C never was the lowest level of abstraction; there are other abstraction models out there and more still to be invented no doubt. C's model did well (though struggled mightily against Fortran for the longest time) at aligning with processor models of the 80's and 90's. It helps that C's ubiquity meant that to a degree the trail was washing the dog: processor designs were often measured against how they executed code compiled with a C compiler. But past preformance is a poor predictor of future success; who is to say that as processor designs continue to evolve, C's abstraction model won't become increasingly leaky against another? Absent a sufficiently smart compiler, it's entirely possible that C compiler writers will find themselves at a disadvantage.

And that assumes they're competing with a traditional compiler. It's possible, though unlikely, there will be competition from other execution models. As you said memory is often the core area of performance bottlenecks these days, and as terribly inefficient as bytecode interpreters are, they tend to have smaller code sizes. Efficient interprets are hand tuned specifically to make the overhead of bytecode interpretation as efficient as possible. Now, intrinsically they are performing a translation step at runtime that a compiler did before runtime, but one can at least theorize of a model where the interpreter is effectively a specialized decompression algorithm that feeds machine code to the CPU (that's really not that far afield from what happens in hardware in modern cpus and in mobile runtimes). Higher levels of abstraction might allow for more efficient decompression... It's crazy, but not inconceivable.

I've had a lot of conversations with javascript engineers over the years who've argued to me that well tuned JS will be nearly as fast as the equivalent C code. I've written plenty of little toy benchmarks over the years, and in my experience they're partly right. Well written JS code in V8 can certainly run fast - sometimes around half the speed of C code. But a massive performance gap opens up when you use nontrivial data structures. Nested fields, non-uniform arrays, trees, and so on will all cripple javascript's performance when compared to C's equivalent of simple embedded nested structs. If you couple clean C data structures with allocation-free hot paths from arenas, the performance of C will easily hit 10-20x the performance of the equivalent JS code.

From memory my plain text based operational transform code does ~800k transforms / second in javascript. The equivalent C code does 20M/second. The C implementation is about twice as many lines of code as the JS version though.

(The code in question: https://github.com/ottypes/text-unicode/blob/master/lib/type... / https://github.com/ottypes/libot )

You're right that flat datastructures are important, but C is far from the only language that can offer those.

I don't think C can ever be the answer; "comparable C code", i.e. code that was produced with the same amount of developer effort, is almost always undefined behaviour that happens to work most of the time on the developer's compiler. C doesn't have the kind of polymorphism that you need to write code that's compositional, testable, but also has good cache locality, at least not for code that also has to interact back and forth with the outside world. There is at least some work in the literature on making efficient use of cache in a Haskell/ML-like evaluation-by-reduction model, and I think that's where the long-term way forward lies (and FWIW in my experience compilers for ML-family languages already more than smart enough).

OTOH, JIT runtimes have more input data than a C compiler. They can implement some runtime equivalent of C++ profile-guided optimization: measure what actually happens in runtime, assume the input data is going to stay roughly the same, and re-generate machine code with this new information into something more efficient.

Pretty sure modern Java does that sometimes.

> In Python, JavaScript, Ruby, you have a lot of pointers to objects.

In C# you can make data structures which don’t use pointers much, or at all. The language is strongly typed, has value types, it’s easy to place structures inside other structures. There’s a native stack just like C, and even stackalloc keyword which is an equivalent of alloca() in C.

Don't JavaScript JITs rely heavily on this to reduce JavaScript's floating-point arithmetic to integer arithmetic?

Not to say it's easy, but hasn't a lot of work been done on this?