1 //===- MachineDebugify.cpp - Attach synthetic debug info to everything ----===// 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 /// \file This pass attaches synthetic debug info to everything. It can be used 10 /// to create targeted tests for debug info preservation, or test for CodeGen 11 /// differences with vs. without debug info. 12 /// 13 /// This isn't intended to have feature parity with Debugify. 14 //===----------------------------------------------------------------------===// 15 16 #include "llvm/ADT/DenseMap.h" 17 #include "llvm/ADT/SmallSet.h" 18 #include "llvm/ADT/SmallVector.h" 19 #include "llvm/CodeGen/MachineInstrBuilder.h" 20 #include "llvm/CodeGen/MachineModuleInfo.h" 21 #include "llvm/CodeGen/Passes.h" 22 #include "llvm/CodeGen/TargetInstrInfo.h" 23 #include "llvm/CodeGen/TargetSubtargetInfo.h" 24 #include "llvm/IR/IntrinsicInst.h" 25 #include "llvm/InitializePasses.h" 26 #include "llvm/Transforms/Utils/Debugify.h" 27 28 #define DEBUG_TYPE "mir-debugify" 29 30 using namespace llvm; 31 32 namespace { 33 bool applyDebugifyMetadataToMachineFunction(MachineModuleInfo &MMI, 34 DIBuilder &DIB, Function &F) { 35 MachineFunction *MaybeMF = MMI.getMachineFunction(F); 36 if (!MaybeMF) 37 return false; 38 MachineFunction &MF = *MaybeMF; 39 const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo(); 40 41 DISubprogram *SP = F.getSubprogram(); 42 assert(SP && "IR Debugify just created it?"); 43 44 Module &M = *F.getParent(); 45 LLVMContext &Ctx = M.getContext(); 46 47 unsigned NextLine = SP->getLine(); 48 for (MachineBasicBlock &MBB : MF) { 49 for (MachineInstr &MI : MBB) { 50 // This will likely emit line numbers beyond the end of the imagined 51 // source function and into subsequent ones. We don't do anything about 52 // that as it doesn't really matter to the compiler where the line is in 53 // the imaginary source code. 54 MI.setDebugLoc(DILocation::get(Ctx, NextLine++, 1, SP)); 55 } 56 } 57 58 // Find local variables defined by debugify. No attempt is made to match up 59 // MIR-level regs to the 'correct' IR-level variables: there isn't a simple 60 // way to do that, and it isn't necessary to find interesting CodeGen bugs. 61 // Instead, simply keep track of one variable per line. Later, we can insert 62 // DBG_VALUE insts that point to these local variables. Emitting DBG_VALUEs 63 // which cover a wide range of lines can help stress the debug info passes: 64 // if we can't do that, fall back to using the local variable which precedes 65 // all the others. 66 Function *DbgValF = M.getFunction("llvm.dbg.value"); 67 DbgValueInst *EarliestDVI = nullptr; 68 DbgVariableRecord *EarliestDVR = nullptr; 69 DenseMap<unsigned, DILocalVariable *> Line2Var; 70 DIExpression *Expr = nullptr; 71 if (DbgValF) { 72 for (const Use &U : DbgValF->uses()) { 73 auto *DVI = dyn_cast<DbgValueInst>(U.getUser()); 74 if (!DVI || DVI->getFunction() != &F) 75 continue; 76 unsigned Line = DVI->getDebugLoc().getLine(); 77 assert(Line != 0 && "debugify should not insert line 0 locations"); 78 Line2Var[Line] = DVI->getVariable(); 79 if (!EarliestDVI || Line < EarliestDVI->getDebugLoc().getLine()) 80 EarliestDVI = DVI; 81 Expr = DVI->getExpression(); 82 } 83 } 84 for (BasicBlock &BB : F) { 85 for (Instruction &I : BB) { 86 for (DbgVariableRecord &DVR : filterDbgVars(I.getDbgRecordRange())) { 87 if (!DVR.isDbgValue()) 88 continue; 89 unsigned Line = DVR.getDebugLoc().getLine(); 90 assert(Line != 0 && "debugify should not insert line 0 locations"); 91 Line2Var[Line] = DVR.getVariable(); 92 if (!EarliestDVR || Line < EarliestDVR->getDebugLoc().getLine()) 93 EarliestDVR = &DVR; 94 Expr = DVR.getExpression(); 95 } 96 } 97 } 98 if (Line2Var.empty()) 99 return true; 100 101 // Now, try to insert a DBG_VALUE instruction after each real instruction. 102 // Do this by introducing debug uses of each register definition. If that is 103 // not possible (e.g. we have a phi or a meta instruction), emit a constant. 104 uint64_t NextImm = 0; 105 SmallSet<DILocalVariable *, 16> VarSet; 106 const MCInstrDesc &DbgValDesc = TII.get(TargetOpcode::DBG_VALUE); 107 for (MachineBasicBlock &MBB : MF) { 108 MachineBasicBlock::iterator FirstNonPHIIt = MBB.getFirstNonPHI(); 109 for (auto I = MBB.begin(), E = MBB.end(); I != E;) { 110 MachineInstr &MI = *I; 111 ++I; 112 113 // `I` may point to a DBG_VALUE created in the previous loop iteration. 114 if (MI.isDebugInstr()) 115 continue; 116 117 // It's not allowed to insert DBG_VALUEs after a terminator. 118 if (MI.isTerminator()) 119 continue; 120 121 // Find a suitable insertion point for the DBG_VALUE. 122 auto InsertBeforeIt = MI.isPHI() ? FirstNonPHIIt : I; 123 124 // Find a suitable local variable for the DBG_VALUE. 125 unsigned Line = MI.getDebugLoc().getLine(); 126 if (!Line2Var.count(Line)) 127 Line = EarliestDVI ? EarliestDVI->getDebugLoc().getLine() 128 : EarliestDVR->getDebugLoc().getLine(); 129 DILocalVariable *LocalVar = Line2Var[Line]; 130 assert(LocalVar && "No variable for current line?"); 131 VarSet.insert(LocalVar); 132 133 // Emit DBG_VALUEs for register definitions. 134 SmallVector<MachineOperand *, 4> RegDefs; 135 for (MachineOperand &MO : MI.all_defs()) 136 if (MO.getReg()) 137 RegDefs.push_back(&MO); 138 for (MachineOperand *MO : RegDefs) 139 BuildMI(MBB, InsertBeforeIt, MI.getDebugLoc(), DbgValDesc, 140 /*IsIndirect=*/false, *MO, LocalVar, Expr); 141 142 // OK, failing that, emit a constant DBG_VALUE. 143 if (RegDefs.empty()) { 144 auto ImmOp = MachineOperand::CreateImm(NextImm++); 145 BuildMI(MBB, InsertBeforeIt, MI.getDebugLoc(), DbgValDesc, 146 /*IsIndirect=*/false, ImmOp, LocalVar, Expr); 147 } 148 } 149 } 150 151 // Here we save the number of lines and variables into "llvm.mir.debugify". 152 // It is useful for mir-check-debugify. 153 NamedMDNode *NMD = M.getNamedMetadata("llvm.mir.debugify"); 154 IntegerType *Int32Ty = Type::getInt32Ty(Ctx); 155 if (!NMD) { 156 NMD = M.getOrInsertNamedMetadata("llvm.mir.debugify"); 157 auto addDebugifyOperand = [&](unsigned N) { 158 NMD->addOperand(MDNode::get( 159 Ctx, ValueAsMetadata::getConstant(ConstantInt::get(Int32Ty, N)))); 160 }; 161 // Add number of lines. 162 addDebugifyOperand(NextLine - 1); 163 // Add number of variables. 164 addDebugifyOperand(VarSet.size()); 165 } else { 166 assert(NMD->getNumOperands() == 2 && 167 "llvm.mir.debugify should have exactly 2 operands!"); 168 auto setDebugifyOperand = [&](unsigned Idx, unsigned N) { 169 NMD->setOperand(Idx, MDNode::get(Ctx, ValueAsMetadata::getConstant( 170 ConstantInt::get(Int32Ty, N)))); 171 }; 172 auto getDebugifyOperand = [&](unsigned Idx) { 173 return mdconst::extract<ConstantInt>(NMD->getOperand(Idx)->getOperand(0)) 174 ->getZExtValue(); 175 }; 176 // Set number of lines. 177 setDebugifyOperand(0, NextLine - 1); 178 // Set number of variables. 179 auto OldNumVars = getDebugifyOperand(1); 180 setDebugifyOperand(1, OldNumVars + VarSet.size()); 181 } 182 183 return true; 184 } 185 186 /// ModulePass for attaching synthetic debug info to everything, used with the 187 /// legacy module pass manager. 188 struct DebugifyMachineModule : public ModulePass { 189 bool runOnModule(Module &M) override { 190 // We will insert new debugify metadata, so erasing the old one. 191 assert(!M.getNamedMetadata("llvm.mir.debugify") && 192 "llvm.mir.debugify metadata already exists! Strip it first"); 193 MachineModuleInfo &MMI = 194 getAnalysis<MachineModuleInfoWrapperPass>().getMMI(); 195 return applyDebugifyMetadata( 196 M, M.functions(), 197 "ModuleDebugify: ", [&](DIBuilder &DIB, Function &F) -> bool { 198 return applyDebugifyMetadataToMachineFunction(MMI, DIB, F); 199 }); 200 } 201 202 DebugifyMachineModule() : ModulePass(ID) {} 203 204 void getAnalysisUsage(AnalysisUsage &AU) const override { 205 AU.addRequired<MachineModuleInfoWrapperPass>(); 206 AU.addPreserved<MachineModuleInfoWrapperPass>(); 207 AU.setPreservesCFG(); 208 } 209 210 static char ID; // Pass identification. 211 }; 212 char DebugifyMachineModule::ID = 0; 213 214 } // end anonymous namespace 215 216 INITIALIZE_PASS_BEGIN(DebugifyMachineModule, DEBUG_TYPE, 217 "Machine Debugify Module", false, false) 218 INITIALIZE_PASS_END(DebugifyMachineModule, DEBUG_TYPE, 219 "Machine Debugify Module", false, false) 220 221 ModulePass *llvm::createDebugifyMachineModulePass() { 222 return new DebugifyMachineModule(); 223 } 224