[llvm] [InstCombine] lshr (mul (X, 2^N + 1)), N -> add (X, lshr(X, N)) (PR #90295)

[via llvm-commits]

AtariDreams wrote:

> > > > A generalization of the proposed x * 3/2 -> x + (x >> 1) transformation.
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> > > Proposed where?
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> > This question was not answered. The way this is written implies there was some discussion separate from this PR that proposed something. There should be a link to that proposal or this commit message should be rephrased.
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> A variant of this PR was originally part of https://github.com/llvm/llvm-project/pull/88193. What was "proposed" is that these unrelated changes be removed from that PR.

And those unrelated changes were!

https://github.com/llvm/llvm-project/pull/90295