Cranelift: Rewrite (x>>k)<<k into masking off the bottom k bits
#5673
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fitzgen
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cfallin
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Jan 31, 2023
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Question about a constant below, but general shape looks good.
Also I'm wondering if we should start a new file of rules, perhaps bits.isle or logical.isle, for cases like this; algebraic.isle is becoming a bit of a catch-all beyond its original "algebraic simplifications" roots.
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cfallin
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LGTM, thanks!
If it's not too much to ask for, then either in this PR or a followup, it would be great to get some runtests that trigger this rewrite as well (maybe just the tests you've added, duplicated with a few concrete invocations); that adds some more objective reassurance on top of golden-CLIF-output tests :-)
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Thanks to Souper for pointing this one out! cc @regehr (let me know if you aren't interested in being cc'd on these!)