[PATCH] D76727: [VectorCombine] transform bitcasted shuffle to narrower elements

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

In D76727#1939961 <https://reviews.llvm.org/D76727#1939961>, @lebedev.ri wrote:

> Do we need to count the cost of bitcasts too?


Hmm...is there a scenario where the old bitcast is different in cost than the new bitcast? That op is effectively getting hoisted in the test cases shown here, so it would cancel out if we put it on both sides of the cost comparison.
The TTI API that I think we'd use for this is: TTI.getCastInstrCost(Instruction::BitCast, DestTy, SrcTy).


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https://reviews.llvm.org/D76727