This PR contains a new crate, `rustc_mir`, which implements the MIR as specified in the RFC (more or less). There are no targeted unit tests at the moment, as I didn't decide what kind of infrastructure would be best and didn't take the time to implement it.
~~NB: In packaging up this PR, I realized that MIR construction code is not triggering for methods right now, I think it's only for fixed fns. I'll push a fix for this soon. Hopefully it doesn't stop any crates from building. :)~~ Fixed. Everything still seems to work.
However, the MIR construction code (`librustc_mir/build`) is intentionally quite distinct from the code which munges the compiler's data structures (`librustc_mir/tcx`). The interface between the two is the `HIR` trait (`librustc_mir/hir`). To avoid confusion with @nrc's work, perhaps a better name for this trait is warranted, although ultimately this trait *will* be connected to the HIR, I imagine, so in a way the name is perfect. Anyway, I'm open to suggestions. The initial motivation for this split was to allow for the MIR construction code to be unit-tested. But while I didn't end up writing unit tests (yet), I did find the split made the code immensely easier to think about, since the messiness of our existing system, with its myriad hashtables, punning, and so forth, is confined to one part, which simply transforms to a more fully explicit AST-like form. I tried to separate out the commits somewhat, but since this mostly new code, it mostly winds up coming in one fell swoop in the MIR commit.
Quick guide to the MIR crate:
- `repr.rs` defines the MIR itself; each MIR instance is parameterized by some HIR `H`
- `build/` is the MIR construction code, parameterized by a particular HIR
- `hir/` is the definition of the HIR interface
- `tcx/` is the impl of the HIR interface for the tcx
- `dump.rs` is the minimal compiler pass that invokes the HIR
One open question:
- In the HIR trait, I used exclusively struct-like variants. I found I like this more, since things have names. Should I convert the repr code?
Currently LLVM does not generate the debug info required to get complete backtraces even when functions are inlined, so that part of the `run-pass/backtrace-debuginfo.rs` test is disabled when targetting MSVC. At worst this results in missing stack frames where functions have been inlined.
The Introduction page generated by rustbook used weird relative links
like "./getting-started.html" instead of just "getting-started.html"
like on the other pages. This adversely affected Windows builds the
worst, since it generated links like ".\getting-started.html" (note the
backslash). If you then try to upload the generated book to a webserver,
you end up with 404's. See this example of what is going on with the
Introduction page links and why this PR should fix it:
http://is.gd/fRUTXk
Compare the links on these two pages, for instance:
https://doc.rust-lang.org/nightly/book/https://doc.rust-lang.org/nightly/book/getting-started.html
Also, fix a few whitespace issues in build.rs.
I took a stab at fixing #28064. Not sure if this all-features-in-one-example approach is the right one. Also I completely made up the terms "star globbing" and "brace expansion globbing" -- they are just called "glob-like syntax" in the reference.
