[PATCH] D128172: [SLP] Add cost model for `llvm.powi.*` intrinsics

[Dave Green via Phabricator via llvm-commits]

dmgreen added a comment.

Thanks, LGTM. Although I was wondering why the cost came out as 12, not 14 from the constant 42. It may be possible to get a slightly better costs that more accurately match the code from ExpandPowI.



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Comment at: llvm/include/llvm/CodeGen/BasicTTIImpl.h:1424
+          // SelectionDAGBuilder.
+          unsigned ActiveBits = RHSC->getValue().getActiveBits();
+          InstructionCost Cost =
----------------
I think a more accurate count might be `ActiveBits + PopCount - 2`, at least from playing around with a few examples.


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https://reviews.llvm.org/D128172