[all-commits] [llvm/llvm-project] 0085ec: [AArch64] Add costs for ROTR and ROTL. (#169335)

[David Green via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0085ecaa5e16edbc6426b91f97a85de8e32f962c
      https://github.com/llvm/llvm-project/commit/0085ecaa5e16edbc6426b91f97a85de8e32f962c
  Author: David Green <david.green at arm.com>
  Date:   2025-11-28 (Fri, 28 Nov 2025)

  Changed paths:
    M llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
    M llvm/test/Analysis/CostModel/AArch64/fshl.ll
    M llvm/test/Analysis/CostModel/AArch64/fshr.ll

  Log Message:
  -----------
  [AArch64] Add costs for ROTR and ROTL. (#169335)

A funnel shift with the first two operands is a rotate. AArch64 has
scalar instructions for ror so can handle a ROTR by a constant or
variant amount cheaply. A ROTL is a ROTR by the opposite amount, which
for constants is cheap and for variable shifts requires an extra neg.



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