An email discussion of optimizing EH led me to wonder why we weren't doing
this already. Not that this change affects EH at all.
Tested x86_64-pc-linux-gnu. Does this seem worthwhile?
libstdc++-v3/ChangeLog:
* libsupc++/dyncast.cc (__dynamic_cast): Avoid virtual function
call in simple success case.
---
libstdc++-v3/libsupc++/dyncast.cc | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/libstdc++-v3/libsupc++/dyncast.cc
b/libstdc++-v3/libsupc++/dyncast.cc
index 853c911a4cf..616e4c05766 100644
--- a/libstdc++-v3/libsupc++/dyncast.cc
+++ b/libstdc++-v3/libsupc++/dyncast.cc
@@ -71,6 +71,12 @@ __dynamic_cast (const void *src_ptr, // object started
from
if (whole_prefix->whole_type != whole_type)
return NULL;
+ // Avoid virtual function call in the simple success case.
+ if (src2dst >= 0
+ && src2dst == -prefix->whole_object
+ && *whole_type == *dst_type)
+ return const_cast <void *> (whole_ptr);
+
whole_type->__do_dyncast (src2dst, __class_type_info::__contained_public,
dst_type, whole_ptr, src_type, src_ptr, result);
if (!result.dst_ptr)
base-commit: 0a2fba3697411c07a8330abfe7460ce62bce5e7f
--
2.31.1
