rust/compiler/rustc_span
bors e71440575c Auto merge of #97575 - nnethercote:lazify-SourceFile-lines, r=Mark-Simulacrum
Lazify `SourceFile::lines`.

`SourceFile::lines` is a big part of metadata. It's stored in a compressed form
(a difference list) to save disk space. Decoding it is a big fraction of
compile time for very small crates/programs.

This commit introduces a new type `SourceFileLines` which has a `Lines`
form and a `Diffs` form. The latter is used when the metadata is first
read, and it is only decoded into the `Lines` form when line data is
actually needed. This avoids the decoding cost for many files,
especially in `std`. It's a performance win of up to 15% for tiny
crates/programs where metadata decoding is a high part of compilation
costs.

A `RefCell` is needed because the methods that access lines data (which can
trigger decoding) take `&self` rather than `&mut self`. To allow for this,
`SourceFile::lines` now takes a `FnMut` that operates on the lines slice rather
than returning the lines slice.

r? `@Mark-Simulacrum`
2022-06-02 18:45:29 +00:00
..
src Auto merge of #97575 - nnethercote:lazify-SourceFile-lines, r=Mark-Simulacrum 2022-06-02 18:45:29 +00:00
Cargo.toml Update sha1, sha2, and md5 dependencies 2022-02-13 15:29:01 -06:00