Something similar, but you can play with the examples in the browser without any local setup https://shikaan.github.io/assembly/x86/guide/2024/09/08/x86-...
For full disclosure, I am the author - apologies for the shameless plug
For full disclosure, I am the author - apologies for the shameless plug
[1]: https://github.com/shikaan/shikaan.github.io/blob/main/_incl...
I have been planning on trying to glue up something with v86[1] as I did in OSle[2] but I did not get to it yet.
In that case, everything would run locally and sandboxes, so you would not have to care.
What I don't understand is why assembly feels so hard to learn in the first place?
I mean, isn't it just a simple language with a few function calls (instructions) and types (operand sizes) and fixed number of variables (registers) and a small number of control flow operators, and that's it? Why does it feel so mysterious?
1. You are primed to think that it is mysterious because that’s all you usually hear about assembly. (“Roller Coaster Tycoon was written in 100% hand crafted assembly… what an absolute wizard!!”)
2. The language’s textual format is odd - columns vs nested indentation. Actually really nice once you get used to it, but it’s definitely alien at first.
3. Mnemonics and directives have short, cryptic spellings. x86 in particular has arbitrary looking register names as well. RV, AArch64, m68k etc do better here.
4. Mnemonics are inconsistently overloaded and encode lots of stuff. SIMD instructions tend to look like a cat sat on your keyboard.
5. Manually laying out memory is technically simpler than the abstractions provided by higher level languages (structs and classes, fancy generic types, pointer syntax), but it’s fiddly and you have to deal with alignment.
6. You have to do a lot of bookkeeping yourself. It’s like malloc/free turned to 11.
7. Register allocation is a hard problem for computers. It’s kinda tough for humans, too.
8. Lots of books and online stuff discuss assembly for use with high performance code, tight compute kernels, raw hardware access, and fiddly CPU configuration for OS startup and virtual memory configuration. This requires even more specialized registers, arcane instructions, and bit fiddling. This stuff - along with reverse engineering and security research/attacks - gets lumped into what people think of as “assembly language”. The resulting concept surface therefore looks much larger than it actually is.
I highly recommend making a non-trivial program entirely in assembly at least once. I need to do it occasionally professionally but even when I don’t I usually have a hobby project or two cooking at home.
Becoming as proficient in asm as - say - C or Python is quite the lovely expression of craft. You feel like a wizard (see point 1) while simultaneously learning what’s really going on.
For people with a certain geeky disposition it pays lots of aesthetic, psychological, and professional dividends.
I think the problem with assemblers in particular is that the canonical definition is the byte code, not the human readable text. x86 is particularly annoying because no one agrees on the syntax of that text, there are hundreds of mnemonics, things are constantly being updated, and the practicing assembly programmer cares deeply about the execution semantics of the microarchitecture more than the specific sequence of instructions. Some of the language is also completely foreign to higher level programmers, like instruction pipelines, uops, instruction latency, and so on.
Rarely do you sit down and write this assembler by hand, you compile some C code and poke at it with vtune/uprof to measure hot sections of the code, break those down, and implement faster versions. It's fundamentally an iterative, experimental process.
It's up to the compiler/programmer to handle calling conventions.
Modern programmers also don't regularly encounter "unstructured programming" in higher-level languages these days.
All of these, and more, make it feel overwhelming, as anything they examine through their disassembler will contain all of these elements.
For a little 8-bit microprocessor with program size < 8k it can be quite easy and even a joy. Anything else and your compiler will outperform you, better to inline hand-coded assembler as needed.