[all-commits] [llvm/llvm-project] f40001: [RISCV] Lower a shuffle which is nearly identity e...

[Philip Reames via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f40001372b54ce68507f36b600f798e832478e16
      https://github.com/llvm/llvm-project/commit/f40001372b54ce68507f36b600f798e832478e16
  Author: Philip Reames <preames at rivosinc.com>
  Date:   2025-04-10 (Thu, 10 Apr 2025)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-shuffle-int.ll

  Log Message:
  -----------
  [RISCV] Lower a shuffle which is nearly identity except one replicated element (#135292)

This can be done with a vrgather.vi/vx, and (possibly) a register move.
The alternative is to do a vrgather.vv with a full width index vector.

We'd already caught the two operands forms of this shuffle; this patch
specifically handles the single operand form.

Unfortunately only in abstract, it would be nice if we canonicalized
shuffles in some way wouldn't it?



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications