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.

Author: nnethercote

compiler/rustc_codegen_llvm/src/back/lto.rs

@@ -573,7 +573,7 @@ pub(crate) fn run_pass_manager(
     module: &mut ModuleCodegen<ModuleLlvm>,
     thin: bool,
 ) -> Result<(), FatalError> {
-    let _timer = cgcx.prof.extra_verbose_generic_activity("LLVM_lto_optimize", &*module.name);
+    let _timer = cgcx.prof.verbose_generic_activity_with_arg("LLVM_lto_optimize", &*module.name);
     let config = cgcx.config(module.kind);
 
     // Now we have one massive module inside of llmod. Time to run the

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -1637,7 +1637,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
         llvm_start_time: &mut Option<VerboseTimingGuard<'a>>,
     ) {
         if config.time_module && llvm_start_time.is_none() {
-            *llvm_start_time = Some(prof.extra_verbose_generic_activity("LLVM_passes", "crate"));
+            *llvm_start_time = Some(prof.verbose_generic_activity("LLVM_passes"));
         }
     }
 }

compiler/rustc_data_structures/src/profiling.rs

@@ -158,30 +158,21 @@ pub struct SelfProfilerRef {
     // actually enabled.
     event_filter_mask: EventFilter,
 
-    // Print verbose generic activities to stderr.
+    // Print verbose generic activities to stderr?
     print_verbose_generic_activities: bool,
-
-    // Print extra verbose generic activities to stderr.
-    print_extra_verbose_generic_activities: bool,
 }
 
 impl SelfProfilerRef {
     pub fn new(
         profiler: Option<Arc<SelfProfiler>>,
         print_verbose_generic_activities: bool,
-        print_extra_verbose_generic_activities: bool,
     ) -> SelfProfilerRef {
         // If there is no SelfProfiler then the filter mask is set to NONE,
         // ensuring that nothing ever tries to actually access it.
         let event_filter_mask =
             profiler.as_ref().map_or(EventFilter::empty(), |p| p.event_filter_mask);
 
-        SelfProfilerRef {
-            profiler,
-            event_filter_mask,
-            print_verbose_generic_activities,
-            print_extra_verbose_generic_activities,
-        }
+        SelfProfilerRef { profiler, event_filter_mask, print_verbose_generic_activities }
     }
 
     /// This shim makes sure that calls only get executed if the filter mask
@@ -214,7 +205,7 @@ impl SelfProfilerRef {
     /// Start profiling a verbose generic activity. Profiling continues until the
     /// VerboseTimingGuard returned from this call is dropped. In addition to recording
     /// a measureme event, "verbose" generic activities also print a timing entry to
-    /// stderr if the compiler is invoked with -Ztime or -Ztime-passes.
+    /// stderr if the compiler is invoked with -Ztime-passes.
     pub fn verbose_generic_activity<'a>(
         &'a self,
         event_label: &'static str,
@@ -225,19 +216,16 @@ impl SelfProfilerRef {
         VerboseTimingGuard::start(message, self.generic_activity(event_label))
     }
 
-    /// Start profiling an extra verbose generic activity. Profiling continues until the
-    /// VerboseTimingGuard returned from this call is dropped. In addition to recording
-    /// a measureme event, "extra verbose" generic activities also print a timing entry to
-    /// stderr if the compiler is invoked with -Ztime-passes.
-    pub fn extra_verbose_generic_activity<'a, A>(
+    /// Like `verbose_generic_activity`, but with an extra arg.
+    pub fn verbose_generic_activity_with_arg<'a, A>(
         &'a self,
         event_label: &'static str,
         event_arg: A,
     ) -> VerboseTimingGuard<'a>
     where
         A: Borrow<str> + Into<String>,
     {
-        let message = if self.print_extra_verbose_generic_activities {
+        let message = if self.print_verbose_generic_activities {
             Some(format!("{}({})", event_label, event_arg.borrow()))
         } else {
             None

compiler/rustc_driver/src/lib.rs

@@ -127,10 +127,13 @@ pub struct TimePassesCallbacks {
 }
 
 impl Callbacks for TimePassesCallbacks {
+    // JUSTIFICATION: the session doesn't exist at this point.
+    #[allow(rustc::bad_opt_access)]
     fn config(&mut self, config: &mut interface::Config) {
         // If a --print=... option has been given, we don't print the "total"
         // time because it will mess up the --print output. See #64339.
-        self.time_passes = config.opts.prints.is_empty() && config.opts.time_passes();
+        //
+        self.time_passes = config.opts.prints.is_empty() && config.opts.unstable_opts.time_passes;
         config.opts.trimmed_def_paths = TrimmedDefPaths::GoodPath;
     }
 }

compiler/rustc_interface/src/tests.rs

@@ -692,7 +692,6 @@ fn test_unstable_options_tracking_hash() {
     untracked!(span_free_formats, true);
     untracked!(temps_dir, Some(String::from("abc")));
     untracked!(threads, 99);
-    untracked!(time, true);
     untracked!(time_llvm_passes, true);
     untracked!(time_passes, true);
     untracked!(trace_macros, true);

compiler/rustc_lint/src/early.rs

@@ -409,7 +409,7 @@ pub fn check_ast_node<'a>(
     if sess.opts.unstable_opts.no_interleave_lints {
         for (i, pass) in passes.iter_mut().enumerate() {
             buffered =
-                sess.prof.extra_verbose_generic_activity("run_lint", pass.name()).run(|| {
+                sess.prof.verbose_generic_activity_with_arg("run_lint", pass.name()).run(|| {
                     early_lint_node(
                         sess,
                         !pre_expansion && i == 0,

compiler/rustc_lint/src/late.rs

@@ -425,20 +425,23 @@ fn late_lint_crate<'tcx, T: LateLintPass<'tcx>>(tcx: TyCtxt<'tcx>, builtin_lints
         late_lint_pass_crate(tcx, builtin_lints);
     } else {
         for pass in &mut passes {
-            tcx.sess.prof.extra_verbose_generic_activity("run_late_lint", pass.name()).run(|| {
-                late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
-            });
+            tcx.sess.prof.verbose_generic_activity_with_arg("run_late_lint", pass.name()).run(
+                || {
+                    late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
+                },
+            );
         }
 
         let mut passes: Vec<_> =
             unerased_lint_store(tcx).late_module_passes.iter().map(|pass| (pass)(tcx)).collect();
 
         for pass in &mut passes {
-            tcx.sess.prof.extra_verbose_generic_activity("run_late_module_lint", pass.name()).run(
-                || {
+            tcx.sess
+                .prof
+                .verbose_generic_activity_with_arg("run_late_module_lint", pass.name())
+                .run(|| {
                     late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
-                },
-            );
+                });
         }
     }
 }

compiler/rustc_query_impl/src/on_disk_cache.rs

@@ -1067,7 +1067,7 @@ pub fn encode_query_results<'a, 'tcx, CTX, Q>(
     let _timer = tcx
         .dep_context()
         .profiler()
-        .extra_verbose_generic_activity("encode_query_results_for", std::any::type_name::<Q>());
+        .verbose_generic_activity_with_arg("encode_query_results_for", std::any::type_name::<Q>());
 
     assert!(Q::query_state(tcx).all_inactive());
     let cache = Q::query_cache(tcx);

compiler/rustc_session/src/options.rs

@@ -280,14 +280,6 @@ macro_rules! options {
 
 ) }
 
-impl Options {
-    // JUSTIFICATION: defn of the suggested wrapper fn
-    #[allow(rustc::bad_opt_access)]
-    pub fn time_passes(&self) -> bool {
-        self.unstable_opts.time_passes || self.unstable_opts.time
-    }
-}
-
 impl CodegenOptions {
     // JUSTIFICATION: defn of the suggested wrapper fn
     #[allow(rustc::bad_opt_access)]
@@ -1596,9 +1588,6 @@ options! {
     #[rustc_lint_opt_deny_field_access("use `Session::threads` instead of this field")]
     threads: usize = (1, parse_threads, [UNTRACKED],
         "use a thread pool with N threads"),
-    #[rustc_lint_opt_deny_field_access("use `Session::time_passes` instead of this field")]
-    time: bool = (false, parse_bool, [UNTRACKED],
-        "measure time of rustc processes (default: no)"),
     #[rustc_lint_opt_deny_field_access("use `Session::time_llvm_passes` instead of this field")]
     time_llvm_passes: bool = (false, parse_bool, [UNTRACKED],
         "measure time of each LLVM pass (default: no)"),

compiler/rustc_session/src/session.rs

@@ -606,10 +606,6 @@ impl Session {
         self.parse_sess.source_map()
     }
 
-    pub fn time_passes(&self) -> bool {
-        self.opts.time_passes()
-    }
-
     /// Returns `true` if internal lints should be added to the lint store - i.e. if
     /// `-Zunstable-options` is provided and this isn't rustdoc (internal lints can trigger errors
     /// to be emitted under rustdoc).
@@ -927,6 +923,10 @@ impl Session {
         self.opts.unstable_opts.instrument_mcount
     }
 
+    pub fn time_passes(&self) -> bool {
+        self.opts.unstable_opts.time_passes
+    }
+
     pub fn time_llvm_passes(&self) -> bool {
         self.opts.unstable_opts.time_llvm_passes
     }
@@ -1403,8 +1403,7 @@ pub fn build_session(
         CguReuseTracker::new_disabled()
     };
 
-    let prof =
-        SelfProfilerRef::new(self_profiler, sopts.time_passes(), sopts.unstable_opts.time_passes);
+    let prof = SelfProfilerRef::new(self_profiler, sopts.unstable_opts.time_passes);
 
     let ctfe_backtrace = Lock::new(match env::var("RUSTC_CTFE_BACKTRACE") {
         Ok(ref val) if val == "immediate" => CtfeBacktrace::Immediate,

src/bootstrap/bin/rustc.rs

@@ -67,7 +67,7 @@ fn main() {
             if target == "all"
                 || target.into_string().unwrap().split(',').any(|c| c.trim() == crate_name)
             {
-                cmd.arg("-Ztime");
+                cmd.arg("-Ztime-passes");
             }
         }
     }

src/doc/rustc/src/command-line-arguments.md

@@ -300,7 +300,7 @@ _Note:_ The order of these lint level arguments is taken into account, see [lint
 ## `-Z`: set unstable options
 
 This flag will allow you to set unstable options of rustc. In order to set multiple options,
-the -Z flag can be used multiple times. For example: `rustc -Z verbose -Z time`.
+the -Z flag can be used multiple times. For example: `rustc -Z verbose -Z time-passes`.
 Specifying options with -Z is only available on nightly. To view all available options
 run: `rustc -Z help`.
 

src/librustdoc/formats/renderer.rs

@@ -58,7 +58,7 @@ pub(crate) fn run_format<'tcx, T: FormatRenderer<'tcx>>(
 
     let emit_crate = options.should_emit_crate();
     let (mut format_renderer, krate) = prof
-        .extra_verbose_generic_activity("create_renderer", T::descr())
+        .verbose_generic_activity_with_arg("create_renderer", T::descr())
         .run(|| T::init(krate, options, cache, tcx))?;
 
     if !emit_crate {
@@ -92,6 +92,6 @@ pub(crate) fn run_format<'tcx, T: FormatRenderer<'tcx>>(
                 .run(|| cx.item(item))?;
         }
     }
-    prof.extra_verbose_generic_activity("renderer_after_krate", T::descr())
+    prof.verbose_generic_activity_with_arg("renderer_after_krate", T::descr())
         .run(|| format_renderer.after_krate())
 }

src/test/rustdoc-ui/z-help.stdout

@@ -170,7 +170,6 @@
     -Z                                 thinlto=val -- enable ThinLTO when possible
     -Z                           thir-unsafeck=val -- use the THIR unsafety checker (default: no)
     -Z                                 threads=val -- use a thread pool with N threads
-    -Z                                    time=val -- measure time of rustc processes (default: no)
     -Z                        time-llvm-passes=val -- measure time of each LLVM pass (default: no)
     -Z                             time-passes=val -- measure time of each rustc pass (default: no)
     -Z                               tls-model=val -- choose the TLS model to use (`rustc --print tls-models` for details)