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Subject: Re: Portability
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From: Lars Brinkhoff <lars.spam@nocrew.org>
Organization: nocrew
Date: Wed, 17 Apr 2013 19:26:16 +0200
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Xref: csiph.com comp.lang.forth:21703

Sieur de Bienville <morrimichael@gmail.com> writes:
> I don't remember how the 68k CMP instruction works

Finally an excuse to break out the old M68000PM/AD.


  CMP

  Operation: Destination - Source => cc

  Description: Subtracts the source operand from the destination data
  register and sets the condition codes to the result; the data
  register is not changed.  The size of the operation can be byte,
  word, or long.

  Condition Codes:

  X - Not affected.
  N - Set if the result is negative; cleared otherwise.
  Z - Set if the result is zero; cleared otherwise.
  V - Set if an overflow occurs; cleared otherwise.
  C - Set if a borrow occurs; cleared otherwise.


And then e.g. BLT uses this test: N && !V || !N && V.

> but the IA-32 and the AMD64 CMP instruction is a nondestructive
> version of the SUB instruction.

So essentially the same.