https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62187
Bug ID: 62187
Summary: std::string==const char* could compare sizes first
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: glisse at gcc dot gnu.org
Hello,
when I compare 2 basic_string with ==, libstdc++ only uses the optimization of
first checking that the sizes are the same (before calling compare) if
__is_char<_CharT> and the traits and allocator are the default ones. I don't
understand why, but assuming there is a good reason, I believe the optimization
should still apply when comparing std::string and const char*.
(this applies to __vstring as well)
This was noticed in PR 62156, where we also see that std::string("foo") does a
memcpy of size 3 then sets the 4th char to '\0', where a single memcpy of size
4 would make sense.
