[llvm-bugs] [Bug 52479] New: [InstCombine] Failure to simplify A|B|(A^B) --> A|B

Thu Nov 11 11:57:29 PST 2021

https://bugs.llvm.org/show_bug.cgi?id=52479

            Bug ID: 52479
           Summary: [InstCombine] Failure to simplify A|B|(A^B) --> A|B
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: jay.foad at gmail.com
                CC: llvm-bugs at lists.llvm.org

InstCombine should simplify A|B|(A^B) --> A|B.

Here's CompilerExplorer showing that (a) the transformation is valid according
to Alive2, and (b) "opt -O3" does not do it:
https://alive2.llvm.org/ce/#z:OYLghAFBqd5QCxAYwPYBMCmBRdBLAF1QCcAaPECAM1QDsCBlZAQwBtMQBGAFlICsupVs1qhWrAG4BbUgGdM7ZATx1KmWugDCqVgFcptLgFZS69ABk8tTADl9AI0zEQANlIAHVLMIra2vQbGHl4%2BdJbWdlKOzm7yisp0DATMxAT%2B%2BoacJnGYSr5JKQThtg5OrnLJqemBWRWFxZHRrgCUcqi6xMgcAORYVFaYANR43IMAAgTABBAjgwCkAExGAAykw6OLRpzN8wDsAEJzywCC9vYgR8eD80sL8wDMACKDJOs3W2uby5fXxJgEb02C0uc12j0ufQGbzGsk6Mw2S1WgKW2z2hxOZwuJ2uQIez1es02nE%2BiJ%2B73ueMGAA8CQiPu9vtj3hsni9iMijAsSUZ7mS/gDCUtuCCwZduq1WCBukZuqRDN1lrLUFLzOYAGoAWUGAEkAEqDWTtTpDRb3TiyghSxXNVoAaxAKyEUu4svlitIyu6stkIFWloV4tIcFgMEQKFQUnceHYZAoEDQkejZVQ7gIpH6rAITh9EHOAdI9isKQAnlLzaQE1J1AQAPK0Vil/NYKQiYDsK2y/B/PISTA%2B/OYKm5XRZsuyqxZyX51h4ezEEvaLBj0gEYh4KRj1o0ehMNgcHj8QTCUQgcTSISzn2QVophK0fsAWhrC29Clyd7UGmqmVMGgapWcYlPG8O9v0EYDQlof8ojKYkcjyRJKjSHQMkEeC7wKVJoKaOCkLA3D6gGRpYNaQ0Oi6LgJSlGU5Q7D0pVvQYIFwQhXlNYlBm0RMYxuM0dlVTUdV1C0OxtUgEEwZgsGcCA7QdVYpxdUgN0dN0lSlb1fRXUSg1DCAkATKMY3IShDKTZw2DwXt02jLNiBzPN3ULWgS2XStqzrBs6ObVt2ybPBu2UXt%2B3dQdh1HbpywnBQ6JnOcFwwHpy1XddN3TOhGBYdsDwELljzESQZDiq9ZI9VNfH7V94l8T8tBQmpfwsIiAPAkJQPqn8ILvbDYLkN8ENoTDkICH90PyJCesAuoqg6tCJuamDANIo0KO2J1pVdOjPUs3sHwICQmJYoh2XYtYuKMpxeIWfj1S1PURIDMSJKkspSsU2UVNWNT6K9OQtP9a05MdKd7k2/NPQewH1pfWjwY07THtaXt7Jq7ggA%3D

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