[PATCH] D115611: [X86][BF16] delete `typedef unsigned short __bfloat16`

[Freddy, Ye via Phabricator via cfe-commits]

FreddyYe 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};
----------------
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. 


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D115611/new/

https://reviews.llvm.org/D115611