Merge branch 'main' into p1425r4-stack-queue-constructors

README.md

@@ -143,7 +143,7 @@ Just try to follow these rules, so we can spend more time fixing bugs and implem
 The STL uses boost-math headers to provide P0226R1 Mathematical Special Functions. We recommend using [vcpkg][] to
 acquire this dependency.
 
-1. Install Visual Studio 2019 16.10 Preview 4 or later.
+1. Install Visual Studio 2019 16.11 Preview 1 or later.
     * We recommend selecting "C++ CMake tools for Windows" in the VS Installer.
     This will ensure that you're using supported versions of CMake and Ninja.
     * Otherwise, install [CMake][] 3.20 or later, and [Ninja][] 1.10.2 or later.
@@ -158,7 +158,7 @@ acquire this dependency.
 
 # How To Build With A Native Tools Command Prompt
 
-1. Install Visual Studio 2019 16.10 Preview 4 or later.
+1. Install Visual Studio 2019 16.11 Preview 1 or later.
     * We recommend selecting "C++ CMake tools for Windows" in the VS Installer.
     This will ensure that you're using supported versions of CMake and Ninja.
     * Otherwise, install [CMake][] 3.20 or later, and [Ninja][] 1.10.2 or later.

azure-devops/create-vmss.ps1

@@ -27,7 +27,7 @@ $ProtoVMName = 'PROTOTYPE'
 $LiveVMPrefix = 'BUILD'
 $ImagePublisher = 'MicrosoftWindowsDesktop'
 $ImageOffer = 'Windows-10'
-$ImageSku = '20h2-ent-g2'
+$ImageSku = '21h1-ent-g2'
 
 $ProgressActivity = 'Creating Scale Set'
 $TotalProgress = 14
@@ -310,6 +310,8 @@ Write-Progress `
   -Status 'Sleeping after restart' `
   -PercentComplete (100 / $TotalProgress * $CurrentProgress++)
 
+# The VM appears to be busy immediately after restarting.
+# This workaround waits for a minute before attempting to run sysprep.ps1.
 Start-Sleep -Seconds 60
 
 ####################################################################################################

azure-pipelines.yml

@@ -8,7 +8,7 @@ variables:
   buildOutputLocation: 'D:\build'
   vcpkgLocation: '$(Build.SourcesDirectory)/vcpkg'
 
-pool: 'StlBuild-2021-05-18'
+pool: 'StlBuild-2021-06-02'
 
 stages:
   - stage: Code_Format

stl/inc/algorithm

@@ -10260,12 +10260,27 @@ namespace ranges {
 
             using _Memcmp_classification_pred =
                 typename decltype(_Lex_compare_memcmp_classify(_First1, _First2, _Pred))::_Pred;
-            if constexpr (!is_void_v<_Memcmp_classification_pred> && sized_sentinel_for<_Se1, _It1> //
-                          && sized_sentinel_for<_Se2, _It2> && same_as<_Pj1, identity> && same_as<_Pj2, identity>) {
+            constexpr bool _Is_sized1 = sized_sentinel_for<_Se1, _It1>;
+            constexpr bool _Is_sized2 = sized_sentinel_for<_Se2, _It2>;
+            if constexpr (!is_void_v<_Memcmp_classification_pred> && _Sized_or_unreachable_sentinel_for<_Se1, _It1> //
+                          && _Sized_or_unreachable_sentinel_for<_Se2, _It2> //
+                          && same_as<_Pj1, identity> && same_as<_Pj2, identity>) {
                 if (!_STD is_constant_evaluated()) {
-                    const auto _Num1 = static_cast<size_t>(_Last1 - _First1);
-                    const auto _Num2 = static_cast<size_t>(_Last2 - _First2);
-                    const int _Ans   = _Memcmp_count(_First1, _First2, (_STD min)(_Num1, _Num2));
+                    size_t _Num1;
+                    if constexpr (_Is_sized1) {
+                        _Num1 = static_cast<size_t>(_Last1 - _First1);
+                    } else {
+                        _Num1 = SIZE_MAX;
+                    }
+
+                    size_t _Num2;
+                    if constexpr (_Is_sized2) {
+                        _Num2 = static_cast<size_t>(_Last2 - _First2);
+                    } else {
+                        _Num2 = SIZE_MAX;
+                    }
+
+                    const int _Ans = _Memcmp_count(_First1, _First2, (_STD min)(_Num1, _Num2));
                     return _Memcmp_classification_pred{}(_Ans, 0) || (_Ans == 0 && _Num1 < _Num2);
                 }
             }

stl/inc/bit

@@ -96,23 +96,6 @@ _NODISCARD constexpr _Ty rotr(const _Ty _Val, const int _Rotation) noexcept {
     }
 }
 
-// Implementation of popcount without using specialized CPU instructions.
-// Used at compile time and when said instructions are not supported.
-template <class _Ty>
-_NODISCARD constexpr int _Popcount_fallback(_Ty _Val) noexcept {
-    constexpr int _Digits = numeric_limits<_Ty>::digits;
-    // we static_cast these bit patterns in order to truncate them to the correct size
-    _Val = static_cast<_Ty>(_Val - ((_Val >> 1) & static_cast<_Ty>(0x5555'5555'5555'5555ull)));
-    _Val = static_cast<_Ty>((_Val & static_cast<_Ty>(0x3333'3333'3333'3333ull))
-                            + ((_Val >> 2) & static_cast<_Ty>(0x3333'3333'3333'3333ull)));
-    _Val = static_cast<_Ty>((_Val + (_Val >> 4)) & static_cast<_Ty>(0x0F0F'0F0F'0F0F'0F0Full));
-    for (int _Shift_digits = 8; _Shift_digits < _Digits; _Shift_digits <<= 1) {
-        _Val = static_cast<_Ty>(_Val + static_cast<_Ty>(_Val >> _Shift_digits));
-    }
-    // we want the bottom "slot" that's big enough to store _Digits
-    return static_cast<int>(_Val & static_cast<_Ty>(_Digits + _Digits - 1));
-}
-
 #if defined(_M_IX86) || (defined(_M_X64) && !defined(_M_ARM64EC))
 
 extern "C" {
@@ -184,32 +167,8 @@ _NODISCARD int _Checked_x86_x64_countl_zero(const _Ty _Val) noexcept {
     }
 #endif // __AVX2__
 }
-
-template <class _Ty>
-_NODISCARD int _Checked_x86_x64_popcount(const _Ty _Val) noexcept {
-    constexpr int _Digits = numeric_limits<_Ty>::digits;
-#ifndef __AVX__
-    const bool _Definitely_have_popcnt = __isa_available >= __ISA_AVAILABLE_SSE42;
-    if (!_Definitely_have_popcnt) {
-        return _Popcount_fallback(_Val);
-    }
-#endif // !defined(__AVX__)
-
-    if constexpr (_Digits <= 16) {
-        return static_cast<int>(__popcnt16(_Val));
-    } else if constexpr (_Digits == 32) {
-        return static_cast<int>(__popcnt(_Val));
-    } else {
-#ifdef _M_IX86
-        return static_cast<int>(__popcnt(_Val >> 32) + __popcnt(static_cast<unsigned int>(_Val)));
-#else // ^^^ _M_IX86 / !_M_IX86 vvv
-        return static_cast<int>(__popcnt64(_Val));
-#endif // _M_IX86
-    }
-}
 #endif // defined(_M_IX86) || (defined(_M_X64) && !defined(_M_ARM64EC))
 
-
 #if defined(_M_ARM) || defined(_M_ARM64)
 #ifdef __clang__ // TRANSITION, GH-1586
 _NODISCARD constexpr int _Clang_arm_arm64_countl_zero(const unsigned short _Val) {
@@ -283,14 +242,9 @@ _NODISCARD constexpr int countr_one(const _Ty _Val) noexcept {
     return _Countr_zero(static_cast<_Ty>(~_Val));
 }
 
-template <class _Ty, enable_if_t<_Is_standard_unsigned_integer<_Ty>, int> _Enabled = 0>
+template <class _Ty, enable_if_t<_Is_standard_unsigned_integer<_Ty>, int> = 0>
 _NODISCARD constexpr int popcount(const _Ty _Val) noexcept {
-#if defined(_M_IX86) || (defined(_M_X64) && !defined(_M_ARM64EC))
-    if (!_STD is_constant_evaluated()) {
-        return _Checked_x86_x64_popcount(_Val);
-    }
-#endif // defined(_M_IX86) || (defined(_M_X64) && !defined(_M_ARM64EC))
-    return _Popcount_fallback(_Val);
+    return _Popcount(_Val);
 }
 
 enum class endian { little = 0, big = 1, native = little };