[PATCH] D129765: [DAG] SimplifyDemandedBits - don't early-out for multiple use values

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


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Comment at: llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp:1106-1112
   } else if (OriginalDemandedBits == 0 || OriginalDemandedElts == 0) {
     // Not demanding any bits/elts from Op.
     return TLO.CombineTo(Op, TLO.DAG.getUNDEF(VT));
   } else if (Depth >= SelectionDAG::MaxRecursionDepth) {
     // Limit search depth.
     return false;
   }
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RKSimon wrote:
> deadalnix wrote:
> > Why not start with the early returns?
> I'll clean it up - we can move the max depth limit to the top now, but the multi-use case still has to come before the no demanded case.
This actually caused regressions because we had a couple of cases where we had no demanded bits/elts but were at the depth limit - returning UNDEF allowed for further simplifications later on.


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  https://reviews.llvm.org/D129765/new/

https://reviews.llvm.org/D129765