Using !ror and !sar, should any registers be protected here?

[Ross Boyd]

In the following code snippet, I used !ror instead of PB's builtin ROTATE RIGHT (timings give an excellent speedup)
The SAR and ROR mnemonics seem to behave without any side effects, well, as far as I know.
Is there any downside to this?

function ChkSum(byval pFCBName as byte ptr) as byte
   local sum as byte
   register idx as long
   for idx = 0 to 10
      !ror sum, 1
      sum += @pFcbName[idx]
   next
   function = sum
end function

Similarly, in this code I use !sar x,4 instead of a SHIFT RIGHT x,4 - or an explicit integer divide eg x \= 16
Much faster to use SAR. But am I living dangerously or is it quite permissible here?

function SumOfNibbles(byval x as long) as long
   register sum as long
   while x
      sum += x and 15
      !sar x, 4   
   wend
   function = sum
end function

[Steve Hutchesson]

Ross,

No problems with using ROR or ROL or SHR SHL as they work on memory operands. They will also work on registers where you take the normal precautions of what registers are used.

[Ross Boyd]

Thanks for confirming that Steve - appreciate your expertise.