[InstCombine] use isSubsetOf() for efficiency

C | ~D == -1
~(C | ~D) == 0
~C & D == 0
D & ~C == 0
D.isSubsetOf(C)

llvm-svn: 301021

llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp

@@ -282,7 +282,7 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
     // combining, SCEV, and codegen.
     const APInt *C;
     if (match(I->getOperand(1), m_APInt(C)) && !C->isAllOnesValue()) {
-      if ((*C | ~DemandedMask).isAllOnesValue()) {
+      if (DemandedMask.isSubsetOf(*C)) {
         // Force bits to 1 to create a 'not' op.
         I->setOperand(1, ConstantInt::getAllOnesValue(VTy));
         return I;