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[libc++] Instantiate hash function externally (#127040)
This has multiple benefits: - There is a single instance of our hash function, reducing object file size - The hash implementation isn't instantiated in every TU anymore, reducing compile times - Behind an ABI configuration macro it would be possible to salt the hash
1 parent ac09b78 commit 17d0569

14 files changed

+54
-5
lines changed

‎libcxx/include/__configuration/availability.h

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@@ -78,6 +78,9 @@
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// in all versions of the library are available.
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#if !_LIBCPP_HAS_VENDOR_AVAILABILITY_ANNOTATIONS
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81+
# define _LIBCPP_INTRODUCED_IN_LLVM_21 1
82+
# define _LIBCPP_INTRODUCED_IN_LLVM_21_ATTRIBUTE /* nothing */
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# define _LIBCPP_INTRODUCED_IN_LLVM_20 1
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# define _LIBCPP_INTRODUCED_IN_LLVM_20_ATTRIBUTE /* nothing */
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@@ -114,6 +117,11 @@
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// clang-format off
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// LLVM 21
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// TODO: Fill this in
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# define _LIBCPP_INTRODUCED_IN_LLVM_21 0
123+
# define _LIBCPP_INTRODUCED_IN_LLVM_21_ATTRIBUTE __attribute__((unavailable))
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// LLVM 20
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// TODO: Fill this in
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# define _LIBCPP_INTRODUCED_IN_LLVM_20 0
@@ -359,6 +367,11 @@
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#define _LIBCPP_AVAILABILITY_HAS_FROM_CHARS_FLOATING_POINT _LIBCPP_INTRODUCED_IN_LLVM_20
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#define _LIBCPP_AVAILABILITY_FROM_CHARS_FLOATING_POINT _LIBCPP_INTRODUCED_IN_LLVM_20_ATTRIBUTE
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// This controls whether `std::__hash_memory` is available in the dylib, which
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// is used for some `std::hash` specializations.
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#define _LIBCPP_AVAILABILITY_HAS_HASH_MEMORY _LIBCPP_INTRODUCED_IN_LLVM_21
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// No attribute, since we've had hash in the headers before
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// Define availability attributes that depend on _LIBCPP_HAS_EXCEPTIONS.
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// Those are defined in terms of the availability attributes above, and
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// should not be vendor-specific.

‎libcxx/include/__functional/hash.h

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@@ -238,6 +238,14 @@ struct __murmur2_or_cityhash<_Size, 64> {
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}
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};
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#if _LIBCPP_AVAILABILITY_HAS_HASH_MEMORY
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[[__gnu__::__pure__]] _LIBCPP_EXPORTED_FROM_ABI size_t __hash_memory(_LIBCPP_NOESCAPE const void*, size_t) _NOEXCEPT;
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#else
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_LIBCPP_HIDE_FROM_ABI inline size_t __hash_memory(const void* __ptr, size_t __size) _NOEXCEPT {
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return __murmur2_or_cityhash<size_t>()(__ptr, __size);
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}
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#endif
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template <class _Tp, size_t = sizeof(_Tp) / sizeof(size_t)>
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struct __scalar_hash;
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@@ -277,7 +285,7 @@ struct __scalar_hash<_Tp, 2> : public __unary_function<_Tp, size_t> {
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} __s;
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} __u;
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__u.__t = __v;
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return __murmur2_or_cityhash<size_t>()(std::addressof(__u), sizeof(__u));
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return std::__hash_memory(std::addressof(__u), sizeof(__u));
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}
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};
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@@ -293,7 +301,7 @@ struct __scalar_hash<_Tp, 3> : public __unary_function<_Tp, size_t> {
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} __s;
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} __u;
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__u.__t = __v;
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return __murmur2_or_cityhash<size_t>()(std::addressof(__u), sizeof(__u));
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return std::__hash_memory(std::addressof(__u), sizeof(__u));
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}
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};
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@@ -310,7 +318,7 @@ struct __scalar_hash<_Tp, 4> : public __unary_function<_Tp, size_t> {
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} __s;
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} __u;
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__u.__t = __v;
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return __murmur2_or_cityhash<size_t>()(std::addressof(__u), sizeof(__u));
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return std::__hash_memory(std::addressof(__u), sizeof(__u));
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}
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};
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@@ -333,7 +341,7 @@ struct _LIBCPP_TEMPLATE_VIS hash<_Tp*> : public __unary_function<_Tp*, size_t> {
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size_t __a;
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} __u;
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__u.__t = __v;
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return __murmur2_or_cityhash<size_t>()(std::addressof(__u), sizeof(__u));
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return std::__hash_memory(std::addressof(__u), sizeof(__u));
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}
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};
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‎libcxx/include/__string/char_traits.h

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Original file line numberDiff line numberDiff line change
@@ -534,7 +534,7 @@ __str_find_last_not_of(const _CharT* __p, _SizeT __sz, _CharT __c, _SizeT __pos)
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template <class _Ptr>
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inline _LIBCPP_HIDE_FROM_ABI size_t __do_string_hash(_Ptr __p, _Ptr __e) {
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typedef typename iterator_traits<_Ptr>::value_type value_type;
537-
return __murmur2_or_cityhash<size_t>()(__p, (__e - __p) * sizeof(value_type));
537+
return std::__hash_memory(__p, (__e - __p) * sizeof(value_type));
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}
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_LIBCPP_END_NAMESPACE_STD

‎libcxx/lib/abi/CHANGELOG.TXT

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@@ -12,6 +12,21 @@ To generate a summary, re-generate the new ABI list using the
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New entries should be added directly below the "Version" header.
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------------
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Version 21.0
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------------
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* [libc++] Instantiate hash function externally
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This has multiple benefits:
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- There is a single instance of our hash function, reducing object file size
23+
- The hash implementation isn't instantiated in every TU anymore, reducing compile times
24+
- Behind an ABI configuration macro, it would be possible to salt the hash
25+
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All platforms
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-------------
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Symbol added: _ZNSt3__113__hash_memoryEPKvm
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------------
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Version 20.0
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------------

‎libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist

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@@ -1305,6 +1305,7 @@
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{'is_defined': True, 'name': '__ZNSt3__113shared_futureIvED1Ev', 'type': 'FUNC'}
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{'is_defined': True, 'name': '__ZNSt3__113shared_futureIvED2Ev', 'type': 'FUNC'}
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{'is_defined': True, 'name': '__ZNSt3__113shared_futureIvEaSERKS1_', 'type': 'FUNC'}
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{'is_defined': True, 'name': '__ZNSt3__113__hash_memoryEPKvm', 'type': 'FUNC'}
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{'is_defined': True, 'name': '__ZNSt3__114__num_get_base10__get_baseERNS_8ios_baseE', 'type': 'FUNC'}
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{'is_defined': True, 'name': '__ZNSt3__114__num_get_base5__srcE', 'size': 0, 'type': 'OBJECT'}
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{'is_defined': True, 'name': '__ZNSt3__114__num_put_base12__format_intEPcPKcbj', 'type': 'FUNC'}

‎libcxx/lib/abi/i686-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist

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@@ -941,6 +941,7 @@
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{'is_defined': True, 'name': '_ZNSt6__ndk113shared_futureIvED1Ev', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt6__ndk113shared_futureIvED2Ev', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt6__ndk113shared_futureIvEaSERKS1_', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt6__ndk113__hash_memoryEPKvj', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt6__ndk114__num_get_base10__get_baseERNS_8ios_baseE', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt6__ndk114__num_get_base5__srcE', 'size': 33, 'type': 'OBJECT'}
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{'is_defined': True, 'name': '_ZNSt6__ndk114__num_put_base12__format_intEPcPKcbj', 'type': 'FUNC'}

‎libcxx/lib/abi/powerpc-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist

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@@ -418,6 +418,7 @@
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{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__113shared_futureIvED1Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
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{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__113shared_futureIvED2Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
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{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__113shared_futureIvEaSERKS1_', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
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{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__113__hash_memoryEPKvm', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
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{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__114__num_get_base10__get_baseERNS_8ios_baseE', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
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{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__114__num_get_base5__srcE', 'storage_mapping_class': 'RO', 'type': 'OBJECT'}
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{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__114__num_put_base12__format_intEPcPKcbj', 'storage_mapping_class': 'DS', 'type': 'FUNC'}

‎libcxx/lib/abi/powerpc64-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist

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@@ -418,6 +418,7 @@
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{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__113shared_futureIvED1Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
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{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__113shared_futureIvED2Ev', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
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{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__113shared_futureIvEaSERKS1_', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
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{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__113__hash_memoryEPKvm', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
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{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__114__num_get_base10__get_baseERNS_8ios_baseE', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
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{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__114__num_get_base5__srcE', 'storage_mapping_class': 'RO', 'type': 'OBJECT'}
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{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__114__num_put_base12__format_intEPcPKcbj', 'storage_mapping_class': 'DS', 'type': 'FUNC'}

‎libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist

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@@ -1305,6 +1305,7 @@
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{'is_defined': True, 'name': '__ZNSt3__113shared_futureIvED1Ev', 'type': 'FUNC'}
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{'is_defined': True, 'name': '__ZNSt3__113shared_futureIvED2Ev', 'type': 'FUNC'}
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{'is_defined': True, 'name': '__ZNSt3__113shared_futureIvEaSERKS1_', 'type': 'FUNC'}
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{'is_defined': True, 'name': '__ZNSt3__113__hash_memoryEPKvm', 'type': 'FUNC'}
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{'is_defined': True, 'name': '__ZNSt3__114__num_get_base10__get_baseERNS_8ios_baseE', 'type': 'FUNC'}
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{'is_defined': True, 'name': '__ZNSt3__114__num_get_base5__srcE', 'size': 0, 'type': 'OBJECT'}
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{'is_defined': True, 'name': '__ZNSt3__114__num_put_base12__format_intEPcPKcbj', 'type': 'FUNC'}

‎libcxx/lib/abi/x86_64-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist

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@@ -941,6 +941,7 @@
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{'is_defined': True, 'name': '_ZNSt6__ndk113shared_futureIvED1Ev', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt6__ndk113shared_futureIvED2Ev', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt6__ndk113shared_futureIvEaSERKS1_', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt6__ndk113__hash_memoryEPKvm', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt6__ndk114__num_get_base10__get_baseERNS_8ios_baseE', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt6__ndk114__num_get_base5__srcE', 'size': 33, 'type': 'OBJECT'}
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{'is_defined': True, 'name': '_ZNSt6__ndk114__num_put_base12__format_intEPcPKcbj', 'type': 'FUNC'}

‎libcxx/lib/abi/x86_64-unknown-freebsd.libcxxabi.v1.stable.exceptions.nonew.abilist

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@@ -956,6 +956,7 @@
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{'is_defined': True, 'name': '_ZNSt3__113shared_futureIvED1Ev', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__113shared_futureIvED2Ev', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__113shared_futureIvEaSERKS1_', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__113__hash_memoryEPKvm', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__114__num_get_base10__get_baseERNS_8ios_baseE', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__114__num_get_base5__srcE', 'size': 33, 'type': 'OBJECT'}
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{'is_defined': True, 'name': '_ZNSt3__114__num_put_base12__format_intEPcPKcbj', 'type': 'FUNC'}

‎libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.nonew.abilist

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@@ -954,6 +954,7 @@
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{'is_defined': True, 'name': '_ZNSt3__113shared_futureIvED1Ev', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__113shared_futureIvED2Ev', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__113shared_futureIvEaSERKS1_', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__113__hash_memoryEPKvm', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__114__num_get_base10__get_baseERNS_8ios_baseE', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__114__num_get_base5__srcE', 'size': 33, 'type': 'OBJECT'}
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{'is_defined': True, 'name': '_ZNSt3__114__num_put_base12__format_intEPcPKcbj', 'type': 'FUNC'}

‎libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.noexceptions.nonew.abilist

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@@ -924,6 +924,7 @@
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{'is_defined': True, 'name': '_ZNSt3__113random_deviceclEv', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__113shared_futureIvED1Ev', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__113shared_futureIvED2Ev', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__113__hash_memoryEPKvm', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__113shared_futureIvEaSERKS1_', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__114__num_get_base10__get_baseERNS_8ios_baseE', 'type': 'FUNC'}
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{'is_defined': True, 'name': '_ZNSt3__114__num_get_base5__srcE', 'size': 33, 'type': 'OBJECT'}

‎libcxx/src/functional.cpp

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@@ -16,4 +16,8 @@ bad_function_call::~bad_function_call() noexcept {}
1616
const char* bad_function_call::what() const noexcept { return "std::bad_function_call"; }
1717
#endif
1818

19+
size_t __hash_memory(_LIBCPP_NOESCAPE const void* ptr, size_t size) noexcept {
20+
return __murmur2_or_cityhash<size_t>()(ptr, size);
21+
}
22+
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_LIBCPP_END_NAMESPACE_STD

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