1 //===- LiveDebugValues.cpp - Tracking Debug Value MIs ---------------------===// 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 #include "LiveDebugValues.h" 10 11 #include "llvm/CodeGen/LiveDebugValuesPass.h" 12 #include "llvm/CodeGen/MachineDominators.h" 13 #include "llvm/CodeGen/MachineFunction.h" 14 #include "llvm/CodeGen/MachineFunctionPass.h" 15 #include "llvm/CodeGen/Passes.h" 16 #include "llvm/CodeGen/TargetPassConfig.h" 17 #include "llvm/InitializePasses.h" 18 #include "llvm/Pass.h" 19 #include "llvm/PassRegistry.h" 20 #include "llvm/Support/CommandLine.h" 21 #include "llvm/Target/TargetMachine.h" 22 #include "llvm/TargetParser/Triple.h" 23 24 /// \file LiveDebugValues.cpp 25 /// 26 /// The LiveDebugValues pass extends the range of variable locations 27 /// (specified by DBG_VALUE instructions) from single blocks to successors 28 /// and any other code locations where the variable location is valid. 29 /// There are currently two implementations: the "VarLoc" implementation 30 /// explicitly tracks the location of a variable, while the "InstrRef" 31 /// implementation tracks the values defined by instructions through locations. 32 /// 33 /// This file implements neither; it merely registers the pass, allows the 34 /// user to pick which implementation will be used to propagate variable 35 /// locations. 36 37 #define DEBUG_TYPE "livedebugvalues" 38 39 using namespace llvm; 40 41 static cl::opt<bool> 42 ForceInstrRefLDV("force-instr-ref-livedebugvalues", cl::Hidden, 43 cl::desc("Use instruction-ref based LiveDebugValues with " 44 "normal DBG_VALUE inputs"), 45 cl::init(false)); 46 47 static cl::opt<cl::boolOrDefault> ValueTrackingVariableLocations( 48 "experimental-debug-variable-locations", 49 cl::desc("Use experimental new value-tracking variable locations")); 50 51 // Options to prevent pathological compile-time behavior. If InputBBLimit and 52 // InputDbgValueLimit are both exceeded, range extension is disabled. 53 static cl::opt<unsigned> InputBBLimit( 54 "livedebugvalues-input-bb-limit", 55 cl::desc("Maximum input basic blocks before DBG_VALUE limit applies"), 56 cl::init(10000), cl::Hidden); 57 static cl::opt<unsigned> InputDbgValueLimit( 58 "livedebugvalues-input-dbg-value-limit", 59 cl::desc( 60 "Maximum input DBG_VALUE insts supported by debug range extension"), 61 cl::init(50000), cl::Hidden); 62 63 namespace { 64 /// Generic LiveDebugValues pass. Calls through to VarLocBasedLDV or 65 /// InstrRefBasedLDV to perform location propagation, via the LDVImpl 66 /// base class. 67 class LiveDebugValuesLegacy : public MachineFunctionPass { 68 public: 69 static char ID; 70 71 LiveDebugValuesLegacy(); 72 ~LiveDebugValuesLegacy() = default; 73 74 /// Calculate the liveness information for the given machine function. 75 bool runOnMachineFunction(MachineFunction &MF) override; 76 77 void getAnalysisUsage(AnalysisUsage &AU) const override { 78 AU.setPreservesCFG(); 79 AU.addRequired<TargetPassConfig>(); 80 MachineFunctionPass::getAnalysisUsage(AU); 81 } 82 }; 83 84 struct LiveDebugValues { 85 LiveDebugValues(); 86 ~LiveDebugValues() = default; 87 bool run(MachineFunction &MF, bool ShouldEmitDebugEntryValues); 88 89 private: 90 std::unique_ptr<LDVImpl> InstrRefImpl; 91 std::unique_ptr<LDVImpl> VarLocImpl; 92 MachineDominatorTree MDT; 93 }; 94 } // namespace 95 96 char LiveDebugValuesLegacy::ID = 0; 97 98 char &llvm::LiveDebugValuesID = LiveDebugValuesLegacy::ID; 99 100 INITIALIZE_PASS(LiveDebugValuesLegacy, DEBUG_TYPE, "Live DEBUG_VALUE analysis", 101 false, false) 102 103 /// Default construct and initialize the pass. 104 LiveDebugValuesLegacy::LiveDebugValuesLegacy() : MachineFunctionPass(ID) { 105 initializeLiveDebugValuesLegacyPass(*PassRegistry::getPassRegistry()); 106 } 107 108 LiveDebugValues::LiveDebugValues() { 109 InstrRefImpl = 110 std::unique_ptr<LDVImpl>(llvm::makeInstrRefBasedLiveDebugValues()); 111 VarLocImpl = std::unique_ptr<LDVImpl>(llvm::makeVarLocBasedLiveDebugValues()); 112 } 113 114 PreservedAnalyses 115 LiveDebugValuesPass::run(MachineFunction &MF, 116 MachineFunctionAnalysisManager &MFAM) { 117 if (!LiveDebugValues().run(MF, ShouldEmitDebugEntryValues)) 118 return PreservedAnalyses::all(); 119 auto PA = getMachineFunctionPassPreservedAnalyses(); 120 PA.preserveSet<CFGAnalyses>(); 121 return PA; 122 } 123 124 void LiveDebugValuesPass::printPipeline( 125 raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) { 126 OS << MapClassName2PassName(name()); 127 if (ShouldEmitDebugEntryValues) 128 OS << "<emit-debug-entry-values>"; 129 } 130 131 bool LiveDebugValuesLegacy::runOnMachineFunction(MachineFunction &MF) { 132 auto *TPC = &getAnalysis<TargetPassConfig>(); 133 return LiveDebugValues().run( 134 MF, TPC->getTM<TargetMachine>().Options.ShouldEmitDebugEntryValues()); 135 } 136 137 bool LiveDebugValues::run(MachineFunction &MF, 138 bool ShouldEmitDebugEntryValues) { 139 bool InstrRefBased = MF.useDebugInstrRef(); 140 // Allow the user to force selection of InstrRef LDV. 141 InstrRefBased |= ForceInstrRefLDV; 142 143 LDVImpl *TheImpl = &*VarLocImpl; 144 145 MachineDominatorTree *DomTree = nullptr; 146 if (InstrRefBased) { 147 DomTree = &MDT; 148 MDT.recalculate(MF); 149 TheImpl = &*InstrRefImpl; 150 } 151 152 return TheImpl->ExtendRanges(MF, DomTree, ShouldEmitDebugEntryValues, 153 InputBBLimit, InputDbgValueLimit); 154 } 155 156 bool llvm::debuginfoShouldUseDebugInstrRef(const Triple &T) { 157 // Enable by default on x86_64, disable if explicitly turned off on cmdline. 158 if (T.getArch() == llvm::Triple::x86_64 && 159 ValueTrackingVariableLocations != cl::boolOrDefault::BOU_FALSE) 160 return true; 161 162 // Enable if explicitly requested on command line. 163 return ValueTrackingVariableLocations == cl::boolOrDefault::BOU_TRUE; 164 } 165