added comment

Author: nebulark

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -220,6 +220,8 @@ pub fn target_machine_factory(
     let use_init_array =
         !sess.opts.unstable_opts.use_ctors_section.unwrap_or(sess.target.use_ctors_section);
 
+    // this annotes in the debug file that code is hotpatchable. In addtion without it -functionpadmin will be ignored.
+    // See: https://github.com/llvm/llvm-project/blob/d703b922961e0d02a5effdd4bfbb23ad50a3cc9f/lld/COFF/Writer.cpp#L1298
     let use_hotpatch = sess.opts.unstable_opts.ms_hotpatch && sess.target.is_x86();
 
     let path_mapping = sess.source_map().path_mapping().clone();