On 26/07/13 22:56, Edward Z. Yang wrote:
Thank you Edward. I am aware of these requirements - my problem is writing the code in which these will always hold (I'm optimizing Cmm and hand-written Cmm files tend to cause many problems that don't appear in automatically generated Cmm). Having a debugging tool in form of Fuel would be helpful for me, because instead of getting a freeze and seeing no output from -ddump-cmm I would see incorrectly transformed Cmm that would allow me to track bugs more easily.
In that case, I would recommend taking a look at when -dopt-fuel got removed and seeing if you can put it back in. I quite liked this feature and it is too bad it is gone.
Guilty. I got rid of the fuel (in GHC's version of the dataflow algorithm). I think removing it was worth a percent or two in compile-time performance - not a lot, but this was one of a whole heap of such things that I did to get the new codegen from about 100% to 5% overhead. I've no objection to the idea of optimisation fuel, but it should be an optional thing that doesn't cost anything if you don't use it. Cheers, Simon