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set register if flag is set instruction
by Victor on May 14, 2004 |
Victor
Posts: 9 Joined: Mar 1, 2002 Last seen: Jul 3, 2002 |
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Hello,
maybe your OpenRISC architecture manual is a bit outdated, as the latest version includes the instruction you are talking about (which I also don't mind at all having), I'll paste the description directly from it: Format: l.cmov rD,rA,rB Description: If SR[F] is set, general-purpose register rA is placed in general-purpose register rD. If SR[F] is cleared, general-purpose register rB is placed in general-purpose register rD. I find it a very good call to include it in the ISA. Regards, Victor Lopez On Sat, 15 May 2004, Damjan Lampret wrote: : Actually, I was doing a lot of analysis in 1999 looking at the Alpha model
: and comparing it to the traditional model of flags. If you remember
at the
: time I defined only one true flag and that is "F" flag; the one set
by sfXX
: instructions. Everything else like CY came later and these are not
real
: flags... The alpha model doesn't have much advantage.
I do not have any problems at all with having a single -flag- register.
But I wouldn't miss a "set register if flag is set" instruction, or
simply a copy-flag-to-gpr instruction. This would not break the
current ISA, but could be seen as an extension. Maybe something to
think about for the next revision?
Hope you're feeling better, Damjan.
~j
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