3 files changed, 25 insertions, 74 deletions
diff --git a/compiler/rustc_mir_transform/src/coverage/counters.rs b/compiler/rustc_mir_transform/src/coverage/counters.rs
index 77e3dee1fef..938c4b2bd3f 100644
--- a/compiler/rustc_mir_transform/src/coverage/counters.rs
+++ b/compiler/rustc_mir_transform/src/coverage/counters.rs
@@ -126,6 +126,14 @@ impl CoverageCounters {
         next
     }
 
+    pub(super) fn num_counters(&self) -> usize {
+        self.next_counter_id.as_usize()
+    }
+
+    pub(super) fn num_expressions(&self) -> usize {
+        self.next_expression_id.as_usize()
+    }
+
     fn set_bcb_counter(
         &mut self,
         bcb: BasicCoverageBlock,
diff --git a/compiler/rustc_mir_transform/src/coverage/mod.rs b/compiler/rustc_mir_transform/src/coverage/mod.rs
index 1ce6ecc3bb5..e1b656bd981 100644
--- a/compiler/rustc_mir_transform/src/coverage/mod.rs
+++ b/compiler/rustc_mir_transform/src/coverage/mod.rs
@@ -214,6 +214,8 @@ impl<'a, 'tcx> Instrumentor<'a, 'tcx> {
 
         self.mir_body.function_coverage_info = Some(Box::new(FunctionCoverageInfo {
             function_source_hash: self.function_source_hash,
+            num_counters: self.coverage_counters.num_counters(),
+            num_expressions: self.coverage_counters.num_expressions(),
         }));
     }
 
diff --git a/compiler/rustc_mir_transform/src/coverage/query.rs b/compiler/rustc_mir_transform/src/coverage/query.rs
index 2c0164e765c..b1f46c8e05c 100644
--- a/compiler/rustc_mir_transform/src/coverage/query.rs
+++ b/compiler/rustc_mir_transform/src/coverage/query.rs
@@ -2,92 +2,33 @@ use super::*;
 
 use rustc_data_structures::captures::Captures;
 use rustc_middle::mir::coverage::*;
-use rustc_middle::mir::{self, Body, Coverage, CoverageInfo};
+use rustc_middle::mir::{self, Body, Coverage, CoverageIdsInfo};
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::def_id::DefId;
 
 /// A `query` provider for retrieving coverage information injected into MIR.
 pub(crate) fn provide(providers: &mut Providers) {
-    providers.coverageinfo = |tcx, def_id| coverageinfo(tcx, def_id);
+    providers.coverage_ids_info = |tcx, def_id| coverage_ids_info(tcx, def_id);
     providers.covered_code_regions = |tcx, def_id| covered_code_regions(tcx, def_id);
 }
 
-/// Coverage codegen needs to know the total number of counter IDs and expression IDs that have
-/// been used by a function's coverage mappings. These totals are used to create vectors to hold
-/// the relevant counter and expression data, and the maximum counter ID (+ 1) is also needed by
-/// the `llvm.instrprof.increment` intrinsic.
-///
-/// MIR optimization may split and duplicate some BasicBlock sequences, or optimize out some code
-/// including injected counters. (It is OK if some counters are optimized out, but those counters
-/// are still included in the total `num_counters` or `num_expressions`.) Simply counting the
-/// calls may not work; but computing the number of counters or expressions by adding `1` to the
-/// highest ID (for a given instrumented function) is valid.
-///
-/// It's possible for a coverage expression to remain in MIR while one or both of its operands
-/// have been optimized away. To avoid problems in codegen, we include those operands' IDs when
-/// determining the maximum counter/expression ID, even if the underlying counter/expression is
-/// no longer present.
-struct CoverageVisitor {
-    max_counter_id: CounterId,
-    max_expression_id: ExpressionId,
-}
-
-impl CoverageVisitor {
-    /// Updates `max_counter_id` to the maximum encountered counter ID.
-    #[inline(always)]
-    fn update_max_counter_id(&mut self, counter_id: CounterId) {
-        self.max_counter_id = self.max_counter_id.max(counter_id);
-    }
-
-    /// Updates `max_expression_id` to the maximum encountered expression ID.
-    #[inline(always)]
-    fn update_max_expression_id(&mut self, expression_id: ExpressionId) {
-        self.max_expression_id = self.max_expression_id.max(expression_id);
-    }
-
-    fn update_from_expression_operand(&mut self, operand: Operand) {
-        match operand {
-            Operand::Counter(id) => self.update_max_counter_id(id),
-            Operand::Expression(id) => self.update_max_expression_id(id),
-            Operand::Zero => {}
-        }
-    }
-
-    fn visit_body(&mut self, body: &Body<'_>) {
-        for coverage in all_coverage_in_mir_body(body) {
-            self.visit_coverage(coverage);
-        }
-    }
-
-    fn visit_coverage(&mut self, coverage: &Coverage) {
-        match coverage.kind {
-            CoverageKind::Counter { id, .. } => self.update_max_counter_id(id),
-            CoverageKind::Expression { id, lhs, rhs, .. } => {
-                self.update_max_expression_id(id);
-                self.update_from_expression_operand(lhs);
-                self.update_from_expression_operand(rhs);
-            }
-            CoverageKind::Unreachable => {}
-        }
-    }
-}
-
-fn coverageinfo<'tcx>(tcx: TyCtxt<'tcx>, instance_def: ty::InstanceDef<'tcx>) -> CoverageInfo {
+/// Query implementation for `coverage_ids_info`.
+fn coverage_ids_info<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    instance_def: ty::InstanceDef<'tcx>,
+) -> CoverageIdsInfo {
     let mir_body = tcx.instance_mir(instance_def);
 
-    let mut coverage_visitor = CoverageVisitor {
-        max_counter_id: CounterId::START,
-        max_expression_id: ExpressionId::START,
-    };
-
-    coverage_visitor.visit_body(mir_body);
+    let max_counter_id = all_coverage_in_mir_body(mir_body)
+        .filter_map(|coverage| match coverage.kind {
+            CoverageKind::Counter { id } => Some(id),
+            _ => None,
+        })
+        .max()
+        .unwrap_or(CounterId::START);
 
-    // Add 1 to the highest IDs to get the total number of IDs.
-    CoverageInfo {
-        num_counters: (coverage_visitor.max_counter_id + 1).as_u32(),
-        num_expressions: (coverage_visitor.max_expression_id + 1).as_u32(),
-    }
+    CoverageIdsInfo { max_counter_id }
 }
 
 fn covered_code_regions(tcx: TyCtxt<'_>, def_id: DefId) -> Vec<&CodeRegion> {