On Thu, Feb 28, 2019 at 12:46 AM <ivan.medoe...@gmail.com> wrote: > Thanks, Ian. > > I remember reading in some compiler book that languages should be designed > for a single pass to reduce compilation speed. > > As a guess: this was true in the past, but in a modern setting it fails to hold.
Andy Keep's phd dissertation[0] implements a "nanopass compiler" which is taking the pass count to the extreme. Rather than having a single pass, the compiler does 50 passes or so over the code, each pass doing a little simplification. The compelling reason to do so is that you can do cut, paste, and copy (snarf) each pass and tinker much more with the compilation pipeline than you would normally be able to do. Also, rerunning certain simplify passes along the way tend to help the final emitted machine code. You might wonder how much this affects compilation speed. Quote: "The new compiler meets the goals set out in the research plan. When compared to the original compiler on a set of benchmarks, the benchmarks, for the new compiler run, on average, between 15.0% and 26.6% faster, depending on the architecture and optimization level. The compile times for the new compiler are also well within the goal, with a range of 1.64 to 1.75 times slower. " [Note: the goal was a factor 2.0 slowdown at most] The compiler it is beating here is Chez Scheme, a highly optimizing Scheme compiler. Some of the reasons are that intermediate representations can be kept in memory nowadays, where it is going to be much faster to process. And that memory is still getting faster, even though at a slower pace than the CPUs are. The nanopass framework is also unique because it has macro tooling for creating intermediate languages out of existing ones. So you have many IR formats in the compiler as well. In conclusion: if a massive pass blowup can be implemented within a 2x factor slowdown, then a couple of additional passes is not likely to make the compiler run any slower. [0] http://andykeep.com/pubs/dissertation.pdf -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
