[PATCH] D82602: [SelectionDAG] don't split branch on logic-of-vector-compares

Fri Jun 26 12:36:02 PDT 2020

RKSimon added a comment.

In D82602#2117418 <https://reviews.llvm.org/D82602#2117418>, @spatel wrote:

> Thanks. I can't tell if there's some generic transform that would help or if something target-specific is missing.
>  We have this after type-legalization:
>
>         t50: v4i32 = BUILD_VECTOR undef:i32, t32, undef:i32, undef:i32
>       t51: v2i64 = bitcast t50
>       t30: v2i64 = BUILD_VECTOR Constant:i64<1>, Constant:i64<1>
>     t36: v2i64 = xor t51, t30
>   t45: v4i32 = bitcast t36
>   
>
> Would converting the xor to v4i32 help? computeKnownBits probably has problems looking through bitcasts.

The bitcasts shouldn't be a problem, but the undefs will cause it to bail if any of those undef elements are demanded.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D82602/new/

https://reviews.llvm.org/D82602