[PATCH] D158622: [RISCV] Cost slide in insertelement/extractelement as linear in LMUL

[Philip Reames via Phabricator via llvm-commits]

reames planned changes to this revision.
reames added a comment.

Ran this against SPEC, and got some surprising results.  This ends up basically disabling SLP.  The reason is that SLP is relying on multiple rounds of vectorization to reach profitable final results, and the intermediate results involve lots of extracts.  Increasing the extract costs - correctly - disables vectorization.  The intermediate result is locally optimal, but global non-optimal.

Marking this as Plan Changes as a bunch of other work needs to happen before this can land.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D158622/new/

https://reviews.llvm.org/D158622