[llvm] [InstCombine] lshr (mul (X, 2^N + 1)), N -> add (X, lshr(X, N)) (PR #92907)

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AtariDreams wrote:

Merging on the basis that this exact commit was approved before I added new stuff and then reverted said new stuff to make a new PR, which means the exact diff down to the byte was approved https://github.com/llvm/llvm-project/pull/90295.

Changes made in said PR that wasn't approved is in its own PR waiting to be reviewed: https://github.com/llvm/llvm-project/pull/92909

https://github.com/llvm/llvm-project/pull/92907