[libc++] Avoid constructing additional objects when using map::at #157866
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@llvm/pr-subscribers-libcxx Author: Nikolas Klauser (philnik777) ChangesThis patch adds additional overloads to Full diff: https://github.com/llvm/llvm-project/pull/157866.diff 8 Files Affected:
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index db918a16e9a61..fed0141daee81 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -862,6 +862,7 @@ set(files
__type_traits/is_specialization.h
__type_traits/is_standard_layout.h
__type_traits/is_swappable.h
+ __type_traits/is_transparently_comparable.h
__type_traits/is_trivial.h
__type_traits/is_trivially_assignable.h
__type_traits/is_trivially_constructible.h
@@ -880,6 +881,7 @@ set(files
__type_traits/make_32_64_or_128_bit.h
__type_traits/make_const_lvalue_ref.h
__type_traits/make_signed.h
+ __type_traits/make_transparent.h
__type_traits/make_unsigned.h
__type_traits/maybe_const.h
__type_traits/nat.h
diff --git a/libcxx/include/__functional/operations.h b/libcxx/include/__functional/operations.h
index 7b0ea11db5844..cee10aea14236 100644
--- a/libcxx/include/__functional/operations.h
+++ b/libcxx/include/__functional/operations.h
@@ -16,6 +16,7 @@
#include <__fwd/functional.h>
#include <__type_traits/desugars_to.h>
#include <__type_traits/is_integral.h>
+#include <__type_traits/make_transparent.h>
#include <__utility/forward.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -377,6 +378,11 @@ struct less<void> {
typedef void is_transparent;
};
+template <class _Tp>
+struct __make_transparent<less<_Tp> > {
+ using type _LIBCPP_NODEBUG = less<>;
+};
+
template <class _Tp, class _Up>
inline const bool __desugars_to_v<__less_tag, less<>, _Tp, _Up> = true;
@@ -466,6 +472,11 @@ struct greater<void> {
template <class _Tp, class _Up>
inline const bool __desugars_to_v<__greater_tag, greater<>, _Tp, _Up> = true;
+
+template <class _Tp>
+struct __make_transparent<greater<_Tp>> {
+ using type _LIBCPP_NODEBUG = greater<>;
+};
#endif
// Logical operations
diff --git a/libcxx/include/__tree b/libcxx/include/__tree
index 61c910c52c536..ef960d481cb7b 100644
--- a/libcxx/include/__tree
+++ b/libcxx/include/__tree
@@ -34,6 +34,7 @@
#include <__type_traits/is_same.h>
#include <__type_traits/is_specialization.h>
#include <__type_traits/is_swappable.h>
+#include <__type_traits/make_transparent.h>
#include <__type_traits/remove_const.h>
#include <__utility/forward.h>
#include <__utility/lazy_synth_three_way_comparator.h>
@@ -1749,7 +1750,8 @@ __tree<_Tp, _Compare, _Allocator>::__find_equal(const _Key& __v) {
}
__node_base_pointer* __node_ptr = __root_ptr();
- auto __comp = __lazy_synth_three_way_comparator<_Compare, _Key, value_type>(value_comp());
+ auto&& __transparent = std::__as_transparent(value_comp());
+ auto __comp = __lazy_synth_three_way_comparator<__make_transparent_t<_Compare>, _Key, value_type>(__transparent);
while (true) {
auto __comp_res = __comp(__v, __nd->__get_value());
diff --git a/libcxx/include/__type_traits/is_transparently_comparable.h b/libcxx/include/__type_traits/is_transparently_comparable.h
new file mode 100644
index 0000000000000..9e27c485360fd
--- /dev/null
+++ b/libcxx/include/__type_traits/is_transparently_comparable.h
@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___TYPE_TRAITS_IS_TRANSPARENTLY_COMPARABLE_H
+#define _LIBCPP___TYPE_TRAITS_IS_TRANSPARENTLY_COMPARABLE_H
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Key, class _Arg>
+inline const bool __is_transparently_comparable_v = __is_same(_Key, _Arg);
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___TYPE_TRAITS_IS_TRANSPARENTLY_COMPARABLE_H
diff --git a/libcxx/include/__type_traits/make_transparent.h b/libcxx/include/__type_traits/make_transparent.h
new file mode 100644
index 0000000000000..9aa247d284707
--- /dev/null
+++ b/libcxx/include/__type_traits/make_transparent.h
@@ -0,0 +1,42 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___TYPE_TRAITS_MAKE_TRANSPARENT_H
+#define _LIBCPP___TYPE_TRAITS_MAKE_TRANSPARENT_H
+
+#include <__config>
+#include <__type_traits/enable_if.h>
+#include <__type_traits/is_same.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Comparator>
+struct __make_transparent {
+ using type _LIBCPP_NODEBUG = _Comparator;
+};
+
+template <class _Comparator>
+using __make_transparent_t _LIBCPP_NODEBUG = typename __make_transparent<_Comparator>::type;
+
+template <class _Comparator, __enable_if_t<is_same<_Comparator, __make_transparent_t<_Comparator> >::value, int> = 0>
+_LIBCPP_HIDE_FROM_ABI _Comparator& __as_transparent(_Comparator& __comp) {
+ return __comp;
+}
+
+template <class _Comparator, __enable_if_t<!is_same<_Comparator, __make_transparent_t<_Comparator> >::value, int> = 0>
+_LIBCPP_HIDE_FROM_ABI __make_transparent_t<_Comparator> __as_transparent(_Comparator&) {
+ return __make_transparent_t<_Comparator>();
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___TYPE_TRAITS_MAKE_TRANSPARENT_H
diff --git a/libcxx/include/map b/libcxx/include/map
index f428c781e5036..cb7a5120a950f 100644
--- a/libcxx/include/map
+++ b/libcxx/include/map
@@ -599,7 +599,11 @@ erase_if(multimap<Key, T, Compare, Allocator>& c, Predicate pred); // C++20
# include <__ranges/from_range.h>
# include <__tree>
# include <__type_traits/container_traits.h>
+# include <__type_traits/desugars_to.h>
# include <__type_traits/is_allocator.h>
+# include <__type_traits/is_convertible.h>
+# include <__type_traits/is_transparently_comparable.h>
+# include <__type_traits/make_transparent.h>
# include <__type_traits/remove_const.h>
# include <__type_traits/type_identity.h>
# include <__utility/forward.h>
@@ -703,6 +707,11 @@ public:
# endif
};
+template <class _Key, class _MapValueT, class _Compare, bool __b>
+struct __make_transparent<__map_value_compare<_Key, _MapValueT, _Compare, __b> > {
+ using type _LIBCPP_NODEBUG = __map_value_compare<_Key, _MapValueT, __make_transparent_t<_Compare> >;
+};
+
# if _LIBCPP_STD_VER >= 14
template <class _MapValueT, class _Key, class _Compare>
struct __lazy_synth_three_way_comparator<__map_value_compare<_Key, _MapValueT, _Compare>, _MapValueT, _MapValueT> {
@@ -1085,6 +1094,30 @@ public:
_LIBCPP_HIDE_FROM_ABI mapped_type& operator[](key_type&& __k);
# endif
+ template <class _Arg,
+ __enable_if_t<is_convertible<_Arg, value_type>::value &&
+ __desugars_to_v<__less_tag, key_compare, key_type, key_type> &&
+ __is_transparently_comparable_v<key_type, __remove_cvref_t<_Arg> >,
+ int> = 0>
+ _LIBCPP_HIDE_FROM_ABI inline mapped_type& at(_Arg&& __arg) {
+ auto [_, __child] = __tree_.__find_equal(__arg);
+ if (__child == nullptr)
+ std::__throw_out_of_range("map::at: key not found");
+ return static_cast<__node_pointer>(__child)->__get_value().second;
+ }
+
+ template <class _Arg,
+ __enable_if_t<is_convertible<_Arg, value_type>::value &&
+ __desugars_to_v<__less_tag, key_compare, key_type, key_type> &&
+ __is_transparently_comparable_v<key_type, __remove_cvref_t<_Arg> >,
+ int> = 0>
+ _LIBCPP_HIDE_FROM_ABI inline const mapped_type& at(_Arg&& __arg) const {
+ auto [_, __child] = __tree_.__find_equal(__arg);
+ if (__child == nullptr)
+ std::__throw_out_of_range("map::at: key not found");
+ return static_cast<__node_pointer>(__child)->__get_value().second;
+ }
+
_LIBCPP_HIDE_FROM_ABI mapped_type& at(const key_type& __k);
_LIBCPP_HIDE_FROM_ABI const mapped_type& at(const key_type& __k) const;
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index 63cf8e847751f..401551bdb8eaa 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -299,6 +299,7 @@ module std_core [system] {
header "__type_traits/is_swappable.h"
export std_core.type_traits.integral_constant
}
+ module is_transparently_comparable { header "__type_traits/is_transparently_comparable.h" }
module is_trivial {
header "__type_traits/is_trivial.h"
export std_core.type_traits.integral_constant
@@ -356,6 +357,7 @@ module std_core [system] {
module make_32_64_or_128_bit { header "__type_traits/make_32_64_or_128_bit.h" }
module make_const_lvalue_ref { header "__type_traits/make_const_lvalue_ref.h" }
module make_signed { header "__type_traits/make_signed.h" }
+ module make_transparent { header "__type_traits/make_transparent.h" }
module make_unsigned { header "__type_traits/make_unsigned.h" }
module maybe_const { header "__type_traits/maybe_const.h" }
module nat { header "__type_traits/nat.h" }
diff --git a/libcxx/include/string b/libcxx/include/string
index f13a7640760f7..9e80c8f8acc43 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -633,6 +633,7 @@ basic_string<char32_t> operator""s( const char32_t *str, size_t len );
# include <__type_traits/is_replaceable.h>
# include <__type_traits/is_same.h>
# include <__type_traits/is_standard_layout.h>
+# include <__type_traits/is_transparently_comparable.h>
# include <__type_traits/is_trivially_constructible.h>
# include <__type_traits/is_trivially_copyable.h>
# include <__type_traits/is_trivially_relocatable.h>
@@ -2536,6 +2537,16 @@ struct __default_three_way_comparator<basic_string<_CharT, _Traits, _Alloc>, bas
};
# endif
+template <class _CharT, class _Traits, class _Alloc>
+inline const bool
+ __is_transparently_comparable_v<basic_string<_CharT, _Traits, _Alloc>, basic_string_view<_CharT, _Traits> > = true;
+
+template <class _CharT, class _Traits, class _Alloc>
+inline const bool __is_transparently_comparable_v<basic_string<_CharT, _Traits, _Alloc>, const _CharT*> = true;
+
+template <class _CharT, class _Traits, class _Alloc, size_t _Np>
+inline const bool __is_transparently_comparable_v<basic_string<_CharT, _Traits, _Alloc>, _CharT[_Np]> = true;
+
# if _LIBCPP_STD_VER >= 17
template <class _InputIterator,
class _CharT = __iter_value_type<_InputIterator>,
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| template <typename _K2, | ||
| enable_if_t<__is_transparent_v<_Compare, _K2> || __is_transparently_comparable_v<_Compare, key_type, _K2>, |
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This is very confusing as-is. The only reason for passing _K2 to __is_transparent_v seems to be to make it dependent. The right way to achieve that is usually:
template <class _K2, class _DependentCompare = _Compare, enable_if_t<__is_transparent_v<_DependentCompare>>, ...>If we did that, then we could get rid of the other arguments of __is_transparent_v, and that would make this code a lot clearer IMO, since we'd easily understand that __is_transparent_v only checks the typedef.
Let's do that as a follow-up refactoring, or as a prerequisite for this patch.
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Not attached to this file: let's do the same optimization in unordered_map,in a followup.
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✅ With the latest revision this PR passed the C/C++ code formatter. |
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libcxx/include/__type_traits/is_generic_transparent_comparator.h
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Please note that this patch has broken lldb-remote-linux-ubuntu. |
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Some specializations in LLVM itself don't look correct. Opened #160684 to track this. |
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* main: (502 commits) GlobalISel: Adjust insert point when expanding G_[SU]DIVREM (llvm#160683) [LV] Add coverage for fixing-up scalar resume values (llvm#160492) AMDGPU: Convert wave_any test to use update_mc_test_checks [LV] Add partial reduction tests multiplying extend with constants. Revert "[MLIR] Implement remark emitting policies in MLIR" (llvm#160681) [NFC][InstSimplify] Refactor fminmax-folds.ll test (llvm#160504) [LoongArch] Pre-commit tests for [x]vldi instructions with special constant splats (llvm#159228) [BOLT] Fix dwarf5-dwoid-no-dwoname.s (llvm#160676) [lldb][test] Refactor and expand TestMemoryRegionDirtyPages.py (llvm#156035) [gn build] Port 833d5f0 AMDGPU: Ensure both wavesize features are not set (llvm#159234) [LoopInterchange] Bail out when finding a dependency with all `*` elements (llvm#149049) [libc++] Avoid constructing additional objects when using map::at (llvm#157866) [lldb][test] Make hex prefix optional in DWARF union types test [X86] Add missing prefixes to trunc-sat tests (llvm#160662) [AMDGPU] Fix vector legalization for bf16 valu ops (llvm#158439) [LoongArch][NFC] Pre-commit tests for `[x]vadda.{b/h/w/d}` [mlir][tosa] Relax constraint on matmul verifier requiring equal operand types (llvm#155799) [clang][Sema] Accept gnu format attributes (llvm#160255) [LoongArch][NFC] Add tests for element extraction from binary add operation (llvm#159725) ...
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/72/builds/15215 Here is the relevant piece of the build log for the reference |
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As Frederick already said, these specializations are definitely non-conforming. I guess users would be allowed to specialize That' being said, I'm fine with reverting temporarily if it takes a bit of time to resolve the issue. |
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This change is currently breaking the emscripten release builders too: I suggest we land the revert |
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…n using map::at" (#160738) Reverts llvm/llvm-project#157866 It breaks a lot of sanitizer buildbots
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I think we can reland this now. |
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…vm#157866) This patch adds additional overloads to `map::at` in case its known that the argument is transparently comparable to the key type. This avoids actually constructing the key type in some cases, potentially removing allocations. ``` -------------------------------------------------------- Benchmark old new -------------------------------------------------------- BM_map_find_string_literal 12.8 ns 2.68 ns ```
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…::at" (llvm#160738) Reverts llvm#157866 It breaks a lot of sanitizer buildbots
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This patch adds additional overloads to
map::atin case its known that the argument is transparently comparable to the key type. This avoids actually constructing the key type in some cases, potentially removing allocations.