[all-commits] [llvm/llvm-project] 50afaf: [RISCV][TTI] Adjust constant materialization cost ...

[Philip Reames via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 50afafbf299385c4836cca5383e9cd7eb7593c9a
      https://github.com/llvm/llvm-project/commit/50afafbf299385c4836cca5383e9cd7eb7593c9a
  Author: Philip Reames <preames at rivosinc.com>
  Date:   2024-09-27 (Fri, 27 Sep 2024)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
    M llvm/test/Analysis/CostModel/RISCV/cast.ll
    M llvm/test/Analysis/CostModel/RISCV/cttz_elts.ll

  Log Message:
  -----------
  [RISCV][TTI] Adjust constant materialization cost for (z/s)ext from i1 (#110282)

When we're lowering to a split sequence, we only need one
materialization of the zero constant. Our codegen looks something like
this:

  vmv.v.i	v24, 0
  vmerge.vim	v8, v24, -1, v0
  vmv1r.v	v0, v16
  vmerge.vim	v16, v24, -1, v0

Note: Doing this specific case since it was pointed out in
https://github.com/llvm/llvm-project/pull/110164#discussion_r1778268391,
but it's worth noting that we have the same basic problem (over costing
split operations with split invariant terms) at multiple places through
this file.



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