mono-item profiler

collector/README.md

@@ -359,6 +359,13 @@ The mandatory `<PROFILER>` argument must be one of the following.
   - **Output**. Human-readable output is written to files with an `ll` prefix.
   - **Notes**. Does not work with the `Check` build kind. Also does not work
     with the `IncrFull`, `IncrUnchanged`, and `IncrPatched` run kinds.
+- `mono-items`: Dump monomorphization items for each (merged) CGU in the crate.
+  These are also post-processed from the raw format into per-file dumps.
+  - **Purpose**. This is useful to investigate changes in CGU partionining.
+  - **Slowdown**. Equivalent to normal compilation.
+  - **Output**. File per CGU, currently, placed in a directory inside results.
+  - **Notes**. Will likely work best with `Full` builds, on either Debug or Opt
+    profiles.
 
 The mandatory `<RUSTC>` argument is a patch to a rustc executable, similar to
 `bench_local`.

collector/src/execute.rs

@@ -13,6 +13,7 @@ use std::fmt;
 use std::fs::{self, File};
 use std::hash;
 use std::io::Read;
+use std::io::Write;
 use std::mem::ManuallyDrop;
 use std::path::{Path, PathBuf};
 use std::process::{self, Command};
@@ -178,6 +179,7 @@ pub enum Profiler {
     Massif,
     Eprintln,
     LlvmLines,
+    MonoItems,
 }
 
 impl Profiler {
@@ -198,6 +200,7 @@ impl Profiler {
             "massif" => Ok(Profiler::Massif),
             "eprintln" => Ok(Profiler::Eprintln),
             "llvm-lines" => Ok(Profiler::LlvmLines),
+            "mono-items" => Ok(Profiler::MonoItems),
             _ => Err(anyhow!("'{}' is not a known profiler", name)),
         }
     }
@@ -218,6 +221,7 @@ impl Profiler {
             Profiler::Massif => "massif",
             Profiler::Eprintln => "eprintln",
             Profiler::LlvmLines => "llvm-lines",
+            Profiler::MonoItems => "mono-items",
         }
     }
 
@@ -237,6 +241,7 @@ impl Profiler {
             | Profiler::Callgrind
             | Profiler::DHAT
             | Profiler::Massif
+            | Profiler::MonoItems
             | Profiler::Eprintln => {
                 if build_kind == BuildKind::Doc {
                     Some("rustdoc")
@@ -265,6 +270,7 @@ impl Profiler {
             | Profiler::Callgrind
             | Profiler::DHAT
             | Profiler::Massif
+            | Profiler::MonoItems
             | Profiler::Eprintln => true,
             Profiler::LlvmLines => scenario_kind == ScenarioKind::Full,
         }
@@ -1132,6 +1138,51 @@ impl<'a> Processor for ProfileProcessor<'a> {
                 fs::copy(&tmp_eprintln_file, &eprintln_file)?;
             }
 
+            // mono item results are redirected (via rustc-fake) to a file
+            // called `mono-items`. We copy it from the temp dir to the output
+            // dir, giving it a new name in the process.
+            Profiler::MonoItems => {
+                let tmp_file = filepath(data.cwd.as_ref(), "mono-items");
+                let out_dir = self.output_dir.join(&out_file("mono-items"));
+                let _ = fs::create_dir_all(&out_dir);
+                let result_file = filepath(&out_dir, "raw");
+
+                fs::copy(&tmp_file, &result_file)?;
+
+                let mut by_cgu: HashMap<&str, Vec<(&str, &str)>> = HashMap::new();
+                let mono_items = std::fs::read_to_string(&tmp_file)?;
+                for line in mono_items.lines() {
+                    let line = if let Some(line) = line.strip_prefix("MONO_ITEM ") {
+                        line
+                    } else {
+                        continue;
+                    };
+
+                    let (name, cgus) = if let Some(parts) = line.split_once(" @@ ") {
+                        parts
+                    } else {
+                        continue;
+                    };
+
+                    for cgu in cgus.split(' ') {
+                        let cgu_name_end = cgu.rfind('[').expect(&cgu);
+                        let cgu_name = &cgu[..cgu_name_end];
+                        let linkage = &cgu[cgu_name_end + 1..cgu.len() - 1];
+                        by_cgu.entry(cgu_name).or_default().push((name, linkage));
+                    }
+                }
+
+                for (cgu, items) in &by_cgu {
+                    let cgu_file = filepath(&out_dir, cgu);
+                    let mut file = std::io::BufWriter::new(
+                        fs::File::create(&cgu_file).with_context(|| format!("{:?}", cgu_file))?,
+                    );
+                    for (name, linkage) in items {
+                        writeln!(&mut file, "{} {}", name, linkage)?;
+                    }
+                }
+            }
+
             // `cargo llvm-lines` writes its output to stdout. We copy that
             // output into a file in the output dir.
             Profiler::LlvmLines => {

collector/src/main.rs

@@ -674,7 +674,7 @@ fn main_result() -> anyhow::Result<i32> {
             (@arg PROFILER: +required +takes_value
              "One of: 'self-profile', 'time-passes', 'perf-record',\n\
              'oprofile', 'cachegrind', 'callgrind', 'dhat', 'massif',\n\
-             'eprintln', 'llvm-lines'")
+             'eprintln', 'llvm-lines', 'mono-items'")
             (@arg RUSTC:    +required +takes_value "The path to the local rustc to benchmark")
             (@arg ID:       +required +takes_value "Identifier to associate benchmark results with")
 
@@ -703,7 +703,7 @@ fn main_result() -> anyhow::Result<i32> {
             (@arg PROFILER: +required +takes_value
              "One of: 'self-profile', 'time-passes', 'perf-record',\n\
              'oprofile', 'cachegrind', 'callgrind', 'dhat', 'massif',\n\
-             'eprintln', 'llvm-lines'")
+             'eprintln', 'llvm-lines', 'mono-items'")
             (@arg RUSTC_BEFORE: +required +takes_value "The path to the local rustc to benchmark")
             (@arg RUSTC_AFTER:  +required +takes_value "The path to the local rustc to benchmark")
 

collector/src/rustc-fake.rs

@@ -285,6 +285,15 @@ fn main() {
                 assert!(cmd.status().expect("failed to spawn").success());
             }
 
+            "mono-items" => {
+                // Lazy item collection is the default (i.e., without this
+                // option)
+                args.push("-Zprint-mono-items=lazy".into());
+                let mut cmd = bash_command(tool, args, "1> mono-items");
+
+                assert!(cmd.status().expect("failed to spawn").success());
+            }
+
             _ => {
                 panic!("unknown wrapper: {}", wrapper);
             }