[PATCH] D102755: [AArch64] Add cost tests for bitreverse

[Dave Green via Phabricator via llvm-commits]

dmgreen added inline comments.


================
Comment at: llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp:259
+    auto LT = TLI->getTypeLegalizationCost(DL, RetTy);
+    if (any_of(ValidBitTys, [&LT](MVT M) { return M == LT.second; }))
+      return LT.first;
----------------
I think that these types should have a slightly higher cost than just 1 (or 1*LT.first, the legalization cost).

It's common in these cost functions to have a table of operand and type, giving a cost to each. That way they can be controlled a little better. Like the getShuffleCost at the end of this file. Would it be worth adding something similar here?

(We could also maybe optimize the v4i32 case better using a vrev32. But it's probably best to use the current cost over what we expect it could be later).


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D102755/new/

https://reviews.llvm.org/D102755