Sort Generator print-type-sizes according to their yield points

Especially when trying to diagnose runaway future sizes, it might be
more intuitive to sort the variants according to the control flow
(aka their yield points) rather than the size of the variants.

Author: Swatinem

compiler/rustc_session/src/code_stats.rs

@@ -84,7 +84,11 @@ impl CodeStats {
         // Sort variants so the largest ones are shown first. A stable sort is
         // used here so that source code order is preserved for all variants
         // that have the same size.
-        variants.sort_by(|info1, info2| info2.size.cmp(&info1.size));
+        // Except for Generators, whose variants are already sorted according to
+        // their yield points in `variant_info_for_generator`.
+        if kind != DataTypeKind::Generator {
+            variants.sort_by(|info1, info2| info2.size.cmp(&info1.size));
+        }
         let info = TypeSizeInfo {
             kind,
             type_description: type_desc.to_string(),

compiler/rustc_ty_utils/src/layout.rs

@@ -970,7 +970,7 @@ fn variant_info_for_generator<'tcx>(
         })
         .collect();
 
-    let variant_infos: Vec<_> = generator
+    let mut variant_infos: Vec<_> = generator
         .variant_fields
         .iter_enumerated()
         .map(|(variant_idx, variant_def)| {
@@ -1033,6 +1033,15 @@ fn variant_info_for_generator<'tcx>(
             }
         })
         .collect();
+
+    // The first three variants are hardcoded to be `UNRESUMED`, `RETURNED` and `POISONED`.
+    // We will move the `RETURNED` and `POISONED` elements to the end so we
+    // are left with a sorting order according to the generators yield points:
+    // First `Unresumed`, then the `SuspendN` followed by `Returned` and `Panicked` (POISONED).
+    let end_states = variant_infos.drain(1..=2);
+    let end_states: Vec<_> = end_states.collect();
+    variant_infos.extend(end_states);
+
     (
         variant_infos,
         match tag_encoding {

tests/ui/async-await/future-sizes/large-arg.stdout

@@ -1,17 +1,17 @@
 print-type-size type: `[async fn body@$DIR/large-arg.rs:6:21: 8:2]`: 3076 bytes, alignment: 1 bytes
 print-type-size     discriminant: 1 bytes
+print-type-size     variant `Unresumed`: 0 bytes
 print-type-size     variant `Suspend0`: 3075 bytes
 print-type-size         local `.__awaitee`: 3075 bytes, offset: 0 bytes, alignment: 1 bytes
-print-type-size     variant `Unresumed`: 0 bytes
 print-type-size     variant `Returned`: 0 bytes
 print-type-size     variant `Panicked`: 0 bytes
 print-type-size type: `[async fn body@$DIR/large-arg.rs:10:30: 12:2]`: 3075 bytes, alignment: 1 bytes
 print-type-size     discriminant: 1 bytes
+print-type-size     variant `Unresumed`: 1024 bytes
+print-type-size         upvar `.t`: 1024 bytes, offset: 0 bytes, alignment: 1 bytes
 print-type-size     variant `Suspend0`: 3074 bytes
 print-type-size         upvar `.t`: 1024 bytes, offset: 0 bytes, alignment: 1 bytes
 print-type-size         local `.__awaitee`: 2050 bytes
-print-type-size     variant `Unresumed`: 1024 bytes
-print-type-size         upvar `.t`: 1024 bytes, offset: 0 bytes, alignment: 1 bytes
 print-type-size     variant `Returned`: 1024 bytes
 print-type-size         upvar `.t`: 1024 bytes, offset: 0 bytes, alignment: 1 bytes
 print-type-size     variant `Panicked`: 1024 bytes
@@ -24,11 +24,11 @@ print-type-size         field `.uninit`: 0 bytes
 print-type-size         field `.value`: 3075 bytes
 print-type-size type: `[async fn body@$DIR/large-arg.rs:13:26: 15:2]`: 2050 bytes, alignment: 1 bytes
 print-type-size     discriminant: 1 bytes
+print-type-size     variant `Unresumed`: 1024 bytes
+print-type-size         upvar `.t`: 1024 bytes, offset: 0 bytes, alignment: 1 bytes
 print-type-size     variant `Suspend0`: 2049 bytes
 print-type-size         upvar `.t`: 1024 bytes, offset: 0 bytes, alignment: 1 bytes
 print-type-size         local `.__awaitee`: 1025 bytes
-print-type-size     variant `Unresumed`: 1024 bytes
-print-type-size         upvar `.t`: 1024 bytes, offset: 0 bytes, alignment: 1 bytes
 print-type-size     variant `Returned`: 1024 bytes
 print-type-size         upvar `.t`: 1024 bytes, offset: 0 bytes, alignment: 1 bytes
 print-type-size     variant `Panicked`: 1024 bytes

tests/ui/print_type_sizes/async.stdout

@@ -1,11 +1,11 @@
 print-type-size type: `[async fn body@$DIR/async.rs:8:36: 11:2]`: 16386 bytes, alignment: 1 bytes
 print-type-size     discriminant: 1 bytes
+print-type-size     variant `Unresumed`: 8192 bytes
+print-type-size         upvar `.arg`: 8192 bytes, offset: 0 bytes, alignment: 1 bytes
 print-type-size     variant `Suspend0`: 16385 bytes
 print-type-size         upvar `.arg`: 8192 bytes, offset: 0 bytes, alignment: 1 bytes
 print-type-size         local `.arg`: 8192 bytes
 print-type-size         local `.__awaitee`: 1 bytes
-print-type-size     variant `Unresumed`: 8192 bytes
-print-type-size         upvar `.arg`: 8192 bytes, offset: 0 bytes, alignment: 1 bytes
 print-type-size     variant `Returned`: 8192 bytes
 print-type-size         upvar `.arg`: 8192 bytes, offset: 0 bytes, alignment: 1 bytes
 print-type-size     variant `Panicked`: 8192 bytes

tests/ui/print_type_sizes/generator.stdout

@@ -2,9 +2,9 @@ print-type-size type: `[generator@$DIR/generator.rs:10:5: 10:14]`: 8193 bytes, a
 print-type-size     discriminant: 1 bytes
 print-type-size     variant `Unresumed`: 8192 bytes
 print-type-size         upvar `.array`: 8192 bytes, offset: 0 bytes, alignment: 1 bytes
+print-type-size     variant `Suspend0`: 8192 bytes
+print-type-size         upvar `.array`: 8192 bytes, offset: 0 bytes, alignment: 1 bytes
 print-type-size     variant `Returned`: 8192 bytes
 print-type-size         upvar `.array`: 8192 bytes, offset: 0 bytes, alignment: 1 bytes
 print-type-size     variant `Panicked`: 8192 bytes
 print-type-size         upvar `.array`: 8192 bytes, offset: 0 bytes, alignment: 1 bytes
-print-type-size     variant `Suspend0`: 8192 bytes
-print-type-size         upvar `.array`: 8192 bytes, offset: 0 bytes, alignment: 1 bytes

tests/ui/print_type_sizes/generator_discr_placement.stdout

@@ -1,11 +1,11 @@
 print-type-size type: `[generator@$DIR/generator_discr_placement.rs:11:13: 11:15]`: 8 bytes, alignment: 4 bytes
 print-type-size     discriminant: 1 bytes
+print-type-size     variant `Unresumed`: 0 bytes
 print-type-size     variant `Suspend0`: 7 bytes
 print-type-size         padding: 3 bytes
 print-type-size         local `.w`: 4 bytes, alignment: 4 bytes
 print-type-size     variant `Suspend1`: 7 bytes
 print-type-size         padding: 3 bytes
 print-type-size         local `.z`: 4 bytes, alignment: 4 bytes
-print-type-size     variant `Unresumed`: 0 bytes
 print-type-size     variant `Returned`: 0 bytes
 print-type-size     variant `Panicked`: 0 bytes