[Coverage][MCDC] Prepare MCDC Builder for pattern matching and llvm 19

compiler/rustc_middle/src/mir/coverage.rs

@@ -50,7 +50,6 @@ rustc_index::newtype_index! {
     #[debug_format = "ExpressionId({})"]
     pub struct ExpressionId {}
 }
-
 rustc_index::newtype_index! {
     /// ID of a mcdc condition. Used by llvm to check mcdc coverage.
     ///
@@ -275,8 +274,10 @@ pub struct CoverageInfoHi {
     /// data structures without having to scan the entire body first.
     pub num_block_markers: usize,
     pub branch_spans: Vec<BranchSpan>,
-    pub mcdc_branch_spans: Vec<MCDCBranchSpan>,
-    pub mcdc_decision_spans: Vec<MCDCDecisionSpan>,
+    /// Branch spans generated by mcdc. Because of some limits mcdc builder give up generating
+    /// decisions including them so that they are handled as normal branch spans.
+    pub mcdc_degraded_spans: Vec<MCDCBranchSpan>,
+    pub mcdc_spans: Vec<(MCDCDecisionSpan, Vec<MCDCBranchSpan>)>,
 }
 
 #[derive(Clone, Debug)]
@@ -309,12 +310,12 @@ impl Default for ConditionInfo {
 #[derive(TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct MCDCBranchSpan {
     pub span: Span,
-    /// If `None`, this actually represents a normal branch span inserted for
-    /// code that was too complex for MC/DC.
-    pub condition_info: Option<ConditionInfo>,
-    pub true_marker: BlockMarkerId,
-    pub false_marker: BlockMarkerId,
-    pub decision_depth: u16,
+    pub condition_info: ConditionInfo,
+    // For boolean decisions and most pattern matching decisions there is only
+    // one true marker and one false marker in each branch. But for matching decisions
+    // with `|` there can be several.
+    pub true_markers: Vec<BlockMarkerId>,
+    pub false_markers: Vec<BlockMarkerId>,
 }
 
 #[derive(Copy, Clone, Debug)]
@@ -328,7 +329,12 @@ pub struct DecisionInfo {
 #[derive(TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct MCDCDecisionSpan {
     pub span: Span,
-    pub num_conditions: usize,
     pub end_markers: Vec<BlockMarkerId>,
     pub decision_depth: u16,
 }
+
+impl MCDCDecisionSpan {
+    pub fn new(span: Span) -> Self {
+        Self { span, end_markers: Vec::new(), decision_depth: 0 }
+    }
+}

compiler/rustc_middle/src/mir/pretty.rs

@@ -490,8 +490,8 @@ fn write_coverage_info_hi(
     let coverage::CoverageInfoHi {
         num_block_markers: _,
         branch_spans,
-        mcdc_branch_spans,
-        mcdc_decision_spans,
+        mcdc_degraded_spans,
+        mcdc_spans,
     } = coverage_info_hi;
 
     // Only add an extra trailing newline if we printed at least one thing.
@@ -505,29 +505,30 @@ fn write_coverage_info_hi(
         did_print = true;
     }
 
-    for coverage::MCDCBranchSpan {
-        span,
-        condition_info,
-        true_marker,
-        false_marker,
-        decision_depth,
-    } in mcdc_branch_spans
-    {
+    for coverage::MCDCBranchSpan { span, true_markers, false_markers, .. } in mcdc_degraded_spans {
         writeln!(
             w,
-            "{INDENT}coverage mcdc branch {{ condition_id: {:?}, true: {true_marker:?}, false: {false_marker:?}, depth: {decision_depth:?} }} => {span:?}",
-            condition_info.map(|info| info.condition_id)
+            "{INDENT}coverage branch {{ true: {true_markers:?}, false: {false_markers:?} }} => {span:?}",
         )?;
         did_print = true;
     }
 
-    for coverage::MCDCDecisionSpan { span, num_conditions, end_markers, decision_depth } in
-        mcdc_decision_spans
+    for (coverage::MCDCDecisionSpan { span, end_markers, decision_depth }, conditions) in mcdc_spans
     {
+        let num_conditions = conditions.len();
         writeln!(
             w,
             "{INDENT}coverage mcdc decision {{ num_conditions: {num_conditions:?}, end: {end_markers:?}, depth: {decision_depth:?} }} => {span:?}"
         )?;
+        for coverage::MCDCBranchSpan { span, condition_info, true_markers, false_markers } in
+            conditions
+        {
+            writeln!(
+                w,
+                "{INDENT}coverage mcdc branch {{ condition_id: {:?}, true: {true_markers:?}, false: {false_markers:?} }} => {span:?}",
+                condition_info.condition_id
+            )?;
+        }
         did_print = true;
     }
 

compiler/rustc_mir_build/messages.ftl

@@ -105,6 +105,8 @@ mir_build_deref_raw_pointer_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
 
 mir_build_exceeds_mcdc_condition_limit = number of conditions in decision ({$num_conditions}) exceeds limit ({$max_conditions}), so MC/DC analysis will not count this expression
 
+mir_build_exceeds_mcdc_decision_depth = number of decisions evaluated simultaneously exceeds limit ({$max_decision_depth}). MCDC analysis will not count this expression
+
 mir_build_extern_static_requires_unsafe =
     use of extern static is unsafe and requires unsafe block
     .note = extern statics are not controlled by the Rust type system: invalid data, aliasing violations or data races will cause undefined behavior

compiler/rustc_mir_build/src/build/coverageinfo.rs

@@ -144,10 +144,10 @@ impl CoverageInfoBuilder {
         // Separate path for handling branches when MC/DC is enabled.
         if let Some(mcdc_info) = self.mcdc_info.as_mut() {
             let inject_block_marker =
-                |source_info, block| self.markers.inject_block_marker(cfg, source_info, block);
+                |block| self.markers.inject_block_marker(cfg, source_info, block);
             mcdc_info.visit_evaluated_condition(
                 tcx,
-                source_info,
+                source_info.span,
                 true_block,
                 false_block,
                 inject_block_marker,
@@ -175,16 +175,16 @@ impl CoverageInfoBuilder {
         let branch_spans =
             branch_info.map(|branch_info| branch_info.branch_spans).unwrap_or_default();
 
-        let (mcdc_decision_spans, mcdc_branch_spans) =
+        let (mcdc_degraded_spans, mcdc_spans) =
             mcdc_info.map(MCDCInfoBuilder::into_done).unwrap_or_default();
 
         // For simplicity, always return an info struct (without Option), even
         // if there's nothing interesting in it.
         Box::new(CoverageInfoHi {
             num_block_markers,
             branch_spans,
-            mcdc_branch_spans,
-            mcdc_decision_spans,
+            mcdc_degraded_spans,
+            mcdc_spans,
         })
     }
 }