It does feel like you have to know a ton of m68k asm already in order to know when its good enough, so you might aswell have written it as inline asm to begin with.
C was always just a "high level" assembler. Eventually you have the techniques in your mental toolbox to nudge your compiler in the right direction. Unless you read the K&R deeply you might not even know there is "volatile" and "register" keyword. Then with poking your compiler do you get to find out what it does when you write code with those modifiers.
As a tutorial on how to go about optimizing code youits good, as a practical matter there wasn't much need to tweak this piece of code for a production system. IMHO. Opinions will vary. I always worked in shops where the schedule was always shrinking and deadlines loomed ever closer - optimizing only where it was absolutely needed.
It'd be interesting to see comparisons to contemporary compilers. IIRC, GCC's output was notably not very good back in the day compared to any commercial 68k compiler, although I assume this is a more recent version of GCC.
As a tutorial on how to go about optimizing code youits good, as a practical matter there wasn't much need to tweak this piece of code for a production system. IMHO. Opinions will vary. I always worked in shops where the schedule was always shrinking and deadlines loomed ever closer - optimizing only where it was absolutely needed.