[gcov] Fix wrong line hit counts when multiple blocks are on the same…

… line

Summary:
The goal of this patch is to have the same behaviour than gcc-gcov.
Currently the hit counts for a line is the sum of the counts for each block on that line.
The idea is to detect the cycles in the graph of blocks in using the algorithm by Hawick & James.
The count for a cycle is the min of the counts for each edge in the cycle.
Once we've the count for each cycle, we can sum them and add the transition counts of those cycles.

Fix both https://bugs.llvm.org/show_bug.cgi?id=38065 and https://bugs.llvm.org/show_bug.cgi?id=38066

Reviewers: marco-c, davidxl

Reviewed By: marco-c

Subscribers: vsk, lebedev.ri, sylvestre.ledru, dblaikie, llvm-commits

Differential Revision: https://reviews.llvm.org/D49659

llvm-svn: 342657

llvm/include/llvm/ProfileData/GCOV.h

@@ -24,9 +24,11 @@
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"
+#include <algorithm>
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
+#include <limits>
 #include <memory>
 #include <string>
 #include <utility>
@@ -266,13 +268,14 @@ struct GCOVEdge {
   GCOVBlock &Src;
   GCOVBlock &Dst;
   uint64_t Count = 0;
+  uint64_t CyclesCount = 0;
 };
 
 /// GCOVFunction - Collects function information.
 class GCOVFunction {
 public:
-  using BlockIterator = pointee_iterator<SmallVectorImpl<
-      std::unique_ptr<GCOVBlock>>::const_iterator>;
+  using BlockIterator = pointee_iterator<
+      SmallVectorImpl<std::unique_ptr<GCOVBlock>>::const_iterator>;
 
   GCOVFunction(GCOVFile &P) : Parent(P) {}
 
@@ -322,6 +325,9 @@ class GCOVBlock {
 
 public:
   using EdgeIterator = SmallVectorImpl<GCOVEdge *>::const_iterator;
+  using BlockVector = SmallVector<const GCOVBlock *, 4>;
+  using BlockVectorLists = SmallVector<BlockVector, 4>;
+  using Edges = SmallVector<GCOVEdge *, 4>;
 
   GCOVBlock(GCOVFunction &P, uint32_t N) : Parent(P), Number(N) {}
   ~GCOVBlock();
@@ -365,6 +371,16 @@ class GCOVBlock {
   void dump() const;
   void collectLineCounts(FileInfo &FI);
 
+  static uint64_t getCycleCount(const Edges &Path);
+  static void unblock(const GCOVBlock *U, BlockVector &Blocked,
+                      BlockVectorLists &BlockLists);
+  static bool lookForCircuit(const GCOVBlock *V, const GCOVBlock *Start,
+                             Edges &Path, BlockVector &Blocked,
+                             BlockVectorLists &BlockLists,
+                             const BlockVector &Blocks, uint64_t &Count);
+  static void getCyclesCount(const BlockVector &Blocks, uint64_t &Count);
+  static uint64_t getLineCount(const BlockVector &Blocks);
+
 private:
   GCOVFunction &Parent;
   uint32_t Number;

llvm/lib/ProfileData/GCOV.cpp

@@ -111,9 +111,7 @@ void GCOVFile::print(raw_ostream &OS) const {
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 /// dump - Dump GCOVFile content to dbgs() for debugging purposes.
-LLVM_DUMP_METHOD void GCOVFile::dump() const {
-  print(dbgs());
-}
+LLVM_DUMP_METHOD void GCOVFile::dump() const { print(dbgs()); }
 #endif
 
 /// collectLineCounts - Collect line counts. This must be used after
@@ -359,9 +357,7 @@ void GCOVFunction::print(raw_ostream &OS) const {
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 /// dump - Dump GCOVFunction content to dbgs() for debugging purposes.
-LLVM_DUMP_METHOD void GCOVFunction::dump() const {
-  print(dbgs());
-}
+LLVM_DUMP_METHOD void GCOVFunction::dump() const { print(dbgs()); }
 #endif
 
 /// collectLineCounts - Collect line counts. This must be used after
@@ -437,11 +433,134 @@ void GCOVBlock::print(raw_ostream &OS) const {
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 /// dump - Dump GCOVBlock content to dbgs() for debugging purposes.
-LLVM_DUMP_METHOD void GCOVBlock::dump() const {
-  print(dbgs());
-}
+LLVM_DUMP_METHOD void GCOVBlock::dump() const { print(dbgs()); }
 #endif
 
+//===----------------------------------------------------------------------===//
+// Cycles detection
+//
+// The algorithm in GCC is based on the algorihtm by Hawick & James:
+//   "Enumerating Circuits and Loops in Graphs with Self-Arcs and Multiple-Arcs"
+//   http://complexity.massey.ac.nz/cstn/013/cstn-013.pdf.
+
+/// Get the count for the detected cycle.
+uint64_t GCOVBlock::getCycleCount(const Edges &Path) {
+  uint64_t CycleCount = std::numeric_limits<uint64_t>::max();
+  for (auto E : Path) {
+    CycleCount = std::min(E->CyclesCount, CycleCount);
+  }
+  for (auto E : Path) {
+    E->CyclesCount -= CycleCount;
+  }
+  return CycleCount;
+}
+
+/// Unblock a vertex previously marked as blocked.
+void GCOVBlock::unblock(const GCOVBlock *U, BlockVector &Blocked,
+                        BlockVectorLists &BlockLists) {
+  auto it = find(Blocked, U);
+  if (it == Blocked.end()) {
+    return;
+  }
+
+  const size_t index = it - Blocked.begin();
+  Blocked.erase(it);
+
+  const BlockVector ToUnblock(BlockLists[index]);
+  BlockLists.erase(BlockLists.begin() + index);
+  for (auto GB : ToUnblock) {
+    GCOVBlock::unblock(GB, Blocked, BlockLists);
+  }
+}
+
+bool GCOVBlock::lookForCircuit(const GCOVBlock *V, const GCOVBlock *Start,
+                               Edges &Path, BlockVector &Blocked,
+                               BlockVectorLists &BlockLists,
+                               const BlockVector &Blocks, uint64_t &Count) {
+  Blocked.push_back(V);
+  BlockLists.emplace_back(BlockVector());
+  bool FoundCircuit = false;
+
+  for (auto E : V->dsts()) {
+    const GCOVBlock *W = &E->Dst;
+    if (W < Start || find(Blocks, W) == Blocks.end()) {
+      continue;
+    }
+
+    Path.push_back(E);
+
+    if (W == Start) {
+      // We've a cycle.
+      Count += GCOVBlock::getCycleCount(Path);
+      FoundCircuit = true;
+    } else if (find(Blocked, W) == Blocked.end() && // W is not blocked.
+               GCOVBlock::lookForCircuit(W, Start, Path, Blocked, BlockLists,
+                                         Blocks, Count)) {
+      FoundCircuit = true;
+    }
+
+    Path.pop_back();
+  }
+
+  if (FoundCircuit) {
+    GCOVBlock::unblock(V, Blocked, BlockLists);
+  } else {
+    for (auto E : V->dsts()) {
+      const GCOVBlock *W = &E->Dst;
+      if (W < Start || find(Blocks, W) == Blocks.end()) {
+        continue;
+      }
+      const size_t index = find(Blocked, W) - Blocked.begin();
+      BlockVector &List = BlockLists[index];
+      if (find(List, V) == List.end()) {
+        List.push_back(V);
+      }
+    }
+  }
+
+  return FoundCircuit;
+}
+
+/// Get the count for the list of blocks which lie on the same line.
+void GCOVBlock::getCyclesCount(const BlockVector &Blocks, uint64_t &Count) {
+  for (auto Block : Blocks) {
+    Edges Path;
+    BlockVector Blocked;
+    BlockVectorLists BlockLists;
+
+    GCOVBlock::lookForCircuit(Block, Block, Path, Blocked, BlockLists, Blocks,
+                              Count);
+  }
+}
+
+/// Get the count for the list of blocks which lie on the same line.
+uint64_t GCOVBlock::getLineCount(const BlockVector &Blocks) {
+  uint64_t Count = 0;
+
+  for (auto Block : Blocks) {
+    if (Block->getNumSrcEdges() == 0) {
+      // The block has no predecessors and a non-null counter
+      // (can be the case with entry block in functions).
+      Count += Block->getCount();
+    } else {
+      // Add counts from predecessors that are not on the same line.
+      for (auto E : Block->srcs()) {
+        const GCOVBlock *W = &E->Src;
+        if (find(Blocks, W) == Blocks.end()) {
+          Count += E->Count;
+        }
+      }
+    }
+    for (auto E : Block->dsts()) {
+      E->CyclesCount = E->Count;
+    }
+  }
+
+  GCOVBlock::getCyclesCount(Blocks, Count);
+
+  return Count;
+}
+
 //===----------------------------------------------------------------------===//
 // FileInfo implementation.
 
@@ -578,8 +697,8 @@ FileInfo::openCoveragePath(StringRef CoveragePath) {
     return llvm::make_unique<raw_null_ostream>();
 
   std::error_code EC;
-  auto OS = llvm::make_unique<raw_fd_ostream>(CoveragePath, EC,
-                                              sys::fs::F_Text);
+  auto OS =
+      llvm::make_unique<raw_fd_ostream>(CoveragePath, EC, sys::fs::F_Text);
   if (EC) {
     errs() << EC.message() << "\n";
     return llvm::make_unique<raw_null_ostream>();
@@ -628,17 +747,7 @@ void FileInfo::print(raw_ostream &InfoOS, StringRef MainFilename,
 
         // Add up the block counts to form line counts.
         DenseMap<const GCOVFunction *, bool> LineExecs;
-        uint64_t LineCount = 0;
         for (const GCOVBlock *Block : Blocks) {
-          if (Options.AllBlocks) {
-            // Only take the highest block count for that line.
-            uint64_t BlockCount = Block->getCount();
-            LineCount = LineCount > BlockCount ? LineCount : BlockCount;
-          } else {
-            // Sum up all of the block counts.
-            LineCount += Block->getCount();
-          }
-
           if (Options.FuncCoverage) {
             // This is a slightly convoluted way to most accurately gather line
             // statistics for functions. Basically what is happening is that we
@@ -674,6 +783,7 @@ void FileInfo::print(raw_ostream &InfoOS, StringRef MainFilename,
           }
         }
 
+        const uint64_t LineCount = GCOVBlock::getLineCount(Blocks);
         if (LineCount == 0)
           CovOS << "    #####:";
         else {

llvm/test/tools/llvm-cov/Inputs/test_-a.cpp.gcov

@@ -49,7 +49,7 @@
         4:   34-block  0
        12:   34-block  1
         8:   34-block  2
-        8:   35:      assign(ii, jj);
+       12:   35:      assign(ii, jj);
         8:   35-block  0
         4:   35-block  1
         2:   36:}

llvm/test/tools/llvm-cov/Inputs/test_-a.h.gcov

@@ -3,7 +3,7 @@
         -:    0:Data:test.gcda
         -:    0:Runs:2
         -:    0:Programs:1
-        2:    1:struct A {
+        4:    1:struct A {
         2:    1-block  0
         2:    1-block  1
         -:    2:  virtual void B();

llvm/test/tools/llvm-cov/Inputs/test_-a_-b.cpp.gcov

@@ -60,7 +60,7 @@ branch  1 taken 33%
 branch  0 taken 67%
 branch  1 taken 33%
         8:   34-block  2
-        8:   35:      assign(ii, jj);
+       12:   35:      assign(ii, jj);
         8:   35-block  0
         4:   35-block  1
         2:   36:}

llvm/test/tools/llvm-cov/Inputs/test_-a_-b.h.gcov

@@ -5,7 +5,7 @@
         -:    0:Programs:1
 function _ZN1AC1Ev called 2 returned 100% blocks executed 100%
 function _ZN1AC2Ev called 2 returned 100% blocks executed 100%
-        2:    1:struct A {
+        4:    1:struct A {
         2:    1-block  0
         2:    1-block  1
         -:    2:  virtual void B();

llvm/test/tools/llvm-cov/Inputs/test_-a_-b_-c_-u.cpp.gcov

@@ -70,7 +70,7 @@ branch  1 taken 8
 branch  2 taken 4
         8:   34-block  2
 unconditional  3 taken 8
-        8:   35:      assign(ii, jj);
+       12:   35:      assign(ii, jj);
         8:   35-block  0
 unconditional  0 taken 8
         4:   35-block  1

llvm/test/tools/llvm-cov/Inputs/test_-a_-b_-c_-u.h.gcov

@@ -5,7 +5,7 @@
         -:    0:Programs:1
 function _ZN1AC1Ev called 2 returned 100% blocks executed 100%
 function _ZN1AC2Ev called 2 returned 100% blocks executed 100%
-        2:    1:struct A {
+        4:    1:struct A {
         2:    1-block  0
 unconditional  0 taken 2
         2:    1-block  1

llvm/test/tools/llvm-cov/Inputs/test_-a_-b_-u.cpp.gcov

@@ -70,7 +70,7 @@ branch  1 taken 67%
 branch  2 taken 33%
         8:   34-block  2
 unconditional  3 taken 100%
-        8:   35:      assign(ii, jj);
+       12:   35:      assign(ii, jj);
         8:   35-block  0
 unconditional  0 taken 100%
         4:   35-block  1

llvm/test/tools/llvm-cov/Inputs/test_-a_-b_-u.h.gcov

@@ -5,7 +5,7 @@
         -:    0:Programs:1
 function _ZN1AC1Ev called 2 returned 100% blocks executed 100%
 function _ZN1AC2Ev called 2 returned 100% blocks executed 100%
-        2:    1:struct A {
+        4:    1:struct A {
         2:    1-block  0
 unconditional  0 taken 100%
         2:    1-block  1

llvm/test/tools/llvm-cov/Inputs/test_missing.cpp.gcov

@@ -35,8 +35,8 @@
        12:   30:/*EOF*/
         -:   31:/*EOF*/
         -:   32:/*EOF*/
-       21:   33:/*EOF*/
-       36:   34:/*EOF*/
+        9:   33:/*EOF*/
+       18:   34:/*EOF*/
        18:   35:/*EOF*/
         3:   36:/*EOF*/
         -:   37:/*EOF*/
@@ -53,7 +53,7 @@
     #####:   48:/*EOF*/
         -:   49:/*EOF*/
         -:   50:/*EOF*/
-       66:   51:/*EOF*/
+       33:   51:/*EOF*/
        30:   52:/*EOF*/
         -:   53:/*EOF*/
         6:   54:/*EOF*/
@@ -71,7 +71,7 @@
        30:   66:/*EOF*/
         -:   67:/*EOF*/
         3:   68:/*EOF*/
-25769803782:   69:/*EOF*/
+12884901891:   69:/*EOF*/
 12884901888:   70:/*EOF*/
         -:   71:/*EOF*/
         3:   72:/*EOF*/

llvm/test/tools/llvm-cov/Inputs/test_no_options.cpp.gcov

@@ -35,8 +35,8 @@
         8:   30:}
         -:   31:
         -:   32:void initialize_grid() {
-       12:   33:  for (int ii = 0; ii < 2; ii++)
-       24:   34:    for (int jj = 0; jj < 2; jj++)
+        6:   33:  for (int ii = 0; ii < 2; ii++)
+       12:   34:    for (int jj = 0; jj < 2; jj++)
        12:   35:      assign(ii, jj);
         2:   36:}
         -:   37:
@@ -53,7 +53,7 @@
     #####:   48:    a += rand();
         -:   49:  }
         -:   50:
-       44:   51:  for (int ii = 0; ii < 10; ++ii) {
+       22:   51:  for (int ii = 0; ii < 10; ++ii) {
        20:   52:    switch (rand() % 5) {
         -:   53:      case 0:
         4:   54:        a += rand();
@@ -71,7 +71,7 @@
        20:   66:  }
         -:   67:
         2:   68:  A thing;
-17179869188:   69:  for (uint64_t ii = 0; ii < 4294967296; ++ii)
+8589934594:   69:  for (uint64_t ii = 0; ii < 4294967296; ++ii)
 8589934592:   70:    thing.B();
         -:   71:
         2:   72:  return a + 8 + grid[2][3] + len;