[all-commits] [llvm/llvm-project] 31c37a: [RISCV][TTI] Adjust VLS shuffle costing to account...

[Philip Reames via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 31c37a4a5ebc0d13d86a91c300e15177e9d77ddf
      https://github.com/llvm/llvm-project/commit/31c37a4a5ebc0d13d86a91c300e15177e9d77ddf
  Author: Philip Reames <preames at rivosinc.com>
  Date:   2025-03-29 (Sat, 29 Mar 2025)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
    M llvm/test/Analysis/CostModel/RISCV/shuffle-exact-vlen.ll

  Log Message:
  -----------
  [RISCV][TTI] Adjust VLS shuffle costing to account for sub-mask reuse (#129793)

If we have a shuffle which can be split via VLA where two or more of the
destinations have exactly the same elements, then we only need to
account for them once in costing. The duplicate copies are are (at
worst) whole register moves.

Note that this change only handles the single source case. Doing the
multiple source case seemed a bit more complicated, and I didn't have a
motivating test case.



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