two-instruction method to rotate carry-Not into register?

ags

Is there any way to rotate the negated value of the carry flag into a register? I see such an instruction doesn't exist, but is there an ingenious way to do this in two instructions? There's a muxnc for muxc, a negnc for negc, but no rcnr for rcr. The application is difficult to explain, and I can simply xor the final result with -1. That causes some other problems. The typical code is:

        shr  reg1, #1  wc
        rcr  reg2, #1

I'm looking to get the inverse of the LSB of reg1 shifted (rotated) into the MSB of reg2, in two instructions. Is that possible?

Mike Green

If you use the same register for the input and the output, you can do:

                shr   reg, #1   wc
                muxnc reg,bit31

bit31 is a long containing |<31. Depending on what you want to do with the result, you may need some cleanup afterwards. If reg just contains an 8-bit value, you're done after 8 of these.

lonesock

I'm guessing pre-XORing reg1 with -1 is not an option either?

Jonathan

P.S. I was wishing for a ADDNX command, but alas, it is not available.

ags

@Mike Green: I need to strip one bit at a time, invert it, and then distribute to one of 32 target registers - so that won't help for my situation.
@lonesock: I am using an xor now, but it's messy and I was hoping for an alternative.

Thanks.

lonesock

Any chance you could post a working segment of code so I can play with it? This sounds like a fun challenge.

Jonathan