[libc++] Refactor bitset::{any, all} (#128445)

This patch refactors the `all()` and `any()` methods in `bitset` to
eliminate redundant code while preserving the performance. Code
generation remains unchanged, as verified on Compiler
Explorer: https://godbolt.org/z/xx8hb4sPM.

Author: winner245

libcxx/include/bitset

@@ -144,6 +144,7 @@ template <size_t N> struct hash<std::bitset<N>>;
 #  include <__cstddef/ptrdiff_t.h>
 #  include <__cstddef/size_t.h>
 #  include <__functional/hash.h>
+#  include <__functional/identity.h>
 #  include <__functional/unary_function.h>
 #  include <__type_traits/is_char_like_type.h>
 #  include <climits>
@@ -226,8 +227,10 @@ protected:
     return to_ullong(integral_constant < bool, _Size< sizeof(unsigned long long) * CHAR_BIT>());
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool all() const _NOEXCEPT;
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool any() const _NOEXCEPT;
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool all() const _NOEXCEPT { return !__scan_bits(__bit_not()); }
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool any() const _NOEXCEPT {
+    return __scan_bits(std::__identity());
+  }
   _LIBCPP_HIDE_FROM_ABI size_t __hash_code() const _NOEXCEPT;
 
   template <bool _Sparse, class _CharT, class _Traits, class _Allocator>
@@ -246,6 +249,12 @@ protected:
   }
 
 private:
+  struct __bit_not {
+    template <class _Tp>
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Tp operator()(const _Tp& __x) const _NOEXCEPT {
+      return ~__x;
+    }
+  };
 #  ifdef _LIBCPP_CXX03_LANG
   void __init(unsigned long long __v, false_type) _NOEXCEPT;
   _LIBCPP_HIDE_FROM_ABI void __init(unsigned long long __v, true_type) _NOEXCEPT;
@@ -256,6 +265,23 @@ private:
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long long to_ullong(true_type) const;
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long long to_ullong(true_type, false_type) const;
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 unsigned long long to_ullong(true_type, true_type) const;
+
+  template <typename _Proj>
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool __scan_bits(_Proj __proj) const _NOEXCEPT {
+    size_t __n                  = _Size;
+    __const_storage_pointer __p = __first_;
+    // do middle whole words
+    for (; __n >= __bits_per_word; ++__p, __n -= __bits_per_word)
+      if (__proj(*__p))
+        return true;
+    // do last partial word
+    if (__n > 0) {
+      __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
+      if (__proj(*__p) & __m)
+        return true;
+    }
+    return false;
+  }
 };
 
 template <size_t _N_words, size_t _Size>
@@ -395,40 +421,6 @@ __bitset<_N_words, _Size>::to_ullong(true_type, true_type) const {
   return __r;
 }
 
-template <size_t _N_words, size_t _Size>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool __bitset<_N_words, _Size>::all() const _NOEXCEPT {
-  // do middle whole words
-  size_t __n                  = _Size;
-  __const_storage_pointer __p = __first_;
-  for (; __n >= __bits_per_word; ++__p, __n -= __bits_per_word)
-    if (~*__p)
-      return false;
-  // do last partial word
-  if (__n > 0) {
-    __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
-    if (~*__p & __m)
-      return false;
-  }
-  return true;
-}
-
-template <size_t _N_words, size_t _Size>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool __bitset<_N_words, _Size>::any() const _NOEXCEPT {
-  // do middle whole words
-  size_t __n                  = _Size;
-  __const_storage_pointer __p = __first_;
-  for (; __n >= __bits_per_word; ++__p, __n -= __bits_per_word)
-    if (*__p)
-      return true;
-  // do last partial word
-  if (__n > 0) {
-    __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
-    if (*__p & __m)
-      return true;
-  }
-  return false;
-}
-
 template <size_t _N_words, size_t _Size>
 inline size_t __bitset<_N_words, _Size>::__hash_code() const _NOEXCEPT {
   size_t __h = 0;
@@ -744,8 +736,8 @@ public:
   _LIBCPP_HIDE_FROM_ABI bool operator!=(const bitset& __rhs) const _NOEXCEPT;
 #  endif
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool test(size_t __pos) const;
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool all() const _NOEXCEPT;
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool any() const _NOEXCEPT;
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool all() const _NOEXCEPT { return __base::all(); }
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool any() const _NOEXCEPT { return __base::any(); }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool none() const _NOEXCEPT { return !any(); }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bitset operator<<(size_t __pos) const _NOEXCEPT;
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bitset operator>>(size_t __pos) const _NOEXCEPT;
@@ -930,16 +922,6 @@ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool bitset<_Size>::test(siz
   return (*this)[__pos];
 }
 
-template <size_t _Size>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool bitset<_Size>::all() const _NOEXCEPT {
-  return __base::all();
-}
-
-template <size_t _Size>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bool bitset<_Size>::any() const _NOEXCEPT {
-  return __base::any();
-}
-
 template <size_t _Size>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bitset<_Size>
 bitset<_Size>::operator<<(size_t __pos) const _NOEXCEPT {