Tooltips for control flow dot graphs

[mark-sed]

Summary

This is 2. out of 3 changes to the CFG pass that aims to make graphs more readable and contain more information.

• 1. Change - D154092
• 2. Change - D154096
• 3. Change - D154102

This change adds tooltips over graph edges so that when zoomed in one can easily determine from to where is the given edge going and also see the probability for this edge.

If all 3 changes will be accepted the final graphs should look as in the attached image:

[knaumov]

LGTM

[mark-sed]

I don't have commit rights, could I get someone to commit this for me please?

[dblaikie]

Presumably this needs test coverage? Could you add some (& link to the review or commit in this review)?

[mark-sed]

@dblaikie Hi, sorry for the late response I want to get back to this and add the test, but got sidetracked by other stuff, I'll add it later. Thanks.

llvm/include/llvm/Analysis/CFGPrinter.h

if (const SwitchInst *SI = dyn_cast<SwitchInst>(Node->getTerminator())) {
       raw_string_ostream OS(Str);
       auto Case = *SwitchInst::ConstCaseIt::fromSuccessorIndex(SI, SuccNo);
       OS << Case.getCaseValue()->getValue();
       return OS.str();
     }
     return "";
   }
 
+  static std::string getBBName(const BasicBlock *Node) {
+    std::string NodeName = Node->getName().str();
+    if (NodeName.empty()) {
+      raw_string_ostream NodeOS(NodeName);
+      Node->printAsOperand(NodeOS, false);
+      NodeName = NodeOS.str();
+      // Removing %
+      NodeName.erase(NodeName.begin());
+    }
+    return NodeName;
+  }
+
   /// Display the raw branch weights from PGO.
   std::string getEdgeAttributes(const BasicBlock *Node, const_succ_iterator I,
                                 DOTFuncInfo *CFGInfo) {
+    unsigned OpNo = I.getSuccessorIndex();
+    const Instruction *TI = Node->getTerminator();
+    BasicBlock *SuccBB = TI->getSuccessor(OpNo);
+    auto BranchProb = CFGInfo->getBPI()->getEdgeProbability(Node, SuccBB);
+    double WeightPercent = ((double)BranchProb.getNumerator()) /
+                           ((double)BranchProb.getDenominator());
+
+    std::string TTAttr =
+        formatv("tooltip=\"{0} -> {1}\\nProbability {2:P}\" ", getBBName(Node),
+                getBBName(SuccBB), WeightPercent);
     if (!CFGInfo->showEdgeWeights())
-      return "";
+      return TTAttr;
 
-    const Instruction *TI = Node->getTerminator();
     if (TI->getNumSuccessors() == 1)
-      return "penwidth=2";
-
-    unsigned OpNo = I.getSuccessorIndex();
+      return TTAttr + "penwidth=2";
 
     if (OpNo >= TI->getNumSuccessors())
-      return "";
+      return TTAttr;
 
-    BasicBlock *SuccBB = TI->getSuccessor(OpNo);
-    auto BranchProb = CFGInfo->getBPI()->getEdgeProbability(Node, SuccBB);
-    double WeightPercent = ((double)BranchProb.getNumerator()) /
-                           ((double)BranchProb.getDenominator());
     double Width = 1 + WeightPercent;
 
     if (!CFGInfo->useRawEdgeWeights())
-      return formatv("label=\"{0:P}\" penwidth={1}", WeightPercent, Width)
+      return TTAttr +
+             formatv("label=\"{0:P}\" penwidth={1}", WeightPercent, Width)
                  .str();
 
     // Prepend a 'W' to indicate that this is a weight rather than the actual
     // profile count (due to scaling).
 
     uint64_t Freq = CFGInfo->getFreq(Node);
-    std::string Attrs = formatv("label=\"W:{0}\" penwidth={1}",
-                                (uint64_t)(Freq * WeightPercent), Width);
+    std::string Attrs =
+        TTAttr + formatv("label=\"W:{0}\" penwidth={1}",
+                         (uint64_t)(Freq * WeightPercent), Width)
+                     .str();
     if (Attrs.size())
       return Attrs;
 
     MDNode *WeightsNode = getBranchWeightMDNode(*TI);
     if (!WeightsNode)
-      return "";
+      return TTAttr;
 
     OpNo = I.getSuccessorIndex() + 1;
     if (OpNo >= WeightsNode->getNumOperands())
-      return "";
+      return TTAttr;
     ConstantInt *Weight =
         mdconst::dyn_extract<ConstantInt>(WeightsNode->getOperand(OpNo));
     if (!Weight)
-      return "";
-    return ("label=\"W:" + std::to_string(Weight->getZExtValue()) +
+      return TTAttr;
+    return (TTAttr + "label=\"W:" + std::to_string(Weight->getZExtValue()) +
             "\" penwidth=" + std::to_string(Width));
   }
 
   std::string getNodeAttributes(const BasicBlock *Node, DOTFuncInfo *CFGInfo) {
 
     if (!CFGInfo->showHeatColors())
       return "";