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| author | Jonathan Wakely <jwakely@redhat.com> | 2024-05-30 20:36:42 +0100 |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2024-06-03 16:49:46 +0100 |
| commit | 482f97e79fc29ea2d61f1425b32564a668b51e1c (patch) | |
| tree | 5977c1087dff551b41300b19261d7ab120efa7b4 | |
| parent | 6ab5145825ca7e96fcbe3aa505d42e4ae8f81009 (diff) | |
| download | gcc-482f97e79fc29ea2d61f1425b32564a668b51e1c.zip gcc-482f97e79fc29ea2d61f1425b32564a668b51e1c.tar.gz gcc-482f97e79fc29ea2d61f1425b32564a668b51e1c.tar.bz2 | |
libstdc++: Optimize std::basic_string_view::starts_with
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.
| -rw-r--r-- | libstdc++-v3/include/std/string_view | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view index a7c5a12..740aa93 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 |