[PATCH] D146711: [RISCV] Lower shuffles as vmerge + vslide{up,down} where possible

[Philip Reames via Phabricator via llvm-commits]

reames added inline comments.


================
Comment at: llvm/lib/Target/RISCV/RISCVISelLowering.cpp:3657
+
+    return DAG.getNode(ISD::VSELECT, DL, VT, SelectMask,
+                       SlideIfNeeded(V1, V1SelectOffset),
----------------
I don't have a concrete example, but thinking about it, this seems suspect.  You're computing the select condition vector using the elements at the original offsets, but actually selecting between elements which have been slide up or down.  That doesn't seem right, we should be having to adjust the select mask too.  


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D146711/new/

https://reviews.llvm.org/D146711