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Let's make a Teeny Tiny compiler

austinhenley.com

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Re: Let's make a Teeny Tiny compiler

#31

Post by catwind7 »

jermaustin1 wrote: post #27
catwind7 wrote: post #25

Earlier quoted context omitted.

there's certainly equivalent assembler, but depending on the architecture you're targeting this can be a pretty monumental task. Even a single function call can be north of a hundred lines or something (i'm making this up :D ) I guess that's why we have things like LLVM that allow you to generate intermediate representations that get converted to a bunch of different instruction sets

For sure, i'm just telling the GP that their request for something that outputs assembly could be done with minor modifications depending on the assembly language they want to output.

gotcha. I also get the feeling that GP was more interested in being right vs actually knowing how to get the emitter to emit assembly. It felt like the followup was just gonna be ... well WHAT ABOUT BINARY?

Re: Let's make a Teeny Tiny compiler

#32

Post by kerkeslager »

jermaustin1 wrote: post #23
kerkeslager wrote: post #15

Earlier quoted context omitted.

I guess I was technically wrong in that it does have an emitter, but I wasn't wrong in that it still doesn't emit assembly. gcc (or whatever you're using to compile your C) is still doing all the nuclear reactor part.

I believe what you are meaning by assembly is native code or the executable bytes that a compiler/linker/assembler output? Assembly is just another language (or more precisely: family of languages).

I wasn't confused about what assembly was.

Compiling a for loop to a slightly different syntax of for loop is a much different problem from compiling a for loop to conditional jumps.

Re: Let's make a Teeny Tiny compiler

#33

Post by jermaustin1 »

kerkeslager wrote: post #29
jermaustin1 wrote: post #20

Earlier quoted context omitted.

Instead of outputting c, could you not just output the equivalent assembler? so instead of self.emitter.emitLine("printf(\"" + self.curToken.text + "\\n\");") you do something like self.emitter.emitLine("STRING DB " + self.curToken.text + "', '$'") ... self.emitter.emitLine("LEA DX,STRING") self.emitter.emitLine("MOV AH,09H") self.emitter.emitLine("INT 21H")

Well, what you just posted already highlights one difficulty: when you come to the PRINT statement, you have to emit the string and the instructions to two different places, so we're already talking about having two different emitters, or some other way of handling this. And we need to generate different non-conflicting names/addresses depending on architecture. You said in your other post that this can be done with…

I honestly can't tell if you are just trolling now, and I'm falling for it, but you seem to think this 2000 word set of tutorial on the basics of compiler design (lexing, parsing, emitting) is supposed to be the one and only document you will ever need to create the next C++.

> You said in your other post that this can be done with minor modifications

And it probably can, depending on the flavor of assembly you want to use, there are dozens (hundreds?) of them, i'm sure some will allow you to inline the string declaration. The example I gave probably doesn't even work since I haven't programmed in 8086 in close to 20 years, and I don't even remember how to set up data blocks and code blocks in it any more.

> And then there's the problem that you may want to target more than one architecture.

This is a toy compiler written by a professor of computer science meant to teach you the basics of building a compiler (lexing, parsing, emitting). This isn't a tutorial on building the next GCC.

Re: Let's make a Teeny Tiny compiler

#34

Post by kerkeslager »

dang wrote: post #18
kerkeslager wrote: post #8

Earlier quoted context omitted.

I'll believe it when I see it.

Please don't be a jerk on HN. I'm sure you don't mean to be, but comments like this can really come across the wrong way. That's one reason the site guidelines include: " Please don't post shallow dismissals, especially of other people's work. A good critical comment teaches us something. " https://news.ycombinator.com/newsguidelines.html

I don't personally think the fact that there are hundreds of other articles that already cover the same topic in greater depth is a shallow dismissal, and I think that could teach people something. But I'm open to the possibility that I maybe could have communicated this in a kinder way. Do you have any suggestions on how?

Re: Let's make a Teeny Tiny compiler

#35

Post by kerkeslager »

azhenley wrote: post #19
kerkeslager wrote: post #15

Earlier quoted context omitted.

I guess I was technically wrong in that it does have an emitter, but I wasn't wrong in that it still doesn't emit assembly. gcc (or whatever you're using to compile your C) is still doing all the nuclear reactor part.

Very few "commercial" compilers emit assembly directly. They use LLVM or C or some other intermediate language.

Sorry that I'm coming across as critical of your work here--that wasn't my intent but I didn't do enough to avoid it. Your article isn't the problem, it's just proximal to the problem I'm describing. I should have been more clear about that in my post.

To address your post: I'm not aware of any widely used compilers that compile from a general-purpose language to C. There are a handful of DSLs that do, and there may be some mainstream general-purpose language compiler that does that I don't know of.

Compiling to LLVM or GCC's RTL has a lot more in common with compiling to Assembly than it does with compiling to C.

Compiling to LLVM/RTL/assembly is fundamentally different from compiling to another high-level language. When compiling to C for example, you get to compile your for loops into C for loops--it's a fairly easy one-to-one conversion. Compiling to conditional jumps is a much more complicated endeavor, requiring more architecture.

Re: Let's make a Teeny Tiny compiler

#36

Post by kerkeslager »

catwind7 wrote: post #30
kerkeslager wrote: post #26

Earlier quoted context omitted.

I'm not gonna argue with you over whether the metaphor I used was applicable or not--the point of the metaphor was to communicate and it's clear I succeeded in communicating. It's clear you understood what I meant, because you provided another example. Yes, whether or not you agree the bike shedding metaphor applies, you have to agree that having the 100th tutorial on how to do something that's in the docs that ships…

i think you succeeded in communicating your thoughts and feelings in spite of the metaphor. there are plenty of documentation in the form of tutorials on for nearly every aspect of every programming language I can think of. I think it's important to keep in mind that we all learn differently and sometimes one explanation can make no sense while another makes a lot of sense. That said, I think I get your frustration i…

> That said, I think I get your frustration in that sometimes the process of _finding_ the explanation that clicks for whatever your question is (how to emit assembler?) can be really painful because all the explanations are shallow.

While I agree with your overall point about different learning styles, that's not really the problem I'm describing. Introductory material on emitting assembly or similar, doesn't exist for any learning style as far as I know. The best that I know of are some dead-tree books, and their emitters target dead or obscure architectures. None of the code examples are ones I could run on my machine.

> However, I don't think it's fair to take that frustration out on the writers (I got the impression you were, but maybe you weren't and just felt like venting).

That's a fair criticism: I apologized to the writer in a different post.

Re: Let's make a Teeny Tiny compiler

#37

Post by kerkeslager »

jermaustin1 wrote: post #33
kerkeslager wrote: post #29

Earlier quoted context omitted.

Well, what you just posted already highlights one difficulty: when you come to the PRINT statement, you have to emit the string and the instructions to two different places, so we're already talking about having two different emitters, or some other way of handling this. And we need to generate different non-conflicting names/addresses depending on architecture. You said in your other post that this can be done with…

I honestly can't tell if you are just trolling now, and I'm falling for it, but you seem to think this 2000 word set of tutorial on the basics of compiler design (lexing, parsing, emitting) is supposed to be the one and only document you will ever need to create the next C++. > You said in your other post that this can be done with minor modifications And it probably can, depending on the flavor of assembly you want…

> I honestly can't tell if you are just trolling now, and I'm falling for it, but you seem to think this 2000 word set of tutorial on the basics of compiler design (lexing, parsing, emitting) is supposed to be the one and only document you will ever need to create the next C++.

That's a fair criticism.

I'm frustrated with the lack of material on emitting assembly, but it wasn't right of me to take that out on the author of this post. I apologized in a different post.

> And it probably can, depending on the flavor of assembly you want to use, there are dozens (hundreds?) of them

How about one I can run on my machine? There are maybe 5 that are useful targets I can think of:

   * x86 or ARM (depending your machine)
   * LLVM
   * GCC RTL
   * Web assembly
   * Parrot? Maybe the JVM has some low-level bytecode?

Re: Let's make a Teeny Tiny compiler

#38

Post by kerkeslager »

catwind7 wrote: post #21
kerkeslager wrote: post #13

Earlier quoted context omitted.

Ah, okay. It looks like you're taking a fairly C-like language and transforming it to C--I'd call this a transpiler rather than a compiler. You're not wrong to call it a compiler, but it's a pretty noncentral example of a compiler. Congrats on at least having an emitter, but I'm still searching for an article that shows how to emit assembly of any kind.

nand2tetris is a great course that shows you how to design a computer from the chip level, build an assembler, and write a high level language + compiler that eventually produces the assembly code for the machine architecture _you_ built. I highly recommend it.

nand2tetris is awesome, and taught me a large portion of the little I know on this subject.

The real barriers to me at this point are targeting a pragmatic real-world architecture.

Re: Let's make a Teeny Tiny compiler

#39

Post by kerkeslager »

catwind7 wrote: post #31
jermaustin1 wrote: post #27

Earlier quoted context omitted.

For sure, i'm just telling the GP that their request for something that outputs assembly could be done with minor modifications depending on the assembly language they want to output.

gotcha. I also get the feeling that GP was more interested in being right vs actually knowing how to get the emitter to emit assembly. It felt like the followup was just gonna be ... well WHAT ABOUT BINARY?

Nah, assembly -> binary isn't that hard. ;)
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