[llvm-bugs] [Bug 36319] New: [ValueTracking] Add DemandedElts support to computeKnownBits/ComputeNumSignBits

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=36319

            Bug ID: 36319
           Summary: [ValueTracking] Add DemandedElts support to
                    computeKnownBits/ComputeNumSignBits
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: llvm-dev at redking.me.uk
                CC: craig.topper at gmail.com, david.majnemer at gmail.com,
                    efriedma at codeaurora.org, llvm-bugs at lists.llvm.org,
                    spatel+llvm at rotateright.com

The addition of a DemandedElts mask helped a lot for vector types in
SelectionDAG::computeKnownBits and SelectionDAG::ComputeNumSignBits, notably
making it easier to determine bits for vector shuffles and element
insertions/extractions.

If possible it'd be great to bring this to ValueTracking as well to assist
InstCombine.

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