[VPlan] Add dump function to VPlan class.

[fhahn]

Summary

This adds a dump() function to VPlan, which uses the existing
operator<<.

This method provides a convenient way to dump a VPlan while debugging,
e.g. from lldb.

[merge_guards_bot]

Build result: FAILURE - Could not check out parent git hash "b4e439d0b00684f11631b6f733e910774455750a". It was not found in the repository. Did you configure the "Parent Revision" in Phabricator properly? Trying to apply the patch to the master branch instead...

ERROR: arc patch failed with error code 1. Check build log for details.
Log files: console-log.txt, CMakeCache.txt

[hsaito]

LGTM. Thanks!

llvm/lib/Transforms/Vectorize/VPlan.h

loop_basicblocks() {
     std::function<bool(VPBlockBase &)> Pred = [TopRegion](VPBlockBase &B) {
       return !TopRegion || &B != TopRegion->getExit();
     };
     auto BBRange = basicblocks();
     return make_filter_range(
         make_range(std::next(BBRange.begin()), BBRange.end()), Pred);
   }
 
+  /// Dump the plan to stderr (for debugging).
+  void dump() const;
+
 private:
   /// Add to the given dominator tree the header block and every new basic block
   /// that was created between it and the latch block, inclusive.
   static void updateDominatorTree(DominatorTree *DT,
                                   BasicBlock *LoopPreHeaderBB,
                                   BasicBlock *LoopLatchBB);
 };
 
 /// VPlanPrinter prints a given VPlan to a given output stream. The printing is
 /// indented and follows the dot format.
 class VPlanPrinter {
-  friend inline raw_ostream &operator<<(raw_ostream &OS, VPlan &Plan);
+  friend inline raw_ostream &operator<<(raw_ostream &OS, const VPlan &Plan);
   friend inline raw_ostream &operator<<(raw_ostream &OS,
                                         const struct VPlanIngredient &I);
 
 private:
   raw_ostream &OS;
-  VPlan &Plan;
+  const VPlan &Plan;
   unsigned Depth = 0;
   unsigned TabWidth = 2;
   std::string Indent;
   unsigned BID = 0;
   SmallDenseMap<const VPBlockBase *, unsigned> BlockID;
 
-  VPlanPrinter(raw_ostream &O, VPlan &P) : OS(O), Plan(P) {}
+  VPlanPrinter(raw_ostream &O, const VPlan &P) : OS(O), Plan(P) {}
 
   /// Handle indentation.
   void bumpIndent(int b) { Indent = std::string((Depth += b) * TabWidth, ' '); }
 
   /// Print a given \p Block of the Plan.
   void dumpBlock(const VPBlockBase *Block);
 
   /// Print the information related to the CFG edges going out of a given
struct VPlanIngredient {
   VPlanIngredient(Value *V) : V(V) {}
 };
 
 inline raw_ostream &operator<<(raw_ostream &OS, const VPlanIngredient &I) {
   VPlanPrinter::printAsIngredient(OS, I.V);
   return OS;
 }
 
-inline raw_ostream &operator<<(raw_ostream &OS, VPlan &Plan) {
+inline raw_ostream &operator<<(raw_ostream &OS, const VPlan &Plan) {
   VPlanPrinter Printer(OS, Plan);
   Printer.dump();
   return OS;
 }
 
-
 //===----------------------------------------------------------------------===//
 // VPlan Utilities
 //===----------------------------------------------------------------------===//
 
 /// Class that provides utilities for VPBlockBases in VPlan.
 class VPBlockUtils {
 public:
   VPBlockUtils() = delete;

llvm/lib/Transforms/Vectorize/VPlan.cpp

void VPlan::execute(VPTransformState *State) {
   assert(Merged && "Could not merge last basic block with latch.");
   VectorLatchBB = LastBB;
 
   // We do not attempt to preserve DT for outer loop vectorization currently.
   if (!EnableVPlanNativePath)
     updateDominatorTree(State->DT, VectorPreHeaderBB, VectorLatchBB);
 }
 
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+LLVM_DUMP_METHOD
+void VPlan::dump() const { dbgs() << *this << '\n'; }
+#endif
+
 void VPlan::updateDominatorTree(DominatorTree *DT, BasicBlock *LoopPreHeaderBB,
                                 BasicBlock *LoopLatchBB) {
   BasicBlock *LoopHeaderBB = LoopPreHeaderBB->getSingleSuccessor();
   assert(LoopHeaderBB && "Loop preheader does not have a single successor.");
   DT->addNewBlock(LoopHeaderBB, LoopPreHeaderBB);
   // The vector body may be more than a single basic-block by this point.
   // Update the dominator tree information inside the vector body by propagating
   // it from header to latch, expecting only triangular control-flow, if any.
void VPlanPrinter::dump() {
   bumpIndent(0);
   OS << "digraph VPlan {\n";
   OS << "graph [labelloc=t, fontsize=30; label=\"Vectorization Plan";
   if (!Plan.getName().empty())
     OS << "\\n" << DOT::EscapeString(Plan.getName());
   if (!Plan.Value2VPValue.empty() || Plan.BackedgeTakenCount) {
     OS << ", where:";
     if (Plan.BackedgeTakenCount)
-      OS << "\\n"
-         << *Plan.getOrCreateBackedgeTakenCount() << " := BackedgeTakenCount";
+      OS << "\\n" << *Plan.BackedgeTakenCount << " := BackedgeTakenCount";
     for (auto Entry : Plan.Value2VPValue) {
       OS << "\\n" << *Entry.second;
       OS << DOT::EscapeString(" := ");
       Entry.first->printAsOperand(OS, false);
     }
   }
   OS << "\"]\n";
   OS << "node [shape=rect, fontname=Courier, fontsize=30]\n";
   OS << "edge [fontname=Courier, fontsize=30]\n";
   OS << "compound=true\n";
 
-  for (VPBlockBase *Block : depth_first(Plan.getEntry()))
+  for (const VPBlockBase *Block : depth_first(Plan.getEntry()))
     dumpBlock(Block);
 
   OS << "}\n";
 }
 
 void VPlanPrinter::dumpBlock(const VPBlockBase *Block) {
   if (const VPBasicBlock *BasicBlock = dyn_cast<VPBasicBlock>(Block))
     dumpBasicBlock(BasicBlock);