[PATCH] D137276: [RISCV] Add cost model for fixed broadcast shuffle

[Philip Reames via Phabricator via llvm-commits]

reames accepted this revision.
reames added a comment.
This revision is now accepted and ready to land.

LGTM



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Comment at: llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp:258
+      // Example sequence:
+      //   vsetivli  zero, 2, e8, mf8, ta, mu (ignored)
+      //   vmv.v.i v8, 0
----------------
I think we have some room to improve this codegen, but that's orthogonal to your actual patch.

Ideas:
* vrgather allows a immediate broadcast index.  
* We know we're broadcasting the low bit, can copy the value to scalar register and mask.  Once we have that, need to form either a zero or all ones mask or the right length.  



Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D137276/new/

https://reviews.llvm.org/D137276