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  1. //===- MachineBlockFrequencyInfo.h - MBB Frequency Analysis -----*- C++ -*-===//
  2. //
  3. // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  4. // See https://llvm.org/LICENSE.txt for license information.
  5. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  6. //
  7. //===----------------------------------------------------------------------===//
  8. //
  9. // Loops should be simplified before this analysis.
  10. //
  11. //===----------------------------------------------------------------------===//
  12.  
  13. #ifndef LLVM_CODEGEN_MACHINEBLOCKFREQUENCYINFO_H
  14. #define LLVM_CODEGEN_MACHINEBLOCKFREQUENCYINFO_H
  15.  
  16. #include "llvm/CodeGen/MachineFunctionPass.h"
  17. #include "llvm/Support/BlockFrequency.h"
  18. #include <cstdint>
  19. #include <memory>
  20. #include <optional>
  21.  
  22. namespace llvm {
  23.  
  24. template <class BlockT> class BlockFrequencyInfoImpl;
  25. class MachineBasicBlock;
  26. class MachineBranchProbabilityInfo;
  27. class MachineFunction;
  28. class MachineLoopInfo;
  29. class raw_ostream;
  30.  
  31. /// MachineBlockFrequencyInfo pass uses BlockFrequencyInfoImpl implementation
  32. /// to estimate machine basic block frequencies.
  33. class MachineBlockFrequencyInfo : public MachineFunctionPass {
  34.   using ImplType = BlockFrequencyInfoImpl<MachineBasicBlock>;
  35.   std::unique_ptr<ImplType> MBFI;
  36.  
  37. public:
  38.   static char ID;
  39.  
  40.   MachineBlockFrequencyInfo();
  41.   explicit MachineBlockFrequencyInfo(MachineFunction &F,
  42.                                      MachineBranchProbabilityInfo &MBPI,
  43.                                      MachineLoopInfo &MLI);
  44.   ~MachineBlockFrequencyInfo() override;
  45.  
  46.   void getAnalysisUsage(AnalysisUsage &AU) const override;
  47.  
  48.   bool runOnMachineFunction(MachineFunction &F) override;
  49.  
  50.   /// calculate - compute block frequency info for the given function.
  51.   void calculate(const MachineFunction &F,
  52.                  const MachineBranchProbabilityInfo &MBPI,
  53.                  const MachineLoopInfo &MLI);
  54.  
  55.   void releaseMemory() override;
  56.  
  57.   /// getblockFreq - Return block frequency. Return 0 if we don't have the
  58.   /// information. Please note that initial frequency is equal to 1024. It means
  59.   /// that we should not rely on the value itself, but only on the comparison to
  60.   /// the other block frequencies. We do this to avoid using of floating points.
  61.   /// For example, to get the frequency of a block relative to the entry block,
  62.   /// divide the integral value returned by this function (the
  63.   /// BlockFrequency::getFrequency() value) by getEntryFreq().
  64.   BlockFrequency getBlockFreq(const MachineBasicBlock *MBB) const;
  65.  
  66.   /// Compute the frequency of the block, relative to the entry block.
  67.   /// This API assumes getEntryFreq() is non-zero.
  68.   float getBlockFreqRelativeToEntryBlock(const MachineBasicBlock *MBB) const {
  69.     return getBlockFreq(MBB).getFrequency() * (1.0f / getEntryFreq());
  70.   }
  71.  
  72.   std::optional<uint64_t>
  73.   getBlockProfileCount(const MachineBasicBlock *MBB) const;
  74.   std::optional<uint64_t> getProfileCountFromFreq(uint64_t Freq) const;
  75.  
  76.   bool isIrrLoopHeader(const MachineBasicBlock *MBB) const;
  77.  
  78.   /// incrementally calculate block frequencies when we split edges, to avoid
  79.   /// full CFG traversal.
  80.   void onEdgeSplit(const MachineBasicBlock &NewPredecessor,
  81.                    const MachineBasicBlock &NewSuccessor,
  82.                    const MachineBranchProbabilityInfo &MBPI);
  83.  
  84.   const MachineFunction *getFunction() const;
  85.   const MachineBranchProbabilityInfo *getMBPI() const;
  86.  
  87.   /// Pop up a ghostview window with the current block frequency propagation
  88.   /// rendered using dot.
  89.   void view(const Twine &Name, bool isSimple = true) const;
  90.  
  91.   // Print the block frequency Freq to OS using the current functions entry
  92.   // frequency to convert freq into a relative decimal form.
  93.   raw_ostream &printBlockFreq(raw_ostream &OS, const BlockFrequency Freq) const;
  94.  
  95.   // Convenience method that attempts to look up the frequency associated with
  96.   // BB and print it to OS.
  97.   raw_ostream &printBlockFreq(raw_ostream &OS,
  98.                               const MachineBasicBlock *MBB) const;
  99.  
  100.   /// Divide a block's BlockFrequency::getFrequency() value by this value to
  101.   /// obtain the entry block - relative frequency of said block.
  102.   uint64_t getEntryFreq() const;
  103. };
  104.  
  105. } // end namespace llvm
  106.  
  107. #endif // LLVM_CODEGEN_MACHINEBLOCKFREQUENCYINFO_H
  108.