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/ADT/Triple.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 22 /// \file LiveDebugValues.cpp 23 /// 24 /// The LiveDebugValues pass extends the range of variable locations 25 /// (specified by DBG_VALUE instructions) from single blocks to successors 26 /// and any other code locations where the variable location is valid. 27 /// There are currently two implementations: the "VarLoc" implementation 28 /// explicitly tracks the location of a variable, while the "InstrRef" 29 /// implementation tracks the values defined by instructions through locations. 30 /// 31 /// This file implements neither; it merely registers the pass, allows the 32 /// user to pick which implementation will be used to propagate variable 33 /// locations. 34 35 #define DEBUG_TYPE "livedebugvalues" 36 37 using namespace llvm; 38 39 static cl::opt<bool> 40 ForceInstrRefLDV("force-instr-ref-livedebugvalues", cl::Hidden, 41 cl::desc("Use instruction-ref based LiveDebugValues with " 42 "normal DBG_VALUE inputs"), 43 cl::init(false)); 44 45 static cl::opt<cl::boolOrDefault> ValueTrackingVariableLocations( 46 "experimental-debug-variable-locations", 47 cl::desc("Use experimental new value-tracking variable locations")); 48 49 // Options to prevent pathological compile-time behavior. If InputBBLimit and 50 // InputDbgValueLimit are both exceeded, range extension is disabled. 51 static cl::opt<unsigned> InputBBLimit( 52 "livedebugvalues-input-bb-limit", 53 cl::desc("Maximum input basic blocks before DBG_VALUE limit applies"), 54 cl::init(10000), cl::Hidden); 55 static cl::opt<unsigned> InputDbgValueLimit( 56 "livedebugvalues-input-dbg-value-limit", 57 cl::desc( 58 "Maximum input DBG_VALUE insts supported by debug range extension"), 59 cl::init(50000), cl::Hidden); 60 61 namespace { 62 /// Generic LiveDebugValues pass. Calls through to VarLocBasedLDV or 63 /// InstrRefBasedLDV to perform location propagation, via the LDVImpl 64 /// base class. 65 class LiveDebugValues : public MachineFunctionPass { 66 public: 67 static char ID; 68 69 LiveDebugValues(); 70 ~LiveDebugValues() = default; 71 72 /// Calculate the liveness information for the given machine function. 73 bool runOnMachineFunction(MachineFunction &MF) override; 74 75 MachineFunctionProperties getRequiredProperties() const override { 76 return MachineFunctionProperties().set( 77 MachineFunctionProperties::Property::NoVRegs); 78 } 79 80 void getAnalysisUsage(AnalysisUsage &AU) const override { 81 AU.setPreservesCFG(); 82 MachineFunctionPass::getAnalysisUsage(AU); 83 } 84 85 private: 86 std::unique_ptr<LDVImpl> InstrRefImpl; 87 std::unique_ptr<LDVImpl> VarLocImpl; 88 TargetPassConfig *TPC; 89 MachineDominatorTree MDT; 90 }; 91 } // namespace 92 93 char LiveDebugValues::ID = 0; 94 95 char &llvm::LiveDebugValuesID = LiveDebugValues::ID; 96 97 INITIALIZE_PASS(LiveDebugValues, DEBUG_TYPE, "Live DEBUG_VALUE analysis", false, 98 false) 99 100 /// Default construct and initialize the pass. 101 LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) { 102 initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry()); 103 InstrRefImpl = 104 std::unique_ptr<LDVImpl>(llvm::makeInstrRefBasedLiveDebugValues()); 105 VarLocImpl = std::unique_ptr<LDVImpl>(llvm::makeVarLocBasedLiveDebugValues()); 106 } 107 108 bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) { 109 bool InstrRefBased = MF.useDebugInstrRef(); 110 // Allow the user to force selection of InstrRef LDV. 111 InstrRefBased |= ForceInstrRefLDV; 112 113 TPC = getAnalysisIfAvailable<TargetPassConfig>(); 114 LDVImpl *TheImpl = &*VarLocImpl; 115 116 MachineDominatorTree *DomTree = nullptr; 117 if (InstrRefBased) { 118 DomTree = &MDT; 119 MDT.calculate(MF); 120 TheImpl = &*InstrRefImpl; 121 } 122 123 return TheImpl->ExtendRanges(MF, DomTree, TPC, InputBBLimit, 124 InputDbgValueLimit); 125 } 126 127 bool llvm::debuginfoShouldUseDebugInstrRef(const Triple &T) { 128 // Enable by default on x86_64, disable if explicitly turned off on cmdline. 129 if (T.getArch() == llvm::Triple::x86_64 && 130 ValueTrackingVariableLocations != cl::boolOrDefault::BOU_FALSE) 131 return true; 132 133 // Enable if explicitly requested on command line. 134 return ValueTrackingVariableLocations == cl::boolOrDefault::BOU_TRUE; 135 } 136