[InstCombine] Remove redundant add+and fold (NFCI)

This is handling a special case of demanded bits simplification
(which has multi-use support for adds, so it's not applicable in
that case either).

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -2248,13 +2248,6 @@ Instruction *InstCombinerImpl::visitAnd(BinaryOperator &I) {
 
     const APInt *AddC;
     if (match(Op0, m_Add(m_Value(X), m_APInt(AddC)))) {
-      // If we add zeros to every bit below a mask, the add has no effect:
-      // (X + AddC) & LowMaskC --> X & LowMaskC
-      unsigned Ctlz = C->countl_zero();
-      APInt LowMask(APInt::getLowBitsSet(Width, Width - Ctlz));
-      if ((*AddC & LowMask).isZero())
-        return BinaryOperator::CreateAnd(X, Op1);
-
       // If we are masking the result of the add down to exactly one bit and
       // the constant we are adding has no bits set below that bit, then the
       // add is flipping a single bit. Example: