[PATCH] D43349: [InstCombine] Make SimplifyDemandedUseBits handle PhiNode

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


================
Comment at: lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp:679
+      KnownBits PhiOperandKnown(BitWidth);
+      SimplifyDemandedBits(I, i, DemandedMask, PhiOperandKnown, Depth + 1);
+      IKnownZero &= PhiOperandKnown.Zero;
----------------
This call is going to be expensive in the case where the PHI node refers to itself (either directly or indirectly).  It's not an infinite loop due to the depth limit, but we might want to limit the recursion some other way.


https://reviews.llvm.org/D43349