Author Topic: Testing assembly much?  (Read 162 times)


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Testing assembly much?
« on: March 12, 2023, 06:13:34 PM »
This is a long overdue post about assembly. Typically, what we know about assembly language today is that those are low level instructions that fiddle very low level operations with CPU registers, memory, interrupts and etc. In this day and age nobody but compiler writers care about assembly. But even then, if you write a compiler LLVM is available to you where you emit LLVM IR (intermediate representation) instructions and LLVM generates assembly code. It could be x86, arm, PowerPC or any number of supported architectures.

Whatever new assembly language comes out specific for certain chip only very few people of programmer population needs to understand that to port it to yet another platform and all that will be available for the rest of the programmers to use. Today, 99%+ developers don't care about assembly. It is good to understand what it is and how it works, to have conceptual understanding, but to actually fiddle assembly code by hand you either need to have extremely good reason or you're just pretentious or insane.

Why am I talking about this? As I'm developing Eden platform now I need to generate a lot of code. Be it Rust code, shell scripts, nomad job files - all of them are generated now. I don't write these by hand. Most people what is generated in my framework today need to write by hand, care about it, maintain it, fiddle with it, have tests for it.

What I see as inevitable future most of the code people write today will turn into assembly automatically generated without mistakes. No more need to maintain those, you just connect high level table data in eden data language and things will just work. You will not be able to misconfigure service with a bad dns name to connect a certain postgres instance like you can in a garbage yaml hell. You will not be able to operate in DNS names - DNS names to consul services will simply be an irrelevant implementation detail. Part of our generated assembly. What you want to say instead is that deployment of this service speaks to this instance of database which has this and this schema. You don't care about implementation details of DNS.

Today virtually everyone tests this higher level assembly. Is service running? Does it open a port? Does it respond to such and such http request with such and such response?

Of course, compiler writers also have huge test suites that test assembly, certain behaviours of generated code. In the beginning of GCC compiler there were probably lots of bugs, with time they became less and less common to a point where average user encountering a compiler bug is similar to a chance of winning a lottery. Usually, once GCC or rustc runs and compiler successfully emits output, you assume that basic behaviours are correct.

But how can that be? Rustc emit executables with assembly code! You would be crazy to rely on assembly? Since there are high level rules in Rust which are enforced with tests and we now mainly trust that compiler is reasonably correct we trust Rust programs much more than Javascript programs (if you have any sanity) even though both programs are running on the same CPU and they're running same assembly instructions underneath.

With the pattern, most yamls, infrastructure configurations that you'd need to maintain by hand become assembly. Most Rust application code not written by the user becomes assembly. Consul configs become assembly. Nomad configs become assembly. Vault configs become assembly. Postgres configs become assembly. SQL migrations become assembly. NATS configs become assembly. MinIO configs become assembly. Consul policies become assembly. Vault policies become assembly. Nomad job declarations become assembly. Server nix configurations become assembly. Application build scripts become assembly. Nginx configs become assembly.

Another property of assembly is that compiler optimizations change and assembly changes but code doesn't have to. Users don't care. Now at this point for instance I use Nix to provision all servers and have reproducible builds. It is my favorite OS and package manager which will make Eden platform rock solid. But hypothetically, what happens if one day for some reason I will no longer like NixOS as server operating system? I'll just change the assembly code generated for server provisioning and VM images built (user doesn't care and doesn't need to know) to something else in one commit and that's it. Assembly will never be the most important. Assembly is swappable. Assembly is an implementation detail.

And what is the future of assembly? It will become irrelevant. Needless to say there are lots of errors in Eden platform compiler I'm working on during development, but the more and more test written, the more mature this project will become it will be like GCC and Rustc - once compiler runs, tests assumptions/consistencies/port clashes/RAM boundaries/typesafety of applications/db query correctness of your entire infrastructure of 1000 servers and 1000 applications and emits source outputs in a few seconds for your entire infrastructure - you'll just assume things will work and deploy with a smile. Without spinning up thousands of machines for testing. Without spinning up thousands of services.

And what is the future of developers that today need to maintain such assembly? Check job postings for x86 assembly programmers and find out ;)

Have a good day bois!