//===- MachineDebugify.cpp - Attach synthetic debug info to everything ----===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// /// /// \file This pass attaches synthetic debug info to everything. It can be used /// to create targeted tests for debug info preservation, or test for CodeGen /// differences with vs. without debug info. /// /// This isn't intended to have feature parity with Debugify. //===----------------------------------------------------------------------===// #include "llvm/ADT/DenseMap.h" #include "llvm/ADT/SmallSet.h" #include "llvm/ADT/SmallVector.h" #include "llvm/CodeGen/MachineInstrBuilder.h" #include "llvm/CodeGen/MachineModuleInfo.h" #include "llvm/CodeGen/Passes.h" #include "llvm/CodeGen/TargetInstrInfo.h" #include "llvm/CodeGen/TargetSubtargetInfo.h" #include "llvm/IR/IntrinsicInst.h" #include "llvm/InitializePasses.h" #include "llvm/Transforms/Utils/Debugify.h" #define DEBUG_TYPE "mir-debugify" using namespace llvm; namespace { bool applyDebugifyMetadataToMachineFunction(MachineModuleInfo &MMI, DIBuilder &DIB, Function &F) { MachineFunction *MaybeMF = MMI.getMachineFunction(F); if (!MaybeMF) return false; MachineFunction &MF = *MaybeMF; const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo(); DISubprogram *SP = F.getSubprogram(); assert(SP && "IR Debugify just created it?"); Module &M = *F.getParent(); LLVMContext &Ctx = M.getContext(); unsigned NextLine = SP->getLine(); for (MachineBasicBlock &MBB : MF) { for (MachineInstr &MI : MBB) { // This will likely emit line numbers beyond the end of the imagined // source function and into subsequent ones. We don't do anything about // that as it doesn't really matter to the compiler where the line is in // the imaginary source code. MI.setDebugLoc(DILocation::get(Ctx, NextLine++, 1, SP)); } } // Find local variables defined by debugify. No attempt is made to match up // MIR-level regs to the 'correct' IR-level variables: there isn't a simple // way to do that, and it isn't necessary to find interesting CodeGen bugs. // Instead, simply keep track of one variable per line. Later, we can insert // DBG_VALUE insts that point to these local variables. Emitting DBG_VALUEs // which cover a wide range of lines can help stress the debug info passes: // if we can't do that, fall back to using the local variable which precedes // all the others. Function *DbgValF = M.getFunction("llvm.dbg.value"); DbgValueInst *EarliestDVI = nullptr; DbgVariableRecord *EarliestDVR = nullptr; DenseMap Line2Var; DIExpression *Expr = nullptr; if (DbgValF) { for (const Use &U : DbgValF->uses()) { auto *DVI = dyn_cast(U.getUser()); if (!DVI || DVI->getFunction() != &F) continue; unsigned Line = DVI->getDebugLoc().getLine(); assert(Line != 0 && "debugify should not insert line 0 locations"); Line2Var[Line] = DVI->getVariable(); if (!EarliestDVI || Line < EarliestDVI->getDebugLoc().getLine()) EarliestDVI = DVI; Expr = DVI->getExpression(); } } for (BasicBlock &BB : F) { for (Instruction &I : BB) { for (DbgVariableRecord &DVR : filterDbgVars(I.getDbgRecordRange())) { if (!DVR.isDbgValue()) continue; unsigned Line = DVR.getDebugLoc().getLine(); assert(Line != 0 && "debugify should not insert line 0 locations"); Line2Var[Line] = DVR.getVariable(); if (!EarliestDVR || Line < EarliestDVR->getDebugLoc().getLine()) EarliestDVR = &DVR; Expr = DVR.getExpression(); } } } if (Line2Var.empty()) return true; // Now, try to insert a DBG_VALUE instruction after each real instruction. // Do this by introducing debug uses of each register definition. If that is // not possible (e.g. we have a phi or a meta instruction), emit a constant. uint64_t NextImm = 0; SmallSet VarSet; const MCInstrDesc &DbgValDesc = TII.get(TargetOpcode::DBG_VALUE); for (MachineBasicBlock &MBB : MF) { MachineBasicBlock::iterator FirstNonPHIIt = MBB.getFirstNonPHI(); for (auto I = MBB.begin(), E = MBB.end(); I != E;) { MachineInstr &MI = *I; ++I; // `I` may point to a DBG_VALUE created in the previous loop iteration. if (MI.isDebugInstr()) continue; // It's not allowed to insert DBG_VALUEs after a terminator. if (MI.isTerminator()) continue; // Find a suitable insertion point for the DBG_VALUE. auto InsertBeforeIt = MI.isPHI() ? FirstNonPHIIt : I; // Find a suitable local variable for the DBG_VALUE. unsigned Line = MI.getDebugLoc().getLine(); if (!Line2Var.count(Line)) Line = EarliestDVI ? EarliestDVI->getDebugLoc().getLine() : EarliestDVR->getDebugLoc().getLine(); DILocalVariable *LocalVar = Line2Var[Line]; assert(LocalVar && "No variable for current line?"); VarSet.insert(LocalVar); // Emit DBG_VALUEs for register definitions. SmallVector RegDefs; for (MachineOperand &MO : MI.all_defs()) if (MO.getReg()) RegDefs.push_back(&MO); for (MachineOperand *MO : RegDefs) BuildMI(MBB, InsertBeforeIt, MI.getDebugLoc(), DbgValDesc, /*IsIndirect=*/false, *MO, LocalVar, Expr); // OK, failing that, emit a constant DBG_VALUE. if (RegDefs.empty()) { auto ImmOp = MachineOperand::CreateImm(NextImm++); BuildMI(MBB, InsertBeforeIt, MI.getDebugLoc(), DbgValDesc, /*IsIndirect=*/false, ImmOp, LocalVar, Expr); } } } // Here we save the number of lines and variables into "llvm.mir.debugify". // It is useful for mir-check-debugify. NamedMDNode *NMD = M.getNamedMetadata("llvm.mir.debugify"); IntegerType *Int32Ty = Type::getInt32Ty(Ctx); if (!NMD) { NMD = M.getOrInsertNamedMetadata("llvm.mir.debugify"); auto addDebugifyOperand = [&](unsigned N) { NMD->addOperand(MDNode::get( Ctx, ValueAsMetadata::getConstant(ConstantInt::get(Int32Ty, N)))); }; // Add number of lines. addDebugifyOperand(NextLine - 1); // Add number of variables. addDebugifyOperand(VarSet.size()); } else { assert(NMD->getNumOperands() == 2 && "llvm.mir.debugify should have exactly 2 operands!"); auto setDebugifyOperand = [&](unsigned Idx, unsigned N) { NMD->setOperand(Idx, MDNode::get(Ctx, ValueAsMetadata::getConstant( ConstantInt::get(Int32Ty, N)))); }; auto getDebugifyOperand = [&](unsigned Idx) { return mdconst::extract(NMD->getOperand(Idx)->getOperand(0)) ->getZExtValue(); }; // Set number of lines. setDebugifyOperand(0, NextLine - 1); // Set number of variables. auto OldNumVars = getDebugifyOperand(1); setDebugifyOperand(1, OldNumVars + VarSet.size()); } return true; } /// ModulePass for attaching synthetic debug info to everything, used with the /// legacy module pass manager. struct DebugifyMachineModule : public ModulePass { bool runOnModule(Module &M) override { // We will insert new debugify metadata, so erasing the old one. assert(!M.getNamedMetadata("llvm.mir.debugify") && "llvm.mir.debugify metadata already exists! Strip it first"); MachineModuleInfo &MMI = getAnalysis().getMMI(); return applyDebugifyMetadata( M, M.functions(), "ModuleDebugify: ", [&](DIBuilder &DIB, Function &F) -> bool { return applyDebugifyMetadataToMachineFunction(MMI, DIB, F); }); } DebugifyMachineModule() : ModulePass(ID) {} void getAnalysisUsage(AnalysisUsage &AU) const override { AU.addRequired(); AU.addPreserved(); AU.setPreservesCFG(); } static char ID; // Pass identification. }; char DebugifyMachineModule::ID = 0; } // end anonymous namespace INITIALIZE_PASS_BEGIN(DebugifyMachineModule, DEBUG_TYPE, "Machine Debugify Module", false, false) INITIALIZE_PASS_END(DebugifyMachineModule, DEBUG_TYPE, "Machine Debugify Module", false, false) ModulePass *llvm::createDebugifyMachineModulePass() { return new DebugifyMachineModule(); }