This commit optimizes the compile time for creating tarballs of cross-host
compilers and as a proof of concept adds two to the standard Travis matrix. Much
of this commit is further refactoring and refining of the `step.rs` definitions
along with the interpretation of `--target` and `--host` flags. This has gotten
confusing enough that I've also added a small test suite to
`src/bootstrap/step.rs` to ensure what we're doing works and doesn't regress.
After this commit when you execute:
./x.py dist --host $MY_HOST --target $MY_HOST
the build system will compile two compilers. The first is for the build platform
and the second is for the host platform. This second compiler is then packaged
up and placed into `build/dist` and is ready to go. With a fully cached LLVM and
docker image I was able to create a cross-host compiler in around 20 minutes
locally.
Eventually we plan to add a whole litany of cross-host entries to the Travis
matrix, but for now we're just adding a few before we eat up all the extra
capacity.
cc #38531
rustbuild: Compile all support tools in stage0
This commit changes all tools and such to get compiled in stage0, not in
later stages. The purpose of this commit is to cut down dependencies on later
stages for future modifications to the build system. Notably we're going to be
adding builders that produce a full suite of cross-compiled artifacts for a
particular host, and that shouldn't compile the `x86_64-unknown-linux-gnu`
compiler more than once. Currently dependencies on, for example, the error index
end up compiling the `x86_64-unknown-linux-gnu` compiler more than necessary.
As a result here we move many dependencies on these tools to being produced by a
stage0 compiler, not a stage1+ compiler. None of these tools actually need to be
staged at all, so they'll exhibit consistent behavior across the stages.
This commit changes all tools and such to get compiled in stage0, not in
later stages. The purpose of this commit is to cut down dependencies on later
stages for future modifications to the build system. Notably we're going to be
adding builders that produce a full suite of cross-compiled artifacts for a
particular host, and that shouldn't compile the `x86_64-unknown-linux-gnu`
compiler more than once. Currently dependencies on, for example, the error index
end up compiling the `x86_64-unknown-linux-gnu` compiler more than necessary.
As a result here we move many dependencies on these tools to being produced by a
stage0 compiler, not a stage1+ compiler. None of these tools actually need to be
staged at all, so they'll exhibit consistent behavior across the stages.
This commit switches the rustbuild build system to compiling the
compiler twice for a normal bootstrap rather than the historical three
times.
Rust is a bootstrapped language which means that a previous version of
the compiler is used to build the next version of the compiler. Over
time, however, we change many parts of compiler artifacts such as the
metadata format, symbol names, etc. These changes make artifacts from
one compiler incompatible from another compiler. Consequently if a
compiler wants to be able to use some artifacts then it itself must have
compiled the artifacts.
Historically the rustc build system has achieved this by compiling the
compiler three times:
* An older compiler (stage0) is downloaded to kick off the chain.
* This compiler now compiles a new compiler (stage1)
* The stage1 compiler then compiles another compiler (stage2)
* Finally, the stage2 compiler needs libraries to link against, so it
compiles all the libraries again.
This entire process amounts in compiling the compiler three times.
Additionally, this process always guarantees that the Rust source tree
can compile itself because the stage2 compiler (created by a freshly
created compiler) would successfully compile itself again. This
property, ensuring Rust can compile itself, is quite important!
In general, though, this third compilation is not required for general
purpose development on the compiler. The third compiler (stage2) can
reuse the libraries that were created during the second compile. In
other words, the second compilation can produce both a compiler and the
libraries that compiler will use. These artifacts *must* be compatible
due to the way plugins work today anyway, and they were created by the
same source code so they *should* be compatible as well.
So given all that, this commit switches the default build process to
only compile the compiler three times, avoiding this third compilation
by copying artifacts from the previous one. Along the way a new entry in
the Travis matrix was also added to ensure that our full bootstrap can
succeed. This entry does not run tests, though, as it should not be
necessary.
To restore the old behavior of a full bootstrap (three compiles) you can
either pass:
./configure --enable-full-bootstrap
or if you're using config.toml:
[build]
full-bootstrap = true
Overall this will hopefully be an easy 33% win in build times of the
compiler. If we do 33% less work we should be 33% faster! This in turn
should affect cycle times and such on Travis and AppVeyor positively as
well as making it easier to work on the compiler itself.
This commit is a rewrite of the user-facing interface to the rustbuild build
system. The intention here is to make it much easier to compile/test the project
without having to remember weird rule names and such. An overall view of the new
interface is:
# build everything
./x.py build
# document everyting
./x.py doc
# test everything
./x.py test
# test libstd
./x.py test src/libstd
# build libcore stage0
./x.py build src/libcore --stage 0
# run stage1 run-pass tests
./x.py test src/test/run-pass --stage 1
The `src/bootstrap/bootstrap.py` script is now aliased as a top-level `x.py`
script. This `x` was chosen to be both short and easily tab-completable (no
collisions in that namespace!). The build system now accepts a "subcommand" of
what to do next, the main ones being build/doc/test.
Each subcommand then receives an optional list of arguments. These arguments are
paths in the source repo of what to work with. That is, if you want to test a
directory, you just pass that directory as an argument.
The purpose of this rewrite is to do away with all of the arcane renames like
"rpass" is the "run-pass" suite, "cfail" is the "compile-fail" suite, etc. By
simply working with directories and files it's much more intuitive of how to run
a test (just pass it as an argument).
The rustbuild step/dependency management was also rewritten along the way to
make this easy to work with and define, but that's largely just a refactoring of
what was there before.
The *intention* is that this support is extended for arbitrary files (e.g.
`src/test/run-pass/my-test-case.rs`), but that isn't quite implemented just yet.
Instead directories work for now but we can follow up with stricter path
filtering logic to plumb through all the arguments.
The organization in rustbuild was a little odd at the moment where the `lib.rs`
was quite small but the binary `main.rs` was much larger. Unfortunately as well
there was a `build/` directory with the implementation of the build system, but
this directory was ignored by GitHub on the file-search prompt which was a
little annoying.
This commit reorganizes rustbuild slightly where all the library files (the
build system) is located directly inside of `src/bootstrap` and all the binaries
now live in `src/bootstrap/bin` (they're small). Hopefully this should allow
GitHub to index and allow navigating all the files while maintaining a
relatively similar layout to the other libraries in `src/`.
