[PATCH] D96440: [knownbits] Preserve known bits for small shift recurrences

[Philip Reames via Phabricator via llvm-commits]

reames added inline comments.


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Comment at: llvm/lib/Analysis/ValueTracking.cpp:1343
+    // An ashr recurrence will extend the initial sign bit
+    RefineRecurrence(I, DemandedElts, Known, Known2, Depth, Q);
     break;
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nikic wrote:
> Why do we need to do this both starting from the shifts and starting from the phi? The existing code for add recurrences only starts from phis.
Great question!  Turns out I don't, I just never thought to check after adding the phi logic.  Will remove these three call sites.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D96440/new/

https://reviews.llvm.org/D96440