https://github.com/mattgodbolt/compiler-explorer/issues/1158

llvm-mca-execution-graph.cpp

// TimelineView.cpp HACK

// [...]
void TimelineView::printTimeline(raw_ostream &OS) const {
// [...]

  std::error_code err;
  raw_fd_ostream f("-", err);
  f << "\ndigraph test {\n";
  struct InstData {
    uint32_t timelineIdx;
    uint32_t executionStartCycle;
    bool operator<(const InstData &b) const { return executionStartCycle < b.executionStartCycle; }
  };
  // we need to sort the instructions by execution start
  // we also insert a dummy entry node
  std::vector<InstData> insts{{~0u, 0u}};
  f << 'i' << ~0u << " [style = invis];\n";

  // create nodes with asm instructions
  for (uint32_t i = 0; i < Timeline.size(); ++i) {
    insts.push_back({i, Timeline[i].CycleIssued});
    f << 'i' << i << " [label = \"";
    MCIP.printInst(&Source[i % Source.size()], f, "", STI);
    f << "\", shape=box];\n";
  }
  std::stable_sort(insts.begin(), insts.end());
  auto emitEdge = [&f](uint32_t i, uint32_t j) {
    f << 'i' << i << " -> " << 'i' << j << '\n';
  };
  // create the edges
  uint32_t lastI = 0;
  for (uint32_t i = 1; i < insts.size(); ++i) {
    // if instructions start getting executed at the same time they are independent
    // create edges from the previous level node to all of them
    if (insts[lastI].executionStartCycle == insts[i].executionStartCycle) {
      emitEdge(insts[lastI - 1].timelineIdx, insts[i].timelineIdx);
      continue;
    }
    // we reached a new execution level
    // create edges from all previous level nodes
    for (; lastI < i; ++lastI) {
      emitEdge(insts[lastI].timelineIdx, insts[i].timelineIdx);
    }
  }
  f << '}';
}