Add an option to print the status of incremental tasks / dep nodes after running them

Author: Zoxc

src/librustc/dep_graph/graph.rs

@@ -292,17 +292,28 @@ impl DepGraph {
                 task_deps.map(|lock| lock.into_inner()),
             );
 
+            let print_status = cfg!(debug_assertions) && hcx.sess().opts.debugging_opts.dep_tasks;
+
             // Determine the color of the new DepNode.
             if let Some(prev_index) = data.previous.node_to_index_opt(&key) {
                 let prev_fingerprint = data.previous.fingerprint_by_index(prev_index);
 
                 let color = if let Some(current_fingerprint) = current_fingerprint {
                     if current_fingerprint == prev_fingerprint {
+                        if print_status {
+                            eprintln!("[task::green] {:?}", key);
+                        }
                         DepNodeColor::Green(dep_node_index)
                     } else {
+                        if print_status {
+                            eprintln!("[task::red] {:?}", key);
+                        }
                         DepNodeColor::Red
                     }
                 } else {
+                    if print_status {
+                        eprintln!("[task::unknown] {:?}", key);
+                    }
                     // Mark the node as Red if we can't hash the result
                     DepNodeColor::Red
                 };
@@ -312,6 +323,10 @@ impl DepGraph {
                             insertion for {:?}", key);
 
                 data.colors.insert(prev_index, color);
+            } else {
+                if print_status {
+                    eprintln!("[task::new] {:?}", key);
+                }
             }
 
             (result, dep_node_index)

src/librustc/session/config.rs

@@ -1233,6 +1233,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "show extended diagnostic help"),
     continue_parse_after_error: bool = (false, parse_bool, [TRACKED],
         "attempt to recover from parse errors (experimental)"),
+    dep_tasks: bool = (false, parse_bool, [UNTRACKED],
+        "print tasks that execute and the color their dep node gets (requires debug build)"),
     incremental: Option<String> = (None, parse_opt_string, [UNTRACKED],
         "enable incremental compilation (experimental)"),
     incremental_queries: bool = (true, parse_bool, [UNTRACKED],