[self-profiler] Use ThreadId::as_u64() instead of transmute

src/librustc_data_structures/lib.rs

@@ -23,6 +23,7 @@
 #![feature(integer_atomics)]
 #![feature(test)]
 #![feature(associated_type_bounds)]
+#![feature(thread_id_value)]
 #![cfg_attr(unix, feature(libc))]
 #![allow(rustc::default_hash_types)]
 

src/librustc_data_structures/profiling.rs

@@ -88,7 +88,6 @@ use std::fs;
 use std::path::Path;
 use std::process;
 use std::sync::Arc;
-use std::thread::ThreadId;
 use std::time::{Duration, Instant};
 use std::u32;
 
@@ -149,10 +148,6 @@ const EVENT_FILTERS_BY_NAME: &[(&str, EventFilter)] = &[
     ("query-keys", EventFilter::QUERY_KEYS),
 ];
 
-fn thread_id_to_u32(tid: ThreadId) -> u32 {
-    unsafe { std::mem::transmute::<ThreadId, u64>(tid) as u32 }
-}
-
 /// Something that uniquely identifies a query invocation.
 pub struct QueryInvocationId(pub u32);
 
@@ -318,7 +313,7 @@ impl SelfProfilerRef {
     ) {
         drop(self.exec(event_filter, |profiler| {
             let event_id = StringId::new_virtual(query_invocation_id.0);
-            let thread_id = thread_id_to_u32(std::thread::current().id());
+            let thread_id = std::thread::current().id().as_u64() as u32;
 
             profiler.profiler.record_instant_event(
                 event_kind(profiler),
@@ -477,7 +472,7 @@ impl<'a> TimingGuard<'a> {
         event_kind: StringId,
         event_id: EventId,
     ) -> TimingGuard<'a> {
-        let thread_id = thread_id_to_u32(std::thread::current().id());
+        let thread_id = std::thread::current().id().as_u64() as u32;
         let raw_profiler = &profiler.profiler;
         let timing_guard =
             raw_profiler.start_recording_interval_event(event_kind, event_id, thread_id);