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 double getBlockFreqRelativeToEntryBlock(const MachineBasicBlock *MBB) const { 69 assert(getEntryFreq() != BlockFrequency(0) && 70 "getEntryFreq() should not return 0 here!"); 71 return static_cast<double>(getBlockFreq(MBB).getFrequency()) / 72 static_cast<double>(getEntryFreq().getFrequency()); 73 } 74 75 std::optional<uint64_t> 76 getBlockProfileCount(const MachineBasicBlock *MBB) const; 77 std::optional<uint64_t> getProfileCountFromFreq(BlockFrequency Freq) const; 78 79 bool isIrrLoopHeader(const MachineBasicBlock *MBB) const; 80 81 /// incrementally calculate block frequencies when we split edges, to avoid 82 /// full CFG traversal. 83 void onEdgeSplit(const MachineBasicBlock &NewPredecessor, 84 const MachineBasicBlock &NewSuccessor, 85 const MachineBranchProbabilityInfo &MBPI); 86 87 const MachineFunction *getFunction() const; 88 const MachineBranchProbabilityInfo *getMBPI() const; 89 90 /// Pop up a ghostview window with the current block frequency propagation 91 /// rendered using dot. 92 void view(const Twine &Name, bool isSimple = true) const; 93 94 /// Divide a block's BlockFrequency::getFrequency() value by this value to 95 /// obtain the entry block - relative frequency of said block. 96 BlockFrequency getEntryFreq() const; 97 }; 98 99 /// Print the block frequency @p Freq relative to the current functions entry 100 /// frequency. Returns a Printable object that can be piped via `<<` to a 101 /// `raw_ostream`. 102 Printable printBlockFreq(const MachineBlockFrequencyInfo &MBFI, 103 BlockFrequency Freq); 104 105 /// Convenience function equivalent to calling 106 /// `printBlockFreq(MBFI, MBFI.getBlockFreq(&MBB))`. 107 Printable printBlockFreq(const MachineBlockFrequencyInfo &MBFI, 108 const MachineBasicBlock &MBB); 109 110 } // end namespace llvm 111 112 #endif // LLVM_CODEGEN_MACHINEBLOCKFREQUENCYINFO_H 113