From 6a37ca39ec7cfc2f4392784fd31936526d55e941 Mon Sep 17 00:00:00 2001
From: Allan Sandfeld Jensen <allan.jensen@qt.io>
Date: Sat, 8 Aug 2020 12:52:36 +0200
Subject: 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>
---
 src/corelib/kernel/qmath.h | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

(limited to 'src/corelib/kernel/qmath.h')

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));
-- 
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