[PATCH] D53659: [ValueTracking] peek through shuffles in ComputeNumSignBits (PR37549)

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


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Comment at: lib/Analysis/ValueTracking.cpp:2515
+  case Instruction::ShuffleVector:
+    // Look through shuffle of 1 source vector.
+    if (isa<UndefValue>(U->getOperand(0)))
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Do we know for certain that we don't reference an under operand at this point? SelectionDAG::ComputeNumSignBits bails i such cases.


https://reviews.llvm.org/D53659