[PATCH] D68103: [InstCombine] Simplify shift-by-sext to shift-by-zext

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a subscriber: efriedma.
spatel added a comment.

There are a handful of existing transforms in InstCombine that look at users rather than operands, so it's not unprecedented. But I'm not sure if there's another/better way. 
One possibility would be to ignore the usual hasOneUse() constraint because we're ok with the trade-off (better analysis despite a potential extra instruction).
You could add the basic fold (with m_OneUse()) as a preliminary and non-controversial step? That would reduce risk and make it clear that whatever extra code that we use is specifically for the multi-use case.  
cc @efriedma in case he has advice.


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https://reviews.llvm.org/D68103