[PATCH] D87384: [PowerPC] Add ISEL patterns for Mul with Imm.

[EsmeYi via Phabricator via llvm-commits]

Esme added a comment.

Thank you for your comments! @jsji @nemanjai

For scenarios 2 and 3, I will modified it as @nemanjai 's hint, and move it to DAGCombiner since it is really similar to existing patterns and then implement our `PPCTargetLowering::decomposeMulByConstant`. If other targets are interested about this, they can add conditions for this in their `decomposeMulByConstant`.

But for scenario 1, I am not sure if there are benefits to other targets, since it is inspired by our HW instruction `MULLI`. So I prefer to keep it in ISEL.


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https://reviews.llvm.org/D87384