addx/subx/movep/Metascope/A68k

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2 total messages Started by Chris Hames [bytey] Mon, 17 Dec 1990 03:11

#7536

Author: Chris Hames [bytey]
Date: Mon, 17 Dec 1990 03:11

21 lines
1313 bytes

   Is it common knowledge that the addx/subx instructions don't set the
zero flag when the result is zero but clear it if the result is not zero?
Why didn't someone tell me!!!!!!!!!!!!  hours hours hours debugging.....

   Charlie Gibb-A68k2.42 movep.w 1(a0),d0  gives and alignment error when it is
valid instruction.  Thanks for a nice assembler.

   Is Metadigm still alive?  Has there been an update of Metascope Debugger
since 1.17 ?   Is there address still :-

          19762 MacArthur Blvd
          Suite 300
          Irvine, CA 92715

Thanks in advance,
-- 
Chris Hames - C/Assembler programmer | Fish: DirWork,FSDirs,VMK..|  /~\/ \
              3:633/353  (Fido)      | Commercial:  Soon...      | (  OZ  )
mail bytey@phoenix.pub.uu.oz.au      +---------------------------+ `--'\_/
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Re: addx/subx/movep/Metascope/A68k

#7538

Author: Checkpoint Technologies
Date: Tue, 18 Dec 1990 04:20

18 lines
1613 bytes

In article <1990Dec17.031120.3658@phoenix.pub.uu.oz.au> bytey@phoenix.pub.uu.oz.au (Chris Hames [bytey]) writes:
>   Is it common knowledge that the addx/subx instructions don't set the
>zero flag when the result is zero but clear it if the result is not zero?
>Why didn't someone tell me!!!!!!!!!!!!  hours hours hours debugging.....

This may come under the heading of "obscure feature" - but yes, it's
always been that way.  It lets you find the total zerosity (??) of the
result of a long multi-precision add/sub.  You set Z before starting,
and if any intermediate instr gives a non-zero it's cleared.  This way if
all the intermediate results are zero, Z remains set at the end,
otherwise Z is cleared.

Did we need this feature?  Ah, that's another topic... :-)
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