Add unimplemented `current_dll_path()` for WASI
This is the only change needed to Rust to allow compiling rustfmt for WASI (rustfmt uses some internal rustc crates).
Computing the current dll path is somewhat expensive relative to other
work when compiling `fn main() {}` as `dladdr` needs to iterate over the
symbol table of librustc_driver.so until it finds a match.
Use `std::mem::{size_of, size_of_val, align_of, align_of_val}` from the
prelude instead of importing or qualifying them.
These functions were added to all preludes in Rust 1.80.
Over in Zed we've noticed that loading crates for a large-ish workspace can take almost 200ms. We've pinned it down to how rustc searches for paths, as it performs a linear search over the list of candidate paths. In our case the candidate list had about 20k entries which we had to iterate over for each dependency being loaded.
This commit introduces a simple FilesIndex that's just a sorted Vec under the hood. Since crates are looked up by both prefix and suffix, we perform a range search on said Vec (which constraints the search space based on prefix) and follow up with a linear scan of entries with matching suffixes.
FilesIndex is also pre-filtered before any queries are performed using available target information; query prefixes/sufixes are based on the target we are compiling for, so we can remove entries that can never match up front.
Overall, this commit brings down build time for us in dev scenarios by about 6%.
100ms might not seem like much, but this is a constant cost that each of our workspace crates has to pay, even when said crate is miniscule.
Add `try_canonicalize` to `rustc_fs_util` and use it over `fs::canonicalize`
This adds `try_canonicalize` which tries to call `fs::canonicalize`, but falls back to `std::path::absolute` if it fails. Existing `canonicalize` calls are replaced with it. `fs::canonicalize` is not guaranteed to work on Windows.
This code and comment appear to be out of date.
`CrateLocator::find_library_crate` is the only caller of this function
and it handles rlib vs dylib overlap itself (see
`CrateLocator::extract_lib`) after inspecting all the files present, so
it doesn't need to see them in any particular order.
