This commit enables pipelined compilation by default in Cargo now that
the requisite support has been stablized in rust-lang/rust#62766. This
involved minor updates in a number of locations here and there, but
nothing of meat has changed from the original implementation (just
tweaks to how rustc is called).
This commit starts to lay the groundwork for #6660 where Cargo will
invoke rustc in a "pipelined" fashion. The goal here is to execute one
command to produce both an `*.rmeta` file as well as an `*.rlib` file
for candidate compilations. In that case if another rlib depends on that
compilation, then it can start as soon as the `*.rmeta` is ready and not
have to wait for the `*.rlib` compilation.
Initially attempted in #6864 with a pretty invasive refactoring this
iteration is much more lightweight and fits much more cleanly into
Cargo's backend. The approach taken here is to update the
`DependencyQueue` structure to carry a piece of data on each dependency
edge. This edge information represents the artifact that one node
requires from another, and then we a node has no outgoing edges it's
ready to build.
A dependency on a metadata file is modeled as just that, a dependency on
just the metadata and not the full build itself. Most of cargo's backend
doesn't really need to know about this edge information so it's
basically just calculated as we insert nodes into the `DependencyQueue`.
Once that's all in place it's just a few pieces here and there to
identify compilations that *can* be pipelined and then they're wired up
to depend on the rmeta file instead of the rlib file.
* Collapse the nested cargotest::support module into the cargotest
module (merge the mod.rs's)
* Rename the cargotest module to support
* Nest the top-level hamcrest module into support
By rewriting the tests, with rerast (https://github.com/google/rerast),
to use the newly introduced "at" method.
First I added the following temporary function to cargotest::support:
pub fn project_foo() -> ProjectBuilder {
project("foo")
}
Then I defined the following rewrite.rs:
use cargotest::support::{ project, project_foo };
fn rule1(a: &'static str) {
replace!(project("foo") => project_foo());
replace!(project(a) => project_foo().at(a));
}
Then I ran rerast:
cargo +nightly rerast --rules_file=rewrite.rs --force --targets tests --file tests/testsuite/main.rs
Finally I searched and replaced the references to project_foo with
argument-less project (a little awkardly on macOS with a git clean).
find tests -type f -exec sed -i -e 's/project_foo/project/g' {} +
git clean -d tests
Note: It errors out if multiple overrides match the same package. This could potentially merge the overrides together with a hierarchy similar to CSS specificity. However, that seems overkill for now.
