GCC Summit 2007

The 2007 GCC Summit just ended; all that’s left is the wrap party. Lately I haven’t been too interested in writing up comprehensive trip reports (but if you liked that style, post a comment — I’d like to know), and instead I’m just going to write about the bits I found particularly interesting. Overall the summit was good; I think the proceedings are online if you want to read the papers.

I had a few personal goals for the summit and I think I’ve accomplished all of them. I wanted to meet up with the various GCC hackers I’ve met over the years and sort of get them used to the idea that I might be around in GCC-land a bit more than previously. This was the easy part — I talked to tons of people and met many more.

I also wanted to pitch my incremental compiler to anybody who would listen, and get feedback about the idea in general and about a few specific potential problem areas. Thanks here go to Ian Taylor and Alan Modra for some assembler and linker advice; and to Mark Mitchell and Nathan Sidwell for telling me some awful truths about C++.

Nobody really complained much about my plans, not even the evil part where GCC will generate a single object per top level definition, or the even eviler part where code generation is done by fork()ing the server and doing the work in the child, to avoid having to clean up a million global variables. Now I’m left hoping I’m not in a tragedy of manners, where everyone holds back their knowledge of impending doom.

Diego, appropriately, gave the opening remarks. He showed how GCC’s SpecINT performance has remained flat over the last five years, inducing widespread depression. SpecFP looks a bit better, though, and plus everyone can agree that GCC’s internals are much nicer than they used to be.

Most of the talks were about optimizations. This is fun stuff but not my current area of interest. There were a few talks touching on the idea of writing plugins for GCC — one paper discussing a custom version of Lisp, and another having impressive amounts of working code including Python bindings and a GIMPLE visualizer. I’m hoping one or both of these go into GCC eventually; I especially like the idea of writing custom code analysis passes in Lisp.

A couple talks were about debugging. I missed one of these but the other had Daniel Jacobowitz demonstrating gdb stepping backward in time. This is awesome stuff! … though at the moment there are several restrictions and not all the patches are available. Lots of people are concerned about GCC’s debuginfo, which I hear from many sources is rather sucky.

It’s a bit strange to embark on a project that seems so unrelated to the rest of the work in GCC. I keep doing mental management on myself so as not to obsessively worry about this. Anyway the GCC crowd is pretty nice and I’m not worrying about how people will react any more.

Several people asked me about gcj of course. I tried to be clear about the fact that the situation is murky: my own gcj hacking has dropped off precipitously, though I still review patches, and what to do about gcj really depends on the level of involvement of other parties in the future (it is hard to pick a time period here but I would say at least two major releases).

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