SjoerdMeijer added a comment. > I'm still not sure why __fp16, which is a storage-only type, is used for the > element type of float16x4_t if we want to avoid promotion to a float vector > type.
About the types: `__fp16` this is the older, storage-only type. So, just historically, I think this element type was used to describe the neon vectors, which translates to vectors with elements of i16 or f16, which all seems fine. > Was there a discussion on llvm-dev or phabricator? I don't think this is necessary, because this is how it's been from let's say the beginning. > Can we change the element type of the vector to _Float16? I don't see a benefit of doing this, and making this perhaps intrusive change. > It seems that the original plan discussed on llvm-dev > (http://lists.llvm.org/pipermail/cfe-dev/2017-May/053768.html) was to > introduce _Float16 and use it instead of __fp16 for ARMv8.2-A, but the > subsequent patches that were committed are making NeonEmitter.cpp emit > typedefs of vectors that have __fp16 as the element type. Then `_Float16` came along, which is a proper half type (not a storage only type), is defined in a C11 extension, and should be used for the ARMv8.2-A native half instructions; the semantics of `__fp16` and `_Float16` are different, and as a result using `__fp16` for the v8.2 half FP instructions is not an option, so it is not a matter of using `_Float16` instead of `__fp16`. As I said, your problem wasn't clear to me, so let's look at your example: > For example, in vneg_f16, __p0 is promoted to a vector of float before it's > negated. > > __ai float16x4_t vneg_f16(float16x4_t __p0) { > > float16x4_t __ret; > __ret = -__p0; > return __ret; > > } when I compile this and emit llvm ir I get this: define dso_local <2 x i32> @vneg_f16(<2 x i32> %__p0.coerce) local_unnamed_addr #0 { entry: %0 = bitcast <2 x i32> %__p0.coerce to <4 x half> %fneg = fneg fast <4 x half> %0 %1 = bitcast <4 x half> %fneg to <2 x i32> ret <2 x i32> %1 } so far so good I think: this shows a fneg on vector of halfs. Where and when do you see problems? Can you describe this, and also provide your compile commands? BRANCHES master, release/10.x Users: ahatanak (Author) https://reviews.llvm.org/rG825235c140e7 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
