We get smaller code at all optimization levels by not creating a
temporary object, just comparing lengths first and then using
traits_type::compare. This does less work than calling substr then
operator==.
libstdc++-v3/ChangeLog:
* include/std/string_view (starts_with(basic_string_view)):
Compare lengths first and then call traits_type::compare
directly.
---
libstdc++-v3/include/std/string_view | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/libstdc++-v3/include/std/string_view
b/libstdc++-v3/include/std/string_view
index a7c5a126461..740aa9344f0 100644
--- a/libstdc++-v3/include/std/string_view
+++ b/libstdc++-v3/include/std/string_view
@@ -385,7 +385,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
[[nodiscard]]
constexpr bool
starts_with(basic_string_view __x) const noexcept
- { return this->substr(0, __x.size()) == __x; }
+ {
+ return _M_len >= __x._M_len
+ && traits_type::compare(_M_str, __x._M_str, __x._M_len) == 0;
+ }
[[nodiscard]]
constexpr bool
--
2.45.1
