diff --git a/src/tools/coverage-dump/src/covfun.rs b/src/tools/coverage-dump/src/covfun.rs
index c779dd0583c4e..33fac3edccd11 100644
--- a/src/tools/coverage-dump/src/covfun.rs
+++ b/src/tools/coverage-dump/src/covfun.rs
@@ -56,6 +56,7 @@ pub(crate) fn dump_covfun_mappings(
             expression_resolver.push_operands(lhs, rhs);
         }
 
+        let mut max_counter = None;
         for i in 0..num_files {
             let num_mappings = parser.read_uleb128_u32()?;
             println!("Number of file {i} mappings: {num_mappings}");
@@ -63,6 +64,11 @@ pub(crate) fn dump_covfun_mappings(
             for _ in 0..num_mappings {
                 let (kind, region) = parser.read_mapping_kind_and_region()?;
                 println!("- {kind:?} at {region:?}");
+                kind.for_each_term(|term| {
+                    if let CovTerm::Counter(n) = term {
+                        max_counter = max_counter.max(Some(n));
+                    }
+                });
 
                 match kind {
                     // Also print expression mappings in resolved form.
@@ -83,6 +89,16 @@ pub(crate) fn dump_covfun_mappings(
         }
 
         parser.ensure_empty()?;
+
+        // Printing the highest counter ID seen in the functions mappings makes
+        // it easier to determine whether a change to coverage instrumentation
+        // has increased or decreased the number of physical counters needed.
+        // (It's possible for the generated code to have more counters that
+        // aren't used by any mappings, but that should hopefully be rare.)
+        println!("Highest counter ID seen: {}", match max_counter {
+            Some(id) => format!("c{id}"),
+            None => "(none)".to_owned(),
+        });
         println!();
     }
     Ok(())
@@ -271,6 +287,32 @@ enum MappingKind {
     },
 }
 
+impl MappingKind {
+    fn for_each_term(&self, mut callback: impl FnMut(CovTerm)) {
+        match *self {
+            Self::Code(term) => callback(term),
+            Self::Gap(term) => callback(term),
+            Self::Expansion(_id) => {}
+            Self::Skip => {}
+            Self::Branch { r#true, r#false } => {
+                callback(r#true);
+                callback(r#false);
+            }
+            Self::MCDCBranch {
+                r#true,
+                r#false,
+                condition_id: _,
+                true_next_id: _,
+                false_next_id: _,
+            } => {
+                callback(r#true);
+                callback(r#false);
+            }
+            Self::MCDCDecision { bitmap_idx: _, conditions_num: _ } => {}
+        }
+    }
+}
+
 struct MappingRegion {
     /// Offset of this region's start line, relative to the *start line* of
     /// the *previous mapping* (or 0). Line numbers are 1-based.
diff --git a/tests/coverage/abort.cov-map b/tests/coverage/abort.cov-map
index 15156ec9811b1..06dce43c3cabc 100644
--- a/tests/coverage/abort.cov-map
+++ b/tests/coverage/abort.cov-map
@@ -34,6 +34,7 @@ Number of file 0 mappings: 13
 - Code(Expression(9, Add)) at (prev + 1, 9) to (start + 0, 23)
     = (c1 + c2)
 - Code(Counter(3)) at (prev + 2, 5) to (start + 1, 2)
+Highest counter ID seen: c5
 
 Function name: abort::might_abort
 Raw bytes (21): 0x[01, 01, 01, 01, 05, 03, 01, 03, 01, 01, 14, 05, 02, 09, 01, 24, 02, 02, 0c, 03, 02]
@@ -46,4 +47,5 @@ Number of file 0 mappings: 3
 - Code(Counter(1)) at (prev + 2, 9) to (start + 1, 36)
 - Code(Expression(0, Sub)) at (prev + 2, 12) to (start + 3, 2)
     = (c0 - c1)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/assert-ne.cov-map b/tests/coverage/assert-ne.cov-map
index 6d9906fd7f573..906abcd3c2e59 100644
--- a/tests/coverage/assert-ne.cov-map
+++ b/tests/coverage/assert-ne.cov-map
@@ -10,4 +10,5 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 13) to (start + 0, 19)
     = (c0 - c1)
 - Code(Counter(2)) at (prev + 3, 5) to (start + 1, 2)
+Highest counter ID seen: c2
 
diff --git a/tests/coverage/assert.cov-map b/tests/coverage/assert.cov-map
index dd413123de729..018fcc2c3dbb3 100644
--- a/tests/coverage/assert.cov-map
+++ b/tests/coverage/assert.cov-map
@@ -25,6 +25,7 @@ Number of file 0 mappings: 9
 - Code(Expression(6, Add)) at (prev + 1, 9) to (start + 0, 23)
     = (c1 + (c2 + c3))
 - Code(Counter(4)) at (prev + 2, 5) to (start + 1, 2)
+Highest counter ID seen: c4
 
 Function name: assert::might_fail_assert
 Raw bytes (21): 0x[01, 01, 01, 01, 05, 03, 01, 04, 01, 02, 0f, 02, 02, 25, 00, 3d, 05, 01, 01, 00, 02]
@@ -37,4 +38,5 @@ Number of file 0 mappings: 3
 - Code(Expression(0, Sub)) at (prev + 2, 37) to (start + 0, 61)
     = (c0 - c1)
 - Code(Counter(1)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/assert_not.cov-map b/tests/coverage/assert_not.cov-map
index 788bc5dbf58f3..401dd6450e952 100644
--- a/tests/coverage/assert_not.cov-map
+++ b/tests/coverage/assert_not.cov-map
@@ -13,4 +13,5 @@ Number of file 0 mappings: 5
 - Code(Counter(3)) at (prev + 1, 5) to (start + 0, 22)
 - Code(Expression(1, Sub)) at (prev + 1, 1) to (start + 0, 2)
     = (c3 - Zero)
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/async.cov-map b/tests/coverage/async.cov-map
index 43b497a1d3fe9..9a67cefcf985f 100644
--- a/tests/coverage/async.cov-map
+++ b/tests/coverage/async.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 12, 1) to (start + 0, 25)
+Highest counter ID seen: c0
 
 Function name: async::c::{closure#0}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 0c, 19, 01, 0e, 05, 02, 09, 00, 0a, 02, 02, 09, 00, 0a, 01, 02, 01, 00, 02]
@@ -18,6 +19,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 0, 10)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: async::d
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 14, 01, 00, 14]
@@ -26,6 +28,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 20, 1) to (start + 0, 20)
+Highest counter ID seen: c0
 
 Function name: async::d::{closure#0}
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 14, 14, 00, 19]
@@ -34,6 +37,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 20, 20) to (start + 0, 25)
+Highest counter ID seen: c0
 
 Function name: async::e (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 16, 01, 00, 14]
@@ -42,6 +46,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 22, 1) to (start + 0, 20)
+Highest counter ID seen: (none)
 
 Function name: async::e::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 16, 14, 00, 19]
@@ -50,6 +55,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 22, 20) to (start + 0, 25)
+Highest counter ID seen: (none)
 
 Function name: async::f
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 18, 01, 00, 14]
@@ -58,6 +64,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 24, 1) to (start + 0, 20)
+Highest counter ID seen: c0
 
 Function name: async::f::{closure#0}
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 18, 14, 00, 19]
@@ -66,6 +73,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 24, 20) to (start + 0, 25)
+Highest counter ID seen: c0
 
 Function name: async::foo (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 1a, 01, 00, 1e]
@@ -74,6 +82,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 26, 1) to (start + 0, 30)
+Highest counter ID seen: (none)
 
 Function name: async::foo::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 1a, 1e, 00, 2d]
@@ -82,6 +91,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 26, 30) to (start + 0, 45)
+Highest counter ID seen: (none)
 
 Function name: async::g
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 1c, 01, 00, 17]
@@ -90,6 +100,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 28, 1) to (start + 0, 23)
+Highest counter ID seen: c0
 
 Function name: async::g::{closure#0} (unused)
 Raw bytes (59): 0x[01, 01, 00, 0b, 00, 1c, 17, 01, 0c, 00, 02, 09, 00, 0a, 00, 00, 0e, 00, 17, 00, 00, 1b, 00, 1c, 00, 00, 20, 00, 22, 00, 01, 09, 00, 0a, 00, 00, 0e, 00, 17, 00, 00, 1b, 00, 1c, 00, 00, 20, 00, 22, 00, 01, 0e, 00, 10, 00, 02, 01, 00, 02]
@@ -108,6 +119,7 @@ Number of file 0 mappings: 11
 - Code(Zero) at (prev + 0, 32) to (start + 0, 34)
 - Code(Zero) at (prev + 1, 14) to (start + 0, 16)
 - Code(Zero) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
 Function name: async::h
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 24, 01, 00, 16]
@@ -116,6 +128,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 36, 1) to (start + 0, 22)
+Highest counter ID seen: c0
 
 Function name: async::h::{closure#0} (unused)
 Raw bytes (39): 0x[01, 01, 00, 07, 00, 24, 16, 03, 0c, 00, 04, 09, 00, 0a, 00, 00, 0e, 00, 19, 00, 00, 1a, 00, 1b, 00, 00, 20, 00, 22, 00, 01, 0e, 00, 10, 00, 02, 01, 00, 02]
@@ -130,6 +143,7 @@ Number of file 0 mappings: 7
 - Code(Zero) at (prev + 0, 32) to (start + 0, 34)
 - Code(Zero) at (prev + 1, 14) to (start + 0, 16)
 - Code(Zero) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
 Function name: async::i
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 2d, 01, 00, 13]
@@ -138,6 +152,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 45, 1) to (start + 0, 19)
+Highest counter ID seen: c0
 
 Function name: async::i::{closure#0}
 Raw bytes (63): 0x[01, 01, 02, 07, 19, 11, 15, 0b, 01, 2d, 13, 04, 0c, 09, 05, 09, 00, 0a, 01, 00, 0e, 00, 18, 05, 00, 1c, 00, 21, 09, 00, 27, 00, 30, 15, 01, 09, 00, 0a, 0d, 00, 0e, 00, 17, 1d, 00, 1b, 00, 20, 15, 00, 24, 00, 26, 19, 01, 0e, 00, 10, 03, 02, 01, 00, 02]
@@ -159,6 +174,7 @@ Number of file 0 mappings: 11
 - Code(Counter(6)) at (prev + 1, 14) to (start + 0, 16)
 - Code(Expression(0, Add)) at (prev + 2, 1) to (start + 0, 2)
     = ((c4 + c5) + c6)
+Highest counter ID seen: c7
 
 Function name: async::j
 Raw bytes (58): 0x[01, 01, 02, 07, 0d, 05, 09, 0a, 01, 38, 01, 00, 0d, 01, 0b, 0b, 00, 0c, 05, 01, 09, 00, 0a, 01, 00, 0e, 00, 1b, 05, 00, 1f, 00, 27, 09, 01, 09, 00, 0a, 11, 00, 0e, 00, 1a, 09, 00, 1e, 00, 20, 0d, 01, 0e, 00, 10, 03, 02, 01, 00, 02]
@@ -179,6 +195,7 @@ Number of file 0 mappings: 10
 - Code(Counter(3)) at (prev + 1, 14) to (start + 0, 16)
 - Code(Expression(0, Add)) at (prev + 2, 1) to (start + 0, 2)
     = ((c1 + c2) + c3)
+Highest counter ID seen: c4
 
 Function name: async::j::c
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 3a, 05, 01, 12, 05, 02, 0d, 00, 0e, 02, 02, 0d, 00, 0e, 01, 02, 05, 00, 06]
@@ -192,6 +209,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 13) to (start + 0, 14)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 5) to (start + 0, 6)
+Highest counter ID seen: c1
 
 Function name: async::j::d
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 41, 05, 00, 17]
@@ -200,6 +218,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 65, 5) to (start + 0, 23)
+Highest counter ID seen: c0
 
 Function name: async::j::f
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 42, 05, 00, 17]
@@ -208,6 +227,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 66, 5) to (start + 0, 23)
+Highest counter ID seen: c0
 
 Function name: async::k (unused)
 Raw bytes (29): 0x[01, 01, 00, 05, 00, 4a, 01, 01, 0c, 00, 02, 0e, 00, 10, 00, 01, 0e, 00, 10, 00, 01, 0e, 00, 10, 00, 02, 01, 00, 02]
@@ -220,6 +240,7 @@ Number of file 0 mappings: 5
 - Code(Zero) at (prev + 1, 14) to (start + 0, 16)
 - Code(Zero) at (prev + 1, 14) to (start + 0, 16)
 - Code(Zero) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
 Function name: async::l
 Raw bytes (37): 0x[01, 01, 04, 01, 07, 05, 09, 0f, 02, 09, 05, 05, 01, 52, 01, 01, 0c, 02, 02, 0e, 00, 10, 05, 01, 0e, 00, 10, 09, 01, 0e, 00, 10, 0b, 02, 01, 00, 02]
@@ -238,6 +259,7 @@ Number of file 0 mappings: 5
 - Code(Counter(2)) at (prev + 1, 14) to (start + 0, 16)
 - Code(Expression(2, Add)) at (prev + 2, 1) to (start + 0, 2)
     = ((c2 + c1) + (c0 - (c1 + c2)))
+Highest counter ID seen: c2
 
 Function name: async::m
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 5a, 01, 00, 19]
@@ -246,6 +268,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 90, 1) to (start + 0, 25)
+Highest counter ID seen: c0
 
 Function name: async::m::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 5a, 19, 00, 22]
@@ -254,6 +277,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 90, 25) to (start + 0, 34)
+Highest counter ID seen: (none)
 
 Function name: async::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 5c, 01, 08, 02]
@@ -262,4 +286,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 92, 1) to (start + 8, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/async2.cov-map b/tests/coverage/async2.cov-map
index 3816401ac6346..ed61e91efc29a 100644
--- a/tests/coverage/async2.cov-map
+++ b/tests/coverage/async2.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 16, 1) to (start + 0, 23)
+Highest counter ID seen: c0
 
 Function name: async2::async_func::{closure#0}
 Raw bytes (24): 0x[01, 01, 00, 04, 01, 10, 17, 03, 09, 05, 03, 0a, 02, 06, 00, 02, 06, 00, 07, 01, 01, 01, 00, 02]
@@ -16,6 +17,7 @@ Number of file 0 mappings: 4
 - Code(Counter(1)) at (prev + 3, 10) to (start + 2, 6)
 - Code(Zero) at (prev + 2, 6) to (start + 0, 7)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: async2::async_func_just_println
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 18, 01, 00, 24]
@@ -24,6 +26,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 24, 1) to (start + 0, 36)
+Highest counter ID seen: c0
 
 Function name: async2::async_func_just_println::{closure#0}
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 18, 24, 02, 02]
@@ -32,6 +35,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 24, 36) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: async2::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 1c, 01, 07, 02]
@@ -40,6 +44,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 28, 1) to (start + 7, 2)
+Highest counter ID seen: c0
 
 Function name: async2::non_async_func
 Raw bytes (24): 0x[01, 01, 00, 04, 01, 08, 01, 03, 09, 05, 03, 0a, 02, 06, 00, 02, 06, 00, 07, 01, 01, 01, 00, 02]
@@ -51,4 +56,5 @@ Number of file 0 mappings: 4
 - Code(Counter(1)) at (prev + 3, 10) to (start + 2, 6)
 - Code(Zero) at (prev + 2, 6) to (start + 0, 7)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/async_block.cov-map b/tests/coverage/async_block.cov-map
index 65f3d821f6e46..e3309bd51b40a 100644
--- a/tests/coverage/async_block.cov-map
+++ b/tests/coverage/async_block.cov-map
@@ -12,6 +12,7 @@ Number of file 0 mappings: 6
 - Code(Counter(1)) at (prev + 0, 20) to (start + 1, 22)
 - Code(Counter(1)) at (prev + 7, 10) to (start + 2, 6)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: async_block::main::{closure#0}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 0a, 1c, 01, 17, 05, 01, 18, 02, 0e, 02, 02, 14, 02, 0e, 01, 03, 09, 00, 0a]
@@ -25,4 +26,5 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 20) to (start + 2, 14)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 3, 9) to (start + 0, 10)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/attr/impl.cov-map b/tests/coverage/attr/impl.cov-map
index 9b0deed8b64c0..4d068c290f42f 100644
--- a/tests/coverage/attr/impl.cov-map
+++ b/tests/coverage/attr/impl.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 14, 5) to (start + 0, 19)
+Highest counter ID seen: (none)
 
 Function name: <impl::MyStruct>::on_inherit (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 16, 05, 00, 17]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 22, 5) to (start + 0, 23)
+Highest counter ID seen: (none)
 
 Function name: <impl::MyStruct>::on_on (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 19, 05, 00, 12]
@@ -21,4 +23,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 25, 5) to (start + 0, 18)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/attr/module.cov-map b/tests/coverage/attr/module.cov-map
index 34898eb4ca81d..b318ac85a6c85 100644
--- a/tests/coverage/attr/module.cov-map
+++ b/tests/coverage/attr/module.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 12, 5) to (start + 0, 15)
+Highest counter ID seen: (none)
 
 Function name: module::on::inherit (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 14, 05, 00, 14]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 20, 5) to (start + 0, 20)
+Highest counter ID seen: (none)
 
 Function name: module::on::on (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 17, 05, 00, 0f]
@@ -21,4 +23,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 23, 5) to (start + 0, 15)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/attr/nested.cov-map b/tests/coverage/attr/nested.cov-map
index 466aec8956e0e..2bd9532537325 100644
--- a/tests/coverage/attr/nested.cov-map
+++ b/tests/coverage/attr/nested.cov-map
@@ -6,6 +6,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 63, 1) to (start + 1, 15)
 - Code(Counter(0)) at (prev + 11, 5) to (start + 1, 2)
+Highest counter ID seen: c0
 
 Function name: nested::closure_tail
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 4e, 01, 01, 0f, 01, 11, 05, 01, 02]
@@ -15,4 +16,5 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 78, 1) to (start + 1, 15)
 - Code(Counter(0)) at (prev + 17, 5) to (start + 1, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/attr/off-on-sandwich.cov-map b/tests/coverage/attr/off-on-sandwich.cov-map
index d5fbac6ebf74b..ae5c9bd19a29b 100644
--- a/tests/coverage/attr/off-on-sandwich.cov-map
+++ b/tests/coverage/attr/off-on-sandwich.cov-map
@@ -6,6 +6,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 15, 5) to (start + 2, 18)
 - Code(Counter(0)) at (prev + 7, 5) to (start + 0, 6)
+Highest counter ID seen: c0
 
 Function name: off_on_sandwich::sparse_a::sparse_b::sparse_c
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 21, 09, 02, 17, 01, 0b, 09, 00, 0a]
@@ -15,6 +16,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 33, 9) to (start + 2, 23)
 - Code(Counter(0)) at (prev + 11, 9) to (start + 0, 10)
+Highest counter ID seen: c0
 
 Function name: off_on_sandwich::sparse_a::sparse_b::sparse_c::sparse_d
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 24, 0d, 02, 1b, 01, 07, 0d, 00, 0e]
@@ -24,4 +26,5 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 36, 13) to (start + 2, 27)
 - Code(Counter(0)) at (prev + 7, 13) to (start + 0, 14)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/await_ready.cov-map b/tests/coverage/await_ready.cov-map
index 38c2cf7b2d36c..95dbf68a191c4 100644
--- a/tests/coverage/await_ready.cov-map
+++ b/tests/coverage/await_ready.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 15, 1) to (start + 0, 30)
+Highest counter ID seen: c0
 
 Function name: await_ready::await_ready::{closure#0}
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 0f, 1e, 03, 0f, 05, 04, 01, 00, 02]
@@ -14,4 +15,5 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 15, 30) to (start + 3, 15)
 - Code(Counter(1)) at (prev + 4, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/bad_counter_ids.cov-map b/tests/coverage/bad_counter_ids.cov-map
index 7eff7f5f02f3c..2b5399f33bbd3 100644
--- a/tests/coverage/bad_counter_ids.cov-map
+++ b/tests/coverage/bad_counter_ids.cov-map
@@ -6,6 +6,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 36, 1) to (start + 2, 31)
 - Code(Zero) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
 Function name: bad_counter_ids::eq_bad_message
 Raw bytes (21): 0x[01, 01, 01, 01, 00, 03, 01, 29, 01, 02, 0f, 02, 02, 20, 00, 2b, 00, 01, 01, 00, 02]
@@ -18,6 +19,7 @@ Number of file 0 mappings: 3
 - Code(Expression(0, Sub)) at (prev + 2, 32) to (start + 0, 43)
     = (c0 - Zero)
 - Code(Zero) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
 Function name: bad_counter_ids::eq_good
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 10, 01, 02, 1f, 05, 03, 01, 00, 02]
@@ -27,6 +29,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 16, 1) to (start + 2, 31)
 - Code(Counter(1)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: bad_counter_ids::eq_good_message
 Raw bytes (19): 0x[01, 01, 00, 03, 01, 15, 01, 02, 0f, 00, 02, 20, 00, 2b, 05, 01, 01, 00, 02]
@@ -37,6 +40,7 @@ Number of file 0 mappings: 3
 - Code(Counter(0)) at (prev + 21, 1) to (start + 2, 15)
 - Code(Zero) at (prev + 2, 32) to (start + 0, 43)
 - Code(Counter(1)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: bad_counter_ids::ne_bad
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 2e, 01, 02, 1f, 00, 03, 01, 00, 02]
@@ -46,6 +50,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 46, 1) to (start + 2, 31)
 - Code(Zero) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
 Function name: bad_counter_ids::ne_bad_message
 Raw bytes (19): 0x[01, 01, 00, 03, 01, 33, 01, 02, 0f, 05, 02, 20, 00, 2b, 00, 01, 01, 00, 02]
@@ -56,6 +61,7 @@ Number of file 0 mappings: 3
 - Code(Counter(0)) at (prev + 51, 1) to (start + 2, 15)
 - Code(Counter(1)) at (prev + 2, 32) to (start + 0, 43)
 - Code(Zero) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: bad_counter_ids::ne_good
 Raw bytes (16): 0x[01, 01, 01, 01, 00, 02, 01, 1a, 01, 02, 1f, 02, 03, 01, 00, 02]
@@ -67,6 +73,7 @@ Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 26, 1) to (start + 2, 31)
 - Code(Expression(0, Sub)) at (prev + 3, 1) to (start + 0, 2)
     = (c0 - Zero)
+Highest counter ID seen: c0
 
 Function name: bad_counter_ids::ne_good_message
 Raw bytes (21): 0x[01, 01, 01, 01, 00, 03, 01, 1f, 01, 02, 0f, 00, 02, 20, 00, 2b, 02, 01, 01, 00, 02]
@@ -79,4 +86,5 @@ Number of file 0 mappings: 3
 - Code(Zero) at (prev + 2, 32) to (start + 0, 43)
 - Code(Expression(0, Sub)) at (prev + 1, 1) to (start + 0, 2)
     = (c0 - Zero)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/bench.cov-map b/tests/coverage/bench.cov-map
index aa702a4868185..9ee6510f69048 100644
--- a/tests/coverage/bench.cov-map
+++ b/tests/coverage/bench.cov-map
@@ -5,4 +5,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 8, 1) to (start + 0, 39)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/branch/generics.cov-map b/tests/coverage/branch/generics.cov-map
index 2e5668c8b568e..656890634ff4e 100644
--- a/tests/coverage/branch/generics.cov-map
+++ b/tests/coverage/branch/generics.cov-map
@@ -13,6 +13,7 @@ Number of file 0 mappings: 5
 - Code(Expression(0, Sub)) at (prev + 2, 12) to (start + 2, 6)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: generics::print_size::<u32>
 Raw bytes (33): 0x[01, 01, 01, 01, 05, 05, 01, 06, 01, 01, 24, 20, 05, 02, 01, 08, 00, 24, 05, 00, 25, 02, 06, 02, 02, 0c, 02, 06, 01, 03, 01, 00, 02]
@@ -29,6 +30,7 @@ Number of file 0 mappings: 5
 - Code(Expression(0, Sub)) at (prev + 2, 12) to (start + 2, 6)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: generics::print_size::<u64>
 Raw bytes (33): 0x[01, 01, 01, 01, 05, 05, 01, 06, 01, 01, 24, 20, 05, 02, 01, 08, 00, 24, 05, 00, 25, 02, 06, 02, 02, 0c, 02, 06, 01, 03, 01, 00, 02]
@@ -45,4 +47,5 @@ Number of file 0 mappings: 5
 - Code(Expression(0, Sub)) at (prev + 2, 12) to (start + 2, 6)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/branch/guard.cov-map b/tests/coverage/branch/guard.cov-map
index d67c3d349a14e..0f33ed17a0acc 100644
--- a/tests/coverage/branch/guard.cov-map
+++ b/tests/coverage/branch/guard.cov-map
@@ -29,4 +29,5 @@ Number of file 0 mappings: 13
     = (c1 + c2)
 - Code(Expression(2, Add)) at (prev + 4, 1) to (start + 0, 2)
     = ((((c1 + c2) + c3) + c4) + c5)
+Highest counter ID seen: c7
 
diff --git a/tests/coverage/branch/if-let.cov-map b/tests/coverage/branch/if-let.cov-map
index 0b098bc6497ce..380765c7af4bc 100644
--- a/tests/coverage/branch/if-let.cov-map
+++ b/tests/coverage/branch/if-let.cov-map
@@ -16,6 +16,7 @@ Number of file 0 mappings: 7
     = (c1 - c2)
 - Code(Counter(2)) at (prev + 2, 12) to (start + 2, 6)
 - Code(Counter(1)) at (prev + 3, 5) to (start + 1, 2)
+Highest counter ID seen: c2
 
 Function name: if_let::if_let_chain
 Raw bytes (66): 0x[01, 01, 04, 01, 05, 05, 09, 0f, 0d, 05, 09, 0a, 01, 17, 01, 00, 33, 20, 02, 05, 01, 0c, 00, 13, 02, 00, 11, 00, 12, 01, 00, 16, 00, 17, 20, 0d, 09, 01, 10, 00, 17, 0d, 00, 15, 00, 16, 02, 00, 1a, 00, 1b, 0d, 01, 05, 03, 06, 0f, 03, 0c, 02, 06, 0b, 03, 05, 01, 02]
@@ -45,4 +46,5 @@ Number of file 0 mappings: 10
     = (c1 + c2)
 - Code(Expression(2, Add)) at (prev + 3, 5) to (start + 1, 2)
     = ((c1 + c2) + c3)
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/branch/if.cov-map b/tests/coverage/branch/if.cov-map
index 7f4ee980e2620..4a8cb664dd831 100644
--- a/tests/coverage/branch/if.cov-map
+++ b/tests/coverage/branch/if.cov-map
@@ -22,6 +22,7 @@ Number of file 0 mappings: 8
     = (c3 + (c1 - c2))
 - Code(Expression(2, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c4 + (c3 + (c1 - c2)))
+Highest counter ID seen: c4
 
 Function name: if::branch_not
 Raw bytes (116): 0x[01, 01, 07, 05, 09, 05, 0d, 05, 0d, 05, 11, 05, 11, 05, 15, 05, 15, 12, 01, 0c, 01, 01, 10, 05, 03, 08, 00, 09, 20, 09, 02, 00, 08, 00, 09, 09, 01, 09, 00, 11, 02, 01, 06, 00, 07, 05, 01, 08, 00, 0a, 20, 0a, 0d, 00, 08, 00, 0a, 0a, 00, 0b, 02, 06, 0d, 02, 06, 00, 07, 05, 01, 08, 00, 0b, 20, 11, 12, 00, 08, 00, 0b, 11, 00, 0c, 02, 06, 12, 02, 06, 00, 07, 05, 01, 08, 00, 0c, 20, 1a, 15, 00, 08, 00, 0c, 1a, 00, 0d, 02, 06, 15, 02, 06, 00, 07, 05, 01, 01, 00, 02]
@@ -66,6 +67,7 @@ Number of file 0 mappings: 18
     = (c1 - c5)
 - Code(Counter(5)) at (prev + 2, 6) to (start + 0, 7)
 - Code(Counter(1)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c5
 
 Function name: if::branch_not_as
 Raw bytes (90): 0x[01, 01, 05, 05, 09, 05, 0d, 05, 0d, 05, 11, 05, 11, 0e, 01, 1d, 01, 01, 10, 05, 03, 08, 00, 14, 20, 02, 09, 00, 08, 00, 14, 02, 00, 15, 02, 06, 09, 02, 06, 00, 07, 05, 01, 08, 00, 15, 20, 0d, 0a, 00, 08, 00, 15, 0d, 00, 16, 02, 06, 0a, 02, 06, 00, 07, 05, 01, 08, 00, 16, 20, 12, 11, 00, 08, 00, 16, 12, 00, 17, 02, 06, 11, 02, 06, 00, 07, 05, 01, 01, 00, 02]
@@ -101,6 +103,7 @@ Number of file 0 mappings: 14
     = (c1 - c4)
 - Code(Counter(4)) at (prev + 2, 6) to (start + 0, 7)
 - Code(Counter(1)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c4
 
 Function name: if::branch_or
 Raw bytes (56): 0x[01, 01, 04, 05, 09, 09, 0d, 0f, 11, 09, 0d, 08, 01, 35, 01, 01, 10, 05, 03, 08, 00, 09, 20, 09, 02, 00, 08, 00, 09, 02, 00, 0d, 00, 0e, 20, 0d, 11, 00, 0d, 00, 0e, 0f, 00, 0f, 02, 06, 11, 02, 0c, 02, 06, 0b, 03, 01, 00, 02]
@@ -127,4 +130,5 @@ Number of file 0 mappings: 8
 - Code(Counter(4)) at (prev + 2, 12) to (start + 2, 6)
 - Code(Expression(2, Add)) at (prev + 3, 1) to (start + 0, 2)
     = ((c2 + c3) + c4)
+Highest counter ID seen: c4
 
diff --git a/tests/coverage/branch/lazy-boolean.cov-map b/tests/coverage/branch/lazy-boolean.cov-map
index 09ce91376733b..c2b6a5b8df24b 100644
--- a/tests/coverage/branch/lazy-boolean.cov-map
+++ b/tests/coverage/branch/lazy-boolean.cov-map
@@ -13,6 +13,7 @@ Number of file 0 mappings: 6
     false = (c1 - c2)
 - Code(Counter(2)) at (prev + 0, 18) to (start + 0, 19)
 - Code(Counter(1)) at (prev + 1, 5) to (start + 1, 2)
+Highest counter ID seen: c2
 
 Function name: lazy_boolean::branch_or
 Raw bytes (38): 0x[01, 01, 01, 05, 09, 06, 01, 1b, 01, 01, 10, 05, 04, 09, 00, 0a, 05, 00, 0d, 00, 0e, 20, 09, 02, 00, 0d, 00, 0e, 02, 00, 12, 00, 13, 05, 01, 05, 01, 02]
@@ -30,6 +31,7 @@ Number of file 0 mappings: 6
 - Code(Expression(0, Sub)) at (prev + 0, 18) to (start + 0, 19)
     = (c1 - c2)
 - Code(Counter(1)) at (prev + 1, 5) to (start + 1, 2)
+Highest counter ID seen: c2
 
 Function name: lazy_boolean::chain
 Raw bytes (149): 0x[01, 01, 13, 11, 07, 0b, 16, 15, 1a, 09, 0d, 05, 09, 05, 09, 09, 0d, 47, 25, 4b, 21, 19, 1d, 03, 19, 03, 19, 3e, 1d, 03, 19, 3e, 1d, 03, 19, 47, 25, 4b, 21, 19, 1d, 13, 01, 24, 01, 01, 10, 03, 04, 09, 00, 0a, 05, 00, 0d, 00, 12, 20, 09, 16, 00, 0d, 00, 12, 09, 00, 16, 00, 1b, 20, 0d, 1a, 00, 16, 00, 1b, 0d, 00, 1f, 00, 24, 20, 11, 15, 00, 1f, 00, 24, 11, 00, 28, 00, 2d, 03, 01, 05, 00, 11, 43, 03, 09, 00, 0a, 03, 00, 0d, 00, 12, 20, 19, 3e, 00, 0d, 00, 12, 3e, 00, 16, 00, 1b, 20, 1d, 3a, 00, 16, 00, 1b, 3a, 00, 1f, 00, 24, 20, 21, 25, 00, 1f, 00, 24, 25, 00, 28, 00, 2d, 43, 01, 05, 01, 02]
@@ -94,6 +96,7 @@ Number of file 0 mappings: 19
 - Code(Counter(9)) at (prev + 0, 40) to (start + 0, 45)
 - Code(Expression(16, Add)) at (prev + 1, 5) to (start + 1, 2)
     = (((c6 + c7) + c8) + c9)
+Highest counter ID seen: c9
 
 Function name: lazy_boolean::nested_mixed
 Raw bytes (155): 0x[01, 01, 16, 33, 1a, 09, 0d, 1e, 0d, 05, 09, 05, 09, 05, 09, 1e, 0d, 05, 09, 09, 0d, 33, 11, 09, 0d, 33, 11, 09, 0d, 19, 57, 1d, 21, 03, 15, 15, 19, 4a, 4e, 15, 19, 03, 15, 19, 57, 1d, 21, 13, 01, 31, 01, 01, 10, 03, 04, 09, 00, 0a, 05, 00, 0e, 00, 13, 20, 09, 1e, 00, 0e, 00, 13, 1e, 00, 17, 00, 1d, 20, 0d, 1a, 00, 17, 00, 1d, 33, 00, 23, 00, 28, 20, 11, 2e, 00, 23, 00, 28, 2e, 00, 2c, 00, 33, 03, 01, 05, 00, 11, 53, 03, 09, 00, 0a, 03, 00, 0e, 00, 13, 20, 15, 4e, 00, 0e, 00, 13, 15, 00, 17, 00, 1c, 20, 19, 4a, 00, 17, 00, 1c, 47, 00, 22, 00, 28, 20, 1d, 21, 00, 22, 00, 28, 1d, 00, 2c, 00, 33, 53, 01, 05, 01, 02]
@@ -163,4 +166,5 @@ Number of file 0 mappings: 19
 - Code(Counter(7)) at (prev + 0, 44) to (start + 0, 51)
 - Code(Expression(20, Add)) at (prev + 1, 5) to (start + 1, 2)
     = (c6 + (c7 + c8))
+Highest counter ID seen: c8
 
diff --git a/tests/coverage/branch/let-else.cov-map b/tests/coverage/branch/let-else.cov-map
index 0707993446478..e6bf7ed6a9258 100644
--- a/tests/coverage/branch/let-else.cov-map
+++ b/tests/coverage/branch/let-else.cov-map
@@ -16,4 +16,5 @@ Number of file 0 mappings: 7
 - Code(Expression(0, Sub)) at (prev + 4, 5) to (start + 0, 11)
     = (c1 - c2)
 - Code(Counter(1)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c2
 
diff --git a/tests/coverage/branch/match-arms.cov-map b/tests/coverage/branch/match-arms.cov-map
index 1f17f11baaa07..fd0366ee81838 100644
--- a/tests/coverage/branch/match-arms.cov-map
+++ b/tests/coverage/branch/match-arms.cov-map
@@ -34,6 +34,7 @@ Number of file 0 mappings: 12
     = ((((Zero + c2) + c3) + c4) + c5)
 - Code(Expression(4, Add)) at (prev + 3, 5) to (start + 1, 2)
     = ((((((((Zero + c2) + c3) + c4) + c5) + c6) + c7) + c8) + c9)
+Highest counter ID seen: c10
 
 Function name: match_arms::match_arms
 Raw bytes (51): 0x[01, 01, 06, 05, 07, 0b, 11, 09, 0d, 13, 02, 17, 09, 11, 0d, 07, 01, 18, 01, 01, 10, 05, 03, 0b, 00, 10, 11, 01, 11, 00, 21, 0d, 01, 11, 00, 21, 09, 01, 11, 00, 21, 02, 01, 11, 00, 21, 0f, 03, 05, 01, 02]
@@ -56,6 +57,7 @@ Number of file 0 mappings: 7
     = (c1 - ((c2 + c3) + c4))
 - Code(Expression(3, Add)) at (prev + 3, 5) to (start + 1, 2)
     = (((c4 + c3) + c2) + (c1 - ((c2 + c3) + c4)))
+Highest counter ID seen: c4
 
 Function name: match_arms::or_patterns
 Raw bytes (75): 0x[01, 01, 0d, 11, 0d, 05, 2f, 33, 11, 09, 0d, 09, 2a, 05, 2f, 33, 11, 09, 0d, 03, 27, 09, 2a, 05, 2f, 33, 11, 09, 0d, 09, 01, 25, 01, 01, 10, 05, 03, 0b, 00, 10, 11, 01, 11, 00, 12, 0d, 00, 1e, 00, 1f, 03, 00, 24, 00, 2e, 09, 01, 11, 00, 12, 2a, 00, 1e, 00, 1f, 27, 00, 24, 00, 2e, 23, 03, 05, 01, 02]
@@ -89,4 +91,5 @@ Number of file 0 mappings: 9
     = (c2 + (c1 - ((c2 + c3) + c4)))
 - Code(Expression(8, Add)) at (prev + 3, 5) to (start + 1, 2)
     = ((c4 + c3) + (c2 + (c1 - ((c2 + c3) + c4))))
+Highest counter ID seen: c4
 
diff --git a/tests/coverage/branch/match-trivial.cov-map b/tests/coverage/branch/match-trivial.cov-map
index 1136a529b255c..6af8ce46f5fae 100644
--- a/tests/coverage/branch/match-trivial.cov-map
+++ b/tests/coverage/branch/match-trivial.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 22, 1) to (start + 1, 16)
+Highest counter ID seen: (none)
 
 Function name: match_trivial::trivial
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 1e, 01, 01, 10, 05, 03, 0b, 05, 02]
@@ -14,4 +15,5 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 30, 1) to (start + 1, 16)
 - Code(Counter(1)) at (prev + 3, 11) to (start + 5, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/branch/no-mir-spans.cov-map b/tests/coverage/branch/no-mir-spans.cov-map
index cb19211913f89..ab12732b1ed38 100644
--- a/tests/coverage/branch/no-mir-spans.cov-map
+++ b/tests/coverage/branch/no-mir-spans.cov-map
@@ -8,6 +8,7 @@ Number of file 0 mappings: 2
 - Branch { true: Counter(1), false: Counter(2) } at (prev + 4, 11) to (start + 0, 16)
     true  = c1
     false = c2
+Highest counter ID seen: c2
 
 Function name: no_mir_spans::while_cond_not
 Raw bytes (16): 0x[01, 01, 00, 02, 01, 19, 01, 00, 15, 20, 09, 05, 04, 0b, 00, 14]
@@ -19,6 +20,7 @@ Number of file 0 mappings: 2
 - Branch { true: Counter(2), false: Counter(1) } at (prev + 4, 11) to (start + 0, 20)
     true  = c2
     false = c1
+Highest counter ID seen: c2
 
 Function name: no_mir_spans::while_op_and
 Raw bytes (25): 0x[01, 01, 01, 09, 0d, 03, 01, 22, 01, 00, 13, 20, 09, 05, 05, 0b, 00, 10, 20, 02, 0d, 00, 14, 00, 19]
@@ -34,6 +36,7 @@ Number of file 0 mappings: 3
 - Branch { true: Expression(0, Sub), false: Counter(3) } at (prev + 0, 20) to (start + 0, 25)
     true  = (c2 - c3)
     false = c3
+Highest counter ID seen: c3
 
 Function name: no_mir_spans::while_op_or
 Raw bytes (25): 0x[01, 01, 01, 09, 0d, 03, 01, 2d, 01, 00, 12, 20, 05, 09, 05, 0b, 00, 10, 20, 0d, 02, 00, 14, 00, 19]
@@ -49,4 +52,5 @@ Number of file 0 mappings: 3
 - Branch { true: Counter(3), false: Expression(0, Sub) } at (prev + 0, 20) to (start + 0, 25)
     true  = c3
     false = (c2 - c3)
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/branch/while.cov-map b/tests/coverage/branch/while.cov-map
index fd05bbb69a556..d5840a2c320be 100644
--- a/tests/coverage/branch/while.cov-map
+++ b/tests/coverage/branch/while.cov-map
@@ -14,6 +14,7 @@ Number of file 0 mappings: 6
     false = c1
 - Code(Counter(2)) at (prev + 0, 17) to (start + 2, 6)
 - Code(Counter(1)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c2
 
 Function name: while::while_cond_not
 Raw bytes (38): 0x[01, 01, 01, 05, 09, 06, 01, 15, 01, 01, 10, 05, 03, 09, 00, 12, 03, 01, 0b, 00, 14, 20, 09, 05, 00, 0b, 00, 14, 09, 00, 15, 02, 06, 05, 03, 01, 00, 02]
@@ -31,6 +32,7 @@ Number of file 0 mappings: 6
     false = c1
 - Code(Counter(2)) at (prev + 0, 21) to (start + 2, 6)
 - Code(Counter(1)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c2
 
 Function name: while::while_op_and
 Raw bytes (56): 0x[01, 01, 04, 05, 09, 03, 0d, 03, 0d, 11, 0d, 08, 01, 1e, 01, 01, 10, 05, 03, 09, 01, 12, 03, 02, 0b, 00, 10, 20, 0a, 0d, 00, 0b, 00, 10, 0a, 00, 14, 00, 19, 20, 09, 11, 00, 14, 00, 19, 09, 00, 1a, 03, 06, 0f, 04, 01, 00, 02]
@@ -57,6 +59,7 @@ Number of file 0 mappings: 8
 - Code(Counter(2)) at (prev + 0, 26) to (start + 3, 6)
 - Code(Expression(3, Add)) at (prev + 4, 1) to (start + 0, 2)
     = (c4 + c3)
+Highest counter ID seen: c4
 
 Function name: while::while_op_or
 Raw bytes (66): 0x[01, 01, 09, 05, 1b, 09, 0d, 03, 09, 03, 09, 22, 0d, 03, 09, 09, 0d, 22, 0d, 03, 09, 08, 01, 29, 01, 01, 10, 05, 03, 09, 01, 12, 03, 02, 0b, 00, 10, 20, 09, 22, 00, 0b, 00, 10, 22, 00, 14, 00, 19, 20, 0d, 1e, 00, 14, 00, 19, 1b, 00, 1a, 03, 06, 1e, 04, 01, 00, 02]
@@ -89,4 +92,5 @@ Number of file 0 mappings: 8
     = (c2 + c3)
 - Code(Expression(7, Sub)) at (prev + 4, 1) to (start + 0, 2)
     = (((c1 + (c2 + c3)) - c2) - c3)
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/closure.cov-map b/tests/coverage/closure.cov-map
index 6edd35921fe95..d50f9f8e7afaa 100644
--- a/tests/coverage/closure.cov-map
+++ b/tests/coverage/closure.cov-map
@@ -30,6 +30,7 @@ Number of file 0 mappings: 24
 - Code(Expression(0, Sub)) at (prev + 4, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 5) to (start + 3, 2)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#0}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 28, 05, 02, 14, 05, 02, 15, 02, 0a, 02, 02, 0a, 00, 0b, 01, 01, 09, 01, 06]
@@ -43,6 +44,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 10) to (start + 0, 11)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 9) to (start + 1, 6)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#10} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, 9b, 01, 07, 00, 21]
@@ -51,6 +53,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 155, 7) to (start + 0, 33)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#11} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, 9f, 01, 07, 00, 21]
@@ -59,6 +62,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 159, 7) to (start + 0, 33)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#12} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, a7, 01, 01, 00, 17]
@@ -67,6 +71,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 167, 1) to (start + 0, 23)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#13} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, ac, 01, 0d, 02, 0e]
@@ -75,6 +80,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 172, 13) to (start + 2, 14)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#14}
 Raw bytes (27): 0x[01, 01, 01, 01, 05, 04, 01, b3, 01, 0d, 02, 1b, 05, 02, 1e, 00, 25, 02, 00, 2f, 00, 33, 01, 01, 0d, 00, 0e]
@@ -88,6 +94,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 0, 47) to (start + 0, 51)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 13) to (start + 0, 14)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#15}
 Raw bytes (37): 0x[01, 01, 01, 01, 05, 06, 01, bb, 01, 09, 00, 0a, 01, 01, 0d, 00, 15, 01, 01, 11, 01, 1b, 05, 01, 1e, 00, 25, 02, 00, 2f, 00, 33, 01, 02, 09, 00, 0a]
@@ -103,6 +110,7 @@ Number of file 0 mappings: 6
 - Code(Expression(0, Sub)) at (prev + 0, 47) to (start + 0, 51)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 9) to (start + 0, 10)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#16}
 Raw bytes (27): 0x[01, 01, 01, 01, 05, 04, 01, c5, 01, 0d, 02, 1b, 05, 02, 1e, 00, 25, 02, 00, 2f, 00, 33, 01, 01, 0d, 00, 0e]
@@ -116,6 +124,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 0, 47) to (start + 0, 51)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 13) to (start + 0, 14)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#17}
 Raw bytes (37): 0x[01, 01, 01, 01, 05, 06, 01, cd, 01, 09, 00, 0a, 01, 01, 0d, 00, 15, 01, 01, 11, 01, 1b, 05, 01, 1e, 00, 25, 02, 00, 2f, 00, 33, 01, 02, 09, 00, 0a]
@@ -131,6 +140,7 @@ Number of file 0 mappings: 6
 - Code(Expression(0, Sub)) at (prev + 0, 47) to (start + 0, 51)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 9) to (start + 0, 10)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#18} (unused)
 Raw bytes (24): 0x[01, 01, 00, 04, 00, 19, 0d, 02, 1c, 00, 02, 1d, 02, 12, 00, 02, 12, 00, 13, 00, 01, 11, 01, 0e]
@@ -142,6 +152,7 @@ Number of file 0 mappings: 4
 - Code(Zero) at (prev + 2, 29) to (start + 2, 18)
 - Code(Zero) at (prev + 2, 18) to (start + 0, 19)
 - Code(Zero) at (prev + 1, 17) to (start + 1, 14)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#19}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 43, 0d, 02, 1c, 05, 02, 1d, 02, 12, 02, 02, 12, 00, 13, 01, 01, 11, 01, 0e]
@@ -155,6 +166,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 18) to (start + 0, 19)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 17) to (start + 1, 14)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#1}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 52, 05, 02, 14, 05, 02, 15, 02, 0a, 02, 02, 0a, 00, 0b, 01, 01, 09, 01, 06]
@@ -168,6 +180,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 10) to (start + 0, 11)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 9) to (start + 1, 6)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#2}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 68, 05, 02, 14, 05, 02, 15, 02, 0a, 02, 02, 0a, 00, 0b, 01, 01, 09, 01, 06]
@@ -181,6 +194,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 10) to (start + 0, 11)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 9) to (start + 1, 6)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#3} (unused)
 Raw bytes (25): 0x[01, 01, 00, 04, 00, 81, 01, 05, 01, 14, 00, 01, 15, 02, 0a, 00, 02, 0a, 00, 0b, 00, 01, 09, 01, 06]
@@ -192,6 +206,7 @@ Number of file 0 mappings: 4
 - Code(Zero) at (prev + 1, 21) to (start + 2, 10)
 - Code(Zero) at (prev + 2, 10) to (start + 0, 11)
 - Code(Zero) at (prev + 1, 9) to (start + 1, 6)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#4} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, 89, 01, 35, 00, 43]
@@ -200,6 +215,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 137, 53) to (start + 0, 67)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#5}
 Raw bytes (10): 0x[01, 01, 00, 01, 01, 8c, 01, 3d, 00, 4f]
@@ -208,6 +224,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 140, 61) to (start + 0, 79)
+Highest counter ID seen: c0
 
 Function name: closure::main::{closure#6}
 Raw bytes (10): 0x[01, 01, 00, 01, 01, 8d, 01, 41, 00, 57]
@@ -216,6 +233,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 141, 65) to (start + 0, 87)
+Highest counter ID seen: c0
 
 Function name: closure::main::{closure#7} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, 8e, 01, 3b, 00, 51]
@@ -224,6 +242,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 142, 59) to (start + 0, 81)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#8} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, 93, 01, 3b, 00, 55]
@@ -232,6 +251,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 147, 59) to (start + 0, 85)
+Highest counter ID seen: (none)
 
 Function name: closure::main::{closure#9} (unused)
 Raw bytes (10): 0x[01, 01, 00, 01, 00, 95, 01, 38, 02, 06]
@@ -240,4 +260,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 149, 56) to (start + 2, 6)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/closure_bug.cov-map b/tests/coverage/closure_bug.cov-map
index 32e8db5fb2f4c..96e1e339e569e 100644
--- a/tests/coverage/closure_bug.cov-map
+++ b/tests/coverage/closure_bug.cov-map
@@ -29,6 +29,7 @@ Number of file 0 mappings: 17
 - Code(Expression(3, Sub)) at (prev + 0, 23) to (start + 0, 24)
     = (c0 - c4)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c4
 
 Function name: closure_bug::main::{closure#0}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 0e, 09, 00, 12, 05, 00, 15, 00, 19, 02, 00, 23, 00, 28, 01, 00, 29, 00, 2a]
@@ -42,6 +43,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 0, 35) to (start + 0, 40)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 0, 41) to (start + 0, 42)
+Highest counter ID seen: c1
 
 Function name: closure_bug::main::{closure#1}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 17, 09, 00, 12, 05, 00, 15, 00, 19, 02, 00, 23, 00, 28, 01, 00, 29, 00, 2a]
@@ -55,6 +57,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 0, 35) to (start + 0, 40)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 0, 41) to (start + 0, 42)
+Highest counter ID seen: c1
 
 Function name: closure_bug::main::{closure#2}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 20, 09, 00, 12, 05, 00, 15, 00, 19, 02, 00, 23, 00, 28, 01, 00, 29, 00, 2a]
@@ -68,6 +71,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 0, 35) to (start + 0, 40)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 0, 41) to (start + 0, 42)
+Highest counter ID seen: c1
 
 Function name: closure_bug::main::{closure#3}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 29, 09, 00, 12, 05, 00, 15, 00, 19, 02, 00, 23, 00, 28, 01, 00, 29, 00, 2a]
@@ -81,4 +85,5 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 0, 35) to (start + 0, 40)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 0, 41) to (start + 0, 42)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/closure_macro.cov-map b/tests/coverage/closure_macro.cov-map
index fb4a137d4c8ec..7c9d3292f988a 100644
--- a/tests/coverage/closure_macro.cov-map
+++ b/tests/coverage/closure_macro.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 29, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: closure_macro::main
 Raw bytes (36): 0x[01, 01, 01, 01, 05, 06, 01, 21, 01, 01, 21, 02, 02, 09, 00, 0f, 01, 00, 12, 00, 54, 05, 00, 54, 00, 55, 02, 02, 09, 02, 0b, 01, 03, 01, 00, 02]
@@ -21,6 +22,7 @@ Number of file 0 mappings: 6
 - Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 2, 11)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: closure_macro::main::{closure#0}
 Raw bytes (35): 0x[01, 01, 03, 01, 05, 05, 0b, 09, 0d, 05, 01, 10, 1c, 03, 21, 05, 04, 11, 01, 27, 02, 03, 11, 00, 16, 0d, 00, 17, 00, 1e, 07, 02, 09, 00, 0a]
@@ -38,4 +40,5 @@ Number of file 0 mappings: 5
 - Code(Counter(3)) at (prev + 0, 23) to (start + 0, 30)
 - Code(Expression(1, Add)) at (prev + 2, 9) to (start + 0, 10)
     = (c1 + (c2 + c3))
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/closure_macro_async.cov-map b/tests/coverage/closure_macro_async.cov-map
index 091e87909f900..e2a52e57015c4 100644
--- a/tests/coverage/closure_macro_async.cov-map
+++ b/tests/coverage/closure_macro_async.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 34, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: closure_macro_async::test
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 26, 01, 00, 2b]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 38, 1) to (start + 0, 43)
+Highest counter ID seen: c0
 
 Function name: closure_macro_async::test::{closure#0}
 Raw bytes (36): 0x[01, 01, 01, 01, 05, 06, 01, 26, 2b, 01, 21, 02, 02, 09, 00, 0f, 01, 00, 12, 00, 54, 05, 00, 54, 00, 55, 02, 02, 09, 02, 0b, 01, 03, 01, 00, 02]
@@ -29,6 +31,7 @@ Number of file 0 mappings: 6
 - Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 2, 11)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: closure_macro_async::test::{closure#0}::{closure#0}
 Raw bytes (35): 0x[01, 01, 03, 01, 05, 05, 0b, 09, 0d, 05, 01, 15, 1c, 03, 21, 05, 04, 11, 01, 27, 02, 03, 11, 00, 16, 0d, 00, 17, 00, 1e, 07, 02, 09, 00, 0a]
@@ -46,4 +49,5 @@ Number of file 0 mappings: 5
 - Code(Counter(3)) at (prev + 0, 23) to (start + 0, 30)
 - Code(Expression(1, Add)) at (prev + 2, 9) to (start + 0, 10)
     = (c1 + (c2 + c3))
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/closure_unit_return.cov-map b/tests/coverage/closure_unit_return.cov-map
index c97b4a44dd6b2..9a66e0b0e7729 100644
--- a/tests/coverage/closure_unit_return.cov-map
+++ b/tests/coverage/closure_unit_return.cov-map
@@ -6,6 +6,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 7, 1) to (start + 1, 16)
 - Code(Counter(0)) at (prev + 5, 5) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: closure_unit_return::explicit_unit::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 08, 16, 02, 06]
@@ -14,6 +15,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 8, 22) to (start + 2, 6)
+Highest counter ID seen: (none)
 
 Function name: closure_unit_return::implicit_unit
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 10, 01, 01, 10, 01, 05, 05, 02, 02]
@@ -23,6 +25,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 16, 1) to (start + 1, 16)
 - Code(Counter(0)) at (prev + 5, 5) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: closure_unit_return::implicit_unit::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 11, 16, 02, 06]
@@ -31,4 +34,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 17, 22) to (start + 2, 6)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/condition/conditions.cov-map b/tests/coverage/condition/conditions.cov-map
index 74726e269fc67..208d671919cf8 100644
--- a/tests/coverage/condition/conditions.cov-map
+++ b/tests/coverage/condition/conditions.cov-map
@@ -29,6 +29,7 @@ Number of file 0 mappings: 9
     false = c4
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = ((c2 + c3) + c4)
+Highest counter ID seen: c4
 
 Function name: conditions::assign_3_or_and
 Raw bytes (73): 0x[01, 01, 09, 05, 07, 0b, 11, 09, 0d, 01, 05, 01, 05, 22, 11, 01, 05, 22, 11, 01, 05, 09, 01, 17, 01, 00, 2f, 03, 01, 09, 00, 0a, 01, 00, 0d, 00, 0e, 20, 05, 22, 00, 0d, 00, 0e, 22, 00, 12, 00, 13, 20, 1e, 11, 00, 12, 00, 13, 1e, 00, 17, 00, 18, 20, 09, 0d, 00, 17, 00, 18, 03, 01, 05, 01, 02]
@@ -64,6 +65,7 @@ Number of file 0 mappings: 9
     false = c3
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = (c1 + ((c2 + c3) + c4))
+Highest counter ID seen: c4
 
 Function name: conditions::assign_and
 Raw bytes (51): 0x[01, 01, 04, 07, 0e, 09, 0d, 01, 05, 01, 05, 07, 01, 0d, 01, 00, 21, 03, 01, 09, 00, 0a, 01, 00, 0d, 00, 0e, 20, 05, 0e, 00, 0d, 00, 0e, 05, 00, 12, 00, 13, 20, 09, 0d, 00, 12, 00, 13, 03, 01, 05, 01, 02]
@@ -88,6 +90,7 @@ Number of file 0 mappings: 7
     false = c3
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = ((c2 + c3) + (c0 - c1))
+Highest counter ID seen: c3
 
 Function name: conditions::assign_or
 Raw bytes (51): 0x[01, 01, 04, 07, 0d, 05, 09, 01, 05, 01, 05, 07, 01, 12, 01, 00, 20, 03, 01, 09, 00, 0a, 01, 00, 0d, 00, 0e, 20, 05, 0e, 00, 0d, 00, 0e, 0e, 00, 12, 00, 13, 20, 09, 0d, 00, 12, 00, 13, 03, 01, 05, 01, 02]
@@ -113,6 +116,7 @@ Number of file 0 mappings: 7
     false = c3
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = ((c1 + c2) + c3)
+Highest counter ID seen: c3
 
 Function name: conditions::foo
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 21, 01, 02, 02]
@@ -121,6 +125,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 33, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: conditions::func_call
 Raw bytes (39): 0x[01, 01, 03, 01, 05, 0b, 02, 09, 0d, 05, 01, 25, 01, 01, 0a, 20, 05, 02, 01, 09, 00, 0a, 05, 00, 0e, 00, 0f, 20, 09, 0d, 00, 0e, 00, 0f, 07, 01, 01, 00, 02]
@@ -141,6 +146,7 @@ Number of file 0 mappings: 5
     false = c3
 - Code(Expression(1, Add)) at (prev + 1, 1) to (start + 0, 2)
     = ((c2 + c3) + (c0 - c1))
+Highest counter ID seen: c3
 
 Function name: conditions::simple_assign
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 08, 01, 03, 02]
@@ -149,4 +155,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 8, 1) to (start + 3, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/conditions.cov-map b/tests/coverage/conditions.cov-map
index 17143775b7b40..a392d1b70288e 100644
--- a/tests/coverage/conditions.cov-map
+++ b/tests/coverage/conditions.cov-map
@@ -260,4 +260,5 @@ Number of file 0 mappings: 68
 - Code(Counter(9)) at (prev + 2, 9) to (start + 0, 15)
 - Code(Expression(137, Add)) at (prev + 2, 1) to (start + 0, 2)
     = ((c4 + (((c5 + c6) + c7) + c8)) + ((((c9 + c10) + c11) + c12) + ((c0 - c2) - c3)))
+Highest counter ID seen: c35
 
diff --git a/tests/coverage/continue.cov-map b/tests/coverage/continue.cov-map
index 810694d7f6623..7781d2d2544c8 100644
--- a/tests/coverage/continue.cov-map
+++ b/tests/coverage/continue.cov-map
@@ -76,4 +76,5 @@ Number of file 0 mappings: 30
 - Code(Counter(16)) at (prev + 3, 9) to (start + 0, 14)
 - Code(Expression(27, Add)) at (prev + 2, 13) to (start + 1, 2)
     = (c18 + c17)
+Highest counter ID seen: c18
 
diff --git a/tests/coverage/coroutine.cov-map b/tests/coverage/coroutine.cov-map
index 6ff5ed74a96db..2fdc3220c1969 100644
--- a/tests/coverage/coroutine.cov-map
+++ b/tests/coverage/coroutine.cov-map
@@ -10,6 +10,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 0, 40)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: coroutine::main
 Raw bytes (65): 0x[01, 01, 08, 07, 0d, 05, 09, 11, 15, 1e, 19, 11, 15, 15, 19, 1e, 19, 11, 15, 09, 01, 13, 01, 02, 16, 01, 08, 0b, 00, 2e, 11, 01, 2b, 00, 2d, 03, 01, 0e, 00, 35, 11, 02, 0b, 00, 2e, 1e, 01, 22, 00, 27, 1a, 00, 2c, 00, 2e, 17, 01, 0e, 00, 35, 1a, 02, 01, 00, 02]
@@ -39,6 +40,7 @@ Number of file 0 mappings: 9
     = (c5 + c6)
 - Code(Expression(6, Sub)) at (prev + 2, 1) to (start + 0, 2)
     = ((c4 - c5) - c6)
+Highest counter ID seen: c4
 
 Function name: coroutine::main::{closure#0}
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 16, 08, 01, 1f, 05, 02, 10, 01, 06]
@@ -48,4 +50,5 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 22, 8) to (start + 1, 31)
 - Code(Counter(1)) at (prev + 2, 16) to (start + 1, 6)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/coverage_attr_closure.cov-map b/tests/coverage/coverage_attr_closure.cov-map
index 5d2c6b00b40f8..fb861996a0d27 100644
--- a/tests/coverage/coverage_attr_closure.cov-map
+++ b/tests/coverage/coverage_attr_closure.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 6, 15) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: coverage_attr_closure::contains_closures_off::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 1d, 13, 02, 06]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 29, 19) to (start + 2, 6)
+Highest counter ID seen: (none)
 
 Function name: coverage_attr_closure::contains_closures_on
 Raw bytes (19): 0x[01, 01, 00, 03, 01, 0f, 01, 01, 1a, 01, 05, 09, 00, 1b, 01, 04, 01, 00, 02]
@@ -23,6 +25,7 @@ Number of file 0 mappings: 3
 - Code(Counter(0)) at (prev + 15, 1) to (start + 1, 26)
 - Code(Counter(0)) at (prev + 5, 9) to (start + 0, 27)
 - Code(Counter(0)) at (prev + 4, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
 Function name: coverage_attr_closure::contains_closures_on::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 11, 13, 02, 06]
@@ -31,4 +34,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 17, 19) to (start + 2, 6)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/dead_code.cov-map b/tests/coverage/dead_code.cov-map
index 31599d9072c92..b94c6e656abfb 100644
--- a/tests/coverage/dead_code.cov-map
+++ b/tests/coverage/dead_code.cov-map
@@ -10,6 +10,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: dead_code::unused_fn (unused)
 Raw bytes (24): 0x[01, 01, 00, 04, 00, 0f, 01, 07, 0f, 00, 07, 10, 02, 06, 00, 02, 06, 00, 07, 00, 01, 01, 00, 02]
@@ -21,6 +22,7 @@ Number of file 0 mappings: 4
 - Code(Zero) at (prev + 7, 16) to (start + 2, 6)
 - Code(Zero) at (prev + 2, 6) to (start + 0, 7)
 - Code(Zero) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
 Function name: dead_code::unused_pub_fn_not_in_library (unused)
 Raw bytes (24): 0x[01, 01, 00, 04, 00, 03, 01, 07, 0f, 00, 07, 10, 02, 06, 00, 02, 06, 00, 07, 00, 01, 01, 00, 02]
@@ -32,4 +34,5 @@ Number of file 0 mappings: 4
 - Code(Zero) at (prev + 7, 16) to (start + 2, 6)
 - Code(Zero) at (prev + 2, 6) to (start + 0, 7)
 - Code(Zero) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/drop_trait.cov-map b/tests/coverage/drop_trait.cov-map
index eb9d7d7acfdfc..a97c0f8794c43 100644
--- a/tests/coverage/drop_trait.cov-map
+++ b/tests/coverage/drop_trait.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 9, 5) to (start + 2, 6)
+Highest counter ID seen: c0
 
 Function name: drop_trait::main
 Raw bytes (24): 0x[01, 01, 00, 04, 01, 0e, 01, 05, 0c, 05, 06, 09, 01, 16, 00, 02, 06, 04, 0b, 01, 05, 01, 00, 02]
@@ -16,4 +17,5 @@ Number of file 0 mappings: 4
 - Code(Counter(1)) at (prev + 6, 9) to (start + 1, 22)
 - Code(Zero) at (prev + 2, 6) to (start + 4, 11)
 - Code(Counter(0)) at (prev + 5, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/fn_sig_into_try.cov-map b/tests/coverage/fn_sig_into_try.cov-map
index 49758954831a1..374811dba9efa 100644
--- a/tests/coverage/fn_sig_into_try.cov-map
+++ b/tests/coverage/fn_sig_into_try.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 10, 1) to (start + 5, 2)
+Highest counter ID seen: c0
 
 Function name: fn_sig_into_try::b
 Raw bytes (26): 0x[01, 01, 01, 01, 00, 04, 01, 11, 01, 03, 0f, 00, 03, 0f, 00, 10, 02, 01, 05, 00, 0c, 01, 01, 01, 00, 02]
@@ -18,6 +19,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 1, 5) to (start + 0, 12)
     = (c0 - Zero)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
 Function name: fn_sig_into_try::c
 Raw bytes (26): 0x[01, 01, 01, 01, 00, 04, 01, 18, 01, 03, 17, 00, 03, 17, 00, 18, 02, 01, 05, 00, 0c, 01, 01, 01, 00, 02]
@@ -31,6 +33,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 1, 5) to (start + 0, 12)
     = (c0 - Zero)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
 Function name: fn_sig_into_try::d
 Raw bytes (26): 0x[01, 01, 01, 01, 00, 04, 01, 1f, 01, 04, 0f, 00, 04, 0f, 00, 10, 02, 01, 05, 00, 0c, 01, 01, 01, 00, 02]
@@ -44,4 +47,5 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 1, 5) to (start + 0, 12)
     = (c0 - Zero)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/generics.cov-map b/tests/coverage/generics.cov-map
index 48e191c1156ff..d082bd54493d7 100644
--- a/tests/coverage/generics.cov-map
+++ b/tests/coverage/generics.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 17, 5) to (start + 2, 6)
+Highest counter ID seen: c0
 
 Function name: <generics::Firework<f64>>::set_strength
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 0a, 05, 02, 06]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 10, 5) to (start + 2, 6)
+Highest counter ID seen: c0
 
 Function name: <generics::Firework<i32> as core::ops::drop::Drop>::drop
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 11, 05, 02, 06]
@@ -21,6 +23,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 17, 5) to (start + 2, 6)
+Highest counter ID seen: c0
 
 Function name: <generics::Firework<i32>>::set_strength
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 0a, 05, 02, 06]
@@ -29,6 +32,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 10, 5) to (start + 2, 6)
+Highest counter ID seen: c0
 
 Function name: generics::main
 Raw bytes (24): 0x[01, 01, 00, 04, 01, 16, 01, 08, 0c, 05, 09, 09, 01, 16, 00, 02, 06, 04, 0b, 01, 05, 01, 00, 02]
@@ -40,4 +44,5 @@ Number of file 0 mappings: 4
 - Code(Counter(1)) at (prev + 9, 9) to (start + 1, 22)
 - Code(Zero) at (prev + 2, 6) to (start + 4, 11)
 - Code(Counter(0)) at (prev + 5, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/holes.cov-map b/tests/coverage/holes.cov-map
index 9350bd9a405cc..3c740d80ea05a 100644
--- a/tests/coverage/holes.cov-map
+++ b/tests/coverage/holes.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 37, 9) to (start + 0, 29)
+Highest counter ID seen: (none)
 
 Function name: holes::main
 Raw bytes (44): 0x[01, 01, 00, 08, 01, 08, 01, 06, 11, 01, 0f, 05, 00, 12, 01, 04, 05, 00, 12, 01, 07, 05, 00, 12, 01, 06, 05, 00, 12, 01, 06, 05, 03, 0f, 01, 0a, 05, 03, 0f, 01, 0a, 05, 01, 02]
@@ -20,6 +21,7 @@ Number of file 0 mappings: 8
 - Code(Counter(0)) at (prev + 6, 5) to (start + 3, 15)
 - Code(Counter(0)) at (prev + 10, 5) to (start + 3, 15)
 - Code(Counter(0)) at (prev + 10, 5) to (start + 1, 2)
+Highest counter ID seen: c0
 
 Function name: holes::main::_unused_fn (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 19, 05, 00, 17]
@@ -28,6 +30,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 25, 5) to (start + 0, 23)
+Highest counter ID seen: (none)
 
 Function name: holes::main::{closure#0} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 12, 09, 02, 0a]
@@ -36,6 +39,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 18, 9) to (start + 2, 10)
+Highest counter ID seen: (none)
 
 Function name: holes::main::{closure#1} (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 3d, 09, 02, 0a]
@@ -44,4 +48,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 61, 9) to (start + 2, 10)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/if.cov-map b/tests/coverage/if.cov-map
index 2b5ae97b406d4..8f12afac02721 100644
--- a/tests/coverage/if.cov-map
+++ b/tests/coverage/if.cov-map
@@ -10,4 +10,5 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 5, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/if_else.cov-map b/tests/coverage/if_else.cov-map
index c2111917e559e..194ad6ca71f83 100644
--- a/tests/coverage/if_else.cov-map
+++ b/tests/coverage/if_else.cov-map
@@ -15,4 +15,5 @@ Number of file 0 mappings: 7
 - Code(Expression(1, Sub)) at (prev + 7, 5) to (start + 5, 6)
     = (c0 - c2)
 - Code(Counter(0)) at (prev + 6, 1) to (start + 0, 2)
+Highest counter ID seen: c2
 
diff --git a/tests/coverage/if_not.cov-map b/tests/coverage/if_not.cov-map
index 9e11ed787a887..a2c276b7bb77b 100644
--- a/tests/coverage/if_not.cov-map
+++ b/tests/coverage/if_not.cov-map
@@ -20,4 +20,5 @@ Number of file 0 mappings: 10
     = (c0 - c3)
 - Code(Counter(3)) at (prev + 2, 12) to (start + 2, 6)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/ignore_run.cov-map b/tests/coverage/ignore_run.cov-map
index 9865efae0a1ef..c8ad3821e16f9 100644
--- a/tests/coverage/ignore_run.cov-map
+++ b/tests/coverage/ignore_run.cov-map
@@ -5,4 +5,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 13)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/inline-dead.cov-map b/tests/coverage/inline-dead.cov-map
index 96b907cbe1532..411f16725bb07 100644
--- a/tests/coverage/inline-dead.cov-map
+++ b/tests/coverage/inline-dead.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 23, 1) to (start + 2, 2)
+Highest counter ID seen: (none)
 
 Function name: inline_dead::live::<false>
 Raw bytes (26): 0x[01, 01, 01, 01, 00, 04, 01, 0e, 01, 01, 09, 00, 02, 09, 00, 0f, 02, 02, 09, 00, 0a, 01, 02, 01, 00, 02]
@@ -18,6 +19,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 0, 10)
     = (c0 - Zero)
 - Code(Counter(0)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
 Function name: inline_dead::main
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 04, 01, 03, 0a, 01, 06, 05, 01, 02]
@@ -27,6 +29,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 4, 1) to (start + 3, 10)
 - Code(Counter(0)) at (prev + 6, 5) to (start + 1, 2)
+Highest counter ID seen: c0
 
 Function name: inline_dead::main::{closure#0}
 Raw bytes (23): 0x[01, 01, 02, 00, 06, 01, 00, 03, 01, 07, 17, 01, 16, 00, 01, 17, 00, 18, 03, 01, 05, 00, 06]
@@ -40,4 +43,5 @@ Number of file 0 mappings: 3
 - Code(Zero) at (prev + 1, 23) to (start + 0, 24)
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 0, 6)
     = (Zero + (c0 - Zero))
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/inline.cov-map b/tests/coverage/inline.cov-map
index 2366a3bc5345a..ab3a505e92505 100644
--- a/tests/coverage/inline.cov-map
+++ b/tests/coverage/inline.cov-map
@@ -11,6 +11,7 @@ Number of file 0 mappings: 5
     = (c0 + c1)
 - Code(Counter(1)) at (prev + 0, 17) to (start + 2, 6)
 - Code(Counter(0)) at (prev + 3, 5) to (start + 1, 2)
+Highest counter ID seen: c1
 
 Function name: inline::error
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 31, 01, 01, 14]
@@ -19,6 +20,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 49, 1) to (start + 1, 20)
+Highest counter ID seen: c0
 
 Function name: inline::length::<char>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 1e, 01, 02, 02]
@@ -27,6 +29,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 30, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: inline::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 05, 01, 02, 02]
@@ -35,6 +38,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 5, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: inline::permutate::<char>
 Raw bytes (52): 0x[01, 01, 04, 01, 05, 02, 0d, 05, 0f, 09, 0d, 08, 01, 0f, 01, 02, 0e, 05, 02, 0f, 02, 06, 02, 02, 0f, 00, 14, 11, 01, 0d, 00, 0e, 06, 00, 12, 00, 16, 11, 00, 17, 04, 0a, 0d, 05, 0c, 02, 06, 0b, 03, 01, 00, 02]
@@ -57,6 +61,7 @@ Number of file 0 mappings: 8
 - Code(Counter(3)) at (prev + 5, 12) to (start + 2, 6)
 - Code(Expression(2, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c1 + (c2 + c3))
+Highest counter ID seen: c4
 
 Function name: inline::permutations::<char>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 0a, 01, 03, 02]
@@ -65,6 +70,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 10, 1) to (start + 3, 2)
+Highest counter ID seen: c0
 
 Function name: inline::swap::<char>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 23, 01, 04, 02]
@@ -73,4 +79,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 35, 1) to (start + 4, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/inner_items.cov-map b/tests/coverage/inner_items.cov-map
index 6ccc3f0bafc8d..16e86b2cadea9 100644
--- a/tests/coverage/inner_items.cov-map
+++ b/tests/coverage/inner_items.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 33, 9) to (start + 3, 10)
+Highest counter ID seen: c0
 
 Function name: <inner_items::main::InStruct as inner_items::main::InTrait>::trait_func
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 28, 09, 03, 0a]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 40, 9) to (start + 3, 10)
+Highest counter ID seen: c0
 
 Function name: inner_items::main
 Raw bytes (43): 0x[01, 01, 02, 01, 05, 01, 09, 07, 01, 03, 01, 07, 0f, 05, 07, 10, 02, 06, 02, 02, 06, 00, 07, 01, 24, 08, 00, 0f, 09, 00, 10, 02, 06, 06, 02, 06, 00, 07, 01, 02, 09, 05, 02]
@@ -31,6 +33,7 @@ Number of file 0 mappings: 7
 - Code(Expression(1, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c2)
 - Code(Counter(0)) at (prev + 2, 9) to (start + 5, 2)
+Highest counter ID seen: c2
 
 Function name: inner_items::main::in_func
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 12, 05, 04, 06]
@@ -39,4 +42,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 18, 5) to (start + 4, 6)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/issue-83601.cov-map b/tests/coverage/issue-83601.cov-map
index f2447e3c92c8a..c188cca1b517a 100644
--- a/tests/coverage/issue-83601.cov-map
+++ b/tests/coverage/issue-83601.cov-map
@@ -9,4 +9,5 @@ Number of file 0 mappings: 3
 - Code(Counter(1)) at (prev + 3, 9) to (start + 1, 28)
 - Code(Expression(0, Sub)) at (prev + 2, 5) to (start + 3, 2)
     = (c1 - c2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/issue-84561.cov-map b/tests/coverage/issue-84561.cov-map
index d3c4671e0ba4c..a8ad17574ba3d 100644
--- a/tests/coverage/issue-84561.cov-map
+++ b/tests/coverage/issue-84561.cov-map
@@ -10,6 +10,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 1, 9) to (start + 0, 15)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 5) to (start + 0, 6)
+Highest counter ID seen: c1
 
 Function name: issue_84561::main
 Raw bytes (10): 0x[01, 01, 00, 01, 01, b4, 01, 01, 04, 02]
@@ -18,6 +19,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 180, 1) to (start + 4, 2)
+Highest counter ID seen: c0
 
 Function name: issue_84561::test1
 Raw bytes (50): 0x[01, 01, 00, 09, 01, 9a, 01, 01, 01, 0b, 05, 01, 0c, 00, 1e, 01, 01, 05, 00, 0b, 09, 00, 0c, 00, 1e, 01, 01, 0d, 01, 0b, 0d, 01, 0c, 00, 1e, 01, 01, 05, 03, 0b, 11, 03, 0c, 00, 1e, 01, 01, 01, 00, 02]
@@ -34,6 +36,7 @@ Number of file 0 mappings: 9
 - Code(Counter(0)) at (prev + 1, 5) to (start + 3, 11)
 - Code(Counter(4)) at (prev + 3, 12) to (start + 0, 30)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c4
 
 Function name: issue_84561::test2
 Raw bytes (20): 0x[01, 01, 00, 03, 01, b0, 01, 01, 01, 10, 05, 01, 11, 00, 23, 01, 01, 01, 00, 02]
@@ -44,6 +47,7 @@ Number of file 0 mappings: 3
 - Code(Counter(0)) at (prev + 176, 1) to (start + 1, 16)
 - Code(Counter(1)) at (prev + 1, 17) to (start + 0, 35)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: issue_84561::test2::call_print
 Raw bytes (10): 0x[01, 01, 00, 01, 01, a7, 01, 09, 02, 0a]
@@ -52,6 +56,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 167, 9) to (start + 2, 10)
+Highest counter ID seen: c0
 
 Function name: issue_84561::test3
 Raw bytes (375): 0x[01, 01, 31, 05, 09, 0d, 00, 15, 19, 12, 00, 15, 19, 21, 00, 1e, 00, 21, 00, 31, 00, 3d, 00, 2e, 45, 3d, 00, 42, 49, 45, 00, 3f, 51, 42, 49, 45, 00, 7a, 55, 51, 00, 7a, 55, 51, 00, 77, 5d, 7a, 55, 51, 00, 77, 61, 7a, 55, 51, 00, 72, 65, 77, 61, 7a, 55, 51, 00, 75, be, 01, c2, 01, 79, 69, 6d, 69, 6d, 69, 6d, c2, 01, 00, 69, 6d, c2, 01, 79, 69, 6d, bb, 01, 7d, 75, be, 01, c2, 01, 79, 69, 6d, b6, 01, 00, bb, 01, 7d, 75, be, 01, c2, 01, 79, 69, 6d, 33, 01, 08, 01, 03, 1c, 05, 04, 09, 01, 1c, 02, 02, 05, 04, 1f, 0d, 05, 05, 00, 1f, 06, 01, 05, 00, 1f, 15, 01, 09, 01, 1c, 12, 02, 05, 00, 1f, 0e, 01, 05, 00, 0f, 00, 00, 20, 00, 30, 21, 01, 05, 03, 0f, 00, 03, 20, 00, 30, 00, 00, 33, 00, 41, 00, 00, 4b, 00, 5a, 1e, 01, 05, 00, 0f, 00, 05, 09, 03, 10, 00, 05, 0d, 00, 1b, 00, 02, 0d, 00, 1c, 1a, 04, 09, 05, 06, 31, 06, 05, 03, 06, 22, 04, 05, 03, 06, 3d, 04, 09, 04, 06, 2e, 05, 08, 00, 0f, 45, 01, 09, 03, 0a, 2a, 05, 09, 03, 0a, 3f, 05, 08, 00, 0f, 51, 01, 09, 00, 13, 00, 03, 0d, 00, 1d, 3a, 03, 09, 00, 13, 00, 03, 0d, 00, 1d, 77, 03, 05, 00, 0f, 77, 01, 0c, 00, 13, 5d, 01, 0d, 00, 13, 56, 02, 0d, 00, 13, 72, 04, 05, 02, 13, 65, 03, 0d, 00, 13, 6e, 02, 0d, 00, 13, bb, 01, 03, 05, 00, 0f, 69, 01, 0c, 00, 13, 6d, 01, 0d, 03, 0e, 75, 04, 0d, 00, 13, c2, 01, 02, 0d, 00, 17, c2, 01, 01, 14, 00, 1b, 00, 01, 15, 00, 1b, 92, 01, 02, 15, 00, 1b, be, 01, 04, 0d, 00, 13, 7d, 03, 09, 00, 19, b6, 01, 02, 05, 00, 0f, b2, 01, 03, 09, 00, 22, 00, 02, 05, 00, 0f, 00, 03, 09, 00, 2c, 00, 02, 01, 00, 02]
@@ -182,4 +187,5 @@ Number of file 0 mappings: 51
 - Code(Zero) at (prev + 2, 5) to (start + 0, 15)
 - Code(Zero) at (prev + 3, 9) to (start + 0, 44)
 - Code(Zero) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c31
 
diff --git a/tests/coverage/issue-85461.cov-map b/tests/coverage/issue-85461.cov-map
index d1c449b9a355e..349bc2cab8030 100644
--- a/tests/coverage/issue-85461.cov-map
+++ b/tests/coverage/issue-85461.cov-map
@@ -5,4 +5,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 8, 1) to (start + 3, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/issue-93054.cov-map b/tests/coverage/issue-93054.cov-map
index 024ef519fcffe..38cb70a3f97aa 100644
--- a/tests/coverage/issue-93054.cov-map
+++ b/tests/coverage/issue-93054.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 21, 1) to (start + 0, 29)
+Highest counter ID seen: (none)
 
 Function name: issue_93054::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 1d, 01, 00, 0d]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 29, 1) to (start + 0, 13)
+Highest counter ID seen: c0
 
 Function name: issue_93054::make (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 19, 01, 02, 02]
@@ -21,4 +23,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 25, 1) to (start + 2, 2)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/lazy_boolean.cov-map b/tests/coverage/lazy_boolean.cov-map
index 8dca205d33f2d..fcb9d8f1ff5cc 100644
--- a/tests/coverage/lazy_boolean.cov-map
+++ b/tests/coverage/lazy_boolean.cov-map
@@ -46,4 +46,5 @@ Number of file 0 mappings: 28
 - Code(Expression(6, Sub)) at (prev + 2, 12) to (start + 2, 6)
     = (c0 - c9)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c9
 
diff --git a/tests/coverage/let_else_loop.cov-map b/tests/coverage/let_else_loop.cov-map
index 13d0d08adb119..04451596eae4b 100644
--- a/tests/coverage/let_else_loop.cov-map
+++ b/tests/coverage/let_else_loop.cov-map
@@ -7,6 +7,7 @@ Number of file 0 mappings: 3
 - Code(Zero) at (prev + 22, 1) to (start + 1, 12)
 - Code(Zero) at (prev + 1, 15) to (start + 0, 22)
 - Code(Zero) at (prev + 0, 32) to (start + 0, 39)
+Highest counter ID seen: (none)
 
 Function name: let_else_loop::_loop_either_way (unused)
 Raw bytes (19): 0x[01, 01, 00, 03, 00, 0f, 01, 01, 14, 00, 01, 1c, 00, 23, 00, 01, 05, 00, 0c]
@@ -17,6 +18,7 @@ Number of file 0 mappings: 3
 - Code(Zero) at (prev + 15, 1) to (start + 1, 20)
 - Code(Zero) at (prev + 1, 28) to (start + 0, 35)
 - Code(Zero) at (prev + 1, 5) to (start + 0, 12)
+Highest counter ID seen: (none)
 
 Function name: let_else_loop::loopy
 Raw bytes (19): 0x[01, 01, 00, 03, 01, 09, 01, 01, 14, 00, 01, 1c, 00, 23, 05, 01, 01, 00, 02]
@@ -27,4 +29,5 @@ Number of file 0 mappings: 3
 - Code(Counter(0)) at (prev + 9, 1) to (start + 1, 20)
 - Code(Zero) at (prev + 1, 28) to (start + 0, 35)
 - Code(Counter(1)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/long_and_wide.cov-map b/tests/coverage/long_and_wide.cov-map
index 97aebf9b18ab0..032b7fe102e8f 100644
--- a/tests/coverage/long_and_wide.cov-map
+++ b/tests/coverage/long_and_wide.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 150, 1) to (start + 0, 21)
+Highest counter ID seen: c0
 
 Function name: long_and_wide::long_function
 Raw bytes (10): 0x[01, 01, 00, 01, 01, 10, 01, 84, 01, 02]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 16, 1) to (start + 132, 2)
+Highest counter ID seen: c0
 
 Function name: long_and_wide::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 07, 01, 04, 02]
@@ -21,6 +23,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 7, 1) to (start + 4, 2)
+Highest counter ID seen: c0
 
 Function name: long_and_wide::wide_function
 Raw bytes (10): 0x[01, 01, 00, 01, 01, 0e, 01, 00, 8b, 01]
@@ -29,4 +32,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 14, 1) to (start + 0, 139)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/loop-break.cov-map b/tests/coverage/loop-break.cov-map
index 890d5d84539e4..63280a0bf7cbe 100644
--- a/tests/coverage/loop-break.cov-map
+++ b/tests/coverage/loop-break.cov-map
@@ -11,4 +11,5 @@ Number of file 0 mappings: 5
 - Code(Counter(0)) at (prev + 1, 13) to (start + 0, 18)
 - Code(Counter(1)) at (prev + 1, 10) to (start + 0, 11)
 - Code(Counter(0)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/loop_break_value.cov-map b/tests/coverage/loop_break_value.cov-map
index d8dca8a85c387..e48d078f6722d 100644
--- a/tests/coverage/loop_break_value.cov-map
+++ b/tests/coverage/loop_break_value.cov-map
@@ -5,4 +5,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 4, 1) to (start + 10, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/loops_branches.cov-map b/tests/coverage/loops_branches.cov-map
index 9187dcbd86518..1d263611a3abc 100644
--- a/tests/coverage/loops_branches.cov-map
+++ b/tests/coverage/loops_branches.cov-map
@@ -75,6 +75,7 @@ Number of file 0 mappings: 20
 - Code(Counter(6)) at (prev + 3, 9) to (start + 0, 15)
 - Code(Expression(34, Add)) at (prev + 1, 5) to (start + 0, 6)
     = ((c9 + (((((c3 + Zero) + (c4 + Zero)) - c6) - Zero) - c4)) + c6)
+Highest counter ID seen: c9
 
 Function name: <loops_branches::DisplayTest as core::fmt::Display>::fmt
 Raw bytes (230): 0x[01, 01, 2b, 01, 00, 02, 00, a3, 01, 19, a7, 01, ab, 01, 00, 0d, 00, 15, a7, 01, ab, 01, 00, 0d, 00, 15, a3, 01, 19, a7, 01, ab, 01, 00, 0d, 00, 15, 9e, 01, 00, a3, 01, 19, a7, 01, ab, 01, 00, 0d, 00, 15, 9a, 01, 00, 9e, 01, 00, a3, 01, 19, a7, 01, ab, 01, 00, 0d, 00, 15, 9e, 01, 00, a3, 01, 19, a7, 01, ab, 01, 00, 0d, 00, 15, 9a, 01, 15, 9e, 01, 00, a3, 01, 19, a7, 01, ab, 01, 00, 0d, 00, 15, 93, 01, 25, 96, 01, 19, 9a, 01, 15, 9e, 01, 00, a3, 01, 19, a7, 01, ab, 01, 00, 0d, 00, 15, 14, 01, 22, 05, 01, 11, 00, 01, 12, 01, 0a, 02, 02, 10, 00, 15, 00, 01, 17, 00, 1b, 00, 00, 1c, 00, 1e, 06, 01, 0e, 00, 0f, 02, 01, 0d, 00, 1e, 25, 00, 1e, 00, 1f, 9e, 01, 02, 0d, 00, 0e, a3, 01, 00, 12, 00, 17, 9e, 01, 01, 10, 00, 15, 00, 00, 16, 01, 0e, 9a, 01, 02, 14, 00, 19, 00, 01, 1b, 00, 1f, 00, 00, 20, 00, 22, 4a, 01, 12, 00, 13, 9a, 01, 01, 11, 00, 22, 96, 01, 00, 22, 00, 23, 19, 03, 09, 00, 0f, 8f, 01, 01, 05, 00, 06]
@@ -156,6 +157,7 @@ Number of file 0 mappings: 20
 - Code(Counter(6)) at (prev + 3, 9) to (start + 0, 15)
 - Code(Expression(35, Add)) at (prev + 1, 5) to (start + 0, 6)
     = (((((((Zero + c3) + (Zero + c5)) - c6) - Zero) - c5) + c6) + c9)
+Highest counter ID seen: c9
 
 Function name: loops_branches::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 37, 01, 05, 02]
@@ -164,4 +166,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 55, 1) to (start + 5, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/macro_in_closure.cov-map b/tests/coverage/macro_in_closure.cov-map
index 2feaab717b5cb..9614154a3668a 100644
--- a/tests/coverage/macro_in_closure.cov-map
+++ b/tests/coverage/macro_in_closure.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 7, 28) to (start + 0, 45)
+Highest counter ID seen: c0
 
 Function name: macro_in_closure::WITH_BLOCK::{closure#0}
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 09, 1e, 02, 02]
@@ -13,4 +14,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 9, 30) to (start + 2, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/macro_name_span.cov-map b/tests/coverage/macro_name_span.cov-map
index f3ee44d2a5abc..58620452b2ba6 100644
--- a/tests/coverage/macro_name_span.cov-map
+++ b/tests/coverage/macro_name_span.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 22, 28) to (start + 1, 64)
+Highest counter ID seen: c0
 
 Function name: macro_name_span::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 0b, 01, 02, 02]
@@ -13,4 +14,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 11, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/match_or_pattern.cov-map b/tests/coverage/match_or_pattern.cov-map
index 60b7024533d2e..f6491ea262dc5 100644
--- a/tests/coverage/match_or_pattern.cov-map
+++ b/tests/coverage/match_or_pattern.cov-map
@@ -72,4 +72,5 @@ Number of file 0 mappings: 25
     = (c14 + c15)
 - Code(Expression(26, Add)) at (prev + 2, 1) to (start + 0, 2)
     = ((c14 + c15) + c16)
+Highest counter ID seen: c16
 
diff --git a/tests/coverage/mcdc/condition-limit.cov-map b/tests/coverage/mcdc/condition-limit.cov-map
index 9d1e7518f9ea4..a3e3b1d09c4d1 100644
--- a/tests/coverage/mcdc/condition-limit.cov-map
+++ b/tests/coverage/mcdc/condition-limit.cov-map
@@ -87,4 +87,5 @@ Number of file 0 mappings: 18
     = ((((((c2 + c3) + c4) + c5) + c6) + c7) + (c0 - c1))
 - Code(Expression(37, Add)) at (prev + 1, 1) to (start + 0, 2)
     = (c8 + ((((((c2 + c3) + c4) + c5) + c6) + c7) + (c0 - c1)))
+Highest counter ID seen: c8
 
diff --git a/tests/coverage/mcdc/if.cov-map b/tests/coverage/mcdc/if.cov-map
index 576c9b14ed14c..46960d31c01e6 100644
--- a/tests/coverage/mcdc/if.cov-map
+++ b/tests/coverage/mcdc/if.cov-map
@@ -22,6 +22,7 @@ Number of file 0 mappings: 8
     = (c2 + (c0 - c1))
 - Code(Expression(2, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c3
 
 Function name: if::mcdc_check_b
 Raw bytes (64): 0x[01, 01, 04, 01, 05, 09, 02, 0d, 0f, 09, 02, 08, 01, 17, 01, 01, 09, 28, 03, 02, 01, 08, 00, 0e, 30, 05, 02, 01, 02, 00, 00, 08, 00, 09, 05, 00, 0d, 00, 0e, 30, 0d, 09, 02, 00, 00, 00, 0d, 00, 0e, 0d, 00, 0f, 02, 06, 0f, 02, 0c, 02, 06, 0b, 03, 01, 00, 02]
@@ -47,6 +48,7 @@ Number of file 0 mappings: 8
     = (c2 + (c0 - c1))
 - Code(Expression(2, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c3
 
 Function name: if::mcdc_check_both
 Raw bytes (64): 0x[01, 01, 04, 01, 05, 09, 02, 0d, 0f, 09, 02, 08, 01, 1f, 01, 01, 09, 28, 03, 02, 01, 08, 00, 0e, 30, 05, 02, 01, 02, 00, 00, 08, 00, 09, 05, 00, 0d, 00, 0e, 30, 0d, 09, 02, 00, 00, 00, 0d, 00, 0e, 0d, 00, 0f, 02, 06, 0f, 02, 0c, 02, 06, 0b, 03, 01, 00, 02]
@@ -72,6 +74,7 @@ Number of file 0 mappings: 8
     = (c2 + (c0 - c1))
 - Code(Expression(2, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c3
 
 Function name: if::mcdc_check_neither
 Raw bytes (64): 0x[01, 01, 04, 01, 05, 09, 02, 0d, 0f, 09, 02, 08, 01, 07, 01, 01, 09, 28, 03, 02, 01, 08, 00, 0e, 30, 05, 02, 01, 02, 00, 00, 08, 00, 09, 05, 00, 0d, 00, 0e, 30, 0d, 09, 02, 00, 00, 00, 0d, 00, 0e, 0d, 00, 0f, 02, 06, 0f, 02, 0c, 02, 06, 0b, 03, 01, 00, 02]
@@ -97,6 +100,7 @@ Number of file 0 mappings: 8
     = (c2 + (c0 - c1))
 - Code(Expression(2, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c3
 
 Function name: if::mcdc_check_not_tree_decision
 Raw bytes (87): 0x[01, 01, 08, 01, 05, 02, 09, 05, 09, 0d, 1e, 02, 09, 11, 1b, 0d, 1e, 02, 09, 0a, 01, 31, 01, 03, 0a, 28, 05, 03, 03, 08, 00, 15, 30, 05, 02, 01, 02, 03, 00, 09, 00, 0a, 02, 00, 0e, 00, 0f, 30, 09, 1e, 03, 02, 00, 00, 0e, 00, 0f, 0b, 00, 14, 00, 15, 30, 11, 0d, 02, 00, 00, 00, 14, 00, 15, 11, 00, 16, 02, 06, 1b, 02, 0c, 02, 06, 17, 03, 01, 00, 02]
@@ -132,6 +136,7 @@ Number of file 0 mappings: 10
     = (c3 + ((c0 - c1) - c2))
 - Code(Expression(5, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c4 + (c3 + ((c0 - c1) - c2)))
+Highest counter ID seen: c4
 
 Function name: if::mcdc_check_tree_decision
 Raw bytes (87): 0x[01, 01, 08, 01, 05, 05, 0d, 05, 0d, 0d, 11, 09, 02, 1b, 1f, 0d, 11, 09, 02, 0a, 01, 27, 01, 03, 09, 28, 04, 03, 03, 08, 00, 15, 30, 05, 02, 01, 02, 00, 00, 08, 00, 09, 05, 00, 0e, 00, 0f, 30, 0d, 0a, 02, 00, 03, 00, 0e, 00, 0f, 0a, 00, 13, 00, 14, 30, 11, 09, 03, 00, 00, 00, 13, 00, 14, 1b, 00, 16, 02, 06, 1f, 02, 0c, 02, 06, 17, 03, 01, 00, 02]
@@ -167,6 +172,7 @@ Number of file 0 mappings: 10
     = (c2 + (c0 - c1))
 - Code(Expression(5, Add)) at (prev + 3, 1) to (start + 0, 2)
     = ((c3 + c4) + (c2 + (c0 - c1)))
+Highest counter ID seen: c4
 
 Function name: if::mcdc_nested_if
 Raw bytes (124): 0x[01, 01, 0d, 01, 05, 02, 09, 05, 09, 1b, 15, 05, 09, 1b, 15, 05, 09, 11, 15, 02, 09, 2b, 32, 0d, 2f, 11, 15, 02, 09, 0e, 01, 3b, 01, 01, 09, 28, 03, 02, 01, 08, 00, 0e, 30, 05, 02, 01, 00, 02, 00, 08, 00, 09, 02, 00, 0d, 00, 0e, 30, 09, 32, 02, 00, 00, 00, 0d, 00, 0e, 1b, 01, 09, 01, 0d, 28, 06, 02, 01, 0c, 00, 12, 30, 16, 15, 01, 02, 00, 00, 0c, 00, 0d, 16, 00, 11, 00, 12, 30, 0d, 11, 02, 00, 00, 00, 11, 00, 12, 0d, 00, 13, 02, 0a, 2f, 02, 0a, 00, 0b, 32, 01, 0c, 02, 06, 27, 03, 01, 00, 02]
@@ -215,4 +221,5 @@ Number of file 0 mappings: 14
     = ((c0 - c1) - c2)
 - Code(Expression(9, Add)) at (prev + 3, 1) to (start + 0, 2)
     = ((c3 + (c4 + c5)) + ((c0 - c1) - c2))
+Highest counter ID seen: c5
 
diff --git a/tests/coverage/mcdc/inlined_expressions.cov-map b/tests/coverage/mcdc/inlined_expressions.cov-map
index bfde7d75d622f..4f44e0f2b855c 100644
--- a/tests/coverage/mcdc/inlined_expressions.cov-map
+++ b/tests/coverage/mcdc/inlined_expressions.cov-map
@@ -18,4 +18,5 @@ Number of file 0 mappings: 6
     false = c3
 - Code(Expression(1, Add)) at (prev + 1, 1) to (start + 0, 2)
     = ((c2 + c3) + (c0 - c1))
+Highest counter ID seen: c3
 
diff --git a/tests/coverage/mcdc/nested_if.cov-map b/tests/coverage/mcdc/nested_if.cov-map
index 3da98ff4a514e..3bed49e7a12d1 100644
--- a/tests/coverage/mcdc/nested_if.cov-map
+++ b/tests/coverage/mcdc/nested_if.cov-map
@@ -56,6 +56,7 @@ Number of file 0 mappings: 20
     = (c2 + (c0 - c1))
 - Code(Expression(12, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c8
 
 Function name: nested_if::nested_if_in_condition
 Raw bytes (120): 0x[01, 01, 0b, 01, 05, 05, 11, 05, 11, 1e, 15, 05, 11, 11, 15, 1e, 15, 05, 11, 09, 02, 0d, 2b, 09, 02, 0e, 01, 07, 01, 01, 09, 28, 06, 02, 01, 08, 00, 2e, 30, 05, 02, 01, 02, 00, 00, 08, 00, 09, 30, 0d, 09, 02, 00, 00, 00, 0d, 00, 2e, 05, 00, 10, 00, 11, 28, 03, 02, 00, 10, 00, 16, 30, 11, 1e, 01, 00, 02, 00, 10, 00, 11, 1e, 00, 15, 00, 16, 30, 15, 1a, 02, 00, 00, 00, 15, 00, 16, 17, 00, 19, 00, 1d, 1a, 00, 27, 00, 2c, 0d, 00, 2f, 02, 06, 2b, 02, 0c, 02, 06, 27, 03, 01, 00, 02]
@@ -101,6 +102,7 @@ Number of file 0 mappings: 14
     = (c2 + (c0 - c1))
 - Code(Expression(9, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c5
 
 Function name: nested_if::nested_in_then_block_in_condition
 Raw bytes (176): 0x[01, 01, 12, 01, 05, 05, 11, 05, 11, 3a, 15, 05, 11, 11, 15, 33, 19, 11, 15, 19, 1d, 19, 1d, 1d, 2e, 33, 19, 11, 15, 3a, 15, 05, 11, 09, 02, 0d, 47, 09, 02, 14, 01, 22, 01, 01, 09, 28, 09, 02, 01, 08, 00, 4b, 30, 05, 02, 01, 02, 00, 00, 08, 00, 09, 30, 0d, 09, 02, 00, 00, 00, 0d, 00, 4b, 05, 00, 10, 00, 11, 28, 03, 02, 00, 10, 00, 16, 30, 11, 3a, 01, 00, 02, 00, 10, 00, 11, 3a, 00, 15, 00, 16, 30, 15, 36, 02, 00, 00, 00, 15, 00, 16, 33, 00, 1c, 00, 1d, 28, 06, 02, 00, 1c, 00, 22, 30, 19, 2e, 01, 02, 00, 00, 1c, 00, 1d, 19, 00, 21, 00, 22, 30, 26, 1d, 02, 00, 00, 00, 21, 00, 22, 26, 00, 25, 00, 29, 2b, 00, 33, 00, 38, 36, 00, 44, 00, 49, 0d, 00, 4c, 02, 06, 47, 02, 0c, 02, 06, 43, 03, 01, 00, 02]
@@ -165,6 +167,7 @@ Number of file 0 mappings: 20
     = (c2 + (c0 - c1))
 - Code(Expression(16, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c7
 
 Function name: nested_if::nested_single_condition_decision
 Raw bytes (85): 0x[01, 01, 06, 01, 05, 05, 11, 05, 11, 09, 02, 0d, 17, 09, 02, 0b, 01, 17, 01, 04, 09, 28, 03, 02, 04, 08, 00, 29, 30, 05, 02, 01, 02, 00, 00, 08, 00, 09, 30, 0d, 09, 02, 00, 00, 00, 0d, 00, 29, 05, 00, 10, 00, 11, 20, 11, 0a, 00, 10, 00, 11, 11, 00, 14, 00, 19, 0a, 00, 23, 00, 27, 0d, 00, 2a, 02, 06, 17, 02, 0c, 02, 06, 13, 03, 01, 00, 02]
@@ -198,4 +201,5 @@ Number of file 0 mappings: 11
     = (c2 + (c0 - c1))
 - Code(Expression(4, Add)) at (prev + 3, 1) to (start + 0, 2)
     = (c3 + (c2 + (c0 - c1)))
+Highest counter ID seen: c4
 
diff --git a/tests/coverage/mcdc/non_control_flow.cov-map b/tests/coverage/mcdc/non_control_flow.cov-map
index d5383a197616b..677e31e404e42 100644
--- a/tests/coverage/mcdc/non_control_flow.cov-map
+++ b/tests/coverage/mcdc/non_control_flow.cov-map
@@ -33,6 +33,7 @@ Number of file 0 mappings: 10
     false = c3
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = (c1 + ((c2 + c3) + c4))
+Highest counter ID seen: c4
 
 Function name: non_control_flow::assign_3_bis
 Raw bytes (85): 0x[01, 01, 07, 07, 11, 09, 0d, 01, 05, 05, 09, 16, 1a, 05, 09, 01, 05, 0a, 01, 1b, 01, 00, 2c, 03, 01, 09, 00, 0a, 01, 00, 0d, 00, 0e, 28, 05, 03, 00, 0d, 00, 18, 30, 05, 1a, 01, 03, 02, 00, 0d, 00, 0e, 05, 00, 12, 00, 13, 30, 09, 16, 03, 00, 02, 00, 12, 00, 13, 13, 00, 17, 00, 18, 30, 0d, 11, 02, 00, 00, 00, 17, 00, 18, 03, 01, 05, 01, 02]
@@ -66,6 +67,7 @@ Number of file 0 mappings: 10
     false = c4
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = ((c2 + c3) + c4)
+Highest counter ID seen: c4
 
 Function name: non_control_flow::assign_and
 Raw bytes (64): 0x[01, 01, 04, 07, 0e, 09, 0d, 01, 05, 01, 05, 08, 01, 0c, 01, 00, 21, 03, 01, 09, 00, 0a, 01, 00, 0d, 00, 0e, 28, 03, 02, 00, 0d, 00, 13, 30, 05, 0e, 01, 02, 00, 00, 0d, 00, 0e, 05, 00, 12, 00, 13, 30, 09, 0d, 02, 00, 00, 00, 12, 00, 13, 03, 01, 05, 01, 02]
@@ -91,6 +93,7 @@ Number of file 0 mappings: 8
     false = c3
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = ((c2 + c3) + (c0 - c1))
+Highest counter ID seen: c3
 
 Function name: non_control_flow::assign_or
 Raw bytes (64): 0x[01, 01, 04, 07, 0d, 05, 09, 01, 05, 01, 05, 08, 01, 11, 01, 00, 20, 03, 01, 09, 00, 0a, 01, 00, 0d, 00, 0e, 28, 03, 02, 00, 0d, 00, 13, 30, 05, 0e, 01, 00, 02, 00, 0d, 00, 0e, 0e, 00, 12, 00, 13, 30, 09, 0d, 02, 00, 00, 00, 12, 00, 13, 03, 01, 05, 01, 02]
@@ -117,6 +120,7 @@ Number of file 0 mappings: 8
     false = c3
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = ((c1 + c2) + c3)
+Highest counter ID seen: c3
 
 Function name: non_control_flow::foo
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 25, 01, 02, 02]
@@ -125,6 +129,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 37, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: non_control_flow::func_call
 Raw bytes (52): 0x[01, 01, 03, 01, 05, 0b, 02, 09, 0d, 06, 01, 29, 01, 01, 0a, 28, 03, 02, 01, 09, 00, 0f, 30, 05, 02, 01, 02, 00, 00, 09, 00, 0a, 05, 00, 0e, 00, 0f, 30, 09, 0d, 02, 00, 00, 00, 0e, 00, 0f, 07, 01, 01, 00, 02]
@@ -146,6 +151,7 @@ Number of file 0 mappings: 6
     false = c3
 - Code(Expression(1, Add)) at (prev + 1, 1) to (start + 0, 2)
     = ((c2 + c3) + (c0 - c1))
+Highest counter ID seen: c3
 
 Function name: non_control_flow::right_comb_tree
 Raw bytes (139): 0x[01, 01, 13, 07, 1a, 0b, 19, 0f, 15, 13, 11, 09, 0d, 01, 05, 01, 05, 05, 19, 05, 19, 4a, 15, 05, 19, 4a, 15, 05, 19, 46, 11, 4a, 15, 05, 19, 46, 11, 4a, 15, 05, 19, 0e, 01, 20, 01, 00, 41, 03, 01, 09, 00, 0a, 01, 00, 0d, 00, 0e, 28, 06, 05, 00, 0d, 00, 2a, 30, 05, 1a, 01, 02, 00, 00, 0d, 00, 0e, 05, 00, 13, 00, 14, 30, 4a, 19, 02, 03, 00, 00, 13, 00, 14, 4a, 00, 19, 00, 1a, 30, 46, 15, 03, 04, 00, 00, 19, 00, 1a, 46, 00, 1f, 00, 20, 30, 42, 11, 04, 05, 00, 00, 1f, 00, 20, 42, 00, 24, 00, 27, 30, 09, 0d, 05, 00, 00, 00, 24, 00, 27, 03, 01, 05, 01, 02]
@@ -201,4 +207,5 @@ Number of file 0 mappings: 14
     false = c3
 - Code(Expression(0, Add)) at (prev + 1, 5) to (start + 1, 2)
     = (((((c2 + c3) + c4) + c5) + c6) + (c0 - c1))
+Highest counter ID seen: c6
 
diff --git a/tests/coverage/nested_loops.cov-map b/tests/coverage/nested_loops.cov-map
index 35d92594e75e3..c145d4c58433b 100644
--- a/tests/coverage/nested_loops.cov-map
+++ b/tests/coverage/nested_loops.cov-map
@@ -48,4 +48,5 @@ Number of file 0 mappings: 13
     = (c1 + c2)
 - Code(Expression(22, Add)) at (prev + 2, 1) to (start + 0, 2)
     = (c4 + c3)
+Highest counter ID seen: c6
 
diff --git a/tests/coverage/no_cov_crate.cov-map b/tests/coverage/no_cov_crate.cov-map
index 75234f6c3b7ba..28d0d9ff8ab1d 100644
--- a/tests/coverage/no_cov_crate.cov-map
+++ b/tests/coverage/no_cov_crate.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 20, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: no_cov_crate::add_coverage_2
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 18, 01, 02, 02]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 24, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: no_cov_crate::add_coverage_not_called (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 1d, 01, 02, 02]
@@ -21,6 +23,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 29, 1) to (start + 2, 2)
+Highest counter ID seen: (none)
 
 Function name: no_cov_crate::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 4d, 01, 0b, 02]
@@ -29,6 +32,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 77, 1) to (start + 11, 2)
+Highest counter ID seen: c0
 
 Function name: no_cov_crate::nested_fns::outer
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 31, 05, 02, 23, 01, 0c, 05, 00, 06]
@@ -38,6 +42,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 49, 5) to (start + 2, 35)
 - Code(Counter(0)) at (prev + 12, 5) to (start + 0, 6)
+Highest counter ID seen: c0
 
 Function name: no_cov_crate::nested_fns::outer_both_covered
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 3f, 05, 02, 17, 01, 0b, 05, 00, 06]
@@ -47,6 +52,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 63, 5) to (start + 2, 23)
 - Code(Counter(0)) at (prev + 11, 5) to (start + 0, 6)
+Highest counter ID seen: c0
 
 Function name: no_cov_crate::nested_fns::outer_both_covered::inner
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 43, 09, 01, 17, 05, 01, 18, 02, 0e, 02, 02, 14, 02, 0e, 01, 03, 09, 00, 0a]
@@ -60,4 +66,5 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 20) to (start + 2, 14)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 3, 9) to (start + 0, 10)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/no_spans.cov-map b/tests/coverage/no_spans.cov-map
index 30171c3f31939..7f43b68fa9043 100644
--- a/tests/coverage/no_spans.cov-map
+++ b/tests/coverage/no_spans.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 26, 28) to (start + 0, 29)
+Highest counter ID seen: c0
 
 Function name: no_spans::affected_function::{closure#0}
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 1b, 0c, 00, 0e]
@@ -13,4 +14,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 27, 12) to (start + 0, 14)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/no_spans_if_not.cov-map b/tests/coverage/no_spans_if_not.cov-map
index bc3e14eddd546..9cb7e6a6cff2e 100644
--- a/tests/coverage/no_spans_if_not.cov-map
+++ b/tests/coverage/no_spans_if_not.cov-map
@@ -9,6 +9,7 @@ Number of file 0 mappings: 3
 - Code(Expression(0, Sub)) at (prev + 2, 13) to (start + 0, 15)
     = (c0 - Zero)
 - Code(Zero) at (prev + 2, 13) to (start + 0, 15)
+Highest counter ID seen: c0
 
 Function name: no_spans_if_not::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 0b, 01, 02, 02]
@@ -17,4 +18,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 11, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/overflow.cov-map b/tests/coverage/overflow.cov-map
index cb31f3d1f3e4d..f842ce3e896b1 100644
--- a/tests/coverage/overflow.cov-map
+++ b/tests/coverage/overflow.cov-map
@@ -25,6 +25,7 @@ Number of file 0 mappings: 9
 - Code(Expression(6, Add)) at (prev + 1, 9) to (start + 0, 23)
     = (c1 + (c2 + c3))
 - Code(Counter(4)) at (prev + 2, 5) to (start + 1, 2)
+Highest counter ID seen: c4
 
 Function name: overflow::might_overflow
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 05, 01, 01, 12, 05, 01, 13, 02, 06, 02, 02, 06, 00, 07, 01, 01, 09, 05, 02]
@@ -38,4 +39,5 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 9) to (start + 5, 2)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/panic_unwind.cov-map b/tests/coverage/panic_unwind.cov-map
index f6089ce55ae29..f4a7894cc1cc1 100644
--- a/tests/coverage/panic_unwind.cov-map
+++ b/tests/coverage/panic_unwind.cov-map
@@ -25,6 +25,7 @@ Number of file 0 mappings: 9
 - Code(Expression(6, Add)) at (prev + 1, 9) to (start + 0, 23)
     = (c1 + (c2 + c3))
 - Code(Counter(4)) at (prev + 2, 5) to (start + 1, 2)
+Highest counter ID seen: c4
 
 Function name: panic_unwind::might_panic
 Raw bytes (21): 0x[01, 01, 01, 01, 05, 03, 01, 04, 01, 01, 14, 05, 02, 09, 01, 19, 02, 02, 0c, 03, 02]
@@ -37,4 +38,5 @@ Number of file 0 mappings: 3
 - Code(Counter(1)) at (prev + 2, 9) to (start + 1, 25)
 - Code(Expression(0, Sub)) at (prev + 2, 12) to (start + 3, 2)
     = (c0 - c1)
+Highest counter ID seen: c1
 
diff --git a/tests/coverage/partial_eq.cov-map b/tests/coverage/partial_eq.cov-map
index 6c39ac0e378b8..21c8714ac99ba 100644
--- a/tests/coverage/partial_eq.cov-map
+++ b/tests/coverage/partial_eq.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 12, 5) to (start + 2, 6)
+Highest counter ID seen: c0
 
 Function name: partial_eq::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 11, 01, 0a, 02]
@@ -13,4 +14,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 17, 1) to (start + 10, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/simple_loop.cov-map b/tests/coverage/simple_loop.cov-map
index 541f7bf8fbdcb..b6f1e8f6afe6a 100644
--- a/tests/coverage/simple_loop.cov-map
+++ b/tests/coverage/simple_loop.cov-map
@@ -15,4 +15,5 @@ Number of file 0 mappings: 7
 - Code(Counter(0)) at (prev + 4, 13) to (start + 0, 18)
 - Code(Counter(2)) at (prev + 2, 10) to (start + 3, 10)
 - Code(Counter(0)) at (prev + 6, 1) to (start + 0, 2)
+Highest counter ID seen: c2
 
diff --git a/tests/coverage/simple_match.cov-map b/tests/coverage/simple_match.cov-map
index 49819b23482f3..b62edf12650ca 100644
--- a/tests/coverage/simple_match.cov-map
+++ b/tests/coverage/simple_match.cov-map
@@ -27,4 +27,5 @@ Number of file 0 mappings: 10
 - Code(Counter(2)) at (prev + 4, 13) to (start + 7, 14)
 - Code(Counter(3)) at (prev + 10, 13) to (start + 0, 15)
 - Code(Counter(4)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c4
 
diff --git a/tests/coverage/sort_groups.cov-map b/tests/coverage/sort_groups.cov-map
index 361b70fb74f76..4e7ed059c879d 100644
--- a/tests/coverage/sort_groups.cov-map
+++ b/tests/coverage/sort_groups.cov-map
@@ -10,6 +10,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: sort_groups::generic_fn::<()>
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 11, 01, 01, 0c, 05, 01, 0d, 02, 06, 02, 02, 06, 00, 07, 01, 01, 01, 00, 02]
@@ -23,6 +24,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: sort_groups::generic_fn::<char>
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 11, 01, 01, 0c, 05, 01, 0d, 02, 06, 02, 02, 06, 00, 07, 01, 01, 01, 00, 02]
@@ -36,6 +38,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: sort_groups::generic_fn::<i32>
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 11, 01, 01, 0c, 05, 01, 0d, 02, 06, 02, 02, 06, 00, 07, 01, 01, 01, 00, 02]
@@ -49,6 +52,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: sort_groups::main
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 06, 01, 04, 23, 05, 04, 24, 02, 06, 02, 02, 06, 00, 07, 01, 01, 05, 02, 02]
@@ -62,6 +66,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 5) to (start + 2, 2)
+Highest counter ID seen: c1
 
 Function name: sort_groups::other_fn
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 17, 01, 00, 11]
@@ -70,4 +75,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 23, 1) to (start + 0, 17)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/test_harness.cov-map b/tests/coverage/test_harness.cov-map
index f75328b11c9ab..b513b3d054945 100644
--- a/tests/coverage/test_harness.cov-map
+++ b/tests/coverage/test_harness.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 10, 1) to (start + 0, 16)
+Highest counter ID seen: c0
 
 Function name: test_harness::unused (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 07, 01, 00, 0f]
@@ -13,4 +14,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 7, 1) to (start + 0, 15)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/thin-lto.cov-map b/tests/coverage/thin-lto.cov-map
index 1f61b805f622b..50a25628ef31d 100644
--- a/tests/coverage/thin-lto.cov-map
+++ b/tests/coverage/thin-lto.cov-map
@@ -5,4 +5,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 17)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/tight_inf_loop.cov-map b/tests/coverage/tight_inf_loop.cov-map
index 7fe3146b0809a..2d2d59bf013ec 100644
--- a/tests/coverage/tight_inf_loop.cov-map
+++ b/tests/coverage/tight_inf_loop.cov-map
@@ -9,4 +9,5 @@ Number of file 0 mappings: 3
 - Code(Zero) at (prev + 2, 9) to (start + 0, 16)
 - Code(Expression(0, Sub)) at (prev + 1, 6) to (start + 1, 2)
     = (c0 - Zero)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/trivial.cov-map b/tests/coverage/trivial.cov-map
index 874e294a1c498..05f64896d9ec9 100644
--- a/tests/coverage/trivial.cov-map
+++ b/tests/coverage/trivial.cov-map
@@ -5,4 +5,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 13)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/try_error_result.cov-map b/tests/coverage/try_error_result.cov-map
index 11a99f5395ec8..246a1ba738b28 100644
--- a/tests/coverage/try_error_result.cov-map
+++ b/tests/coverage/try_error_result.cov-map
@@ -10,6 +10,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 13) to (start + 0, 26)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 5) to (start + 0, 6)
+Highest counter ID seen: c1
 
 Function name: <try_error_result::Thing2>::call
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 34, 05, 01, 18, 05, 02, 0d, 00, 14, 02, 02, 0d, 00, 13, 01, 02, 05, 00, 06]
@@ -23,6 +24,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 13) to (start + 0, 19)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 5) to (start + 0, 6)
+Highest counter ID seen: c1
 
 Function name: try_error_result::call
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 05, 01, 01, 14, 05, 02, 09, 00, 10, 02, 02, 09, 00, 0f, 01, 02, 01, 00, 02]
@@ -36,6 +38,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 9) to (start + 0, 15)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: try_error_result::main
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 71, 01, 02, 0c, 05, 03, 05, 00, 06, 02, 02, 05, 00, 0b, 01, 01, 01, 00, 02]
@@ -49,6 +52,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 5) to (start + 0, 11)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: c1
 
 Function name: try_error_result::test1
 Raw bytes (75): 0x[01, 01, 08, 01, 07, 00, 09, 03, 0d, 12, 1d, 03, 0d, 1b, 0d, 1f, 00, 11, 00, 0b, 01, 0d, 01, 02, 17, 03, 07, 09, 00, 0e, 12, 02, 09, 04, 1a, 1d, 06, 0d, 00, 29, 11, 00, 29, 00, 2a, 00, 01, 0d, 00, 2a, 00, 00, 2a, 00, 2b, 0e, 04, 0d, 00, 2a, 00, 00, 2a, 00, 2b, 0d, 03, 05, 00, 0b, 17, 01, 01, 00, 02]
@@ -79,6 +83,7 @@ Number of file 0 mappings: 11
 - Code(Counter(3)) at (prev + 3, 5) to (start + 0, 11)
 - Code(Expression(5, Add)) at (prev + 1, 1) to (start + 0, 2)
     = (((c4 + Zero) + Zero) + c3)
+Highest counter ID seen: c7
 
 Function name: try_error_result::test2
 Raw bytes (358): 0x[01, 01, 3b, 01, 07, 05, 09, 03, 0d, 41, 11, 4a, 15, 41, 11, 42, 1d, 46, 19, 4a, 15, 41, 11, 4a, 15, 41, 11, 46, 19, 4a, 15, 41, 11, 42, 1d, 46, 19, 4a, 15, 41, 11, 5e, 25, 49, 21, 49, 21, 5e, 25, 49, 21, 8a, 01, 2d, 8e, 01, 29, 92, 01, 41, 03, 0d, 92, 01, 41, 03, 0d, 8e, 01, 29, 92, 01, 41, 03, 0d, 8a, 01, 2d, 8e, 01, 29, 92, 01, 41, 03, 0d, a6, 01, 35, 45, 31, 45, 31, a6, 01, 35, 45, 31, ba, 01, 3d, 4d, 39, 4d, 39, ba, 01, 3d, 4d, 39, c3, 01, 0d, c7, 01, db, 01, cb, 01, cf, 01, 11, 15, d3, 01, d7, 01, 19, 1d, 21, 25, df, 01, e3, 01, 29, 2d, e7, 01, eb, 01, 31, 35, 39, 3d, 28, 01, 3d, 01, 03, 17, 03, 08, 09, 00, 0e, 92, 01, 02, 09, 04, 1a, 41, 06, 0d, 00, 2f, 11, 00, 2f, 00, 30, 4a, 00, 31, 03, 35, 15, 04, 11, 00, 12, 46, 02, 11, 04, 12, 3e, 05, 11, 00, 14, 46, 00, 17, 00, 41, 19, 00, 41, 00, 42, 42, 00, 43, 00, 5f, 1d, 00, 5f, 00, 60, 3e, 01, 0d, 00, 20, 5a, 01, 11, 00, 14, 49, 00, 17, 00, 41, 21, 00, 41, 00, 42, 5e, 00, 43, 00, 60, 25, 00, 60, 00, 61, 5a, 01, 0d, 00, 20, 86, 01, 04, 11, 00, 14, 8e, 01, 00, 17, 00, 42, 29, 00, 42, 00, 43, 8a, 01, 00, 44, 00, 61, 2d, 00, 61, 00, 62, 86, 01, 01, 0d, 00, 20, a2, 01, 01, 11, 00, 14, 45, 00, 17, 01, 36, 31, 01, 36, 00, 37, a6, 01, 01, 12, 00, 2f, 35, 00, 2f, 00, 30, a2, 01, 01, 0d, 00, 20, b6, 01, 01, 11, 00, 14, 4d, 00, 17, 01, 36, 39, 02, 11, 00, 12, ba, 01, 01, 12, 00, 2f, 3d, 01, 11, 00, 12, b6, 01, 02, 0d, 00, 20, 0d, 03, 05, 00, 0b, bf, 01, 01, 01, 00, 02]
@@ -207,4 +212,5 @@ Number of file 0 mappings: 40
 - Code(Counter(3)) at (prev + 3, 5) to (start + 0, 11)
 - Code(Expression(47, Add)) at (prev + 1, 1) to (start + 0, 2)
     = ((((c4 + c5) + ((c6 + c7) + (c8 + c9))) + ((c10 + c11) + ((c12 + c13) + (c14 + c15)))) + c3)
+Highest counter ID seen: c19
 
diff --git a/tests/coverage/unicode.cov-map b/tests/coverage/unicode.cov-map
index 06a2c930498b5..ac4e691ea7abf 100644
--- a/tests/coverage/unicode.cov-map
+++ b/tests/coverage/unicode.cov-map
@@ -22,6 +22,7 @@ Number of file 0 mappings: 9
     = ((c0 - c2) + c3)
 - Code(Expression(3, Add)) at (prev + 2, 5) to (start + 1, 2)
     = (c4 + ((c0 - c2) + c3))
+Highest counter ID seen: c4
 
 Function name: unicode::他 (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 1e, 19, 00, 25]
@@ -30,6 +31,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 30, 25) to (start + 0, 37)
+Highest counter ID seen: (none)
 
 Function name: unicode::申し訳ございません
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 18, 01, 02, 02]
@@ -38,4 +40,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 24, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/unreachable.cov-map b/tests/coverage/unreachable.cov-map
index 09d3b2345431b..d4a5936a78483 100644
--- a/tests/coverage/unreachable.cov-map
+++ b/tests/coverage/unreachable.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 15, 39) to (start + 0, 71)
+Highest counter ID seen: (none)
 
 Function name: unreachable::unreachable_function (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 11, 01, 01, 25]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 17, 1) to (start + 1, 37)
+Highest counter ID seen: (none)
 
 Function name: unreachable::unreachable_intrinsic (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 16, 01, 01, 2c]
@@ -21,4 +23,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 22, 1) to (start + 1, 44)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/unused.cov-map b/tests/coverage/unused.cov-map
index 9383d1e90ac20..9f1ad59ce83dd 100644
--- a/tests/coverage/unused.cov-map
+++ b/tests/coverage/unused.cov-map
@@ -17,6 +17,7 @@ Number of file 0 mappings: 6
 - Code(Expression(3, Add)) at (prev + 1, 9) to (start + 0, 15)
     = (c1 + c2)
 - Code(Counter(3)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c3
 
 Function name: unused::foo::<u32>
 Raw bytes (42): 0x[01, 01, 04, 01, 0f, 05, 09, 03, 0d, 05, 09, 06, 01, 03, 01, 01, 12, 03, 02, 0b, 00, 11, 0a, 01, 09, 00, 0f, 09, 00, 13, 00, 19, 0f, 01, 09, 00, 0f, 0d, 02, 01, 00, 02]
@@ -37,6 +38,7 @@ Number of file 0 mappings: 6
 - Code(Expression(3, Add)) at (prev + 1, 9) to (start + 0, 15)
     = (c1 + c2)
 - Code(Counter(3)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c3
 
 Function name: unused::main
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 25, 01, 04, 02]
@@ -45,6 +47,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 37, 1) to (start + 4, 2)
+Highest counter ID seen: c0
 
 Function name: unused::unused_func (unused)
 Raw bytes (24): 0x[01, 01, 00, 04, 00, 13, 01, 01, 0e, 00, 01, 0f, 02, 06, 00, 02, 06, 00, 07, 00, 01, 01, 00, 02]
@@ -56,6 +59,7 @@ Number of file 0 mappings: 4
 - Code(Zero) at (prev + 1, 15) to (start + 2, 6)
 - Code(Zero) at (prev + 2, 6) to (start + 0, 7)
 - Code(Zero) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
 Function name: unused::unused_func2 (unused)
 Raw bytes (24): 0x[01, 01, 00, 04, 00, 19, 01, 01, 0e, 00, 01, 0f, 02, 06, 00, 02, 06, 00, 07, 00, 01, 01, 00, 02]
@@ -67,6 +71,7 @@ Number of file 0 mappings: 4
 - Code(Zero) at (prev + 1, 15) to (start + 2, 6)
 - Code(Zero) at (prev + 2, 6) to (start + 0, 7)
 - Code(Zero) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
 Function name: unused::unused_func3 (unused)
 Raw bytes (24): 0x[01, 01, 00, 04, 00, 1f, 01, 01, 0e, 00, 01, 0f, 02, 06, 00, 02, 06, 00, 07, 00, 01, 01, 00, 02]
@@ -78,6 +83,7 @@ Number of file 0 mappings: 4
 - Code(Zero) at (prev + 1, 15) to (start + 2, 6)
 - Code(Zero) at (prev + 2, 6) to (start + 0, 7)
 - Code(Zero) at (prev + 1, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
 Function name: unused::unused_template_func::<_> (unused)
 Raw bytes (34): 0x[01, 01, 00, 06, 00, 0b, 01, 01, 12, 00, 02, 0b, 00, 11, 00, 01, 09, 00, 0f, 00, 00, 13, 00, 19, 00, 01, 09, 00, 0f, 00, 02, 01, 00, 02]
@@ -91,4 +97,5 @@ Number of file 0 mappings: 6
 - Code(Zero) at (prev + 0, 19) to (start + 0, 25)
 - Code(Zero) at (prev + 1, 9) to (start + 0, 15)
 - Code(Zero) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/unused_mod.cov-map b/tests/coverage/unused_mod.cov-map
index 241cb2610ffc0..af10906fa3c54 100644
--- a/tests/coverage/unused_mod.cov-map
+++ b/tests/coverage/unused_mod.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 4, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: unused_mod::unused_module::never_called_function (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 02, 01, 02, 02]
@@ -13,4 +14,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Zero) at (prev + 2, 1) to (start + 2, 2)
+Highest counter ID seen: (none)
 
diff --git a/tests/coverage/uses_crate.cov-map b/tests/coverage/uses_crate.cov-map
index 9c06eab700507..5c23f88269714 100644
--- a/tests/coverage/uses_crate.cov-map
+++ b/tests/coverage/uses_crate.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 27, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: used_crate::used_only_from_bin_crate_generic_function::<&alloc::vec::Vec<i32>>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 13, 01, 02, 02]
@@ -13,6 +14,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 19, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: used_crate::used_only_from_bin_crate_generic_function::<&str>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 13, 01, 02, 02]
@@ -21,6 +23,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 19, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: used_crate::used_with_same_type_from_bin_crate_and_lib_crate_generic_function::<&str>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 1f, 01, 02, 02]
@@ -29,6 +32,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 31, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: uses_crate::main
 Raw bytes (9): 0x[01, 02, 00, 01, 01, 0c, 01, 07, 02]
@@ -37,4 +41,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 12, 1) to (start + 7, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/uses_inline_crate.cov-map b/tests/coverage/uses_inline_crate.cov-map
index 55ceb46b0602d..a6909768162bd 100644
--- a/tests/coverage/uses_inline_crate.cov-map
+++ b/tests/coverage/uses_inline_crate.cov-map
@@ -5,6 +5,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 44, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: used_inline_crate::used_inline_function
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 14, 01, 06, 0f, 05, 06, 10, 02, 06, 02, 02, 06, 00, 07, 01, 01, 05, 01, 02]
@@ -18,6 +19,7 @@ Number of file 0 mappings: 4
 - Code(Expression(0, Sub)) at (prev + 2, 6) to (start + 0, 7)
     = (c0 - c1)
 - Code(Counter(0)) at (prev + 1, 5) to (start + 1, 2)
+Highest counter ID seen: c1
 
 Function name: used_inline_crate::used_only_from_bin_crate_generic_function::<&alloc::vec::Vec<i32>>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 21, 01, 02, 02]
@@ -26,6 +28,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 33, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: used_inline_crate::used_only_from_bin_crate_generic_function::<&str>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 21, 01, 02, 02]
@@ -34,6 +37,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 33, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: used_inline_crate::used_with_same_type_from_bin_crate_and_lib_crate_generic_function::<&str>
 Raw bytes (9): 0x[01, 01, 00, 01, 01, 31, 01, 02, 02]
@@ -42,6 +46,7 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 49, 1) to (start + 2, 2)
+Highest counter ID seen: c0
 
 Function name: uses_inline_crate::main
 Raw bytes (9): 0x[01, 02, 00, 01, 01, 0c, 01, 0a, 02]
@@ -50,4 +55,5 @@ Number of files: 1
 Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 12, 1) to (start + 10, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/while.cov-map b/tests/coverage/while.cov-map
index 4d813a935a058..29493a651dcbb 100644
--- a/tests/coverage/while.cov-map
+++ b/tests/coverage/while.cov-map
@@ -10,4 +10,5 @@ Number of file 0 mappings: 4
     = (c0 + Zero)
 - Code(Zero) at (prev + 0, 21) to (start + 2, 6)
 - Code(Counter(0)) at (prev + 3, 1) to (start + 0, 2)
+Highest counter ID seen: c0
 
diff --git a/tests/coverage/while_early_ret.cov-map b/tests/coverage/while_early_ret.cov-map
index c883eb4baf200..6254dfbcf010e 100644
--- a/tests/coverage/while_early_ret.cov-map
+++ b/tests/coverage/while_early_ret.cov-map
@@ -23,4 +23,5 @@ Number of file 0 mappings: 9
 - Code(Counter(2)) at (prev + 6, 5) to (start + 0, 11)
 - Code(Expression(4, Add)) at (prev + 1, 1) to (start + 0, 2)
     = ((c3 + c4) + c2)
+Highest counter ID seen: c4
 
diff --git a/tests/coverage/yield.cov-map b/tests/coverage/yield.cov-map
index a273c688e248a..578994a45305d 100644
--- a/tests/coverage/yield.cov-map
+++ b/tests/coverage/yield.cov-map
@@ -39,6 +39,7 @@ Number of file 0 mappings: 16
 - Code(Expression(10, Add)) at (prev + 1, 14) to (start + 0, 52)
     = (c9 + c10)
 - Code(Counter(11)) at (prev + 2, 1) to (start + 0, 2)
+Highest counter ID seen: c11
 
 Function name: yield::main::{closure#0}
 Raw bytes (14): 0x[01, 01, 00, 02, 01, 09, 08, 01, 10, 05, 02, 10, 01, 06]
@@ -48,6 +49,7 @@ Number of expressions: 0
 Number of file 0 mappings: 2
 - Code(Counter(0)) at (prev + 9, 8) to (start + 1, 16)
 - Code(Counter(1)) at (prev + 2, 16) to (start + 1, 6)
+Highest counter ID seen: c1
 
 Function name: yield::main::{closure#1}
 Raw bytes (24): 0x[01, 01, 00, 04, 01, 18, 08, 01, 10, 05, 02, 09, 00, 10, 09, 01, 09, 00, 10, 0d, 01, 10, 01, 06]
@@ -59,4 +61,5 @@ Number of file 0 mappings: 4
 - Code(Counter(1)) at (prev + 2, 9) to (start + 0, 16)
 - Code(Counter(2)) at (prev + 1, 9) to (start + 0, 16)
 - Code(Counter(3)) at (prev + 1, 16) to (start + 1, 6)
+Highest counter ID seen: c3