4 files changed, 31 insertions, 360 deletions
diff --git a/src/corelib/kernel/qmetaobject.cpp b/src/corelib/kernel/qmetaobject.cpp
index 17a9856dfd2..8e11bd52578 100644
--- a/src/corelib/kernel/qmetaobject.cpp
+++ b/src/corelib/kernel/qmetaobject.cpp
@@ -2481,7 +2481,7 @@ bool QMetaMethod::isConst() const
 */
 QMetaMethod::Access QMetaMethod::access() const
 {
-    constexpr int AccessShift = QtPrivate::qConstexprCountTrailingZeroBits(AccessMask);
+    constexpr int AccessShift = qCountTrailingZeroBits(AccessMask);
     static_assert(AccessPrivate >> AccessShift == Private);
     static_assert(AccessProtected >> AccessShift == Protected);
     static_assert(AccessPublic >> AccessShift == Public);
@@ -2497,7 +2497,7 @@ QMetaMethod::Access QMetaMethod::access() const
 */
 QMetaMethod::MethodType QMetaMethod::methodType() const
 {
-    constexpr int MethodShift = QtPrivate::qConstexprCountTrailingZeroBits(MethodTypeMask);
+    constexpr int MethodShift = qCountTrailingZeroBits(MethodTypeMask);
     static_assert(MethodMethod >> MethodShift == Method);
     static_assert(MethodSignal >> MethodShift == Signal);
     static_assert(MethodSlot >> MethodShift == Slot);
diff --git a/src/corelib/time/qcalendarmath_p.h b/src/corelib/time/qcalendarmath_p.h
index 03153b0eed1..e3c89429ae2 100644
--- a/src/corelib/time/qcalendarmath_p.h
+++ b/src/corelib/time/qcalendarmath_p.h
@@ -89,7 +89,7 @@ template <unsigned b, typename Int,
                            bool> = true>
 constexpr auto qDivMod(Int a)
 {
-    constexpr unsigned w = QtPrivate::qConstexprCountTrailingZeroBits(b);
+    constexpr unsigned w = qCountTrailingZeroBits(b);
     struct R { Int quotient; Int remainder; };
     if constexpr (std::is_signed_v<Int>) {
         if (a < 0)
diff --git a/src/corelib/tools/qalgorithms.h b/src/corelib/tools/qalgorithms.h
index 5b579c0938f..74b46e80ebc 100644
--- a/src/corelib/tools/qalgorithms.h
+++ b/src/corelib/tools/qalgorithms.h
@@ -9,16 +9,11 @@
 #endif
 
 #include <QtCore/qglobal.h>
+#include <QtCore/q20bit.h>
 #include <QtCore/q20functional.h>
-
-#if __has_include(<bit>) && __cplusplus > 201703L
-#include <bit>
-#endif
 #include <type_traits>
 
-#ifdef Q_CC_MSVC
-#include <intrin.h>
-#endif
+#define QT_HAS_CONSTEXPR_BITOPS
 
 QT_BEGIN_NAMESPACE
 
@@ -37,406 +32,82 @@ inline void qDeleteAll(const Container &c)
     qDeleteAll(c.begin(), c.end());
 }
 
-/*
-    Warning: The contents of QAlgorithmsPrivate is not a part of the public Qt API
-    and may be changed from version to version or even be completely removed.
-*/
-namespace QAlgorithmsPrivate {
-
-#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L
-// We use C++20 <bit> operations instead which ensures constexpr bit ops
-#  define QT_HAS_CONSTEXPR_BITOPS
-#elif defined(Q_CC_GNU)
-#  define QT_HAS_CONSTEXPR_BITOPS
-#  define QT_HAS_BUILTIN_CTZS
-constexpr Q_ALWAYS_INLINE uint qt_builtin_ctzs(quint16 v) noexcept
-{
-#  if __has_builtin(__builtin_ctzs)
-    return __builtin_ctzs(v);
-#  else
-    return __builtin_ctz(v);
-#  endif
-}
-#define QT_HAS_BUILTIN_CLZS
-constexpr Q_ALWAYS_INLINE uint qt_builtin_clzs(quint16 v) noexcept
-{
-#  if __has_builtin(__builtin_clzs)
-    return __builtin_clzs(v);
-#  else
-    return __builtin_clz(v) - 16U;
-#  endif
-}
-#define QT_HAS_BUILTIN_CTZ
-constexpr Q_ALWAYS_INLINE uint qt_builtin_ctz(quint32 v) noexcept
-{
-    return __builtin_ctz(v);
-}
-#define QT_HAS_BUILTIN_CLZ
-constexpr Q_ALWAYS_INLINE uint qt_builtin_clz(quint32 v) noexcept
-{
-    return __builtin_clz(v);
-}
-#define QT_HAS_BUILTIN_CTZLL
-constexpr Q_ALWAYS_INLINE uint qt_builtin_ctzll(quint64 v) noexcept
-{
-    return __builtin_ctzll(v);
-}
-#define QT_HAS_BUILTIN_CLZLL
-constexpr Q_ALWAYS_INLINE uint qt_builtin_clzll(quint64 v) noexcept
-{
-    return __builtin_clzll(v);
-}
-#define QALGORITHMS_USE_BUILTIN_POPCOUNT
-constexpr Q_ALWAYS_INLINE uint qt_builtin_popcount(quint32 v) noexcept
-{
-    return __builtin_popcount(v);
-}
-constexpr Q_ALWAYS_INLINE uint qt_builtin_popcount(quint8 v) noexcept
-{
-    return __builtin_popcount(v);
-}
-constexpr Q_ALWAYS_INLINE uint qt_builtin_popcount(quint16 v) noexcept
-{
-    return __builtin_popcount(v);
-}
-#define QALGORITHMS_USE_BUILTIN_POPCOUNTLL
-constexpr Q_ALWAYS_INLINE uint qt_builtin_popcountll(quint64 v) noexcept
-{
-    return __builtin_popcountll(v);
-}
-#elif defined(Q_CC_MSVC) && !defined(Q_PROCESSOR_ARM)
-#define QT_HAS_BUILTIN_CTZ
-Q_ALWAYS_INLINE unsigned long qt_builtin_ctz(quint32 val)
-{
-    unsigned long result;
-    _BitScanForward(&result, val);
-    return result;
-}
-#define QT_HAS_BUILTIN_CLZ
-Q_ALWAYS_INLINE unsigned long qt_builtin_clz(quint32 val)
-{
-    unsigned long result;
-    _BitScanReverse(&result, val);
-    // Now Invert the result: clz will count *down* from the msb to the lsb, so the msb index is 31
-    // and the lsb index is 0. The result for the index when counting up: msb index is 0 (because it
-    // starts there), and the lsb index is 31.
-    result ^= sizeof(quint32) * 8 - 1;
-    return result;
-}
-#if Q_PROCESSOR_WORDSIZE == 8
-// These are only defined for 64bit builds.
-#define QT_HAS_BUILTIN_CTZLL
-Q_ALWAYS_INLINE unsigned long qt_builtin_ctzll(quint64 val)
-{
-    unsigned long result;
-    _BitScanForward64(&result, val);
-    return result;
-}
-// MSVC calls it _BitScanReverse and returns the carry flag, which we don't need
-#define QT_HAS_BUILTIN_CLZLL
-Q_ALWAYS_INLINE unsigned long qt_builtin_clzll(quint64 val)
-{
-    unsigned long result;
-    _BitScanReverse64(&result, val);
-    // see qt_builtin_clz
-    result ^= sizeof(quint64) * 8 - 1;
-    return result;
-}
-#endif // MSVC 64bit
-#  define QT_HAS_BUILTIN_CTZS
-Q_ALWAYS_INLINE uint qt_builtin_ctzs(quint16 v) noexcept
-{
-    return qt_builtin_ctz(v);
-}
-#define QT_HAS_BUILTIN_CLZS
-Q_ALWAYS_INLINE uint qt_builtin_clzs(quint16 v) noexcept
-{
-    return qt_builtin_clz(v) - 16U;
-}
-
-// Neither MSVC nor the Intel compiler define a macro for the POPCNT processor
-// feature, so we're using either the SSE4.2 or the AVX macro as a proxy (Clang
-// does define the macro). It's incorrect for two reasons:
-// 1. It's a separate bit in CPUID, so a processor could implement SSE4.2 and
-//    not POPCNT, but that's unlikely to happen.
-// 2. There are processors that support POPCNT but not AVX (Intel Nehalem
-//    architecture), but unlike the other compilers, MSVC has no option
-//    to generate code for those processors.
-// So it's an acceptable compromise.
-#if defined(__AVX__) || defined(__SSE4_2__) || defined(__POPCNT__)
-#define QT_POPCOUNT_CONSTEXPR
-#define QT_POPCOUNT_RELAXED_CONSTEXPR
-#define QALGORITHMS_USE_BUILTIN_POPCOUNT
-#define QALGORITHMS_USE_BUILTIN_POPCOUNTLL
-Q_ALWAYS_INLINE uint qt_builtin_popcount(quint32 v) noexcept
-{
-    return __popcnt(v);
-}
-Q_ALWAYS_INLINE uint qt_builtin_popcount(quint8 v) noexcept
-{
-    return __popcnt16(v);
-}
-Q_ALWAYS_INLINE uint qt_builtin_popcount(quint16 v) noexcept
-{
-    return __popcnt16(v);
-}
-Q_ALWAYS_INLINE uint qt_builtin_popcountll(quint64 v) noexcept
-{
-#if Q_PROCESSOR_WORDSIZE == 8
-    return __popcnt64(v);
-#else
-    return __popcnt(quint32(v)) + __popcnt(quint32(v >> 32));
-#endif // MSVC 64bit
-}
-
-#endif // __AVX__ || __SSE4_2__ || __POPCNT__
-
-#endif // MSVC
 
-#ifndef QT_POPCOUNT_CONSTEXPR
-#define QT_POPCOUNT_CONSTEXPR constexpr
-#define QT_POPCOUNT_RELAXED_CONSTEXPR constexpr
-#endif
-
-} //namespace QAlgorithmsPrivate
-
-Q_DECL_CONST_FUNCTION QT_POPCOUNT_CONSTEXPR inline uint qPopulationCount(quint32 v) noexcept
+Q_DECL_CONST_FUNCTION constexpr inline uint qPopulationCount(quint32 v) noexcept
 {
-#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L
-    return std::popcount(v);
-#elif defined QALGORITHMS_USE_BUILTIN_POPCOUNT
-    return QAlgorithmsPrivate::qt_builtin_popcount(v);
-#else
-    // See http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
-    return
-        (((v      ) & 0xfff)    * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f +
-        (((v >> 12) & 0xfff)    * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f +
-        (((v >> 24) & 0xfff)    * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f;
-#endif
+    return q20::popcount(v);
 }
 
-Q_DECL_CONST_FUNCTION QT_POPCOUNT_CONSTEXPR inline uint qPopulationCount(quint8 v) noexcept
+Q_DECL_CONST_FUNCTION constexpr inline uint qPopulationCount(quint8 v) noexcept
 {
-#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L
-    return std::popcount(v);
-#elif defined QALGORITHMS_USE_BUILTIN_POPCOUNT
-    return QAlgorithmsPrivate::qt_builtin_popcount(v);
-#else
-    return
-        (((v      ) & 0xfff)    * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f;
-#endif
+    return q20::popcount(v);
 }
 
-Q_DECL_CONST_FUNCTION QT_POPCOUNT_CONSTEXPR inline uint qPopulationCount(quint16 v) noexcept
+Q_DECL_CONST_FUNCTION constexpr inline uint qPopulationCount(quint16 v) noexcept
 {
-#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L
-    return std::popcount(v);
-#elif defined QALGORITHMS_USE_BUILTIN_POPCOUNT
-    return QAlgorithmsPrivate::qt_builtin_popcount(v);
-#else
-    return
-        (((v      ) & 0xfff)    * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f +
-        (((v >> 12) & 0xfff)    * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f;
-#endif
-}
-
-Q_DECL_CONST_FUNCTION QT_POPCOUNT_CONSTEXPR inline uint qPopulationCount(quint64 v) noexcept
-{
-#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L
-    return std::popcount(v);
-#elif defined QALGORITHMS_USE_BUILTIN_POPCOUNTLL
-    return QAlgorithmsPrivate::qt_builtin_popcountll(v);
-#else
-    return
-        (((v      ) & 0xfff)    * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f +
-        (((v >> 12) & 0xfff)    * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f +
-        (((v >> 24) & 0xfff)    * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f +
-        (((v >> 36) & 0xfff)    * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f +
-        (((v >> 48) & 0xfff)    * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f +
-        (((v >> 60) & 0xfff)    * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f;
-#endif
+    return q20::popcount(v);
 }
 
-Q_DECL_CONST_FUNCTION QT_POPCOUNT_CONSTEXPR inline uint qPopulationCount(long unsigned int v) noexcept
+Q_DECL_CONST_FUNCTION constexpr inline uint qPopulationCount(quint64 v) noexcept
 {
-    return qPopulationCount(static_cast<quint64>(v));
+    return q20::popcount(v);
 }
 
-#if defined(QALGORITHMS_USE_BUILTIN_POPCOUNT)
-#undef QALGORITHMS_USE_BUILTIN_POPCOUNT
-#endif
-#undef QT_POPCOUNT_CONSTEXPR
-
-namespace QtPrivate {
-constexpr inline uint qConstexprCountTrailingZeroBits(quint32 v) noexcept
+Q_DECL_CONST_FUNCTION constexpr inline uint qPopulationCount(long unsigned int v) noexcept
 {
-    // see http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightParallel
-    unsigned int c = 32; // c will be the number of zero bits on the right
-    v &= -signed(v);
-    if (v) c--;
-    if (v & 0x0000FFFF) c -= 16;
-    if (v & 0x00FF00FF) c -= 8;
-    if (v & 0x0F0F0F0F) c -= 4;
-    if (v & 0x33333333) c -= 2;
-    if (v & 0x55555555) c -= 1;
-    return c;
-}
-
-constexpr inline uint qConstexprCountTrailingZeroBits(quint64 v) noexcept
-{
-    quint32 x = static_cast<quint32>(v);
-    return x ? qConstexprCountTrailingZeroBits(x)
-             : 32 + qConstexprCountTrailingZeroBits(static_cast<quint32>(v >> 32));
-}
-
-constexpr inline uint qConstexprCountTrailingZeroBits(quint8 v) noexcept
-{
-    unsigned int c = 8; // c will be the number of zero bits on the right
-    v &= quint8(-signed(v));
-    if (v) c--;
-    if (v & 0x0000000F) c -= 4;
-    if (v & 0x00000033) c -= 2;
-    if (v & 0x00000055) c -= 1;
-    return c;
-}
-
-constexpr inline uint qConstexprCountTrailingZeroBits(quint16 v) noexcept
-{
-    unsigned int c = 16; // c will be the number of zero bits on the right
-    v &= quint16(-signed(v));
-    if (v) c--;
-    if (v & 0x000000FF) c -= 8;
-    if (v & 0x00000F0F) c -= 4;
-    if (v & 0x00003333) c -= 2;
-    if (v & 0x00005555) c -= 1;
-    return c;
-}
-
-constexpr inline uint qConstexprCountTrailingZeroBits(unsigned long v) noexcept
-{
-    return qConstexprCountTrailingZeroBits(QIntegerForSizeof<long>::Unsigned(v));
-}
+    return q20::popcount(v);
 }
 
 constexpr inline uint qCountTrailingZeroBits(quint32 v) noexcept
 {
-#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L
-    return std::countr_zero(v);
-#elif defined(QT_HAS_BUILTIN_CTZ)
-    return v ? QAlgorithmsPrivate::qt_builtin_ctz(v) : 32U;
-#else
-    return QtPrivate::qConstexprCountTrailingZeroBits(v);
-#endif
+    return q20::countr_zero(v);
 }
 
 constexpr inline uint qCountTrailingZeroBits(quint8 v) noexcept
 {
-#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L
-    return std::countr_zero(v);
-#elif defined(QT_HAS_BUILTIN_CTZ)
-    return v ? QAlgorithmsPrivate::qt_builtin_ctz(v) : 8U;
-#else
-    return QtPrivate::qConstexprCountTrailingZeroBits(v);
-#endif
+    return q20::countr_zero(v);
 }
 
 constexpr inline uint qCountTrailingZeroBits(quint16 v) noexcept
 {
-#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L
-    return std::countr_zero(v);
-#elif defined(QT_HAS_BUILTIN_CTZS)
-    return v ? QAlgorithmsPrivate::qt_builtin_ctzs(v) : 16U;
-#else
-    return QtPrivate::qConstexprCountTrailingZeroBits(v);
-#endif
+    return q20::countr_zero(v);
 }
 
 constexpr inline uint qCountTrailingZeroBits(quint64 v) noexcept
 {
-#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L
-    return std::countr_zero(v);
-#elif defined(QT_HAS_BUILTIN_CTZLL)
-    return v ? QAlgorithmsPrivate::qt_builtin_ctzll(v) : 64;
-#else
-    return QtPrivate::qConstexprCountTrailingZeroBits(v);
-#endif
+    return q20::countr_zero(v);
 }
 
 constexpr inline uint qCountTrailingZeroBits(unsigned long v) noexcept
 {
-    return qCountTrailingZeroBits(QIntegerForSizeof<long>::Unsigned(v));
+    return q20::countr_zero(v);
 }
 
-QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint32 v) noexcept
+constexpr inline uint qCountLeadingZeroBits(quint32 v) noexcept
 {
-#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L
-    return std::countl_zero(v);
-#elif defined(QT_HAS_BUILTIN_CLZ)
-    return v ? QAlgorithmsPrivate::qt_builtin_clz(v) : 32U;
-#else
-    // Hacker's Delight, 2nd ed. Fig 5-16, p. 102
-    v = v | (v >> 1);
-    v = v | (v >> 2);
-    v = v | (v >> 4);
-    v = v | (v >> 8);
-    v = v | (v >> 16);
-    return qPopulationCount(~v);
-#endif
+    return q20::countl_zero(v);
 }
 
-QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint8 v) noexcept
+constexpr inline uint qCountLeadingZeroBits(quint8 v) noexcept
 {
-#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L
-    return std::countl_zero(v);
-#elif defined(QT_HAS_BUILTIN_CLZ)
-    return v ? QAlgorithmsPrivate::qt_builtin_clz(v)-24U : 8U;
-#else
-    v = v | (v >> 1);
-    v = v | (v >> 2);
-    v = v | (v >> 4);
-    return qPopulationCount(static_cast<quint8>(~v));
-#endif
+    return q20::countl_zero(v);
 }
 
-QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint16 v) noexcept
+constexpr inline uint qCountLeadingZeroBits(quint16 v) noexcept
 {
-#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L
-    return std::countl_zero(v);
-#elif defined(QT_HAS_BUILTIN_CLZS)
-    return v ? QAlgorithmsPrivate::qt_builtin_clzs(v) : 16U;
-#else
-    v = v | (v >> 1);
-    v = v | (v >> 2);
-    v = v | (v >> 4);
-    v = v | (v >> 8);
-    return qPopulationCount(static_cast<quint16>(~v));
-#endif
+    return q20::countl_zero(v);
 }
 
-QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint64 v) noexcept
+constexpr inline uint qCountLeadingZeroBits(quint64 v) noexcept
 {
-#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L
-    return std::countl_zero(v);
-#elif defined(QT_HAS_BUILTIN_CLZLL)
-    return v ? QAlgorithmsPrivate::qt_builtin_clzll(v) : 64U;
-#else
-    v = v | (v >> 1);
-    v = v | (v >> 2);
-    v = v | (v >> 4);
-    v = v | (v >> 8);
-    v = v | (v >> 16);
-    v = v | (v >> 32);
-    return qPopulationCount(~v);
-#endif
+    return q20::countl_zero(v);
 }
 
-QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(unsigned long v) noexcept
+constexpr inline uint qCountLeadingZeroBits(unsigned long v) noexcept
 {
-    return qCountLeadingZeroBits(QIntegerForSizeof<long>::Unsigned(v));
+    return q20::countl_zero(v);
 }
 
-#undef QT_POPCOUNT_RELAXED_CONSTEXPR
-
 template <typename InputIterator, typename Result, typename Separator = Result,
           typename Projection = q20::identity>
 Result qJoin(InputIterator first, InputIterator last, Result init, const Separator &separator = {},
diff --git a/src/corelib/tools/qtaggedpointer.h b/src/corelib/tools/qtaggedpointer.h
index 6c467d59f84..36d679b4ec9 100644
--- a/src/corelib/tools/qtaggedpointer.h
+++ b/src/corelib/tools/qtaggedpointer.h
@@ -21,7 +21,7 @@ namespace QtPrivate {
         static_assert((alignment & (alignment - 1)) == 0,
             "Alignment of template parameter must be power of two");
 
-        static constexpr quint8 tagBits = quint8{QtPrivate::qConstexprCountTrailingZeroBits(alignment)};
+        static constexpr quint8 tagBits = quint8{qCountTrailingZeroBits(alignment)};
         static_assert(tagBits > 0,
             "Alignment of template parameter does not allow any tags");