Dist builds should always be as fast as we can make them, and since
those run on CI we don't care quite as much for the build being somewhat
slower. As such, we don't automatically enable ThinLTO on builds for the
dist builders.
This commit introduces a separately compiled backend for Emscripten, avoiding
compiling the `JSBackend` target in the main LLVM codegen backend. This builds
on the foundation provided by #47671 to create a new codegen backend dedicated
solely to Emscripten, removing the `JSBackend` of the main codegen backend in
the process.
A new field was added to each target for this commit which specifies the backend
to use for translation, the default being `llvm` which is the main backend that
we use. The Emscripten targets specify an `emscripten` backend instead of the
main `llvm` one.
There's a whole bunch of consequences of this change, but I'll try to enumerate
them here:
* A *second* LLVM submodule was added in this commit. The main LLVM submodule
will soon start to drift from the Emscripten submodule, but currently they're
both at the same revision.
* Logic was added to rustbuild to *not* build the Emscripten backend by default.
This is gated behind a `--enable-emscripten` flag to the configure script. By
default users should neither check out the emscripten submodule nor compile
it.
* The `init_repo.sh` script was updated to fetch the Emscripten submodule from
GitHub the same way we do the main LLVM submodule (a tarball fetch).
* The Emscripten backend, turned off by default, is still turned on for a number
of targets on CI. We'll only be shipping an Emscripten backend with Tier 1
platforms, though. All cross-compiled platforms will not be receiving an
Emscripten backend yet.
This commit means that when you download the `rustc` package in Rustup for Tier
1 platforms you'll be receiving two trans backends, one for Emscripten and one
that's the general LLVM backend. If you never compile for Emscripten you'll
never use the Emscripten backend, so we may update this one day to only download
the Emscripten backend when you add the Emscripten target. For now though it's
just an extra 10MB gzip'd.
Closes#46819
Getting the value of this argument needs another level of indexing,
as `known_args` are stored in `{dict}[list](opt, value)` form.
Also, when option-checking is disabled, let this bypass the check that
options are only passed once, and just apply the last value.
Fix PEP8 style issues in bootstrap code
This fixes PEP8 style issues (other than line-length) in the bootstrap Python code.
The most important fix is in the `set` function where the code was indented with 6 spaces instead of 4.
Fix path to x.py in bootstrap/configure.py script
We may see a help message in the end of the output of the ./configure script:
```
$ ./configure
configure: processing command line
configure:
configure: build.configure-args := []
configure:
configure: writing `config.toml` in current directory
configure:
configure: run `python ./src/bootstrap/x.py --help`
configure:
```
but the `x.py` script is actually in the rust root directory and
executing of such help string will give us error:
```
$ python ./src/bootstrap/x.py --help
python: can't open file './src/bootstrap/x.py': [Errno 2] No such file
or directory
```
This patch fixes path to the x.py script in the output of the ./configure
We may see a help message in the end of the output of the ./configure script:
$ ./configure
configure: processing command line
configure:
configure: build.configure-args := []
configure:
configure: writing `config.toml` in current directory
configure:
configure: run `python ./src/bootstrap/x.py --help`
configure:
but the x.py script is actually in the rust root directory and
executing of such help string will give us error:
$ python ./src/bootstrap/x.py --help
python: can't open file './src/bootstrap/x.py': [Errno 2] No such file
or directory
This patch fixes path to the x.py script in the output of the ./configure
Fix variable name reference
As best I can tell, this was a typo due to how similar it looks to the function above it. PyCharm found this as a unbound local variable.
This commit rewrites our ancient `./configure` script from shell into Python.
The impetus for this change is to remove `config.mk` which is just a vestige of
the old makefile build system at this point. Instead all configuration is now
solely done through `config.toml`.
The python script allows us to more flexibly program (aka we can use loops
easily) and create a `config.toml` which is based off `config.toml.example`.
This way we can preserve comments and munge various values as we see fit.
It is intended that the configure script here is a drop-in replacement for the
previous configure script, no functional change is intended. Also note that the
rationale for this is also because our build system requires Python, so having a
python script a bit earlier shouldn't cause too many problems.
Closes#40730
