-offset-in-offsetof-idiom.cpp

@@ -34,6 +34,14 @@ uintptr_t get_offset_of_y_naively_nested() {
   return ((uintptr_t)(&(((T *)nullptr)->s.y)));
 }
 
+// CHECK-LABEL: @_Z42get_offset_of_y_naively_nested_with_parensv(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    ret i64 ptrtoint (ptr getelementptr nuw ([[STRUCT_S:%.*]], ptr getelementptr nuw ([[STRUCT_T:%.*]], ptr null, i32 0, i32 1), i32 0, i32 1) to i64)
+//
+uintptr_t get_offset_of_y_naively_nested_with_parens() {
+  return ((uintptr_t)(&((((T *)nullptr)->s).y)));
+}
+
 // CHECK-LABEL: @_Z26get_offset_of_zero_storagev(
 // CHECK-NEXT:  entry:
 // CHECK-NEXT:    ret i64 ptrtoint (ptr getelementptr (i8, ptr null, i64 16) to i64)