diff options
Diffstat (limited to 'src/corelib/tools/qalgorithms.h')
| -rw-r--r-- | src/corelib/tools/qalgorithms.h | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/src/corelib/tools/qalgorithms.h b/src/corelib/tools/qalgorithms.h index fb7031ce71..c0f7709fec 100644 --- a/src/corelib/tools/qalgorithms.h +++ b/src/corelib/tools/qalgorithms.h @@ -638,6 +638,17 @@ Q_ALWAYS_INLINE uint qt_builtin_clzs(quint16 v) Q_DECL_NOTHROW { 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 QALGORITHMS_USE_BUILTIN_POPCOUNT Q_ALWAYS_INLINE uint qt_builtin_popcount(quint32 v) Q_DECL_NOTHROW { @@ -658,6 +669,8 @@ Q_ALWAYS_INLINE uint qt_builtin_popcountll(quint64 v) Q_DECL_NOTHROW return __popcnt64(v); } #endif // MSVC 64bit +#endif // __AVX__ || __SSE4_2__ || __POPCNT__ + #endif // MSVC #endif // QT_HAS_CONSTEXPR_BUILTINS |