[LLVMbugs] [Bug 19985] New: InstCombiner::SimplifyDemandedBit can modify an instruction without adding it to the worklist

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=19985

            Bug ID: 19985
           Summary: InstCombiner::SimplifyDemandedBit can modify an
                    instruction without adding it to the worklist
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: rafael.espindola at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

bool InstCombiner::SimplifyDemandedBits(Use &U, APInt DemandedMask,
                                        APInt &KnownZero, APInt &KnownOne,
                                        unsigned Depth) {
  Value *NewVal = SimplifyDemandedUseBits(U.get(), DemandedMask,
                                          KnownZero, KnownOne, Depth);
  if (!NewVal) return false;
  U = NewVal;
  return true;
}

The use is modified, but the instructions in not added back to the worklist.

I don't have a testcase where this changes the result. I just noticed an
instruction being modified and not immediately being revisited while looking at
another issuer in a debugger.

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