coverage. Generate Mappings of decisions and conditions for MC/DC

compiler/rustc_middle/src/mir/coverage.rs

@@ -51,6 +51,25 @@ rustc_index::newtype_index! {
     pub struct ExpressionId {}
 }
 
+rustc_index::newtype_index! {
+    /// ID of a mcdc condition. Used by llvm to check mcdc coverage.
+    ///
+    /// Note for future: the max limit of 0xFFFF is probably too loose. Actually llvm does not
+    /// support decisions with too many conditions (7 and more at LLVM 18 while may be hundreds at 19)
+    /// and represents it with `int16_t`. This max value may be changed once we could
+    /// figure out an accurate limit.
+    #[derive(HashStable)]
+    #[encodable]
+    #[orderable]
+    #[max = 0xFFFF]
+    #[debug_format = "ConditionId({})"]
+    pub struct ConditionId {}
+}
+
+impl ConditionId {
+    pub const NONE: Self = Self::from_u32(0);
+}
+
 /// Enum that can hold a constant zero value, the ID of an physical coverage
 /// counter, or the ID of a coverage-counter expression.
 ///
@@ -106,6 +125,22 @@ pub enum CoverageKind {
     /// mappings. Intermediate expressions with no direct mappings are
     /// retained/zeroed based on whether they are transitively used.)
     ExpressionUsed { id: ExpressionId },
+
+    /// Marks the point in MIR control flow represented by a evaluated condition.
+    ///
+    /// This is eventually lowered to `llvm.instrprof.mcdc.condbitmap.update` in LLVM IR.
+    ///
+    /// If this statement does not survive MIR optimizations, the condition would never be
+    /// taken as evaluated.
+    CondBitmapUpdate { id: ConditionId, value: bool },
+
+    /// Marks the point in MIR control flow represented by a evaluated decision.
+    ///
+    /// This is eventually lowered to `llvm.instrprof.mcdc.tvbitmap.update` in LLVM IR.
+    ///
+    /// If this statement does not survive MIR optimizations, the decision would never be
+    /// taken as evaluated.
+    TestVectorBitmapUpdate { bitmap_idx: u32 },
 }
 
 impl Debug for CoverageKind {
@@ -116,6 +151,12 @@ impl Debug for CoverageKind {
             BlockMarker { id } => write!(fmt, "BlockMarker({:?})", id.index()),
             CounterIncrement { id } => write!(fmt, "CounterIncrement({:?})", id.index()),
             ExpressionUsed { id } => write!(fmt, "ExpressionUsed({:?})", id.index()),
+            CondBitmapUpdate { id, value } => {
+                write!(fmt, "CondBitmapUpdate({:?}, {:?})", id.index(), value)
+            }
+            TestVectorBitmapUpdate { bitmap_idx } => {
+                write!(fmt, "TestVectorUpdate({:?})", bitmap_idx)
+            }
         }
     }
 }
@@ -172,16 +213,23 @@ pub enum MappingKind {
     Code(CovTerm),
     /// Associates a branch region with separate counters for true and false.
     Branch { true_term: CovTerm, false_term: CovTerm },
+    /// Associates a branch region with separate counters for true and false.
+    MCDCBranch { true_term: CovTerm, false_term: CovTerm, mcdc_params: ConditionInfo },
+    /// Associates a decision region with a bitmap and number of conditions.
+    MCDCDecision(DecisionInfo),
 }
 
 impl MappingKind {
     /// Iterator over all coverage terms in this mapping kind.
     pub fn terms(&self) -> impl Iterator<Item = CovTerm> {
-        let one = |a| std::iter::once(a).chain(None);
-        let two = |a, b| std::iter::once(a).chain(Some(b));
+        let zero = || None.into_iter().chain(None);
+        let one = |a| Some(a).into_iter().chain(None);
+        let two = |a, b| Some(a).into_iter().chain(Some(b));
         match *self {
             Self::Code(term) => one(term),
             Self::Branch { true_term, false_term } => two(true_term, false_term),
+            Self::MCDCBranch { true_term, false_term, .. } => two(true_term, false_term),
+            Self::MCDCDecision(_) => zero(),
         }
     }
 
@@ -193,6 +241,12 @@ impl MappingKind {
             Self::Branch { true_term, false_term } => {
                 Self::Branch { true_term: map_fn(true_term), false_term: map_fn(false_term) }
             }
+            Self::MCDCBranch { true_term, false_term, mcdc_params } => Self::MCDCBranch {
+                true_term: map_fn(true_term),
+                false_term: map_fn(false_term),
+                mcdc_params,
+            },
+            Self::MCDCDecision(param) => Self::MCDCDecision(param),
         }
     }
 }
@@ -212,7 +266,7 @@ pub struct Mapping {
 pub struct FunctionCoverageInfo {
     pub function_source_hash: u64,
     pub num_counters: usize,
-
+    pub mcdc_bitmap_bytes: u32,
     pub expressions: IndexVec<ExpressionId, Expression>,
     pub mappings: Vec<Mapping>,
 }
@@ -226,6 +280,8 @@ pub struct BranchInfo {
     /// 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>,
 }
 
 #[derive(Clone, Debug)]
@@ -235,3 +291,45 @@ pub struct BranchSpan {
     pub true_marker: BlockMarkerId,
     pub false_marker: BlockMarkerId,
 }
+
+#[derive(Copy, Clone, Debug)]
+#[derive(TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
+pub struct ConditionInfo {
+    pub condition_id: ConditionId,
+    pub true_next_id: ConditionId,
+    pub false_next_id: ConditionId,
+}
+
+impl Default for ConditionInfo {
+    fn default() -> Self {
+        Self {
+            condition_id: ConditionId::NONE,
+            true_next_id: ConditionId::NONE,
+            false_next_id: ConditionId::NONE,
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+#[derive(TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
+pub struct MCDCBranchSpan {
+    pub span: Span,
+    pub condition_info: ConditionInfo,
+    pub true_marker: BlockMarkerId,
+    pub false_marker: BlockMarkerId,
+}
+
+#[derive(Copy, Clone, Debug)]
+#[derive(TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
+pub struct DecisionInfo {
+    pub bitmap_idx: u32,
+    pub conditions_num: u16,
+}
+
+#[derive(Clone, Debug)]
+#[derive(TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
+pub struct MCDCDecisionSpan {
+    pub span: Span,
+    pub conditions_num: usize,
+    pub end_markers: Vec<BlockMarkerId>,
+}