1 //===- CFGPrinter.cpp - DOT printer for the control flow graph ------------===// 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 // This file defines a `-dot-cfg` analysis pass, which emits the 10 // `<prefix>.<fnname>.dot` file for each function in the program, with a graph 11 // of the CFG for that function. The default value for `<prefix>` is `cfg` but 12 // can be customized as needed. 13 // 14 // The other main feature of this file is that it implements the 15 // Function::viewCFG method, which is useful for debugging passes which operate 16 // on the CFG. 17 // 18 //===----------------------------------------------------------------------===// 19 20 #include "llvm/Analysis/CFGPrinter.h" 21 #include "llvm/ADT/PostOrderIterator.h" 22 #include "llvm/Support/CommandLine.h" 23 #include "llvm/Support/FileSystem.h" 24 #include "llvm/Support/GraphWriter.h" 25 26 using namespace llvm; 27 28 static cl::opt<std::string> 29 CFGFuncName("cfg-func-name", cl::Hidden, 30 cl::desc("The name of a function (or its substring)" 31 " whose CFG is viewed/printed.")); 32 33 static cl::opt<std::string> CFGDotFilenamePrefix( 34 "cfg-dot-filename-prefix", cl::Hidden, 35 cl::desc("The prefix used for the CFG dot file names.")); 36 37 static cl::opt<bool> HideUnreachablePaths("cfg-hide-unreachable-paths", 38 cl::init(false)); 39 40 static cl::opt<bool> HideDeoptimizePaths("cfg-hide-deoptimize-paths", 41 cl::init(false)); 42 43 static cl::opt<double> HideColdPaths( 44 "cfg-hide-cold-paths", cl::init(0.0), 45 cl::desc("Hide blocks with relative frequency below the given value")); 46 47 static cl::opt<bool> ShowHeatColors("cfg-heat-colors", cl::init(true), 48 cl::Hidden, 49 cl::desc("Show heat colors in CFG")); 50 51 static cl::opt<bool> UseRawEdgeWeight("cfg-raw-weights", cl::init(false), 52 cl::Hidden, 53 cl::desc("Use raw weights for labels. " 54 "Use percentages as default.")); 55 56 static cl::opt<bool> 57 ShowEdgeWeight("cfg-weights", cl::init(false), cl::Hidden, 58 cl::desc("Show edges labeled with weights")); 59 60 static void writeCFGToDotFile(Function &F, BlockFrequencyInfo *BFI, 61 BranchProbabilityInfo *BPI, uint64_t MaxFreq, 62 bool CFGOnly = false) { 63 std::string Filename = 64 (CFGDotFilenamePrefix + "." + F.getName() + ".dot").str(); 65 errs() << "Writing '" << Filename << "'..."; 66 67 std::error_code EC; 68 raw_fd_ostream File(Filename, EC, sys::fs::OF_Text); 69 70 DOTFuncInfo CFGInfo(&F, BFI, BPI, MaxFreq); 71 CFGInfo.setHeatColors(ShowHeatColors); 72 CFGInfo.setEdgeWeights(ShowEdgeWeight); 73 CFGInfo.setRawEdgeWeights(UseRawEdgeWeight); 74 75 if (!EC) 76 WriteGraph(File, &CFGInfo, CFGOnly); 77 else 78 errs() << " error opening file for writing!"; 79 errs() << "\n"; 80 } 81 82 static void viewCFG(Function &F, const BlockFrequencyInfo *BFI, 83 const BranchProbabilityInfo *BPI, uint64_t MaxFreq, 84 bool CFGOnly = false) { 85 DOTFuncInfo CFGInfo(&F, BFI, BPI, MaxFreq); 86 CFGInfo.setHeatColors(ShowHeatColors); 87 CFGInfo.setEdgeWeights(ShowEdgeWeight); 88 CFGInfo.setRawEdgeWeights(UseRawEdgeWeight); 89 90 ViewGraph(&CFGInfo, "cfg." + F.getName(), CFGOnly); 91 } 92 93 PreservedAnalyses CFGViewerPass::run(Function &F, FunctionAnalysisManager &AM) { 94 if (!CFGFuncName.empty() && !F.getName().contains(CFGFuncName)) 95 return PreservedAnalyses::all(); 96 auto *BFI = &AM.getResult<BlockFrequencyAnalysis>(F); 97 auto *BPI = &AM.getResult<BranchProbabilityAnalysis>(F); 98 viewCFG(F, BFI, BPI, getMaxFreq(F, BFI)); 99 return PreservedAnalyses::all(); 100 } 101 102 PreservedAnalyses CFGOnlyViewerPass::run(Function &F, 103 FunctionAnalysisManager &AM) { 104 if (!CFGFuncName.empty() && !F.getName().contains(CFGFuncName)) 105 return PreservedAnalyses::all(); 106 auto *BFI = &AM.getResult<BlockFrequencyAnalysis>(F); 107 auto *BPI = &AM.getResult<BranchProbabilityAnalysis>(F); 108 viewCFG(F, BFI, BPI, getMaxFreq(F, BFI), /*CFGOnly=*/true); 109 return PreservedAnalyses::all(); 110 } 111 112 PreservedAnalyses CFGPrinterPass::run(Function &F, 113 FunctionAnalysisManager &AM) { 114 if (!CFGFuncName.empty() && !F.getName().contains(CFGFuncName)) 115 return PreservedAnalyses::all(); 116 auto *BFI = &AM.getResult<BlockFrequencyAnalysis>(F); 117 auto *BPI = &AM.getResult<BranchProbabilityAnalysis>(F); 118 writeCFGToDotFile(F, BFI, BPI, getMaxFreq(F, BFI)); 119 return PreservedAnalyses::all(); 120 } 121 122 PreservedAnalyses CFGOnlyPrinterPass::run(Function &F, 123 FunctionAnalysisManager &AM) { 124 if (!CFGFuncName.empty() && !F.getName().contains(CFGFuncName)) 125 return PreservedAnalyses::all(); 126 auto *BFI = &AM.getResult<BlockFrequencyAnalysis>(F); 127 auto *BPI = &AM.getResult<BranchProbabilityAnalysis>(F); 128 writeCFGToDotFile(F, BFI, BPI, getMaxFreq(F, BFI), /*CFGOnly=*/true); 129 return PreservedAnalyses::all(); 130 } 131 132 /// viewCFG - This function is meant for use from the debugger. You can just 133 /// say 'call F->viewCFG()' and a ghostview window should pop up from the 134 /// program, displaying the CFG of the current function. This depends on there 135 /// being a 'dot' and 'gv' program in your path. 136 /// 137 void Function::viewCFG() const { viewCFG(false, nullptr, nullptr); } 138 139 void Function::viewCFG(bool ViewCFGOnly, const BlockFrequencyInfo *BFI, 140 const BranchProbabilityInfo *BPI) const { 141 if (!CFGFuncName.empty() && !getName().contains(CFGFuncName)) 142 return; 143 DOTFuncInfo CFGInfo(this, BFI, BPI, BFI ? getMaxFreq(*this, BFI) : 0); 144 ViewGraph(&CFGInfo, "cfg" + getName(), ViewCFGOnly); 145 } 146 147 /// viewCFGOnly - This function is meant for use from the debugger. It works 148 /// just like viewCFG, but it does not include the contents of basic blocks 149 /// into the nodes, just the label. If you are only interested in the CFG 150 /// this can make the graph smaller. 151 /// 152 void Function::viewCFGOnly() const { viewCFGOnly(nullptr, nullptr); } 153 154 void Function::viewCFGOnly(const BlockFrequencyInfo *BFI, 155 const BranchProbabilityInfo *BPI) const { 156 viewCFG(true, BFI, BPI); 157 } 158 159 /// Find all blocks on the paths which terminate with a deoptimize or 160 /// unreachable (i.e. all blocks which are post-dominated by a deoptimize 161 /// or unreachable). These paths are hidden if the corresponding cl::opts 162 /// are enabled. 163 void DOTGraphTraits<DOTFuncInfo *>::computeDeoptOrUnreachablePaths( 164 const Function *F) { 165 auto evaluateBB = [&](const BasicBlock *Node) { 166 if (succ_empty(Node)) { 167 const Instruction *TI = Node->getTerminator(); 168 isOnDeoptOrUnreachablePath[Node] = 169 (HideUnreachablePaths && isa<UnreachableInst>(TI)) || 170 (HideDeoptimizePaths && Node->getTerminatingDeoptimizeCall()); 171 return; 172 } 173 isOnDeoptOrUnreachablePath[Node] = 174 llvm::all_of(successors(Node), [this](const BasicBlock *BB) { 175 return isOnDeoptOrUnreachablePath[BB]; 176 }); 177 }; 178 /// The post order traversal iteration is done to know the status of 179 /// isOnDeoptOrUnreachablePath for all the successors on the current BB. 180 llvm::for_each(post_order(&F->getEntryBlock()), evaluateBB); 181 } 182 183 bool DOTGraphTraits<DOTFuncInfo *>::isNodeHidden(const BasicBlock *Node, 184 const DOTFuncInfo *CFGInfo) { 185 if (HideColdPaths.getNumOccurrences() > 0) 186 if (auto *BFI = CFGInfo->getBFI()) { 187 BlockFrequency NodeFreq = BFI->getBlockFreq(Node); 188 BlockFrequency EntryFreq = BFI->getEntryFreq(); 189 // Hide blocks with relative frequency below HideColdPaths threshold. 190 if ((double)NodeFreq.getFrequency() / EntryFreq.getFrequency() < 191 HideColdPaths) 192 return true; 193 } 194 if (HideUnreachablePaths || HideDeoptimizePaths) { 195 if (!isOnDeoptOrUnreachablePath.contains(Node)) 196 computeDeoptOrUnreachablePaths(Node->getParent()); 197 return isOnDeoptOrUnreachablePath[Node]; 198 } 199 return false; 200 } 201