* [committed] libstdc++: Extend std::equal memcmp optimization to std::byte [PR101485]
@ 2024-06-28 19:24 Jonathan Wakely
0 siblings, 0 replies; only message in thread
From: Jonathan Wakely @ 2024-06-28 19:24 UTC (permalink / raw)
To: libstdc++, gcc-patches
Tested x86_64-linux. Pushed to trunk.
-- >8 --
We optimize std::equal to memcmp for integers and pointers, which means
that std::byte comparisons generate bigger code than char comparisons.
We can't use memcmp for arbitrary enum types, because they could have an
overloaded operator== that has custom semantics, but we know that
std::byte doesn't do that.
libstdc++-v3/ChangeLog:
PR libstdc++/101485
* include/bits/stl_algobase.h (__equal_aux1): Check for
std::byte as well.
* testsuite/25_algorithms/equal/101485.cc: New test.
---
libstdc++-v3/include/bits/stl_algobase.h | 6 +++++-
libstdc++-v3/testsuite/25_algorithms/equal/101485.cc | 11 +++++++++++
2 files changed, 16 insertions(+), 1 deletion(-)
create mode 100644 libstdc++-v3/testsuite/25_algorithms/equal/101485.cc
diff --git a/libstdc++-v3/include/bits/stl_algobase.h b/libstdc++-v3/include/bits/stl_algobase.h
index 57ff2f7cb08..dec1e4c79d8 100644
--- a/libstdc++-v3/include/bits/stl_algobase.h
+++ b/libstdc++-v3/include/bits/stl_algobase.h
@@ -1257,7 +1257,11 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
typedef typename iterator_traits<_II1>::value_type _ValueType1;
const bool __simple = ((__is_integer<_ValueType1>::__value
#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_pointer)
- || __is_pointer(_ValueType1)
+ || __is_pointer(_ValueType1)
+#endif
+#if __glibcxx_byte && __glibcxx_type_trait_variable_templates
+ // bits/cpp_type_traits.h declares std::byte
+ || is_same_v<_ValueType1, byte>
#endif
) && __memcmpable<_II1, _II2>::__value);
return std::__equal<__simple>::equal(__first1, __last1, __first2);
diff --git a/libstdc++-v3/testsuite/25_algorithms/equal/101485.cc b/libstdc++-v3/testsuite/25_algorithms/equal/101485.cc
new file mode 100644
index 00000000000..1fbb40acae9
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/equal/101485.cc
@@ -0,0 +1,11 @@
+// { dg-options "-O0" }
+// { dg-do compile { target c++17 } }
+// { dg-final { scan-assembler "memcmp" } }
+
+#include <algorithm>
+#include <cstddef>
+
+bool eq(std::byte const* p, std::byte const* q, unsigned n)
+{
+ return std::equal(p, p + n, q);
+}
--
2.45.2
^ permalink raw reply [flat|nested] only message in thread
only message in thread, other threads:[~2024-06-28 19:25 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2024-06-28 19:24 [committed] libstdc++: Extend std::equal memcmp optimization to std::byte [PR101485] Jonathan Wakely
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).