Re: Does Duff Device break C compilers

Preston Briggs (preston@tera.com) wrote:
: >item called Duff's Device. I showed to a couple of guys here at my
: >work place and they never seen it before. Then they declared that such
: >an unorthodox technique could potential break some C compilers.


: I agree with the moderator. It's not obvious, but it's not that hard
: to compile. I'd expect everyone to get it right. On the other hand,
: I wouldn't be surprised if the resulting code wasn't that great. Why?
: It makes an irreducible loop and lots of optimizers don't do much with
: irreducible loops. Also hard to software pipeline, etc.


Certainly the compiler I worked on recognized 'conventionally written'
switch statements and converted them to a structured statement that was
properly optimized. The Duffs device code would not be handled this way, it
would be routed to the 'I don't know whats happening here, I had better play
safe and turn of all optimizations' code generator.


--
Stephen Baynes baynes@ukpsshp1.serigate.philips.nl
Philips Semiconductors Ltd
Southampton
United Kingdom
--

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