From 1551495d3221b6162b96a14fc5cdb45f2783ed3c Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Thu, 18 May 2023 14:45:52 +1000
Subject: [PATCH 1/2] Fix an ICE in CGU dumping code.

---
 compiler/rustc_monomorphize/src/partitioning/mod.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_monomorphize/src/partitioning/mod.rs b/compiler/rustc_monomorphize/src/partitioning/mod.rs
index c10180ee3f4..eae3585febf 100644
--- a/compiler/rustc_monomorphize/src/partitioning/mod.rs
+++ b/compiler/rustc_monomorphize/src/partitioning/mod.rs
@@ -365,14 +365,14 @@ fn debug_dump<'a, 'tcx, I>(tcx: TyCtxt<'tcx>, label: &str, cgus: I)
                 let symbol_hash_start = symbol_name.rfind('h');
                 let symbol_hash = symbol_hash_start.map_or("<no hash>", |i| &symbol_name[i..]);
 
-                let _ = writeln!(
+                let _ = with_no_trimmed_paths!(writeln!(
                     s,
                     " - {} [{:?}] [{}] estimated size {}",
                     mono_item,
                     linkage,
                     symbol_hash,
                     mono_item.size_estimate(tcx)
-                );
+                ));
             }
 
             let _ = writeln!(s);

From 1bb957efc6ac69b0b19af282c51e04ef70f4233c Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Thu, 18 May 2023 13:32:28 +1000
Subject: [PATCH 2/2] Improve CGU partitioning debug output.

- Pass a slice instead of an iterator to `debug_dump`.
- For each CGU set, print: the number of CGUs, the max and min size, and
  the ratio of the max and min size (which indicates how evenly sized
  they are).
- Print a `FINAL` entry, showing the absolute final results.
---
 .../src/partitioning/mod.rs                   | 26 ++++++++++++-------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/compiler/rustc_monomorphize/src/partitioning/mod.rs b/compiler/rustc_monomorphize/src/partitioning/mod.rs
index eae3585febf..eafe57a0c02 100644
--- a/compiler/rustc_monomorphize/src/partitioning/mod.rs
+++ b/compiler/rustc_monomorphize/src/partitioning/mod.rs
@@ -250,13 +250,13 @@ pub fn partition<'tcx, I>(
         cgu.create_size_estimate(tcx);
     }
 
-    debug_dump(tcx, "INITIAL PARTITIONING:", initial_partitioning.codegen_units.iter());
+    debug_dump(tcx, "INITIAL PARTITIONING", &initial_partitioning.codegen_units);
 
     // Merge until we have at most `max_cgu_count` codegen units.
     {
         let _prof_timer = tcx.prof.generic_activity("cgu_partitioning_merge_cgus");
         partitioner.merge_codegen_units(cx, &mut initial_partitioning);
-        debug_dump(tcx, "POST MERGING:", initial_partitioning.codegen_units.iter());
+        debug_dump(tcx, "POST MERGING", &initial_partitioning.codegen_units);
     }
 
     // In the next step, we use the inlining map to determine which additional
@@ -272,7 +272,7 @@ pub fn partition<'tcx, I>(
         cgu.create_size_estimate(tcx);
     }
 
-    debug_dump(tcx, "POST INLINING:", post_inlining.codegen_units.iter());
+    debug_dump(tcx, "POST INLINING", &post_inlining.codegen_units);
 
     // Next we try to make as many symbols "internal" as possible, so LLVM has
     // more freedom to optimize.
@@ -322,6 +322,8 @@ pub fn partition<'tcx, I>(
 
     result.sort_by(|a, b| a.name().as_str().cmp(b.name().as_str()));
 
+    debug_dump(tcx, "FINAL", &result);
+
     result
 }
 
@@ -346,19 +348,23 @@ struct PostInliningPartitioning<'tcx> {
     internalization_candidates: FxHashSet<MonoItem<'tcx>>,
 }
 
-fn debug_dump<'a, 'tcx, I>(tcx: TyCtxt<'tcx>, label: &str, cgus: I)
-where
-    I: Iterator<Item = &'a CodegenUnit<'tcx>>,
-    'tcx: 'a,
-{
+fn debug_dump<'a, 'tcx: 'a>(tcx: TyCtxt<'tcx>, label: &str, cgus: &[CodegenUnit<'tcx>]) {
     let dump = move || {
         use std::fmt::Write;
 
+        let num_cgus = cgus.len();
+        let max = cgus.iter().map(|cgu| cgu.size_estimate()).max().unwrap();
+        let min = cgus.iter().map(|cgu| cgu.size_estimate()).min().unwrap();
+        let ratio = max as f64 / min as f64;
+
         let s = &mut String::new();
-        let _ = writeln!(s, "{label}");
+        let _ = writeln!(
+            s,
+            "{label} ({num_cgus} CodegenUnits, max={max}, min={min}, max/min={ratio:.1}):"
+        );
         for cgu in cgus {
             let _ =
-                writeln!(s, "CodegenUnit {} estimated size {} :", cgu.name(), cgu.size_estimate());
+                writeln!(s, "CodegenUnit {} estimated size {}:", cgu.name(), cgu.size_estimate());
 
             for (mono_item, linkage) in cgu.items() {
                 let symbol_name = mono_item.symbol_name(tcx).name;