[PATCH] D155218: [InstCombine] Optimize addition/subtraction operations of splats of vscale multiplied by a constant

[Paul Walker via Phabricator via llvm-commits]

paulwalker-arm added subscribers: reames, craig.topper.
paulwalker-arm added a comment.

I guess I'm making a generalisation here based on scalable vectors needing to calculate addresses and the like based on vscale and so am assuming specialised add/sub instructions will always exist.  My eyes are not tuned in to reading rvv asm, can @craig.topper  or @reames help clarify whether this combine also makes sense from a RISCV point of view.

I should add there's a growing need to sinking some of the vscale related logic back into loops to help with instruction selection, but regardless of this I still think it's preferable for this logic to be scalar rather than vector computations.


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https://reviews.llvm.org/D155218