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