src/librustc_session/cgu_reuse_tracker.rs

   1 //! Some facilities for tracking how codegen-units are reused during incremental
   2 //! compilation. This is used for incremental compilation tests and debug
   3 //! output.
   4
   5 use rustc_data_structures::fx::FxHashMap;
   6 use rustc_span::{Span, Symbol};
   7 use std::sync::{Arc, Mutex};
   8 use tracing::debug;
   9
  10 #[derive(Copy, Clone, Debug, PartialEq, PartialOrd)]
  11 pub enum CguReuse {
  12     No,
  13     PreLto,
  14     PostLto,
  15 }
  16
  17 #[derive(Copy, Clone, Debug, PartialEq)]
  18 pub enum ComparisonKind {
  19     Exact,
  20     AtLeast,
  21 }
  22
  23 struct TrackerData {
  24     actual_reuse: FxHashMap<String, CguReuse>,
  25     expected_reuse: FxHashMap<String, (String, SendSpan, CguReuse, ComparisonKind)>,
  26 }
  27
  28 // Span does not implement `Send`, so we can't just store it in the shared
  29 // `TrackerData` object. Instead of splitting up `TrackerData` into shared and
  30 // non-shared parts (which would be complicated), we just mark the `Span` here
  31 // explicitly as `Send`. That's safe because the span data here is only ever
  32 // accessed from the main thread.
  33 struct SendSpan(Span);
  34 unsafe impl Send for SendSpan {}
  35
  36 #[derive(Clone)]
  37 pub struct CguReuseTracker {
  38     data: Option<Arc<Mutex<TrackerData>>>,
  39 }
  40
  41 impl CguReuseTracker {
  42     pub fn new() -> CguReuseTracker {
  43         let data =
  44             TrackerData { actual_reuse: Default::default(), expected_reuse: Default::default() };
  45
  46         CguReuseTracker { data: Some(Arc::new(Mutex::new(data))) }
  47     }
  48
  49     pub fn new_disabled() -> CguReuseTracker {
  50         CguReuseTracker { data: None }
  51     }
  52
  53     pub fn set_actual_reuse(&self, cgu_name: &str, kind: CguReuse) {
  54         if let Some(ref data) = self.data {
  55             debug!("set_actual_reuse({:?}, {:?})", cgu_name, kind);
  56
  57             let prev_reuse = data.lock().unwrap().actual_reuse.insert(cgu_name.to_string(), kind);
  58
  59             if let Some(prev_reuse) = prev_reuse {
  60                 // The only time it is legal to overwrite reuse state is when
  61                 // we discover during ThinLTO that we can actually reuse the
  62                 // post-LTO version of a CGU.
  63                 assert_eq!(prev_reuse, CguReuse::PreLto);
  64             }
  65         }
  66     }
  67
  68     pub fn set_expectation(
  69         &self,
  70         cgu_name: Symbol,
  71         cgu_user_name: &str,
  72         error_span: Span,
  73         expected_reuse: CguReuse,
  74         comparison_kind: ComparisonKind,
  75     ) {
  76         if let Some(ref data) = self.data {
  77             debug!("set_expectation({:?}, {:?}, {:?})", cgu_name, expected_reuse, comparison_kind);
  78             let mut data = data.lock().unwrap();
  79
  80             data.expected_reuse.insert(
  81                 cgu_name.to_string(),
  82                 (cgu_user_name.to_string(), SendSpan(error_span), expected_reuse, comparison_kind),
  83             );
  84         }
  85     }
  86
  87     pub fn check_expected_reuse(&self, diag: &rustc_errors::Handler) {
  88         if let Some(ref data) = self.data {
  89             let data = data.lock().unwrap();
  90
  91             for (cgu_name, &(ref cgu_user_name, ref error_span, expected_reuse, comparison_kind)) in
  92                 &data.expected_reuse
  93             {
  94                 if let Some(&actual_reuse) = data.actual_reuse.get(cgu_name) {
  95                     let (error, at_least) = match comparison_kind {
  96                         ComparisonKind::Exact => (expected_reuse != actual_reuse, false),
  97                         ComparisonKind::AtLeast => (actual_reuse < expected_reuse, true),
  98                     };
  99
 100                     if error {
 101                         let at_least = if at_least { "at least " } else { "" };
 102                         let msg = format!(
 103                             "CGU-reuse for `{}` is `{:?}` but \
 104                                            should be {}`{:?}`",
 105                             cgu_user_name, actual_reuse, at_least, expected_reuse
 106                         );
 107                         diag.span_err(error_span.0, &msg);
 108                     }
 109                 } else {
 110                     let msg = format!(
 111                         "CGU-reuse for `{}` (mangled: `{}`) was \
 112                                        not recorded",
 113                         cgu_user_name, cgu_name
 114                     );
 115                     diag.span_fatal(error_span.0, &msg).raise();
 116                 }
 117             }
 118         }
 119     }
 120 }