llvm/lib/Target/BPF/BPFPreserveDIType.cpp

   1 //===----------- BPFPreserveDIType.cpp - Preserve DebugInfo Types ---------===//
   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 // Preserve Debuginfo types encoded in __builtin_btf_type_id() metadata.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "BPF.h"
  14 #include "BPFCORE.h"
  15 #include "llvm/IR/DebugInfoMetadata.h"
  16 #include "llvm/IR/GlobalVariable.h"
  17 #include "llvm/IR/Instruction.h"
  18 #include "llvm/IR/Instructions.h"
  19 #include "llvm/IR/Module.h"
  20 #include "llvm/IR/PassManager.h"
  21 #include "llvm/IR/Type.h"
  22 #include "llvm/IR/User.h"
  23 #include "llvm/IR/Value.h"
  24 #include "llvm/Pass.h"
  25 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  26
  27 #define DEBUG_TYPE "bpf-preserve-di-type"
  28
  29 namespace llvm {
  30 constexpr StringRef BPFCoreSharedInfo::TypeIdAttr;
  31 } // namespace llvm
  32
  33 using namespace llvm;
  34
  35 namespace {
  36
  37 static bool BPFPreserveDITypeImpl(Function &F) {
  38   LLVM_DEBUG(dbgs() << "********** preserve debuginfo type **********\n");
  39
  40   Module *M = F.getParent();
  41
  42   // Bail out if no debug info.
  43   if (M->debug_compile_units().empty())
  44     return false;
  45
  46   std::vector<CallInst *> PreserveDITypeCalls;
  47
  48   for (auto &BB : F) {
  49     for (auto &I : BB) {
  50       auto *Call = dyn_cast<CallInst>(&I);
  51       if (!Call)
  52         continue;
  53
  54       const auto *GV = dyn_cast<GlobalValue>(Call->getCalledOperand());
  55       if (!GV)
  56         continue;
  57
  58       if (GV->getName().startswith("llvm.bpf.btf.type.id")) {
  59         if (!Call->getMetadata(LLVMContext::MD_preserve_access_index))
  60           report_fatal_error(
  61               "Missing metadata for llvm.bpf.btf.type.id intrinsic");
  62         PreserveDITypeCalls.push_back(Call);
  63       }
  64     }
  65   }
  66
  67   if (PreserveDITypeCalls.empty())
  68     return false;
  69
  70   std::string BaseName = "llvm.btf_type_id.";
  71   static int Count = 0;
  72   for (auto Call : PreserveDITypeCalls) {
  73     const ConstantInt *Flag = dyn_cast<ConstantInt>(Call->getArgOperand(1));
  74     assert(Flag);
  75     uint64_t FlagValue = Flag->getValue().getZExtValue();
  76
  77     if (FlagValue >= BPFCoreSharedInfo::MAX_BTF_TYPE_ID_FLAG)
  78       report_fatal_error("Incorrect flag for llvm.bpf.btf.type.id intrinsic");
  79
  80     MDNode *MD = Call->getMetadata(LLVMContext::MD_preserve_access_index);
  81
  82     uint32_t Reloc;
  83     if (FlagValue == BPFCoreSharedInfo::BTF_TYPE_ID_LOCAL_RELOC) {
  84       Reloc = BPFCoreSharedInfo::BTF_TYPE_ID_LOCAL;
  85     } else {
  86       Reloc = BPFCoreSharedInfo::BTF_TYPE_ID_REMOTE;
  87       DIType *Ty = cast<DIType>(MD);
  88       while (auto *DTy = dyn_cast<DIDerivedType>(Ty)) {
  89         unsigned Tag = DTy->getTag();
  90         if (Tag != dwarf::DW_TAG_const_type &&
  91             Tag != dwarf::DW_TAG_volatile_type)
  92           break;
  93         Ty = DTy->getBaseType();
  94       }
  95
  96       if (Ty->getName().empty())
  97         report_fatal_error("Empty type name for BTF_TYPE_ID_REMOTE reloc");
  98       MD = Ty;
  99     }
 100
 101     BasicBlock *BB = Call->getParent();
 102     IntegerType *VarType = Type::getInt64Ty(BB->getContext());
 103     std::string GVName = BaseName + std::to_string(Count) + "$" +
 104         std::to_string(Reloc);
 105     GlobalVariable *GV = new GlobalVariable(
 106         *M, VarType, false, GlobalVariable::ExternalLinkage, NULL, GVName);
 107     GV->addAttribute(BPFCoreSharedInfo::TypeIdAttr);
 108     GV->setMetadata(LLVMContext::MD_preserve_access_index, MD);
 109
 110     // Load the global variable which represents the type info.
 111     auto *LDInst =
 112         new LoadInst(Type::getInt64Ty(BB->getContext()), GV, "", Call);
 113     Instruction *PassThroughInst =
 114         BPFCoreSharedInfo::insertPassThrough(M, BB, LDInst, Call);
 115     Call->replaceAllUsesWith(PassThroughInst);
 116     Call->eraseFromParent();
 117     Count++;
 118   }
 119
 120   return true;
 121 }
 122
 123 class BPFPreserveDIType final : public FunctionPass {
 124   bool runOnFunction(Function &F) override;
 125
 126 public:
 127   static char ID;
 128   BPFPreserveDIType() : FunctionPass(ID) {}
 129 };
 130 } // End anonymous namespace
 131
 132 char BPFPreserveDIType::ID = 0;
 133 INITIALIZE_PASS(BPFPreserveDIType, DEBUG_TYPE, "BPF Preserve Debuginfo Type",
 134                 false, false)
 135
 136 FunctionPass *llvm::createBPFPreserveDIType() {
 137   return new BPFPreserveDIType();
 138 }
 139
 140 bool BPFPreserveDIType::runOnFunction(Function &F) {
 141   return BPFPreserveDITypeImpl(F);
 142 }
 143
 144 PreservedAnalyses BPFPreserveDITypePass::run(Function &F,
 145                                              FunctionAnalysisManager &AM) {
 146   return BPFPreserveDITypeImpl(F) ? PreservedAnalyses::none()
 147                                   : PreservedAnalyses::all();
 148 }