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authorAllan Sandfeld Jensen <allan.jensen@qt.io>2020-08-08 12:52:36 +0200
committerAllan Sandfeld Jensen <allan.jensen@qt.io>2020-09-13 18:26:49 +0200
commit6a37ca39ec7cfc2f4392784fd31936526d55e941 (patch)
tree240d1a2034b87a0094b0fc96a07a46e3a3b0902b /src
parent65afcef2173cabe297778d19dda3198595820cfa (diff)
Use universal C++20 bit operations when available
Avoids using compiler builtins, and can in future replace them. Change-Id: I3f0afe7d28b6ba05bcd1c1132b44a8db7b182d8a Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Diffstat (limited to 'src')
-rw-r--r--src/corelib/kernel/qmath.h12
-rw-r--r--src/corelib/text/qstringconverter.cpp8
-rw-r--r--src/corelib/tools/qalgorithms.h66
3 files changed, 67 insertions, 19 deletions
diff --git a/src/corelib/kernel/qmath.h b/src/corelib/kernel/qmath.h
index 5f36de303c..4c5a980f3a 100644
--- a/src/corelib/kernel/qmath.h
+++ b/src/corelib/kernel/qmath.h
@@ -47,6 +47,10 @@
#include <QtCore/qglobal.h>
#include <QtCore/qalgorithms.h>
+#if __has_include(<bit>)
+#include <bit>
+#endif
+
#ifndef _USE_MATH_DEFINES
# define _USE_MATH_DEFINES
# define undef_USE_MATH_DEFINES
@@ -298,7 +302,9 @@ constexpr inline quint64 qConstexprNextPowerOfTwo(qint64 v)
constexpr inline quint32 qNextPowerOfTwo(quint32 v)
{
-#if defined(QT_HAS_BUILTIN_CLZ)
+#if defined(__cpp_lib_int_pow2) && __cpp_lib_int_pow2 >= 202002L
+ return std::bit_ceil(v + 1);
+#elif defined(QT_HAS_BUILTIN_CLZ)
if (v == 0)
return 1;
return 2U << (31 ^ QAlgorithmsPrivate::qt_builtin_clz(v));
@@ -309,7 +315,9 @@ constexpr inline quint32 qNextPowerOfTwo(quint32 v)
constexpr inline quint64 qNextPowerOfTwo(quint64 v)
{
-#if defined(QT_HAS_BUILTIN_CLZLL)
+#if defined(__cpp_lib_int_pow2) && __cpp_lib_int_pow2 >= 202002L
+ return std::bit_ceil(v + 1);
+#elif defined(QT_HAS_BUILTIN_CLZLL)
if (v == 0)
return 1;
return Q_UINT64_C(2) << (63 ^ QAlgorithmsPrivate::qt_builtin_clzll(v));
diff --git a/src/corelib/text/qstringconverter.cpp b/src/corelib/text/qstringconverter.cpp
index 84f293ae5f..778674ebd8 100644
--- a/src/corelib/text/qstringconverter.cpp
+++ b/src/corelib/text/qstringconverter.cpp
@@ -50,6 +50,10 @@
#include <qt_windows.h>
#endif
+#if __has_include(<bit>)
+#include <bit>
+#endif
+
QT_BEGIN_NAMESPACE
enum { Endian = 0, Data = 1 };
@@ -60,12 +64,16 @@ static const uchar utf8bom[] = { 0xef, 0xbb, 0xbf };
|| (defined(__ARM_NEON__) && defined(Q_PROCESSOR_ARM_64))
static Q_ALWAYS_INLINE uint qBitScanReverse(unsigned v) noexcept
{
+#if defined(__cpp_lib_int_pow2) && __cpp_lib_int_pow2 >= 202002L
+ return std::bit_width(v) - 1;
+#else
uint result = qCountLeadingZeroBits(v);
// 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 _bit_scan_reverse is expected to be the index when
// counting up: msb index is 0 (because it starts there), and the lsb index is 31.
result ^= sizeof(unsigned) * 8 - 1;
return result;
+#endif
}
#endif
diff --git a/src/corelib/tools/qalgorithms.h b/src/corelib/tools/qalgorithms.h
index 6b55136bc3..58709f7fdf 100644
--- a/src/corelib/tools/qalgorithms.h
+++ b/src/corelib/tools/qalgorithms.h
@@ -42,6 +42,10 @@
#include <QtCore/qglobal.h>
+#if __has_include(<bit>)
+#include <bit>
+#endif
+
#ifdef Q_CC_MSVC
#include <intrin.h>
#endif
@@ -139,8 +143,6 @@ 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_POPCOUNT_CONSTEXPR
-#define QT_POPCOUNT_RELAXED_CONSTEXPR
#define QT_HAS_BUILTIN_CTZ
Q_ALWAYS_INLINE unsigned long qt_builtin_ctz(quint32 val)
{
@@ -199,7 +201,11 @@ Q_ALWAYS_INLINE uint qt_builtin_clzs(quint16 v) noexcept
// 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__)
+#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L
+// We use C++20 <bit> operations instead which ensures constexpr popcount
+#elif 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
@@ -237,7 +243,9 @@ Q_ALWAYS_INLINE uint qt_builtin_popcountll(quint64 v) noexcept
Q_DECL_CONST_FUNCTION QT_POPCOUNT_CONSTEXPR inline uint qPopulationCount(quint32 v) noexcept
{
-#ifdef QALGORITHMS_USE_BUILTIN_POPCOUNT
+#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
@@ -250,7 +258,9 @@ Q_DECL_CONST_FUNCTION QT_POPCOUNT_CONSTEXPR inline uint qPopulationCount(quint32
Q_DECL_CONST_FUNCTION QT_POPCOUNT_CONSTEXPR inline uint qPopulationCount(quint8 v) noexcept
{
-#ifdef QALGORITHMS_USE_BUILTIN_POPCOUNT
+#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
@@ -260,7 +270,9 @@ Q_DECL_CONST_FUNCTION QT_POPCOUNT_CONSTEXPR inline uint qPopulationCount(quint8
Q_DECL_CONST_FUNCTION QT_POPCOUNT_CONSTEXPR inline uint qPopulationCount(quint16 v) noexcept
{
-#ifdef QALGORITHMS_USE_BUILTIN_POPCOUNT
+#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
@@ -271,7 +283,9 @@ Q_DECL_CONST_FUNCTION QT_POPCOUNT_CONSTEXPR inline uint qPopulationCount(quint16
Q_DECL_CONST_FUNCTION QT_POPCOUNT_CONSTEXPR inline uint qPopulationCount(quint64 v) noexcept
{
-#ifdef QALGORITHMS_USE_BUILTIN_POPCOUNTLL
+#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
@@ -289,7 +303,7 @@ Q_DECL_CONST_FUNCTION QT_POPCOUNT_CONSTEXPR inline uint qPopulationCount(long un
return qPopulationCount(static_cast<quint64>(v));
}
-#if defined(Q_CC_GNU) && !defined(Q_CC_CLANG)
+#if defined(QALGORITHMS_USE_BUILTIN_POPCOUNT)
#undef QALGORITHMS_USE_BUILTIN_POPCOUNT
#endif
#undef QT_POPCOUNT_CONSTEXPR
@@ -347,7 +361,9 @@ constexpr inline uint qConstexprCountTrailingZeroBits(unsigned long v) noexcept
constexpr inline uint qCountTrailingZeroBits(quint32 v) noexcept
{
-#if defined(QT_HAS_BUILTIN_CTZ)
+#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);
@@ -356,7 +372,9 @@ constexpr inline uint qCountTrailingZeroBits(quint32 v) noexcept
constexpr inline uint qCountTrailingZeroBits(quint8 v) noexcept
{
-#if defined(QT_HAS_BUILTIN_CTZ)
+#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);
@@ -365,7 +383,9 @@ constexpr inline uint qCountTrailingZeroBits(quint8 v) noexcept
constexpr inline uint qCountTrailingZeroBits(quint16 v) noexcept
{
-#if defined(QT_HAS_BUILTIN_CTZS)
+#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);
@@ -374,7 +394,9 @@ constexpr inline uint qCountTrailingZeroBits(quint16 v) noexcept
constexpr inline uint qCountTrailingZeroBits(quint64 v) noexcept
{
-#if defined(QT_HAS_BUILTIN_CTZLL)
+#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);
@@ -386,9 +408,11 @@ constexpr inline uint qCountTrailingZeroBits(unsigned long v) noexcept
return qCountTrailingZeroBits(QIntegerForSizeof<long>::Unsigned(v));
}
-constexpr inline uint qCountLeadingZeroBits(quint32 v) noexcept
+QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint32 v) noexcept
{
-#if defined(QT_HAS_BUILTIN_CLZ)
+#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
@@ -403,7 +427,9 @@ constexpr inline uint qCountLeadingZeroBits(quint32 v) noexcept
QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint8 v) noexcept
{
-#if defined(QT_HAS_BUILTIN_CLZ)
+#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);
@@ -415,7 +441,9 @@ QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint8 v) noexce
QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint16 v) noexcept
{
-#if defined(QT_HAS_BUILTIN_CLZS)
+#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);
@@ -428,7 +456,9 @@ QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint16 v) noexc
QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(quint64 v) noexcept
{
-#if defined(QT_HAS_BUILTIN_CLZLL)
+#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);
@@ -446,6 +476,8 @@ QT_POPCOUNT_RELAXED_CONSTEXPR inline uint qCountLeadingZeroBits(unsigned long v)
return qCountLeadingZeroBits(QIntegerForSizeof<long>::Unsigned(v));
}
+#undef QT_POPCOUNT_RELAXED_CONSTEXPR
+
QT_END_NAMESPACE
#endif // QALGORITHMS_H