It seems they accepted this sacrifice for some other unimportant feature*
*edit: Looks as though the feature they sacrificed performance for was writing Go in Go.
1) Perf for a product should be marked against some shipping benchmark and intermediate regressions don't matter as long as we come below the benchmark at ship time.
2) Perf improvements should be "locked in" and not regressed, unless strenuously justified.
I think the parent is of group (2), where it doesn't necessarily matter that it's better than the benchmark of "against other compilers" but only that Go regressed from their earlier perf metrics for what they believe to be inadequate justification.
I think both groups have valid points. I think (2) is especially good at preventing "perf creep" wherein you continually justify small perf regressions for new features, explaining it away that competitors are doing the same. Eventually, you get to the point where everyone's just slow, but they have no impetus to improve because they're still better than the competition.
If the developers take a specific principled stance against $really_useful_feature on account that it would introduce complexity and thus degrade performance, then compromise this same principle in order to accomplish $entirely_unnecessary_port, it put the obvious lie to their avowed principles.
I don't mind that go compiles more slowly. To Thomas's point, it's still really fast. What I mind is that a good portion of the go community has accepted the lack of generics on the basis of principles that they haphazardly violated in order to scratch the useless but fun intellectual itch of bootstrapping the compiler.
Now that they've done this, they have revealed themselves to be entirely dishonest about their complexity/performance principles, and now the one legitimate objection that has kept generics out of the language has nothing to stand on.
Again, I don't care about performance per se, I care about dishonesty and hypocrisy in the platform's objectives.
Absolutely nobody in the universe promised you generics in Go. You may never, ever get them; the longer the language thrives without them, the less urgent they seem.
> Generics are convenient but they come at a cost in complexity in the type system and run-time. We haven't yet found a design that gives value proportionate to the complexity, although we continue to think about it.
The word performance doesn't appear in that paragraph.
Writing Go in Go is a huge feature, not an unimportant feature.
Writing the runtime in Go means we write the runtime in a much safer language. We found and fixed lots of bugs just by rewriting the runtime. Everybody, every user benefits from this tremendously.
Writing the runtime in Go means you can have a precise garbage collector. Every user of Go benefits from this tremendously.
Writing the runtime in Go means the runtime implementation becomes in many respects simpler, because there are no longer complex C-Go interactions (the Plan 9-derived C compiler used a slightly different calling convention!). This again reduces bugs and makes debugging easier. Everybody wins.
Writing the runtime in Go means there's one less custom compiler to maintain (no more Plan 9-derived C compiler!). Less maintenance means more time available for more important things. Also this simplifies new ports. Again, everybody wins.
Writing the compiler in Go means you can have a compiler that's not written in a language that sucks for writing compilers. Because writing compilers is now easier and consumes less time, there's more time available for more important things. Everybody wins.
Writing the compiler in Go means you benefit from all the tooling built for Go. This includes source code transformation tools. Automatic refactoring is very easy to do in Go because you have Go parsers in the standard library. This is not merely hypothetical, it's something that's actually used. The end result is that changing the compiler is faster, again allowing more work to be done.
Writing the compiler in Go also means the compiler can eventually become an idiomatic Go program that can be understood by Go programmers instead of being a ken-idiomatic C program that can only be understood by a few people. More people can work on the compiler. More work is being done as we speak, including work that will make generated code much faster. Everybody wins.
Writing the compiler in Go means you don't depend on million of lines of C++ toolchains in order to exist. As a Go compiler writer this has simplified my life a lot. I can compile the Go distribution in under a minute. On my phone. Which is 5 years old. Last time I tried to compile LLVM it died with a compile error after 6 (six!) hours.
Writing the compiler in Go means I can have fun while writing compilers for fun, so you benefit because I write it. Everybody wins.
I've written three compiler targets by now, one in C and two in Go. I don't plan to stop because I like what I am doing, but I'm not sure I would continue to do it if it were still written in C. People benefit from this not only by having more toys to play with, but new ports mean more comprehensive testing and new bugs found. Different platforms exercise different bugs differently, bugs which are present on all platforms.
Also the actual work done on the ports stimulates further refactoring efforts that will make Go even easier to port in the future. Again everybody wins! And it's only because this "unimportant feature" that is not even visible to most users of Go, coupled with the powerful refactoring technology which makes this possible.