From 6c6482f813d48c96c54d8fa5307c7b030574a214 Mon Sep 17 00:00:00 2001 From: Dmitry Shachnev Date: Wed, 23 Oct 2024 19:35:31 +0200 Subject: [PATCH] use _Float16 only when SSE2 is enabled MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Forwarded: https://codereview.qt-project.org/c/qt/qtbase/+/579205 Last-Update: 2024-08-01 The GCC documentation [1] says: “On x86 targets with SSE2 enabled, GCC supports half-precision (16-bit) floating point via the _Float16 type”. On non-SSE2 x86 (such as Debian i386 baseline [2]), __FLT16_MAX__ is defined starting with GCC 14 [3], however any non-trivial use of the _Float16 type results in an error: error: operation not permitted on type ‘_Float16’ without option ‘-msse2’ which makes some packages fail to build on i386 architecture [4]. [1]: https://gcc.gnu.org/onlinedocs/gcc/Half-Precision.html [2]: https://wiki.debian.org/ArchitectureSpecificsMemo#i386-1 [3]: https://gcc.gnu.org/g:9a19fa8b616f83474c35cc5b34a3865073ced829 [4]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1076986 Gbp-Pq: Name use_float16_only_with_sse2.patch --- src/corelib/global/qtypes.h | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/src/corelib/global/qtypes.h b/src/corelib/global/qtypes.h index db9ba38e..28458f63 100644 --- a/src/corelib/global/qtypes.h +++ b/src/corelib/global/qtypes.h @@ -263,13 +263,12 @@ using NativeFloat16Type = std::float16_t; // disabled due to https://github.com/llvm/llvm-project/issues/56963 # define QFLOAT16_IS_NATIVE 1 using NativeFloat16Type = decltype(__FLT16_MAX__); -#elif defined(Q_CC_GNU_ONLY) && defined(__FLT16_MAX__) +#elif defined(Q_CC_GNU_ONLY) && defined(__FLT16_MAX__) && defined(__ARM_FP16_FORMAT_IEEE) # define QFLOAT16_IS_NATIVE 1 -# ifdef __ARM_FP16_FORMAT_IEEE using NativeFloat16Type = __fp16; -# else +#elif defined(Q_CC_GNU_ONLY) && defined(__FLT16_MAX__) && defined(__SSE2__) +# define QFLOAT16_IS_NATIVE 1 using NativeFloat16Type = _Float16; -# endif #else # define QFLOAT16_IS_NATIVE 0 using NativeFloat16Type = void; -- 2.30.2