🚀 go-pugleaf

In article <1993Jan7.154426.3421@odin.diku.dk>, terra@diku.dk (Morten Welinder) writes:
|> 
|> The Intel 486 programmer's reference manual very clearly states that
|> the shift operations -- except for "Shrd" and "Shld" -- always set 
|> the basic flags. The code:
|> 
|> 	Mov	Ax,0
|> 	Mov	Cl,0
|> 	Cmp	Ax,-1		; Clear zero flag
|> 	Shr	Ax,Cl		; Result is zero.
|> 
|> should leave you with the zero flag set. However, tests on my i486 
|> shows that this is not true. The shift is executed as a "Nop".
|> 
|> I would like to know how other processors respond to this piece of
|> code. Please try it and email the result to "terra@diku.dk" stating
|> the processor type, of course. Also if you have a manual for another
|> processor, please look up the description of the shifts. I would like
|> to know if there are any differences.


From the Intel 486(TM) Microprocessor Family Programmer's Reference
Manual:

        SAL/SAR/SHL/SHR - Shift Instructions

        Flags Affected

            If count = 0, the flags are not affected.

        (page 26-253 in the 1992 edition)

--Chris
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