Re: Intermediate forms (again?): worthwhile?

"Robbert Haarman" <comp.compilers@inglorion.net> wrote in message
> Hi Tony,
>
> On Thu, Jan 13, 2011 at 11:53:30PM -0600, Tony wrote:


>> As a language designer/developer, I feel like I'm in between the
>> proverbial rock and hard place. I'm A-OK with doing the "front end"
>> of the compiler, but the "back end" is "kinda scary" for me. To
>> "spill", my path is, currently, compiling to assembly language (am
>> I naive?). I mean, it's "simple", right? What can go wrong, having
>> full control (ignore multi-platform compatibility, for it is NOT in
>> my requirement now)?


> Like John already said, there is nothing wrong with keeping it
> simple. Why would you spend a lot of time on designing and
> implementing an intermediate form if you can already do everything
> you need to do and the result is good enough for your purposes?


> In my experince, intermediate forms start to really make things
> easier for you once you want more complex compilers: multiple target
> platforms, program transformations, optimization. Many people end up
> wanting these things, and so, immediate forms make sense for
> them. But if going straight from parsing to emitting target code is
> good enough to meet your needs, I see nothing wrong with it. Keep it
> small and simple; it's the best way to complete the project and make
> it work.


Yeah, that's what I'm focused on right now: just getting it to work. I
can raise the level of sophistication in the future. But I am starting to
think about it now. And actually, what would be simpler is if the backend
was already done for me and I could just develop the front end. The
theory of that is very lucrative.


>> Clarification: I got to here from disenchantment/unenamorment with
>> existing HLLs (yep, every one of them). I like the freedom afforded by
>> writing to the hardware level for my language's
>> initial/prototype/reference output. I have looked at (well, "you know
>> me", cursory inspection) LLVM and GCC, but get the feeling it throws
>> me back from where I started.


> I know you warned against drifting off-topic, so feel free to move
> this to a different thread, but I am curious as to what your
> experiences, both good and bad, with LLVM and GCC have been. As you
> may know, I am working on Voodoo, which is sort of an abstract
> assembly language which can be (and has been) implemented for a
> number of actual target platforms. The idea is that a compiler
> writer can get the benefits of generating assembly for multiple
> target platforms for the cost of implementing a generator for a
> single target (namely Voodoo). This is not unlike LLVM assembly
> language or GCC's GIMPLE, so I am curious what they did right and
> wrong so that I may learn from it.




Everytime I look into some intermediate LANGUAGE, I feel I am getting too
3rd-party proprietary so I may as well just emit the assembly language
and forego the IL. That or invent my own based upon quadruples or
something. Writing to the hardware (assembly language) gives me the warm
fuzzies about being a safe thing to do. i.e., Intel x86 is much the
commodity whereas ILs are esoteric. Also, it is something I am picking up
quite quickly and I can find examples of generating control flow
constructs etc. all over the place. Finally, writing to the GCC IL has
that viral GPL that I think would be applied if it was used which is not
acceptable.


Something just a tad higher level than assembly and a bit more regular
would be nice, but so far, I haven't seen anything I'd want to commit to.
Surely if I could just concentrate on the compiler front end and attach
it to a back end black box supporting multiple platforms, that would be
great.
[The usual suggestion these days is LLVM. -John]

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