Add idempotent promote for i8 and sync ykllvm

ykrt/src/mt.rs

@@ -1345,6 +1345,24 @@ impl MTThread {
         true
     }
 
+    /// Records `val` as a value to be promoted. Returns `true` if either: no trace is being
+    /// recorded; or recording the promotion succeeded.
+    ///
+    /// If `false` is returned, the current trace is unable to record the promotion successfully
+    /// and further calls are probably pointless, though they will not cause the tracer to enter
+    /// undefined behaviour territory.
+    ///
+    /// # Panics
+    ///
+    /// If the stack is empty. There should always be at least one element on the stack, so a panic
+    /// here means that something has gone wrong elsewhere.
+    pub(crate) fn promote_i8(&mut self, val: i8) -> bool {
+        if let MTThreadState::Tracing { promotions, .. } = self.peek_mut_tstate() {
+            promotions.push(val.cast_unsigned());
+        }
+        true
+    }
+
     /// Records `val` as a value to be promoted. Returns `true` if either: no trace is being
     /// recorded; or recording the promotion succeeded.
     ///

ykrt/src/promote.rs

@@ -92,3 +92,15 @@ pub extern "C" fn __yk_idempotent_promote_i32(val: i32) -> i32 {
     }
     val
 }
+
+/// Records an 8-bit return value of an idempotent function during trace recording.
+#[unsafe(no_mangle)]
+pub extern "C" fn __yk_idempotent_promote_i8(val: i8) -> i8 {
+    if MTThread::is_tracing() {
+        MTThread::with_borrow_mut(|mtt| {
+            // We ignore the return value as we can't really cancel tracing from this function.
+            mtt.promote_i8(val);
+        });
+    }
+    val
+}