From: "ufuk (Ufuk Kayserilioglu)" <noreply@...>
Date: 2022-11-10T19:01:11+00:00
Subject: [ruby-core:110699] [Ruby master Misc#19120] How does YJIT work in --enable-shared case?

Issue #19120 has been updated by ufuk (Ufuk Kayserilioglu).


jaruga (Jun Aruga) wrote in #note-3:
> ... the commands worked without the `rust` command. Could you tell me why it worked?

I can answer this part of the question.

> ```
> <mock-chroot> sh-5.2$ which rustc
> which: no rustc in (/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/sbin)
> 
> <mock-chroot> sh-5.2$ ~/local/ruby-yjit-199b59f065/bin/ruby --yjit --yjit-call-threshold=1 -e '100.times { |n| puts "Hello #{n}" }'
> ...
> Hello 98
> Hello 99
> ```

YJIT does NOT generate Rust code at runtime to perform its JIT compilation. YJIT is, itself, a Rust code-base that generates the correct assembly code for optimized methods at runtime. So `rustc` is only needed to compile the YJIT code itself, once you've compiled Ruby with YJIT, there is no dependency on `rustc` at runtime anymore.



----------------------------------------
Misc #19120: How does YJIT work in --enable-shared case?
https://bugs.ruby-lang.org/issues/19120#change-100041

* Author: jaruga (Jun Aruga)
* Status: Open
* Priority: Normal
----------------------------------------
We are trying to add the new YJIT feature that is ported to Rust[1][2] in Ruby 3.2 RPM on Fedora project.[3]
I am trying to understand how the YJIT works in the case the `./configure --enable-yjit --enable-shared`. In the case below, when building Ruby on the latest master branch `199b59f065ce6f1c13b8424f35a70c513523211b`, the static libraries `libruby-static.a` and `./libruby-static.a` were built.

```
<mock-chroot> sh-5.2$ cat /etc/fedora-release 
Fedora release 38 (Rawhide)

<mock-chroot> sh-5.2$ ./autogen.sh

<mock-chroot> sh-5.2$ ./configure --prefix=$HOME/local/ruby-yjit-199b59f065 --enable-shared --enable-yjit 2>&1 | tee configure.log
...
   * MJIT support:        yes
   * YJIT support:        yes

<mock-chroot> sh-5.2$ make

<mock-chroot> sh-5.2$ find . -name "*.a"
./yjit/target/release/libyjit.a
./libruby-static.a
```

After running `make install`, these static libraries (`*.a` files) were not copied to the installed directory. That makes sense, as Ruby works with shared libraries (`*.so` files).

```
<mock-chroot> sh-5.2$ make install 2>&1 | tee make_install.log

<mock-chroot> sh-5.2$ find ~/local/ruby-yjit-199b59f065/ -name "*.a"
=> empty
```

In this case, we really don't need the `libyjit.a` to run the YJIT right? I couldn't find the .so file something like `yjit.so`. Which .so file contains the YJIT feature (maybe the content of the `yjit/src/**/*.rs`)?

```
<mock-chroot> sh-5.2$ find ~/local/ruby-yjit-199b59f065/ -name "*.so" | grep yjit.so
=> empty
```

How can we test the content of the `yjit/src/**/*.rs`? For example, if the command below works, I can say that I tested the content of the `yjit/src/**/*.rs`?

```
<mock-chroot> sh-5.2$ which rustc
/usr/bin/rustc

<mock-chroot> sh-5.2$ rustc --version
rustc 1.65.0 (Fedora 1.65.0-1.fc38)

<mock-chroot> sh-5.2$ ~/local/ruby-yjit-199b59f065/bin/ruby --yjit -e 'puts "abc"'
abc
```

## References

* [1] https://bugs.ruby-lang.org/issues/18481
* [2] https://github.com/ruby/ruby/commit/f90549cd38518231a6a74432fe1168c943a7cc18#diff-1d53751ddf3ffeb25cfe609c6bd28746651e23ea81d51fe582b0f635f0896e0d
* [3] https://src.fedoraproject.org/rpms/ruby/pull-request/139




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