coverage. Group MCDC decisions and conditions until instrument mappings

Author: zhuyunxing

compiler/rustc_codegen_llvm/src/builder.rs

@@ -1698,9 +1698,9 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
         &mut self,
         fn_name: &'ll Value,
         hash: &'ll Value,
-        bitmap_bytes: &'ll Value,
+        bitmap_bits: &'ll Value,
     ) {
-        debug!("mcdc_parameters() with args ({:?}, {:?}, {:?})", fn_name, hash, bitmap_bytes);
+        debug!("mcdc_parameters() with args ({:?}, {:?}, {:?})", fn_name, hash, bitmap_bits);
 
         assert!(
             crate::llvm_util::get_version() >= (19, 0, 0),
@@ -1712,7 +1712,7 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
             &[self.cx.type_ptr(), self.cx.type_i64(), self.cx.type_i32()],
             self.cx.type_void(),
         );
-        let args = &[fn_name, hash, bitmap_bytes];
+        let args = &[fn_name, hash, bitmap_bits];
         let args = self.check_call("call", llty, llfn, args);
 
         unsafe {
@@ -1732,13 +1732,12 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
         &mut self,
         fn_name: &'ll Value,
         hash: &'ll Value,
-        bitmap_bytes: &'ll Value,
         bitmap_index: &'ll Value,
         mcdc_temp: &'ll Value,
     ) {
         debug!(
-            "mcdc_tvbitmap_update() with args ({:?}, {:?}, {:?}, {:?}, {:?})",
-            fn_name, hash, bitmap_bytes, bitmap_index, mcdc_temp
+            "mcdc_tvbitmap_update() with args ({:?}, {:?}, {:?}, {:?})",
+            fn_name, hash, bitmap_index, mcdc_temp
         );
         assert!(
             crate::llvm_util::get_version() >= (19, 0, 0),
@@ -1748,16 +1747,10 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
         let llfn =
             unsafe { llvm::LLVMRustGetInstrProfMCDCTVBitmapUpdateIntrinsic(self.cx().llmod) };
         let llty = self.cx.type_func(
-            &[
-                self.cx.type_ptr(),
-                self.cx.type_i64(),
-                self.cx.type_i32(),
-                self.cx.type_i32(),
-                self.cx.type_ptr(),
-            ],
+            &[self.cx.type_ptr(), self.cx.type_i64(), self.cx.type_i32(), self.cx.type_ptr()],
             self.cx.type_void(),
         );
-        let args = &[fn_name, hash, bitmap_bytes, bitmap_index, mcdc_temp];
+        let args = &[fn_name, hash, bitmap_index, mcdc_temp];
         let args = self.check_call("call", llty, llfn, args);
         unsafe {
             let _ = llvm::LLVMRustBuildCall(
@@ -1773,45 +1766,15 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
         self.store(self.const_i32(0), mcdc_temp, self.tcx.data_layout.i32_align.abi);
     }
 
-    pub(crate) fn mcdc_condbitmap_update(
-        &mut self,
-        fn_name: &'ll Value,
-        hash: &'ll Value,
-        cond_loc: &'ll Value,
-        mcdc_temp: &'ll Value,
-        bool_value: &'ll Value,
-    ) {
-        debug!(
-            "mcdc_condbitmap_update() with args ({:?}, {:?}, {:?}, {:?}, {:?})",
-            fn_name, hash, cond_loc, mcdc_temp, bool_value
-        );
+    pub(crate) fn mcdc_condbitmap_update(&mut self, cond_index: &'ll Value, mcdc_temp: &'ll Value) {
+        debug!("mcdc_condbitmap_update() with args ({:?}, {:?})", cond_index, mcdc_temp);
         assert!(
             crate::llvm_util::get_version() >= (19, 0, 0),
             "MCDC intrinsics require LLVM 19 or later"
         );
-        let llfn = unsafe { llvm::LLVMRustGetInstrProfMCDCCondBitmapIntrinsic(self.cx().llmod) };
-        let llty = self.cx.type_func(
-            &[
-                self.cx.type_ptr(),
-                self.cx.type_i64(),
-                self.cx.type_i32(),
-                self.cx.type_ptr(),
-                self.cx.type_i1(),
-            ],
-            self.cx.type_void(),
-        );
-        let args = &[fn_name, hash, cond_loc, mcdc_temp, bool_value];
-        self.check_call("call", llty, llfn, args);
-        unsafe {
-            let _ = llvm::LLVMRustBuildCall(
-                self.llbuilder,
-                llty,
-                llfn,
-                args.as_ptr() as *const &llvm::Value,
-                args.len() as c_uint,
-                [].as_ptr(),
-                0 as c_uint,
-            );
-        }
+        let align = self.tcx.data_layout.i32_align.abi;
+        let current_tv_index = self.load(self.cx.type_i32(), mcdc_temp, align);
+        let new_tv_index = self.add(current_tv_index, cond_index);
+        self.store(new_tv_index, mcdc_temp, align);
     }
 }

compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs

@@ -98,14 +98,14 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
         };
 
         // If there are no MC/DC bitmaps to set up, return immediately.
-        if function_coverage_info.mcdc_bitmap_bytes == 0 {
+        if function_coverage_info.mcdc_bitmap_bits == 0 {
             return;
         }
 
         let fn_name = self.get_pgo_func_name_var(instance);
         let hash = self.const_u64(function_coverage_info.function_source_hash);
-        let bitmap_bytes = self.const_u32(function_coverage_info.mcdc_bitmap_bytes);
-        self.mcdc_parameters(fn_name, hash, bitmap_bytes);
+        let bitmap_bits = self.const_u32(function_coverage_info.mcdc_bitmap_bits as u32);
+        self.mcdc_parameters(fn_name, hash, bitmap_bits);
 
         // Create pointers named `mcdc.addr.{i}` to stack-allocated condition bitmaps.
         let mut cond_bitmaps = vec![];
@@ -185,35 +185,28 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
             CoverageKind::ExpressionUsed { id } => {
                 func_coverage.mark_expression_id_seen(id);
             }
-            CoverageKind::CondBitmapUpdate { id, value, decision_depth } => {
+            CoverageKind::CondBitmapUpdate { index, decision_depth } => {
                 drop(coverage_map);
-                assert_ne!(
-                    id.as_u32(),
-                    0,
-                    "ConditionId of evaluated conditions should never be zero"
-                );
                 let cond_bitmap = coverage_context
                     .try_get_mcdc_condition_bitmap(&instance, decision_depth)
                     .expect("mcdc cond bitmap should have been allocated for updating");
-                let cond_loc = bx.const_i32(id.as_u32() as i32 - 1);
-                let bool_value = bx.const_bool(value);
-                let fn_name = bx.get_pgo_func_name_var(instance);
-                let hash = bx.const_u64(function_coverage_info.function_source_hash);
-                bx.mcdc_condbitmap_update(fn_name, hash, cond_loc, cond_bitmap, bool_value);
+                let cond_index = bx.const_i32(index as i32);
+                bx.mcdc_condbitmap_update(cond_index, cond_bitmap);
             }
             CoverageKind::TestVectorBitmapUpdate { bitmap_idx, decision_depth } => {
                 drop(coverage_map);
                 let cond_bitmap = coverage_context
                                     .try_get_mcdc_condition_bitmap(&instance, decision_depth)
                                     .expect("mcdc cond bitmap should have been allocated for merging into the global bitmap");
-                let bitmap_bytes = function_coverage_info.mcdc_bitmap_bytes;
-                assert!(bitmap_idx < bitmap_bytes, "bitmap index of the decision out of range");
+                assert!(
+                    bitmap_idx as usize <= function_coverage_info.mcdc_bitmap_bits,
+                    "bitmap index of the decision out of range"
+                );
 
                 let fn_name = bx.get_pgo_func_name_var(instance);
                 let hash = bx.const_u64(function_coverage_info.function_source_hash);
-                let bitmap_bytes = bx.const_u32(bitmap_bytes);
                 let bitmap_index = bx.const_u32(bitmap_idx);
-                bx.mcdc_tvbitmap_update(fn_name, hash, bitmap_bytes, bitmap_index, cond_bitmap);
+                bx.mcdc_tvbitmap_update(fn_name, hash, bitmap_index, cond_bitmap);
             }
         }
     }

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1613,7 +1613,6 @@ unsafe extern "C" {
     pub fn LLVMRustGetInstrProfIncrementIntrinsic(M: &Module) -> &Value;
     pub fn LLVMRustGetInstrProfMCDCParametersIntrinsic(M: &Module) -> &Value;
     pub fn LLVMRustGetInstrProfMCDCTVBitmapUpdateIntrinsic(M: &Module) -> &Value;
-    pub fn LLVMRustGetInstrProfMCDCCondBitmapIntrinsic(M: &Module) -> &Value;
 
     pub fn LLVMRustBuildCall<'a>(
         B: &Builder<'a>,

compiler/rustc_middle/src/mir/coverage.rs

@@ -128,8 +128,8 @@ pub enum CoverageKind {
 
     /// 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.
-    CondBitmapUpdate { id: ConditionId, value: bool, decision_depth: u16 },
+    /// This is eventually lowered to instruments updating mcdc temp variables.
+    CondBitmapUpdate { index: u32, decision_depth: u16 },
 
     /// Marks the point in MIR control flow represented by a evaluated decision.
     ///
@@ -145,14 +145,8 @@ 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, decision_depth } => {
-                write!(
-                    fmt,
-                    "CondBitmapUpdate({:?}, {:?}, depth={:?})",
-                    id.index(),
-                    value,
-                    decision_depth
-                )
+            CondBitmapUpdate { index, decision_depth } => {
+                write!(fmt, "CondBitmapUpdate(index={:?}, depth={:?})", index, decision_depth)
             }
             TestVectorBitmapUpdate { bitmap_idx, decision_depth } => {
                 write!(fmt, "TestVectorUpdate({:?}, depth={:?})", bitmap_idx, decision_depth)
@@ -253,7 +247,7 @@ pub struct Mapping {
 pub struct FunctionCoverageInfo {
     pub function_source_hash: u64,
     pub num_counters: usize,
-    pub mcdc_bitmap_bytes: u32,
+    pub mcdc_bitmap_bits: usize,
     pub expressions: IndexVec<ExpressionId, Expression>,
     pub mappings: Vec<Mapping>,
     /// The depth of the deepest decision is used to know how many
@@ -275,8 +269,10 @@ 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_branch_spans: Vec<MCDCBranchSpan>,
+    pub mcdc_spans: Vec<(MCDCDecisionSpan, Vec<MCDCBranchSpan>)>,
 }
 
 #[derive(Clone, Debug)]
@@ -299,12 +295,9 @@ pub struct 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 condition_info: ConditionInfo,
     pub true_marker: BlockMarkerId,
     pub false_marker: BlockMarkerId,
-    pub decision_depth: u16,
 }
 
 #[derive(Copy, Clone, Debug)]
@@ -318,7 +311,7 @@ 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,
+    pub num_conditions: usize,
 }

compiler/rustc_middle/src/mir/pretty.rs

@@ -538,8 +538,8 @@ fn write_coverage_info_hi(
     let coverage::CoverageInfoHi {
         num_block_markers: _,
         branch_spans,
-        mcdc_branch_spans,
-        mcdc_decision_spans,
+        mcdc_degraded_branch_spans,
+        mcdc_spans,
     } = coverage_info_hi;
 
     // Only add an extra trailing newline if we printed at least one thing.
@@ -553,29 +553,35 @@ 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_marker, false_marker, .. } in
+        mcdc_degraded_branch_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_marker:?}, false: {false_marker:?} }} => {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, num_conditions: _ },
+        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_marker, false_marker } in
+            conditions
+        {
+            writeln!(
+                w,
+                "{INDENT}coverage mcdc branch {{ condition_id: {:?}, true: {true_marker:?}, false: {false_marker:?} }} => {span:?}",
+                condition_info.condition_id
+            )?;
+        }
         did_print = true;
     }
 

compiler/rustc_mir_build/src/build/coverageinfo.rs

@@ -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_spans, mcdc_degraded_branch_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_branch_spans,
+            mcdc_spans,
         })
     }
 }