[PATCH] D41643: [DAG] Fix for Bug PR34620 - Allow SimplifyDemandedBits to look through bitcasted constants

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


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Comment at: lib/CodeGen/SelectionDAG/TargetLowering.cpp:1225
+    // do this on a recursive call where Known may be useful to the caller.
+    if (Depth > 0 && isConstOrConstSplat(Op.getOperand(0))) {
+      TLO.DAG.computeKnownBits(Op, Known, Depth);
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RKSimon wrote:
> Would this catch more if we used isConstantOrConstantVector from DAGCombiner.cpp (we'd have to move it to SelectionDAG.h or similar)?
Why do we need to the constant qualifier at all? Isn't it generally useful to get any known bits from the other side of the bitcast?


https://reviews.llvm.org/D41643