:wave: I’m attempting to use the FirTotalResolvePr...

# compiler

[Tracey Yoshima]

👋 I’m attempting to use the FirTotalResolveProcessor to process FirFiles in hopes of adding type attribution.
The FirFile is in the RAW_FILE phase when I call #process(List<FirFile) and does not change even though the transform runs.
I’d like to know what I am doing wrong since I am still learning about the Kotlin compiler.

Questions:
• Is there a recommended example of what I may look at to see how to progress a FirFile through the compilation phases?
• Would it be possible to schedule a zoom to provide context about how we’re using the Kotlin compiler to construct a type-aware, whitespace-preserving AST?
• Or could anyone take a look at what I have so far?

[Tracey Yoshima]

WIP compiler configuration so far.

[dmitriy.novozhilov]

There is no need to run resolve processors by hand. After creating session and FIR files you can just run runResolution function on session (like here)

[dmitriy.novozhilov]

But actually runResolution does exact same thing as you do (run total resolve processor)

[dmitriy.novozhilov]

If you are confused that resolvePhase has not changed, that it's ok. This field can be changed only in lazy mode in IDE. Regular CLI compiler does not take care about this phase and does not update it

[Tracey Yoshima]

Ah, good to know — I noticed runResolution, but wasn’t sure if I should use it. I’ve replaced it locally; thank you so much!

• Would you happen to have any recommended examples related to session configuration?
• In the Java compiler, each type contains a symbol that provides information like superclasses, fields, methods, etc. I’d like to use that information to connect to AST elements. Is or where is that represented in Kotlin?
◦ I’m not currently seeing anything like that, and I am under the impression that it exists, but it is missing due to a lack of configurations. Is my understanding correct?
Example of `java.io.Serializable`:

[Tracey Yoshima]

Alternatively, is what I am looking for a part of Fir2Ir?

[dmitriy.novozhilov]

Would you happen to have any recommended examples related to session configuration?

FirFrontendFacade (from tests) or FirKotlinToJvmBytecodeCompiler (from CLI compiler)

I’d like to use that information to connect to AST elements

I'm not fully understand what do you want. You mean that you are trying to create mapping between FIR elements and PSI nodes (which represent C(oncrete)ST from parser)? Or smth else?

[dmitriy.novozhilov]

If you want to see the source of some FIR element, just check FirElement.source

[Tracey Yoshima]

FirKotlinToJvmBytecodeCompiler (from CLI compiler)

This is precisely what I am looking for; thank you!

I’m not fully understand what do you want. You mean that you are trying to create mapping between FIR elements and PSI nodes (which represent C(oncrete)ST from parser)? Or smth else?

I may find what I need using the KotlinToJVMBytecodeCompiler to correctly configure the FirSession. (I’ve skipped a few steps.)

The missing configuration may be causing the issue that I am experiencing. So, I’ll try that first — Thanks again!

[Tracey Yoshima]

@dmitriy.novozhilov, the FIR is converted successfully to an IR. Thanks again!

Questions for Monday:
• Could you provide a TLDR on the backend part of the compilation process or point me to documentation? Meaning what happens to the IR and how is the IR used to generate byte code?
• Is there a utility that links the IR information, like a List, to its methods, fields, super types, etc.?

[dmitriy.novozhilov]

Could you provide a TLDR on the backend part of the compilation process or point me to documentation? Meaning what happens to the IR and how is the IR used to generate byte code?

TLDR: backend consist with two parts: lowerings and codegen
Lowering is a pass which somehow transfroms the IR tree to something more similar to real code in bytecode/js/llvm. Examples of lowerings:
• transformation of for (x in 1..n) loop into for (int x = 1; x <= n; x++)
• transformation of extension receivers into parameters

// before
fun String.foo(x: Int) {}

s.foo(10)
// after
fun foo(reciever: String, x: Int)

foo(s, 10)

• inlining of inline functions
• transformation of suspend functions into state machine with continuation
• etc (AFAIR there are several tens of lowering)
Codegen is the part which takes lowered IR at input and produces bytecode/js/llvm bitcode from it

For more information/articles/talks it's better to ask someone else in this channel. All materials I have are in Russian

[dmitriy.novozhilov]

Is there a utility that links the IR information, like a List, to its methods, fields, super types, etc.?

Could you elaborate question, please?
All IR declarations contain all it's content right inside the tree

[dmitriy.novozhilov]

BTW I remembered that we have a detailed doc about coroutines codegen. It may be interesting for you

[Tracey Yoshima]

@dmitriy.novozhilov, thank you for the TLDR and documentation; I appreciate it.

Could you elaborate question, please?

All IR declarations contain all it’s content right inside the tree

I misunderstood the output when I was debugging — it looks like I have access to everything I need. Thank you for all your help

[dmitriy.novozhilov]

There are two steps for properties:
1. All property accesses are replaced with calls of getters/setters
2. If property has an extension receiver then it moved to parameters of getter/setter as it does for functions

[MerlinTHS]

For more information/articles/talks it's better to ask someone else in this channel. All materials I have are in Russian.

@dmitriy.novozhilov I would like to take a look at these russian materials. Are they public?

[dmitriy.novozhilov]

There were two great talks from my teammate
https://kotlinlang.slack.com/archives/C7L3JB43G/p1615463600012400?thread_ts=1615394755.006000&cid=C7L3JB43G

Also I had a talk about compiler plugins in K2 compiler this summer on Podlodka platform, but it seems it's not public (but maybe you are subscriber)

[dmitriy.novozhilov]

Also there are a lot of interesting discussions in #compiler channel, you can check the history

[MerlinTHS]

That's right, but I recently searched for informations about old frontend ( FE 1.0 ) transformations. I have mostly worked with FIR and now I try to do the same stuff ( generating top-level method stubs and changing return types of existing functions ) in the old frontend to get IntelliJ support as long there's no Kotlin Plugin supporting FIR. I know a preview version can be built from the IntelliJ repo but I think it's a good idea to support the old frontend anyway.

[dmitriy.novozhilov]

Unfortunately, I don't aware about any materials about FE 1.0 (but I never searched for them)
You can ask about it in #compiler, community may know more than me about this topic

[MerlinTHS]

I will try.