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Bug 52518 - [InstCombine] Failure to simplify (~A|B)^A --> ~(A&B)
Summary: [InstCombine] Failure to simplify (~A|B)^A --> ~(A&B)
Status: NEW
Alias: None
Product: libraries
Classification: Unclassified
Component: Scalar Optimizations (show other bugs)
Version: trunk
Hardware: PC Linux
: P enhancement
Assignee: Mehrnoosh Heidarpour
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2021-11-16 01:07 PST by Jay Foad
Modified: 2021-11-21 11:19 PST (History)
4 users (show)

See Also:
Fixed By Commit(s):


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Description Jay Foad 2021-11-16 01:07:56 PST
InstCombine should simplify (~A|B)^A --> ~(A&B).

Here's CompilerExplorer showing that (a) the transformation is valid according to Alive2, and (b) "opt -O2" does not do it:
https://alive2.llvm.org/ce/#z:OYLghAFBqd5QCxAYwPYBMCmBRdBLAF1QCcAaPECAM1QDsCBlZAQwBtMQBGAFlICsupVs1qhWrAG4BbUgGdM7ZATx1KmWugDCqVgFcptLgFZS69ABk8tTADl9AI0zEQAdlIAHVLMIra2vQbGHl4%2BdJbWdlKOzm7yisp0DATMxAT%2B%2BoacJnGYSr5JKQThtg5OrnLJqemBWRWFxZHRrgCUcqi6xMgcAORYVFaYANR43IMAAgTABBAjgwCkAExGAAykw6OLRpzNg6yoLKwA%2Brq0tMxSmOiHzOjoxPMLAMzL8y4AQnPLAIL29iCfX0GDyMC3mjwAIoMROh1sDOGtNssAUDNo8wZCAB4kWGbBZrAC0nGRg2ImAIOKWjwBcxc4IBfQGsLGsk6Mw2S1WFK2Oz2B2Op3Ol2ut3ui2erw%2B31%2B/2%2BKKWoLmEMGWPus0RBKJsuBaMVkOxavlCKWmsBwI2SpVXMeRpWxNJ5INRm41NpAO6rVYIG6Rm6pEM3WWvtQXvM5gAagBZQYASQASoNZO1OkMxZxfQQvYHmq0ANYgFZCL3cX3%2BwOkYPdX2yECrDMB92kOCwGCIFCoKTuPDsMgUCBoDtdsqodwEUj9VgEJzViB/eukexWFIATy9adI/Yu9AA8rRWCu51gpCJgOxM778KS8hJMNW55gMbldJPV76rJPPXPWHh7MRl9osC%2BpAEMQeBSC%2BrQ0PQTBsBwPD8IIwiiCA4jSEI37VpArTDgktC3viW4LFWCi5DhagaNUmSmBoDSlM48KeN4OEUYIDGhLQNFRGU8I5HkiSVGkOgZIIPE4QUqQcU03H8cxUn1AMjRca0iYdF0XAel6Pp%2Bme5ZethgwQLghDYqmazaAO3YPI82yDKGkYxrG6ZntmpAIJgNxlBAub5qsH7FqQYEFqWQZelWNZAU5jYthASD9p23bkJQsWDs4bB4NeY5dpOxDTrOZYLmcxD7muG7qAQO57tph7HqeB54JeyjXreZb3o%2Bz7dGub4KNpX4/n%2BGA9GuwGgeBY50IwBywbwAh4ohYiSDIPUYZ55Yjr4t5EfEvhkVogk1FRFjybRLEhExu2UaxOESVxcjEbxtBiQJASUSJ%2BT8VddF1FUZ3CW9h2cXRSlJqp2yFt6JbaRWqXXviBASPphlEKKTzwoMZlxU4lkLDstlRnGjn1s5rnuc4y2%2Bb6AWrEFOmVnIYV1lmXkFh%2Bjzg3OFb4wzoOEVpbMheFBOtNe2VbdwQA%3D%3D%3D