Add codegen timing section

compiler/rustc_errors/src/timings.rs

@@ -1,10 +1,15 @@
 use std::time::Instant;
 
+use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::sync::Lock;
+
 use crate::DiagCtxtHandle;
 
 /// A high-level section of the compilation process.
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
 pub enum TimingSection {
+    /// Time spent doing codegen.
+    Codegen,
     /// Time spent linking.
     Linking,
 }
@@ -36,23 +41,59 @@ pub struct TimingSectionHandler {
     /// Time when the compilation session started.
     /// If `None`, timing is disabled.
     origin: Option<Instant>,
+    /// Sanity check to ensure that we open and close sections correctly.
+    opened_sections: Lock<FxHashSet<TimingSection>>,
 }
 
 impl TimingSectionHandler {
     pub fn new(enabled: bool) -> Self {
         let origin = if enabled { Some(Instant::now()) } else { None };
-        Self { origin }
+        Self { origin, opened_sections: Lock::new(FxHashSet::default()) }
     }
 
     /// Returns a RAII guard that will immediately emit a start the provided section, and then emit
     /// its end when it is dropped.
-    pub fn start_section<'a>(
+    pub fn section_guard<'a>(
         &self,
         diag_ctxt: DiagCtxtHandle<'a>,
         section: TimingSection,
     ) -> TimingSectionGuard<'a> {
+        if self.is_enabled() && self.opened_sections.borrow().contains(&section) {
+            diag_ctxt
+                .bug(format!("Section `{section:?}` was started again before it was finished"));
+        }
+
         TimingSectionGuard::create(diag_ctxt, section, self.origin)
     }
+
+    /// Start the provided section.
+    pub fn start_section(&self, diag_ctxt: DiagCtxtHandle<'_>, section: TimingSection) {
+        if let Some(origin) = self.origin {
+            let mut opened = self.opened_sections.borrow_mut();
+            if !opened.insert(section) {
+                diag_ctxt
+                    .bug(format!("Section `{section:?}` was started again before it was finished"));
+            }
+
+            diag_ctxt.emit_timing_section_start(TimingRecord::from_origin(origin, section));
+        }
+    }
+
+    /// End the provided section.
+    pub fn end_section(&self, diag_ctxt: DiagCtxtHandle<'_>, section: TimingSection) {
+        if let Some(origin) = self.origin {
+            let mut opened = self.opened_sections.borrow_mut();
+            if !opened.remove(&section) {
+                diag_ctxt.bug(format!("Section `{section:?}` was ended before being started"));
+            }
+
+            diag_ctxt.emit_timing_section_end(TimingRecord::from_origin(origin, section));
+        }
+    }
+
+    fn is_enabled(&self) -> bool {
+        self.origin.is_some()
+    }
 }
 
 /// RAII wrapper for starting and ending section timings.