coverage: Make the zero counter a constant

Author: Zalathar

compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs

@@ -30,11 +30,8 @@ pub struct Counter {
 }
 
 impl Counter {
-    /// Constructs a new `Counter` of kind `Zero`. For this `CounterKind`, the
-    /// `id` is not used.
-    pub fn zero() -> Self {
-        Self { kind: CounterKind::Zero, id: 0 }
-    }
+    /// A `Counter` of kind `Zero`. For this counter kind, the `id` is not used.
+    pub(crate) const ZERO: Self = Self { kind: CounterKind::Zero, id: 0 };
 
     /// Constructs a new `Counter` of kind `CounterValueReference`.
     pub fn counter_value_reference(counter_id: CounterId) -> Self {
@@ -172,7 +169,7 @@ impl CounterMappingRegion {
     ) -> Self {
         Self {
             counter,
-            false_counter: Counter::zero(),
+            false_counter: Counter::ZERO,
             file_id,
             expanded_file_id: 0,
             start_line,
@@ -220,8 +217,8 @@ impl CounterMappingRegion {
         end_col: u32,
     ) -> Self {
         Self {
-            counter: Counter::zero(),
-            false_counter: Counter::zero(),
+            counter: Counter::ZERO,
+            false_counter: Counter::ZERO,
             file_id,
             expanded_file_id,
             start_line,
@@ -243,8 +240,8 @@ impl CounterMappingRegion {
         end_col: u32,
     ) -> Self {
         Self {
-            counter: Counter::zero(),
-            false_counter: Counter::zero(),
+            counter: Counter::ZERO,
+            false_counter: Counter::ZERO,
             file_id,
             expanded_file_id: 0,
             start_line,
@@ -268,7 +265,7 @@ impl CounterMappingRegion {
     ) -> Self {
         Self {
             counter,
-            false_counter: Counter::zero(),
+            false_counter: Counter::ZERO,
             file_id,
             expanded_file_id: 0,
             start_line,

compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs

@@ -191,7 +191,7 @@ impl<'tcx> FunctionCoverage<'tcx> {
         // vector is only complete up to the current `ExpressionIndex`.
         type NewIndexes = IndexSlice<ExpressionId, Option<MappedExpressionIndex>>;
         let id_to_counter = |new_indexes: &NewIndexes, operand: Operand| match operand {
-            Operand::Zero => Some(Counter::zero()),
+            Operand::Zero => Some(Counter::ZERO),
             Operand::Counter(id) => Some(Counter::counter_value_reference(id)),
             Operand::Expression(id) => {
                 self.expressions
@@ -201,7 +201,7 @@ impl<'tcx> FunctionCoverage<'tcx> {
                     // If an expression was optimized out, assume it would have produced a count
                     // of zero. This ensures that expressions dependent on optimized-out
                     // expressions are still valid.
-                    .map_or(Some(Counter::zero()), |_| new_indexes[id].map(Counter::expression))
+                    .map_or(Some(Counter::ZERO), |_| new_indexes[id].map(Counter::expression))
             }
         };
 
@@ -237,7 +237,7 @@ impl<'tcx> FunctionCoverage<'tcx> {
                         original_index={:?}, lhs={:?}, op={:?}, rhs={:?}, region={:?}",
                         original_index, lhs, op, rhs, optional_region,
                     );
-                    rhs_counter = Counter::zero();
+                    rhs_counter = Counter::ZERO;
                 }
                 debug_assert!(
                     lhs_counter.is_zero()
@@ -306,6 +306,6 @@ impl<'tcx> FunctionCoverage<'tcx> {
     }
 
     fn unreachable_regions(&self) -> impl Iterator<Item = (Counter, &CodeRegion)> {
-        self.unreachable_regions.iter().map(|region| (Counter::zero(), region))
+        self.unreachable_regions.iter().map(|region| (Counter::ZERO, region))
     }
 }