Add a comment mentioning LTO/PGO

Author: Kobzol

collector/src/artifact_stats.rs

@@ -112,6 +112,9 @@ impl ArtifactStats {
 /// `foo::abcd` -> `foo`.
 /// - Removes suffixes after a dot from the symbol, e.g. `anon.abcdef.123` -> `anon` or
 /// `foo.llvm.123` -> `foo`.
+///
+/// These modifications should remove things added by LLVM in the LTO/PGO phase.
+/// See more information here: https://rust-lang.github.io/rfcs/2603-rust-symbol-name-mangling-v0.html#vendor-specific-suffix
 fn normalize_symbol_name(symbol: &str) -> String {
     /// Tries to match hashes in brackets produces by rustc in mangled symbol names.
     static RUSTC_BRACKET_HASH_REGEX: OnceLock<Regex> = OnceLock::new();
@@ -313,7 +316,7 @@ mod tests {
 
     #[test]
     fn normalize_hash_without_brackets() {
-        // Check that hashes withouto brackets are removed.
+        // Check that hashes without brackets are removed.
         check(
             "_ZN10proc_macro5quote5quote28_$u7b$$u7b$closure$u7d$$u7d$17h90045007b0e69fc9E",
             "proc_macro::quote::quote::{{closure}}::h90045007b0e69fc9",