From e69d80e14d24001f93442ab59b8babb7e9df0092 Mon Sep 17 00:00:00 2001 From: Thiago Macieira Date: Tue, 7 Feb 2023 18:51:59 -0800 Subject: qalgorithms.h: fix mistake that MSVC has constexpr bitops in C++17 mode MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit exists in C++20 and is properly both constexpr and optimized. But in C++17 mode, we don't have constexpr bitops and instead elect to have performance at runtime instead. But somewhere along the line, either when they were added, when C++20 support was, or in any of the bugfixes for other compilers, the nesting of #ifdef got messed up and we declared that we had constexpr builtins for MSVC in C++17 too. The macro QT_HAS_CONSTEXPR_BUILTINS isn't supposed to be used by anyone else... but we ended up not being able to use it ourselves either. So I'm renaming it to a more precise label. Pick-to: 6.5 Change-Id: I9671dee8ceb64aa9b9cafffd1741b9b4060c9753 Reviewed-by: Mårten Nordheim Reviewed-by: Edward Welbourne --- src/corelib/tools/qalgorithms.h | 21 +++++---------------- 1 file changed, 5 insertions(+), 16 deletions(-) (limited to 'src/corelib/tools/qalgorithms.h') diff --git a/src/corelib/tools/qalgorithms.h b/src/corelib/tools/qalgorithms.h index 94aa2da012..8889effece 100644 --- a/src/corelib/tools/qalgorithms.h +++ b/src/corelib/tools/qalgorithms.h @@ -41,19 +41,11 @@ inline void qDeleteAll(const Container &c) */ namespace QAlgorithmsPrivate { -#ifdef Q_CC_CLANG -// Clang had a bug where __builtin_ctz/clz/popcount were not marked as constexpr. -# if (defined __apple_build_version__ && __clang_major__ >= 7) || (Q_CC_CLANG >= 307) -# define QT_HAS_CONSTEXPR_BUILTINS -# endif -#elif defined(Q_CC_MSVC) && !defined(Q_PROCESSOR_ARM) -# define QT_HAS_CONSTEXPR_BUILTINS +#if defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L +// We use C++20 operations instead which ensures constexpr bit ops +# define QT_HAS_CONSTEXPR_BITOPS #elif defined(Q_CC_GNU) -# define QT_HAS_CONSTEXPR_BUILTINS -#endif - -#if defined QT_HAS_CONSTEXPR_BUILTINS -#if defined(Q_CC_GNU) || defined(Q_CC_CLANG) +# define QT_HAS_CONSTEXPR_BITOPS # define QT_HAS_BUILTIN_CTZS constexpr Q_ALWAYS_INLINE uint qt_builtin_ctzs(quint16 v) noexcept { @@ -169,9 +161,7 @@ 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(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L -// We use C++20 operations instead which ensures constexpr popcount -#elif defined(__AVX__) || defined(__SSE4_2__) || defined(__POPCNT__) +#if defined(__AVX__) || defined(__SSE4_2__) || defined(__POPCNT__) #define QT_POPCOUNT_CONSTEXPR #define QT_POPCOUNT_RELAXED_CONSTEXPR #define QALGORITHMS_USE_BUILTIN_POPCOUNT @@ -200,7 +190,6 @@ Q_ALWAYS_INLINE uint qt_builtin_popcountll(quint64 v) noexcept #endif // __AVX__ || __SSE4_2__ || __POPCNT__ #endif // MSVC -#endif // QT_HAS_CONSTEXPR_BUILTINS #ifndef QT_POPCOUNT_CONSTEXPR #define QT_POPCOUNT_CONSTEXPR constexpr -- cgit v1.2.3