[PATCH] D133739: [RISCV][WIP] Form more VW instructions

[Quentin Colombet via Phabricator via llvm-commits]

qcolombet added a comment.

> My point about restricting that transform to one use while not restricting the variant that doesn't require the shift at all still seems reasonable

Just to react on that, although this could be a relatively easy win (see next sentence), in our motivating example it would not help because we keep the intermediate extends, while having several uses.

Going back to dropping the one-use check for the variant that completely fold, I'm unclear how we could make sure this is always a net win. We still have the register pressure issue if the extension is not completely eliminated.


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https://reviews.llvm.org/D133739