private void RewriteShiftMem(Func <Expression, Expression, Expression> fn)
{
var mem = RewriteOp(instr.Operands[0]);
var tmp = binder.CreateTemporary(PrimitiveType.Byte);
m.Assign(tmp, fn(mem, m.Int8(1)));
m.Assign(mem, tmp);
NZVC(tmp);
}
