diff options
| author | Thiago Macieira <thiago.macieira@intel.com> | 2023-02-07 18:51:59 -0800 |
|---|---|---|
| committer | Thiago Macieira <thiago.macieira@intel.com> | 2023-02-22 11:06:49 -0800 |
| commit | e69d80e14d24001f93442ab59b8babb7e9df0092 (patch) | |
| tree | a755b37314ed71deb47f6f60ebfc01a9009c4c11 /src/corelib/tools/qalgorithms.h | |
| parent | ac9d25340aec5c165db5e58a3d8b869967c5ff97 (diff) | |
qalgorithms.h: fix mistake that MSVC has constexpr bitops in C++17 mode
<bit> 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 <bit> 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 <marten.nordheim@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Diffstat (limited to 'src/corelib/tools/qalgorithms.h')
| -rw-r--r-- | src/corelib/tools/qalgorithms.h | 21 |
1 files changed, 5 insertions, 16 deletions
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 <bit> 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 <bit> 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 |