`llvm-cov` assertion failure when handling MC/DC that involves macros #80098

whentojump · 2024-01-31T04:40:18Z

Problem

The behavior is described with this tiny example: https://github.com/whentojump/llvm-mcdc-assertion-failure

Essentially, current MC/DC implementation cannot properly handle decisions that involve macros, like this example:

Root cause

Some terms I'll use:

Decision region: the composite logical expression
Branch region: smaller conditions or branches within a larger expression

In the full lifecycle of these regions, here are several important stages:

Compilation
1. Generated at front end: source code
2. Written to the binary as coverage mapping sections: source code
Generate report
1. Read from the binary: source code

The assertion in question is in step 2.i and goes like this:

llvm-cov walks all regions of the target program
It encounters a decision region, say R3. By reading R3's metadata, it knows it has two branches
llvm-cov then asserts: the next two regions it's gonna see must be two branch regions, not otherwise

This assertion assumes the order of MCDC regions. However, this order doesn't always hold

In step 1.ii all regions are sorted first by their file IDs, then by locations within the file and finally by region types. Macros, however, are traced back to definitions, which can be far away from their invocations or even separated in different files. As a result, the MC/DC regions could be sorted in a way where they are separated from each other. In the shown example, the order could be: R3 (many irrelevant regions) R1 R2 which apparently breaks the assertion at step 2.i.

Solution

This can be solved in two ways

(This PR) Sort with MC/DC in consideration and group relevant decisions and branches together.

I honestly don't know if this's gonna break other things. But at least I can confirm it solves the problem mentioned. Again please see an example in this repo https://github.com/whentojump/llvm-mcdc-assertion-failure
In CoverageMapping::loadFunctionRecord(), use a cleverer way to correlate decisions and branches that are sorted far away from each other.

Other to-do's

Tests are not yet taken care of
A bit comments/docs

Last but not least, a huge thanks to @evodius96 et al for the great work regarding MC/DC :))

… macros (1/2) This patch lets MC/DC code regions for the same composite logical expression get sorted next to each other, so that `llvm-cov show` won't hit assertion failures. The problematic cases are mostly when macros are involved: (FOO(x) && BAR(y)) <-R2-> <-R3-> <-------R1-------> Let's call the full expression Region 1, `FOO(x)` Region 2 and `BAR(y)` Region 3. If these macros are defined far away from their invocations, the eventual order of all regions would look like: Region 1, (many other irrelevant regions), Region 2, Region 3. This will break an assertion in CoverageMapping::loadFunctionRecord() which assumes branch regions of an MC/DC decision would immediately follow the decision region itself. This patch adds a new field `GroupID` to `MCDCParameters` struct, sort all regions based on this information, and place related MC/DC regions together. The `GroupID` assignment is included in the other patch to Clang CodeGen. This patch also disables 3 assertions that's based on the old sorting criteria.

…cros (2/2) This patch lets MC/DC code regions for the same composite logical expression get sorted next to each other, so that `llvm-cov show` won't hit assertion failures. The problematic cases are mostly when macros are involved: (FOO(x) && BAR(y)) <-R2-> <-R3-> <-------R1-------> Let's call the full expression Region 1, `FOO(x)` Region 2 and `BAR(y)` Region 3. If these macros are defined far away from their invocations, the eventual order of all regions would look like: Region 1, (many other irrelevant regions), Region 2, Region 3. This will break an assertion in CoverageMapping::loadFunctionRecord() which assumes branch regions of an MC/DC decision would immediately follow the decision region itself. An earlier patch adds a new field `GroupID` to `MCDCParameters` struct, sort all regions based on this information, and place related MC/DC regions together. This patch let Clang assign the same `GroupID` to decision- and branch-regions that are related to each other.

github-actions · 2024-01-31T04:40:36Z

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llvmbot · 2024-01-31T04:41:05Z

@llvm/pr-subscribers-clang-codegen

@llvm/pr-subscribers-clang

Author: Wentao Zhang (whentojump)

Changes

Problem

The behavior is described with this tiny example: https://github.com/whentojump/llvm-mcdc-assertion-failure

Essentially, current MC/DC implementation cannot properly handle decisions that involve macros, like this example:

Root cause

Some terms I'll use:

Decision region: the composite logical expression
Branch region: smaller conditions or branches within a larger expression

In the full lifecycle of these regions, here are several important stages:

Compilation
1. Generated at front end: source code
2. Written to the binary as coverage mapping sections: source code
Generate report
1. Read from the binary: source code

The assertion in question is in step 2.i and goes like this:

llvm-cov walks all regions of the target program
It encounters a decision region, say R3. By reading R3's metadata, it knows it has two branches
llvm-cov then asserts: the next two regions it's gonna see must be two branch regions, not otherwise

This assertion assumes the order of MCDC regions. However, this order doesn't always hold

In step 1.ii all regions are sorted first by their file IDs, then by locations within the file and finally by region types. Macros, however, are traced back to definitions, which can be far away from their invocations or even separated in different files. As a result, the MC/DC regions could be sorted in a way where they are separated from each other. In the shown example, the order could be: R3 (many irrelevant regions) R1 R2 which apparently breaks the assertion at step 2.i.

Solution

This can be solved in two ways

(This PR) Sort with MC/DC in consideration and group relevant decisions and branches together.

I honestly don't know if this's gonna break other things. But at least I can confirm it solves the problem mentioned. Again please see an example in this repo https://github.com/whentojump/llvm-mcdc-assertion-failure
In CoverageMapping::loadFunctionRecord(), use a cleverer way to correlate decisions and branches that are sorted far away from each other.

Other to-do's

Tests are not yet taken care of
A bit comments/docs

Last but not least, a huge thanks to @evodius96 et al for the great work regarding MC/DC :))

Full diff: https://github.com/llvm/llvm-project/pull/80098.diff

4 Files Affected:

(modified) clang/lib/CodeGen/CoverageMappingGen.cpp (+29-17)
(modified) llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h (+1)
(modified) llvm/lib/ProfileData/Coverage/CoverageMappingReader.cpp (+6-2)
(modified) llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp (+7-3)

diff --git a/clang/lib/CodeGen/CoverageMappingGen.cpp b/clang/lib/CodeGen/CoverageMappingGen.cpp
index 8b5e6c4ad8272..ecd90fe0585fc 100644
--- a/clang/lib/CodeGen/CoverageMappingGen.cpp
+++ b/clang/lib/CodeGen/CoverageMappingGen.cpp
@@ -857,6 +857,8 @@ struct CounterCoverageMappingBuilder
 
   unsigned getRegionBitmap(const Stmt *S) { return MCDCBitmapMap[S]; }
 
+  unsigned long MCDCDebugCounter;
+
   /// Push a region onto the stack.
   ///
   /// Returns the index on the stack where the region was pushed. This can be
@@ -866,7 +868,7 @@ struct CounterCoverageMappingBuilder
                     std::optional<SourceLocation> EndLoc = std::nullopt,
                     std::optional<Counter> FalseCount = std::nullopt,
                     MCDCConditionID ID = 0, MCDCConditionID TrueID = 0,
-                    MCDCConditionID FalseID = 0) {
+                    MCDCConditionID FalseID = 0, MCDCConditionID GroupID = 0) {
 
     if (StartLoc && !FalseCount) {
       MostRecentLocation = *StartLoc;
@@ -886,17 +888,19 @@ struct CounterCoverageMappingBuilder
     if (EndLoc && EndLoc->isInvalid())
       EndLoc = std::nullopt;
     RegionStack.emplace_back(Count, FalseCount,
-                             MCDCParameters{0, 0, ID, TrueID, FalseID},
+                             MCDCParameters{
+                               0, 0,
+                               ID, TrueID, FalseID, GroupID},
                              StartLoc, EndLoc);
 
     return RegionStack.size() - 1;
   }
 
-  size_t pushRegion(unsigned BitmapIdx, unsigned Conditions,
+  size_t pushRegion(unsigned BitmapIdx, unsigned Conditions, MCDCConditionID GroupID,
                     std::optional<SourceLocation> StartLoc = std::nullopt,
                     std::optional<SourceLocation> EndLoc = std::nullopt) {
 
-    RegionStack.emplace_back(MCDCParameters{BitmapIdx, Conditions}, StartLoc,
+    RegionStack.emplace_back(MCDCParameters{BitmapIdx, Conditions, 0, 0, 0, GroupID}, StartLoc,
                              EndLoc);
 
     return RegionStack.size() - 1;
@@ -1032,7 +1036,8 @@ struct CounterCoverageMappingBuilder
   /// result in the generation of a branch.
   void
   createBranchRegion(const Expr *C, Counter TrueCnt, Counter FalseCnt,
-                     const MCDCDecisionIDPair &IDPair = MCDCDecisionIDPair()) {
+                     const MCDCDecisionIDPair &IDPair = MCDCDecisionIDPair(),
+                     MCDCConditionID GroupID = 0) {
     // Check for NULL conditions.
     if (!C)
       return;
@@ -1054,19 +1059,19 @@ struct CounterCoverageMappingBuilder
       // CodeGenFunction.c always returns false, but that is very heavy-handed.
       if (ConditionFoldsToBool(C))
         popRegions(pushRegion(Counter::getZero(), getStart(C), getEnd(C),
-                              Counter::getZero(), ID, TrueID, FalseID));
+                              Counter::getZero(), ID, TrueID, FalseID, GroupID));
       else
         // Otherwise, create a region with the True counter and False counter.
         popRegions(pushRegion(TrueCnt, getStart(C), getEnd(C), FalseCnt, ID,
-                              TrueID, FalseID));
+                              TrueID, FalseID, GroupID));
     }
   }
 
   /// Create a Decision Region with a BitmapIdx and number of Conditions. This
   /// type of region "contains" branch regions, one for each of the conditions.
   /// The visualization tool will group everything together.
-  void createDecisionRegion(const Expr *C, unsigned BitmapIdx, unsigned Conds) {
-    popRegions(pushRegion(BitmapIdx, Conds, getStart(C), getEnd(C)));
+  void createDecisionRegion(const Expr *C, unsigned BitmapIdx, unsigned Conds, MCDCConditionID GroupID) {
+    popRegions(pushRegion(BitmapIdx, Conds, GroupID, getStart(C), getEnd(C)));
   }
 
   /// Create a Branch Region around a SwitchCase for code coverage
@@ -1153,7 +1158,8 @@ struct CounterCoverageMappingBuilder
                 I.getCounter(), I.getFalseCounter(),
                 MCDCParameters{0, 0, I.getMCDCParams().ID,
                                I.getMCDCParams().TrueID,
-                               I.getMCDCParams().FalseID},
+                               I.getMCDCParams().FalseID,
+                               I.getMCDCParams().GroupID},
                 Loc, getEndOfFileOrMacro(Loc), I.isBranch());
           else
             SourceRegions.emplace_back(I.getCounter(), Loc,
@@ -1342,7 +1348,9 @@ struct CounterCoverageMappingBuilder
       SourceManager &SM, const LangOptions &LangOpts)
       : CoverageMappingBuilder(CVM, SM, LangOpts), CounterMap(CounterMap),
         MCDCBitmapMap(MCDCBitmapMap),
-        MCDCBuilder(CVM.getCodeGenModule(), CondIDMap, MCDCBitmapMap) {}
+        MCDCBuilder(CVM.getCodeGenModule(), CondIDMap, MCDCBitmapMap) {
+    MCDCDebugCounter = 0;
+  }
 
   /// Write the mapping data to the output stream
   void write(llvm::raw_ostream &OS) {
@@ -1973,6 +1981,8 @@ struct CounterCoverageMappingBuilder
   void VisitBinLAnd(const BinaryOperator *E) {
     bool IsRootNode = MCDCBuilder.isIdle();
 
+    MCDCDebugCounter++;
+
     // Keep track of Binary Operator and assign MCDC condition IDs.
     MCDCBuilder.pushAndAssignIDs(E);
 
@@ -1993,7 +2003,7 @@ struct CounterCoverageMappingBuilder
     // Create MCDC Decision Region if at top-level (root).
     unsigned NumConds = 0;
     if (IsRootNode && (NumConds = MCDCBuilder.getTotalConditionsAndReset(E)))
-      createDecisionRegion(E, getRegionBitmap(E), NumConds);
+      createDecisionRegion(E, getRegionBitmap(E), NumConds, MCDCDebugCounter);
 
     // Extract the RHS's Execution Counter.
     Counter RHSExecCnt = getRegionCounter(E);
@@ -2006,11 +2016,11 @@ struct CounterCoverageMappingBuilder
 
     // Create Branch Region around LHS condition.
     createBranchRegion(E->getLHS(), RHSExecCnt,
-                       subtractCounters(ParentCnt, RHSExecCnt), DecisionLHS);
+                       subtractCounters(ParentCnt, RHSExecCnt), DecisionLHS, MCDCDebugCounter);
 
     // Create Branch Region around RHS condition.
     createBranchRegion(E->getRHS(), RHSTrueCnt,
-                       subtractCounters(RHSExecCnt, RHSTrueCnt), DecisionRHS);
+                       subtractCounters(RHSExecCnt, RHSTrueCnt), DecisionRHS, MCDCDebugCounter);
   }
 
   // Determine whether the right side of OR operation need to be visited.
@@ -2026,6 +2036,8 @@ struct CounterCoverageMappingBuilder
   void VisitBinLOr(const BinaryOperator *E) {
     bool IsRootNode = MCDCBuilder.isIdle();
 
+    MCDCDebugCounter++;
+
     // Keep track of Binary Operator and assign MCDC condition IDs.
     MCDCBuilder.pushAndAssignIDs(E);
 
@@ -2046,7 +2058,7 @@ struct CounterCoverageMappingBuilder
     // Create MCDC Decision Region if at top-level (root).
     unsigned NumConds = 0;
     if (IsRootNode && (NumConds = MCDCBuilder.getTotalConditionsAndReset(E)))
-      createDecisionRegion(E, getRegionBitmap(E), NumConds);
+      createDecisionRegion(E, getRegionBitmap(E), NumConds, MCDCDebugCounter);
 
     // Extract the RHS's Execution Counter.
     Counter RHSExecCnt = getRegionCounter(E);
@@ -2063,11 +2075,11 @@ struct CounterCoverageMappingBuilder
 
     // Create Branch Region around LHS condition.
     createBranchRegion(E->getLHS(), subtractCounters(ParentCnt, RHSExecCnt),
-                       RHSExecCnt, DecisionLHS);
+                       RHSExecCnt, DecisionLHS, MCDCDebugCounter);
 
     // Create Branch Region around RHS condition.
     createBranchRegion(E->getRHS(), subtractCounters(RHSExecCnt, RHSFalseCnt),
-                       RHSFalseCnt, DecisionRHS);
+                       RHSFalseCnt, DecisionRHS, MCDCDebugCounter);
   }
 
   void VisitLambdaExpr(const LambdaExpr *LE) {
diff --git a/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h b/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h
index 33fa17ba811fa..5ca5923cbd82e 100644
--- a/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h
+++ b/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h
@@ -260,6 +260,7 @@ struct CounterMappingRegion {
     /// IDs used to represent a branch region and other branch regions
     /// evaluated based on True and False branches.
     MCDCConditionID ID = 0, TrueID = 0, FalseID = 0;
+    MCDCConditionID GroupID;
   };
 
   /// Primary Counter that is also used for Branch Regions (TrueCount).
diff --git a/llvm/lib/ProfileData/Coverage/CoverageMappingReader.cpp b/llvm/lib/ProfileData/Coverage/CoverageMappingReader.cpp
index ac8e6b56379f2..1638a4d7dcfa0 100644
--- a/llvm/lib/ProfileData/Coverage/CoverageMappingReader.cpp
+++ b/llvm/lib/ProfileData/Coverage/CoverageMappingReader.cpp
@@ -244,7 +244,7 @@ Error RawCoverageMappingReader::readMappingRegionsSubArray(
   unsigned LineStart = 0;
   for (size_t I = 0; I < NumRegions; ++I) {
     Counter C, C2;
-    uint64_t BIDX = 0, NC = 0, ID = 0, TID = 0, FID = 0;
+    uint64_t BIDX = 0, NC = 0, ID = 0, TID = 0, FID = 0, GID = 0;
     CounterMappingRegion::RegionKind Kind = CounterMappingRegion::CodeRegion;
 
     // Read the combined counter + region kind.
@@ -308,6 +308,8 @@ Error RawCoverageMappingReader::readMappingRegionsSubArray(
             return Err;
           if (auto Err = readIntMax(FID, std::numeric_limits<unsigned>::max()))
             return Err;
+          if (auto Err = readIntMax(GID, std::numeric_limits<unsigned>::max()))
+            return Err;
           break;
         case CounterMappingRegion::MCDCDecisionRegion:
           Kind = CounterMappingRegion::MCDCDecisionRegion;
@@ -315,6 +317,8 @@ Error RawCoverageMappingReader::readMappingRegionsSubArray(
             return Err;
           if (auto Err = readIntMax(NC, std::numeric_limits<unsigned>::max()))
             return Err;
+          if (auto Err = readIntMax(GID, std::numeric_limits<unsigned>::max()))
+            return Err;
           break;
         default:
           return make_error<CoverageMapError>(coveragemap_error::malformed,
@@ -374,7 +378,7 @@ Error RawCoverageMappingReader::readMappingRegionsSubArray(
         CounterMappingRegion::MCDCParameters{
             static_cast<unsigned>(BIDX), static_cast<unsigned>(NC),
             static_cast<unsigned>(ID), static_cast<unsigned>(TID),
-            static_cast<unsigned>(FID)},
+            static_cast<unsigned>(FID), static_cast<unsigned>(GID)},
         InferredFileID, ExpandedFileID, LineStart, ColumnStart,
         LineStart + NumLines, ColumnEnd, Kind);
     if (CMR.startLoc() > CMR.endLoc())
diff --git a/llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp b/llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp
index 1c7d8a8909c48..5f85e8243fcd5 100644
--- a/llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp
+++ b/llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp
@@ -163,6 +163,8 @@ void CoverageMappingWriter::write(raw_ostream &OS) {
   // location. Sort by region kinds to ensure stable order for tests.
   llvm::stable_sort(MappingRegions, [](const CounterMappingRegion &LHS,
                                        const CounterMappingRegion &RHS) {
+    if (LHS.MCDCParams.GroupID != RHS.MCDCParams.GroupID)
+      return LHS.MCDCParams.GroupID < RHS.MCDCParams.GroupID;
     if (LHS.FileID != RHS.FileID)
       return LHS.FileID < RHS.FileID;
     if (LHS.startLoc() != RHS.startLoc())
@@ -192,7 +194,7 @@ void CoverageMappingWriter::write(raw_ostream &OS) {
   for (auto I = MappingRegions.begin(), E = MappingRegions.end(); I != E; ++I) {
     if (I->FileID != CurrentFileID) {
       // Ensure that all file ids have at least one mapping region.
-      assert(I->FileID == (CurrentFileID + 1));
+      // assert(I->FileID == (CurrentFileID + 1));
       // Find the number of regions with this file id.
       unsigned RegionCount = 1;
       for (auto J = I + 1; J != E && I->FileID == J->FileID; ++J)
@@ -246,6 +248,7 @@ void CoverageMappingWriter::write(raw_ostream &OS) {
       encodeULEB128(unsigned(I->MCDCParams.ID), OS);
       encodeULEB128(unsigned(I->MCDCParams.TrueID), OS);
       encodeULEB128(unsigned(I->MCDCParams.FalseID), OS);
+      encodeULEB128(unsigned(I->MCDCParams.GroupID), OS);
       break;
     case CounterMappingRegion::MCDCDecisionRegion:
       encodeULEB128(unsigned(I->Kind)
@@ -253,9 +256,10 @@ void CoverageMappingWriter::write(raw_ostream &OS) {
                     OS);
       encodeULEB128(unsigned(I->MCDCParams.BitmapIdx), OS);
       encodeULEB128(unsigned(I->MCDCParams.NumConditions), OS);
+      encodeULEB128(unsigned(I->MCDCParams.GroupID), OS);
       break;
     }
-    assert(I->LineStart >= PrevLineStart);
+    // assert(I->LineStart >= PrevLineStart);
     encodeULEB128(I->LineStart - PrevLineStart, OS);
     encodeULEB128(I->ColumnStart, OS);
     assert(I->LineEnd >= I->LineStart);
@@ -264,7 +268,7 @@ void CoverageMappingWriter::write(raw_ostream &OS) {
     PrevLineStart = I->LineStart;
   }
   // Ensure that all file ids have at least one mapping region.
-  assert(CurrentFileID == (VirtualFileMapping.size() - 1));
+  // assert(CurrentFileID == (VirtualFileMapping.size() - 1));
 }
 
 void TestingFormatWriter::write(raw_ostream &OS, TestingFormatVersion Version) {

github-actions · 2024-01-31T04:42:38Z

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff c19436eec1c236cbe622c04e33f35f1f9478fa15 cd5a33851187c872c0de7a766528be097bcc68ad -- clang/lib/CodeGen/CoverageMappingGen.cpp llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h llvm/lib/ProfileData/Coverage/CoverageMappingReader.cpp llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp

View the diff from clang-format here.

diff --git a/clang/lib/CodeGen/CoverageMappingGen.cpp b/clang/lib/CodeGen/CoverageMappingGen.cpp
index ecd90fe058..565979c5c3 100644
--- a/clang/lib/CodeGen/CoverageMappingGen.cpp
+++ b/clang/lib/CodeGen/CoverageMappingGen.cpp
@@ -888,20 +888,20 @@ struct CounterCoverageMappingBuilder
     if (EndLoc && EndLoc->isInvalid())
       EndLoc = std::nullopt;
     RegionStack.emplace_back(Count, FalseCount,
-                             MCDCParameters{
-                               0, 0,
-                               ID, TrueID, FalseID, GroupID},
+                             MCDCParameters{0, 0, ID, TrueID, FalseID, GroupID},
                              StartLoc, EndLoc);
 
     return RegionStack.size() - 1;
   }
 
-  size_t pushRegion(unsigned BitmapIdx, unsigned Conditions, MCDCConditionID GroupID,
+  size_t pushRegion(unsigned BitmapIdx, unsigned Conditions,
+                    MCDCConditionID GroupID,
                     std::optional<SourceLocation> StartLoc = std::nullopt,
                     std::optional<SourceLocation> EndLoc = std::nullopt) {
 
-    RegionStack.emplace_back(MCDCParameters{BitmapIdx, Conditions, 0, 0, 0, GroupID}, StartLoc,
-                             EndLoc);
+    RegionStack.emplace_back(
+        MCDCParameters{BitmapIdx, Conditions, 0, 0, 0, GroupID}, StartLoc,
+        EndLoc);
 
     return RegionStack.size() - 1;
   }
@@ -1059,7 +1059,8 @@ struct CounterCoverageMappingBuilder
       // CodeGenFunction.c always returns false, but that is very heavy-handed.
       if (ConditionFoldsToBool(C))
         popRegions(pushRegion(Counter::getZero(), getStart(C), getEnd(C),
-                              Counter::getZero(), ID, TrueID, FalseID, GroupID));
+                              Counter::getZero(), ID, TrueID, FalseID,
+                              GroupID));
       else
         // Otherwise, create a region with the True counter and False counter.
         popRegions(pushRegion(TrueCnt, getStart(C), getEnd(C), FalseCnt, ID,
@@ -1070,7 +1071,8 @@ struct CounterCoverageMappingBuilder
   /// Create a Decision Region with a BitmapIdx and number of Conditions. This
   /// type of region "contains" branch regions, one for each of the conditions.
   /// The visualization tool will group everything together.
-  void createDecisionRegion(const Expr *C, unsigned BitmapIdx, unsigned Conds, MCDCConditionID GroupID) {
+  void createDecisionRegion(const Expr *C, unsigned BitmapIdx, unsigned Conds,
+                            MCDCConditionID GroupID) {
     popRegions(pushRegion(BitmapIdx, Conds, GroupID, getStart(C), getEnd(C)));
   }
 
@@ -1156,10 +1158,9 @@ struct CounterCoverageMappingBuilder
           if (I.isBranch())
             SourceRegions.emplace_back(
                 I.getCounter(), I.getFalseCounter(),
-                MCDCParameters{0, 0, I.getMCDCParams().ID,
-                               I.getMCDCParams().TrueID,
-                               I.getMCDCParams().FalseID,
-                               I.getMCDCParams().GroupID},
+                MCDCParameters{
+                    0, 0, I.getMCDCParams().ID, I.getMCDCParams().TrueID,
+                    I.getMCDCParams().FalseID, I.getMCDCParams().GroupID},
                 Loc, getEndOfFileOrMacro(Loc), I.isBranch());
           else
             SourceRegions.emplace_back(I.getCounter(), Loc,
@@ -2016,11 +2017,13 @@ struct CounterCoverageMappingBuilder
 
     // Create Branch Region around LHS condition.
     createBranchRegion(E->getLHS(), RHSExecCnt,
-                       subtractCounters(ParentCnt, RHSExecCnt), DecisionLHS, MCDCDebugCounter);
+                       subtractCounters(ParentCnt, RHSExecCnt), DecisionLHS,
+                       MCDCDebugCounter);
 
     // Create Branch Region around RHS condition.
     createBranchRegion(E->getRHS(), RHSTrueCnt,
-                       subtractCounters(RHSExecCnt, RHSTrueCnt), DecisionRHS, MCDCDebugCounter);
+                       subtractCounters(RHSExecCnt, RHSTrueCnt), DecisionRHS,
+                       MCDCDebugCounter);
   }
 
   // Determine whether the right side of OR operation need to be visited.

evodius96 · 2024-01-31T04:43:21Z

Hi! I think this may be the same issue as #77871 and a fix is under review by @chapuni Can you verify?

whentojump · 2024-01-31T04:46:30Z

Hi thanks for the prompt reply and the pointer! Will definitely check.

chapuni

I suppose this is still a draft.

chapuni · 2024-01-31T05:30:41Z

llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp

      break;
    case CounterMappingRegion::MCDCDecisionRegion:
      encodeULEB128(unsigned(I->Kind)
                        << Counter::EncodingCounterTagAndExpansionRegionTagBits,
                    OS);
      encodeULEB128(unsigned(I->MCDCParams.BitmapIdx), OS);
      encodeULEB128(unsigned(I->MCDCParams.NumConditions), OS);
+      encodeULEB128(unsigned(I->MCDCParams.GroupID), OS);


Is it the enhancement?

chapuni · 2024-01-31T05:33:05Z

clang/lib/CodeGen/CoverageMappingGen.cpp

@@ -857,6 +857,8 @@ struct CounterCoverageMappingBuilder

  unsigned getRegionBitmap(const Stmt *S) { return MCDCBitmapMap[S]; }

+  unsigned long MCDCDebugCounter;


What is its preferable name? I guess you expects unique ID for debug for now.

chapuni · 2024-01-31T05:34:54Z

clang/lib/CodeGen/CoverageMappingGen.cpp

@@ -1973,6 +1981,8 @@ struct CounterCoverageMappingBuilder
  void VisitBinLAnd(const BinaryOperator *E) {
    bool IsRootNode = MCDCBuilder.isIdle();

+    MCDCDebugCounter++;


I didn't understand the strategy to assign it.

Hi thanks again for taking the look!
My intuition was to make the ID different whenever a new decision region is going to be added by calling createDecisionRegion(). There might be something obvious that I ignored.
And after reading some of the other posts (I'm still learning most of them, please bear with that!), I generally agree with the approaches whose modifications are minimized within llvm-cov, instead of touching the front end.

Regards

chapuni · 2024-01-31T05:39:24Z

See also, #78920, I guess it is also relevant to you.

whentojump · 2024-01-31T05:47:01Z

Hey @chapuni thanks for the comments!

This is indeed a draft. Since there're already reports regarding this issue, let me close this one. I will try those linked patches and report if I have findings.

Sorry for not searching for the ongoing effort and thanks for your work!

whentojump added 2 commits January 30, 2024 22:39

llvmbot added clang Clang issues not falling into any other category clang:codegen labels Jan 31, 2024

chapuni requested changes Jan 31, 2024

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whentojump closed this Jan 31, 2024

whentojump mentioned this pull request Jan 31, 2024

[Coverage] Let Decision take account of expansions #78969

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`llvm-cov` assertion failure when handling MC/DC that involves macros #80098

`llvm-cov` assertion failure when handling MC/DC that involves macros #80098

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		@@ -857,6 +857,8 @@ struct CounterCoverageMappingBuilder

		unsigned getRegionBitmap(const Stmt *S) { return MCDCBitmapMap[S]; }

		unsigned long MCDCDebugCounter;

llvm-cov assertion failure when handling MC/DC that involves macros #80098

llvm-cov assertion failure when handling MC/DC that involves macros #80098

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`llvm-cov` assertion failure when handling MC/DC that involves macros #80098

`llvm-cov` assertion failure when handling MC/DC that involves macros #80098

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