Add setBlockFreq interface to BlockFrequencyInfo, BlockFrequencyInfoImplBase, and BlockFrequencyInfoImpl.

[congh]

Summary

This patch make it possible to directly change the block frequency through BFI instead of updating block frequencies for the whole function (which is relatively expensive). This is useful when there are small local frequency changes and the up-to-date BFI is needed soon.

[congh]

Create new entry for newly added basic block in BlockFrequencyInfoImpl.

include/llvm/Analysis/BlockFrequencyInfo.h

public:
 
   /// getblockFreq - Return block frequency. Return 0 if we don't have the
   /// information. Please note that initial frequency is equal to ENTRY_FREQ. It
   /// means that we should not rely on the value itself, but only on the
   /// comparison to the other block frequencies. We do this to avoid using of
   /// floating points.
   BlockFrequency getBlockFreq(const BasicBlock *BB) const;
 
+  // Set the frequency of the given basic block. Return true if it succeeds and
+  // false otherwise.
+  bool setBlockFreq(const BasicBlock *BB, uint64_t Freq);
+
   // Print the block frequency Freq to OS using the current functions entry
   // frequency to convert freq into a relative decimal form.
   raw_ostream &printBlockFreq(raw_ostream &OS, const BlockFrequency Freq) const;
 
   // Convenience method that attempts to look up the frequency associated with
   // BB and print it to OS.
   raw_ostream &printBlockFreq(raw_ostream &OS, const BasicBlock *BB) const;
 
   uint64_t getEntryFreq() const;
 
 };
 
 }
 
 #endif

include/llvm/Analysis/BlockFrequencyInfoImpl.h

public:
 
   virtual raw_ostream &print(raw_ostream &OS) const { return OS; }
   void dump() const { print(dbgs()); }
 
   Scaled64 getFloatingBlockFreq(const BlockNode &Node) const;
 
   BlockFrequency getBlockFreq(const BlockNode &Node) const;
 
+  bool setBlockFreq(const BlockNode &Node, uint64_t Freq);
+
   raw_ostream &printBlockFreq(raw_ostream &OS, const BlockNode &Node) const;
   raw_ostream &printBlockFreq(raw_ostream &OS,
                               const BlockFrequency &Freq) const;
 
   uint64_t getEntryFreq() const {
     assert(!Freqs.empty());
     return Freqs[0].Integer;
   }
public:
   void doFunction(const FunctionT *F, const BranchProbabilityInfoT *BPI,
                   const LoopInfoT *LI);
   BlockFrequencyInfoImpl() : BPI(nullptr), LI(nullptr), F(nullptr) {}
 
   using BlockFrequencyInfoImplBase::getEntryFreq;
   BlockFrequency getBlockFreq(const BlockT *BB) const {
     return BlockFrequencyInfoImplBase::getBlockFreq(getNode(BB));
   }
+  bool setBlockFreq(const BlockT *BB, uint64_t Freq);
   Scaled64 getFloatingBlockFreq(const BlockT *BB) const {
     return BlockFrequencyInfoImplBase::getFloatingBlockFreq(getNode(BB));
   }
 
   /// \brief Print the frequencies for the current function.
   ///
   /// Prints the frequencies for the blocks in the current function.
   ///
void BlockFrequencyInfoImpl<BT>::doFunction(const FunctionT *F,
   // Visit loops in post-order to find the local mass distribution, and then do
   // the full function.
   computeMassInLoops();
   computeMassInFunction();
   unwrapLoops();
   finalizeMetrics();
 }
 
+template <class BT>
+bool BlockFrequencyInfoImpl<BT>::setBlockFreq(const BlockT *BB, uint64_t Freq) {
+  if (Nodes.count(BB))
+    return BlockFrequencyInfoImplBase::setBlockFreq(getNode(BB), Freq);
+  else {
+    // If BB is a newly added block after BFI is done, we need to create a new
+    // BlockNode for it assigned with a new index. The index can be determined
+    // by the size of Freqs.
+    BlockNode NewNode(Freqs.size());
+    Nodes[BB] = NewNode;
+    Freqs.emplace_back();
+    return BlockFrequencyInfoImplBase::setBlockFreq(NewNode, Freq);
+  }
+}
+
 template <class BT> void BlockFrequencyInfoImpl<BT>::initializeRPOT() {
   const BlockT *Entry = F->begin();
   RPOT.reserve(F->size());
   std::copy(po_begin(Entry), po_end(Entry), std::back_inserter(RPOT));
   std::reverse(RPOT.begin(), RPOT.end());
 
   assert(RPOT.size() - 1 <= BlockNode::getMaxIndex() &&
          "More nodes in function than Block Frequency Info supports");

lib/Analysis/BlockFrequencyInfo.cpp

 void BlockFrequencyInfo::print(raw_ostream &O, const Module *) const {
   if (BFI) BFI->print(O);
 }
 
 BlockFrequency BlockFrequencyInfo::getBlockFreq(const BasicBlock *BB) const {
   return BFI ? BFI->getBlockFreq(BB) : 0;
 }
 
+bool BlockFrequencyInfo::setBlockFreq(const BasicBlock *BB,
+                                      uint64_t Freq) {
+  return BFI ? BFI->setBlockFreq(BB, Freq) : false;
+}
+
 /// Pop up a ghostview window with the current block frequency propagation
 /// rendered using dot.
 void BlockFrequencyInfo::view() const {
 // This code is only for debugging.
 #ifndef NDEBUG
   ViewGraph(const_cast<BlockFrequencyInfo *>(this), "BlockFrequencyDAGs");
 #else
   errs() << "BlockFrequencyInfo::view is only available in debug builds on "

lib/Analysis/BlockFrequencyInfoImpl.cpp

 }
 Scaled64
 BlockFrequencyInfoImplBase::getFloatingBlockFreq(const BlockNode &Node) const {
   if (!Node.isValid())
     return Scaled64::getZero();
   return Freqs[Node.Index].Scaled;
 }
 
+bool BlockFrequencyInfoImplBase::setBlockFreq(const BlockNode &Node,
+                                              uint64_t Freq) {
+  if (!Node.isValid())
+    return false;
+  Freqs[Node.Index].Integer = Freq;
+  return true;
+}
+
 std::string
 BlockFrequencyInfoImplBase::getBlockName(const BlockNode &Node) const {
   return std::string();
 }
 std::string
 BlockFrequencyInfoImplBase::getLoopName(const LoopData &Loop) const {
   return getBlockName(Loop.getHeader()) + (Loop.isIrreducible() ? "**" : "*");
 }