rust/compiler/rustc_driver
Nicholas Nethercote 9110d925d0 Remove -Ztime option.
The compiler currently has `-Ztime` and `-Ztime-passes`. I've used
`-Ztime-passes` for years but only recently learned about `-Ztime`.

What's the difference? Let's look at the `-Zhelp` output:
```
  -Z        time=val -- measure time of rustc processes (default: no)
  -Z time-passes=val -- measure time of each rustc pass (default: no)
```
The `-Ztime-passes` description is clear, but the `-Ztime` one is less so.
Sounds like it measures the time for the entire process?

No. The real difference is that `-Ztime-passes` prints out info about passes,
and `-Ztime` does the same, but only for a subset of those passes. More
specifically, there is a distinction in the profiling code between a "verbose
generic activity" and an "extra verbose generic activity". `-Ztime-passes`
prints both kinds, while `-Ztime` only prints the first one. (It took me
a close reading of the source code to determine this difference.)

In practice this distinction has low value. Perhaps in the past the "extra
verbose" output was more voluminous, but now that we only print stats for a
pass if it exceeds 5ms or alters the RSS, `-Ztime-passes` is less spammy. Also,
a lot of the "extra verbose" cases are for individual lint passes, and you need
to also use `-Zno-interleave-lints` to see those anyway.

Therefore, this commit removes `-Ztime` and the associated machinery. One thing
to note is that the existing "extra verbose" activities all have an extra
string argument, so the commit adds the ability to accept an extra argument to
the "verbose" activities.
2022-10-06 15:49:44 +11:00
..
src Remove -Ztime option. 2022-10-06 15:49:44 +11:00
Cargo.toml rustc_typeck to rustc_hir_analysis 2022-09-27 10:37:23 +02:00
README.md

The driver crate is effectively the "main" function for the rust compiler. It orchestrates the compilation process and "knits together" the code from the other crates within rustc. This crate itself does not contain any of the "main logic" of the compiler (though it does have some code related to pretty printing or other minor compiler options).

For more information about how the driver works, see the rustc dev guide.