Source's side-effects should happen before Dest's
Source's side-effects should happen before Dest's

An operation such as ABCD -(A0), -(A0) that uses the same register
twice, with side-effects, must do so in the correct order. It must
determine the EA and value of the destination after having evaluated the
source.

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emoon/r68k,marhel/r68k,emoon/r68k,marhel/r68k