Hacker News Reader

Comment by Rochus | Hacker News Reader

QBE is really interesting, but for people like me who still use 32 bit architectures unfortunately a bit limited. Someone recently pointed me to the Eigen compiler kit (see e.g. https://github.com/EigenCompilerSuite/) which - like QBE - is a lean alternative to LLVM, but supports much more architectures than QBE, even some 16 bit ones; since last week also Xtensa (ESP32) is officially supported. It's still beyond me why the Eigen kit, which has been in development for more than ten years, is not more popular.

View on HN

Although unfortunately not open source proper, vbcc[0][1] is interesting.

0. http://www.compilers.de/vbcc.html

1. https://en.wikipedia.org/wiki/Vbcc

QBE (and Eigen) are compiler kits, i.e. useful if you implement your own compiler. There are a lot of open-source C compilers already available for nearly any architecture.

Fair. But note that while not a "compiler kit", VBCC has front/backend separation. This is why I mentioned it.

Of course, as it isn't open source, third party backends/frontends are unlikely to occur.

Fortunately, despite not open source, the code and documentation can still be studied.

ECS looks cool, and also supports the 68000. The described ABI seems very incompatible with AmigaOS (a6) although it is likely possible to instruct the compiler to do otherwise.

Unfortunately missing in ECS is RISC-V, which QBE supports.

> Unfortunately missing in ECS is RISC-V, which QBE supports

Well, the Tensilica ABI only took a few weeks to implement; so I assume that when enough people ask for a RISC-V backend, there will be one in reasonable time. Personally I consider ESP32 and ARM32 support more useful.

>Personally I consider ESP32

Sure you don't mean Tensilica i.e. legacy ESP32?

Espressif has notably switched to RISC-V.

> Espressif has notably switched to RISC-V

Not really switched; they offer ESP32 models with (so far) single-core RISC-V; I don't think they planned to stop selling the original ESP32 designs (they wouldn't do themselves a favour).

>Not really switched

Yes very much switched. Thoroughly[0].

While obviously only for new chips, years have already passed, and many new chips have been released. Tensilica are now only present in a minority of their offerings.

>I don't think they planned to stop selling the original ESP32 designs

In this market, having long term availability is important.

0. https://riscv.or.jp/en/2021/02/latest-esp32-includes-risc-v/

> While obviously only for new chips, years have already passed

Well, in 2022 they upgraded to the L7 cores.

> having long term availability is important

So they will obviously continue to produce the tensilica models (which they wouldn't if they really "switched"); that's all I (and many other developers) need.

Out of curiosity, why are you still using 32-bit architectures?

Dunno if this is where you're coming from, but working in 32-bit isn't that wacky. For example a very popular microcontroller [0] is 32-bit.

EDIT: definitely not "maybe the most" popular

[0]: https://en.wikipedia.org/wiki/ESP32

As far as I know, webassembly only supports a 32 bit address space on all platforms at the moment. There’s a memory64 proposal, but it doesn’t look to be widely adopted yet.

It's good enough for the majority of use cases and systems; even an eight bit MCU is sufficient for many cases. If you design a product, saving power and cost makes the difference.

Memory efficiency just for one. For most programs, and especially in the embedded space, 64b systems carry around (and process) a lot more zeros than 32b systems do. You can still do 64b math when you need it, but you don’t have to pay for it when you don’t.

Given that software is always too big, this can often be a product-making distinction.

32 bit is still very common for smaller CPUs that aren't in the "application processor" class.

They are cheaper because they use less area, and they're also more memory efficient because pointers are all half as big. On these CPUs you don't have 4GB of RAM so you don't need a big address space.

But much better and faster optimizations than egc

Reply on news.ycombinator.com