pengfei added inline comments.
================
Comment at: clang/lib/Headers/avx512vlbf16intrin.h:416
/// and fraction field is truncated to 7 bits.
-static __inline__ __bfloat16 __DEFAULT_FN_ATTRS128 _mm_cvtness_sbh(float __A) {
+static __inline__ short __DEFAULT_FN_ATTRS128 _mm_cvtness_sbh(float __A) {
__v4sf __V = {__A, 0, 0, 0};
----------------
pengfei wrote:
> FreddyYe wrote:
> > craig.topper wrote:
> > > I'm not sure if this change is a good idea this late. Users could have
> > > been dependent on it being an unsigned value before. I believe this
> > > changes the behavior of this code
> > >
> > > ```
> > > int result = _mm_cvtness_sbh(X)
> > > ```
> > >
> > > Previously it would have zero extended, but now it will sign extend.
> > Yes, this should be a huge concern.
> >
> > Notice that intrinsic update has just documented these two intrinsics on
> > 12/7/2021. So maybe we still have change to change it? And it's more theory
> > right to do sign extension from a bfloat16 to int32.
> I think this is the problem that we choose integer to represent BF16. Neither
> zero extend nor sign extend makes sense to a floating type. But considering
> the MSB of floating point is sign bit. Sign extend should be better in theory.
> Maybe it's a good approach to use `__bf16`, but it is supported only by
> Clang. We can't use it for intrinsics.
> Anyway, I'm fine with keeping zero extend here. @craig.topper , do you think
> it's acceptable to you if we just change `__bfloat16` to `short`?
Sorry, I mean `unsigned short`
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D115611/new/
https://reviews.llvm.org/D115611
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