Overhaul to_readable_str.

It's a function that prints numbers with underscores inserted for
readability (e.g. "1_234_567"), used by `-Zmeta-stats` and
`-Zinput-stats`. It's the only thing in `rustc_middle::util::common`,
which is a bizarre location for it.

This commit:
- moves it to `rustc_data_structures`, a more logical crate for it;
- puts it in a module `thousands`, like the similar crates.io crate;
- renames it `format_with_underscores`, which is a clearer name;
- rewrites it to be more concise;
- slightly improves the testing.

compiler/rustc_data_structures/src/lib.rs

@@ -76,6 +76,7 @@ pub mod sync;
 pub mod tagged_ptr;
 pub mod temp_dir;
 pub mod thinvec;
+pub mod thousands;
 pub mod transitive_relation;
 pub mod unhash;
 pub mod unord;

compiler/rustc_data_structures/src/thousands/mod.rs

@@ -0,0 +1,16 @@
+//! This is an extremely bare-bones alternative to the `thousands` crate on
+//! crates.io, for printing large numbers in a readable fashion.
+
+#[cfg(test)]
+mod tests;
+
+// Converts the number to a string, with underscores as the thousands separator.
+pub fn format_with_underscores(n: usize) -> String {
+    let mut s = n.to_string();
+    let mut i = s.len();
+    while i > 3 {
+        i -= 3;
+        s.insert(i, '_');
+    }
+    s
+}

compiler/rustc_data_structures/src/thousands/tests.rs

@@ -0,0 +1,14 @@
+use super::*;
+
+#[test]
+fn test_format_with_underscores() {
+    assert_eq!("0", format_with_underscores(0));
+    assert_eq!("1", format_with_underscores(1));
+    assert_eq!("99", format_with_underscores(99));
+    assert_eq!("345", format_with_underscores(345));
+    assert_eq!("1_000", format_with_underscores(1_000));
+    assert_eq!("12_001", format_with_underscores(12_001));
+    assert_eq!("999_999", format_with_underscores(999_999));
+    assert_eq!("1_000_000", format_with_underscores(1_000_000));
+    assert_eq!("12_345_678", format_with_underscores(12_345_678));
+}

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -9,6 +9,7 @@ use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::memmap::{Mmap, MmapMut};
 use rustc_data_structures::sync::{Lrc, join, par_for_each_in};
 use rustc_data_structures::temp_dir::MaybeTempDir;
+use rustc_data_structures::thousands::format_with_underscores;
 use rustc_feature::Features;
 use rustc_hir as hir;
 use rustc_hir::def_id::{CRATE_DEF_ID, CRATE_DEF_INDEX, LOCAL_CRATE, LocalDefId, LocalDefIdSet};
@@ -22,7 +23,6 @@ use rustc_middle::traits::specialization_graph;
 use rustc_middle::ty::codec::TyEncoder;
 use rustc_middle::ty::fast_reject::{self, TreatParams};
 use rustc_middle::ty::{AssocItemContainer, SymbolName};
-use rustc_middle::util::common::to_readable_str;
 use rustc_middle::{bug, span_bug};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder, opaque};
 use rustc_session::config::{CrateType, OptLevel};
@@ -782,7 +782,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                     "{} {:<23}{:>10} ({:4.1}%)",
                     prefix,
                     label,
-                    to_readable_str(size),
+                    format_with_underscores(size),
                     perc(size)
                 );
             }
@@ -791,7 +791,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 "{} {:<23}{:>10} (of which {:.1}% are zero bytes)",
                 prefix,
                 "Total",
-                to_readable_str(total_bytes),
+                format_with_underscores(total_bytes),
                 perc(zero_bytes)
             );
             eprintln!("{prefix}");

compiler/rustc_middle/src/util/common.rs

@@ -1,22 +0,0 @@
-#[cfg(test)]
-mod tests;
-
-pub fn to_readable_str(mut val: usize) -> String {
-    let mut groups = vec![];
-    loop {
-        let group = val % 1000;
-
-        val /= 1000;
-
-        if val == 0 {
-            groups.push(group.to_string());
-            break;
-        } else {
-            groups.push(format!("{group:03}"));
-        }
-    }
-
-    groups.reverse();
-
-    groups.join("_")
-}

compiler/rustc_middle/src/util/common/tests.rs

@@ -1,14 +0,0 @@
-use super::*;
-
-#[test]
-fn test_to_readable_str() {
-    assert_eq!("0", to_readable_str(0));
-    assert_eq!("1", to_readable_str(1));
-    assert_eq!("99", to_readable_str(99));
-    assert_eq!("999", to_readable_str(999));
-    assert_eq!("1_000", to_readable_str(1_000));
-    assert_eq!("1_001", to_readable_str(1_001));
-    assert_eq!("999_999", to_readable_str(999_999));
-    assert_eq!("1_000_000", to_readable_str(1_000_000));
-    assert_eq!("1_234_567", to_readable_str(1_234_567));
-}

compiler/rustc_middle/src/util/mod.rs

@@ -1,5 +1,4 @@
 pub mod bug;
-pub mod common;
 
 #[derive(Default, Copy, Clone)]
 pub struct Providers {

compiler/rustc_passes/src/input_stats.rs

@@ -5,10 +5,10 @@
 use rustc_ast::visit::BoundKind;
 use rustc_ast::{self as ast, NodeId, visit as ast_visit};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::thousands::format_with_underscores;
 use rustc_hir::{self as hir, AmbigArg, HirId, intravisit as hir_visit};
 use rustc_middle::hir::map::Map;
 use rustc_middle::ty::TyCtxt;
-use rustc_middle::util::common::to_readable_str;
 use rustc_span::Span;
 use rustc_span::def_id::LocalDefId;
 
@@ -144,10 +144,10 @@ impl<'k> StatCollector<'k> {
                 "{} {:<18}{:>10} ({:4.1}%){:>14}{:>14}",
                 prefix,
                 label,
-                to_readable_str(size),
+                format_with_underscores(size),
                 percent(size, total_size),
-                to_readable_str(node.stats.count),
-                to_readable_str(node.stats.size)
+                format_with_underscores(node.stats.count),
+                format_with_underscores(node.stats.size)
             );
             if !node.subnodes.is_empty() {
                 // We will soon sort, so the initial order does not matter.
@@ -163,9 +163,9 @@ impl<'k> StatCollector<'k> {
                         "{} - {:<18}{:>10} ({:4.1}%){:>14}",
                         prefix,
                         label,
-                        to_readable_str(size),
+                        format_with_underscores(size),
                         percent(size, total_size),
-                        to_readable_str(subnode.count),
+                        format_with_underscores(subnode.count),
                     );
                 }
             }
@@ -175,8 +175,8 @@ impl<'k> StatCollector<'k> {
             "{} {:<18}{:>10}        {:>14}",
             prefix,
             "Total",
-            to_readable_str(total_size),
-            to_readable_str(total_count),
+            format_with_underscores(total_size),
+            format_with_underscores(total_count),
         );
         eprintln!("{prefix}");
     }