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/MachineDominators.h" 12 #include "llvm/CodeGen/MachineFunction.h" 13 #include "llvm/CodeGen/MachineFunctionPass.h" 14 #include "llvm/CodeGen/Passes.h" 15 #include "llvm/CodeGen/TargetPassConfig.h" 16 #include "llvm/InitializePasses.h" 17 #include "llvm/Pass.h" 18 #include "llvm/PassRegistry.h" 19 #include "llvm/Support/CommandLine.h" 20 #include "llvm/Target/TargetMachine.h" 21 #include "llvm/TargetParser/Triple.h" 22 23 /// \file LiveDebugValues.cpp 24 /// 25 /// The LiveDebugValues pass extends the range of variable locations 26 /// (specified by DBG_VALUE instructions) from single blocks to successors 27 /// and any other code locations where the variable location is valid. 28 /// There are currently two implementations: the "VarLoc" implementation 29 /// explicitly tracks the location of a variable, while the "InstrRef" 30 /// implementation tracks the values defined by instructions through locations. 31 /// 32 /// This file implements neither; it merely registers the pass, allows the 33 /// user to pick which implementation will be used to propagate variable 34 /// locations. 35 36 #define DEBUG_TYPE "livedebugvalues" 37 38 using namespace llvm; 39 40 static cl::opt<bool> 41 ForceInstrRefLDV("force-instr-ref-livedebugvalues", cl::Hidden, 42 cl::desc("Use instruction-ref based LiveDebugValues with " 43 "normal DBG_VALUE inputs"), 44 cl::init(false)); 45 46 static cl::opt<cl::boolOrDefault> ValueTrackingVariableLocations( 47 "experimental-debug-variable-locations", 48 cl::desc("Use experimental new value-tracking variable locations")); 49 50 // Options to prevent pathological compile-time behavior. If InputBBLimit and 51 // InputDbgValueLimit are both exceeded, range extension is disabled. 52 static cl::opt<unsigned> InputBBLimit( 53 "livedebugvalues-input-bb-limit", 54 cl::desc("Maximum input basic blocks before DBG_VALUE limit applies"), 55 cl::init(10000), cl::Hidden); 56 static cl::opt<unsigned> InputDbgValueLimit( 57 "livedebugvalues-input-dbg-value-limit", 58 cl::desc( 59 "Maximum input DBG_VALUE insts supported by debug range extension"), 60 cl::init(50000), cl::Hidden); 61 62 namespace { 63 /// Generic LiveDebugValues pass. Calls through to VarLocBasedLDV or 64 /// InstrRefBasedLDV to perform location propagation, via the LDVImpl 65 /// base class. 66 class LiveDebugValues : public MachineFunctionPass { 67 public: 68 static char ID; 69 70 LiveDebugValues(); 71 ~LiveDebugValues() = default; 72 73 /// Calculate the liveness information for the given machine function. 74 bool runOnMachineFunction(MachineFunction &MF) override; 75 76 void getAnalysisUsage(AnalysisUsage &AU) const override { 77 AU.setPreservesCFG(); 78 MachineFunctionPass::getAnalysisUsage(AU); 79 } 80 81 private: 82 std::unique_ptr<LDVImpl> InstrRefImpl; 83 std::unique_ptr<LDVImpl> VarLocImpl; 84 TargetPassConfig *TPC = nullptr; 85 MachineDominatorTree MDT; 86 }; 87 } // namespace 88 89 char LiveDebugValues::ID = 0; 90 91 char &llvm::LiveDebugValuesID = LiveDebugValues::ID; 92 93 INITIALIZE_PASS(LiveDebugValues, DEBUG_TYPE, "Live DEBUG_VALUE analysis", false, 94 false) 95 96 /// Default construct and initialize the pass. 97 LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) { 98 initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry()); 99 InstrRefImpl = 100 std::unique_ptr<LDVImpl>(llvm::makeInstrRefBasedLiveDebugValues()); 101 VarLocImpl = std::unique_ptr<LDVImpl>(llvm::makeVarLocBasedLiveDebugValues()); 102 } 103 104 bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) { 105 // Except for Wasm, all targets should be only using physical register at this 106 // point. Wasm only use virtual registers throught its pipeline, but its 107 // virtual registers don't participate in this LiveDebugValues analysis; only 108 // its target indices do. 109 assert(MF.getTarget().getTargetTriple().isWasm() || 110 MF.getProperties().hasProperty( 111 MachineFunctionProperties::Property::NoVRegs)); 112 113 bool InstrRefBased = MF.useDebugInstrRef(); 114 // Allow the user to force selection of InstrRef LDV. 115 InstrRefBased |= ForceInstrRefLDV; 116 117 TPC = getAnalysisIfAvailable<TargetPassConfig>(); 118 LDVImpl *TheImpl = &*VarLocImpl; 119 120 MachineDominatorTree *DomTree = nullptr; 121 if (InstrRefBased) { 122 DomTree = &MDT; 123 MDT.calculate(MF); 124 TheImpl = &*InstrRefImpl; 125 } 126 127 return TheImpl->ExtendRanges(MF, DomTree, TPC, InputBBLimit, 128 InputDbgValueLimit); 129 } 130 131 bool llvm::debuginfoShouldUseDebugInstrRef(const Triple &T) { 132 // Enable by default on x86_64, disable if explicitly turned off on cmdline. 133 if (T.getArch() == llvm::Triple::x86_64 && 134 ValueTrackingVariableLocations != cl::boolOrDefault::BOU_FALSE) 135 return true; 136 137 // Enable if explicitly requested on command line. 138 return ValueTrackingVariableLocations == cl::boolOrDefault::BOU_TRUE; 139 } 140