[PATCH] D110076: [AMDGPU][GlobalISel] Code quality: Combine V_RSQ

[Jay Foad via Phabricator via llvm-commits]

foad added a comment.

> Added implementation for all possible cases which should be combined into rsq (rcp(sqrt(x)), sqrt(rcp(x)), 1/sqrt(x), sqrt(1/x)).

I thought this would be two separate combines:

1. (1.0 / x) -> (rcp x)
2. (sqrt (rcp x)) or (rcp (sqrt x)) -> (rsq x)

Is there some reason we don't implement the first combine, e.g. because of the precision of the rcp instruction is not good enough? What does SelectionDAG do?


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  https://reviews.llvm.org/D110076/new/

https://reviews.llvm.org/D110076