bolt/lib/Passes/AsmDump.cpp

   1 //===- bolt/Passes/AsmDump.cpp - Dump BinaryFunction into assembly --------===//
   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 // This file implements the AsmDumpPass class.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "bolt/Passes/AsmDump.h"
  14 #include "llvm/CodeGen/AsmPrinter.h"
  15 #include "llvm/MC/TargetRegistry.h"
  16 #include "llvm/Support/FileSystem.h"
  17 #include "llvm/Support/Path.h"
  18 #include "llvm/Target/TargetMachine.h"
  19 #include <unordered_set>
  20
  21 #define DEBUG_TYPE "asm-dump"
  22
  23 using namespace llvm;
  24
  25 namespace opts {
  26 extern bool shouldPrint(const bolt::BinaryFunction &Function);
  27 extern cl::OptionCategory BoltCategory;
  28 extern cl::opt<unsigned> Verbosity;
  29
  30 cl::opt<std::string> AsmDump("asm-dump",
  31                              cl::desc("dump function into assembly"),
  32                              cl::value_desc("dump folder"), cl::ValueOptional,
  33                              cl::Hidden, cl::cat(BoltCategory));
  34 } // end namespace opts
  35
  36 namespace llvm {
  37 namespace bolt {
  38
  39 void dumpCFI(const BinaryFunction &BF, const MCInst &Instr, AsmPrinter &MAP) {
  40   const MCCFIInstruction *CFIInstr = BF.getCFIFor(Instr);
  41   switch (CFIInstr->getOperation()) {
  42   // Skip unsupported CFI instructions.
  43   case MCCFIInstruction::OpRememberState:
  44   case MCCFIInstruction::OpRestoreState:
  45     if (opts::Verbosity >= 2)
  46       errs()
  47           << "BOLT-WARNING: AsmDump: skipping unsupported CFI instruction in "
  48           << BF << ".\n";
  49
  50     return;
  51
  52   default:
  53     // Emit regular CFI instructions.
  54     MAP.emitCFIInstruction(*CFIInstr);
  55   }
  56 }
  57
  58 void dumpTargetFunctionStub(raw_ostream &OS, const BinaryContext &BC,
  59                             const MCSymbol *CalleeSymb,
  60                             const BinarySection *&LastCS) {
  61   const BinaryFunction *CalleeFunc = BC.getFunctionForSymbol(CalleeSymb);
  62   if (!CalleeFunc || CalleeFunc->isPLTFunction())
  63     return;
  64
  65   if (CalleeFunc->getOriginSection() != LastCS) {
  66     OS << ".section " << CalleeFunc->getOriginSectionName() << '\n';
  67     LastCS = CalleeFunc->getOriginSection();
  68   }
  69   StringRef CalleeName = CalleeFunc->getOneName();
  70   OS << ".set \"" << CalleeName << "\", 0\n";
  71 }
  72
  73 void dumpJumpTableSymbols(raw_ostream &OS, const JumpTable *JT, AsmPrinter &MAP,
  74                           const BinarySection *&LastBS) {
  75   if (&JT->getSection() != LastBS) {
  76     OS << ".section " << JT->getSectionName() << '\n';
  77     LastBS = &JT->getSection();
  78   }
  79   OS << "\"" << JT->getName() << "\":\n";
  80   for (MCSymbol *JTEntry : JT->Entries)
  81     MAP.OutStreamer->emitSymbolValue(JTEntry, JT->OutputEntrySize);
  82   OS << '\n';
  83 }
  84
  85 void dumpBinaryDataSymbols(raw_ostream &OS, const BinaryData *BD,
  86                            const BinarySection *&LastBS) {
  87   if (BD->isJumpTable())
  88     return;
  89   if (&BD->getSection() != LastBS) {
  90     OS << ".section " << BD->getSectionName() << '\n';
  91     LastBS = &BD->getSection();
  92   }
  93   OS << "\"" << BD->getName() << "\": ";
  94   OS << '\n';
  95 }
  96
  97 void dumpFunction(const BinaryFunction &BF) {
  98   const BinaryContext &BC = BF.getBinaryContext();
  99   if (!opts::shouldPrint(BF))
 100     return;
 101
 102   // Make sure the new directory exists, creating it if necessary.
 103   if (!opts::AsmDump.empty()) {
 104     if (std::error_code EC = sys::fs::create_directories(opts::AsmDump)) {
 105       errs() << "BOLT-ERROR: could not create directory '" << opts::AsmDump
 106              << "': " << EC.message() << '\n';
 107       exit(1);
 108     }
 109   }
 110
 111   std::string PrintName = BF.getPrintName();
 112   std::replace(PrintName.begin(), PrintName.end(), '/', '-');
 113   std::string Filename =
 114       opts::AsmDump.empty()
 115           ? (PrintName + ".s")
 116           : (opts::AsmDump + sys::path::get_separator() + PrintName + ".s")
 117                 .str();
 118   outs() << "BOLT-INFO: Dumping function assembly to " << Filename << "\n";
 119
 120   std::error_code EC;
 121   raw_fd_ostream OS(Filename, EC, sys::fs::OF_None);
 122   if (EC) {
 123     errs() << "BOLT-ERROR: " << EC.message() << ", unable to open " << Filename
 124            << " for output.\n";
 125     exit(1);
 126   }
 127   OS.SetUnbuffered();
 128
 129   // Create local MC context to isolate the effect of ephemeral assembly
 130   // emission.
 131   BinaryContext::IndependentCodeEmitter MCEInstance =
 132       BC.createIndependentMCCodeEmitter();
 133   MCContext *LocalCtx = MCEInstance.LocalCtx.get();
 134   std::unique_ptr<MCAsmBackend> MAB(
 135       BC.TheTarget->createMCAsmBackend(*BC.STI, *BC.MRI, MCTargetOptions()));
 136   int AsmPrinterVariant = BC.AsmInfo->getAssemblerDialect();
 137   MCInstPrinter *InstructionPrinter(BC.TheTarget->createMCInstPrinter(
 138       *BC.TheTriple, AsmPrinterVariant, *BC.AsmInfo, *BC.MII, *BC.MRI));
 139   auto FOut = std::make_unique<formatted_raw_ostream>(OS);
 140   FOut->SetUnbuffered();
 141   std::unique_ptr<MCStreamer> AsmStreamer(
 142       createAsmStreamer(*LocalCtx, std::move(FOut),
 143                         /*isVerboseAsm=*/true,
 144                         /*useDwarfDirectory=*/false, InstructionPrinter,
 145                         std::move(MCEInstance.MCE), std::move(MAB),
 146                         /*ShowInst=*/false));
 147   AsmStreamer->initSections(true, *BC.STI);
 148   std::unique_ptr<TargetMachine> TM(BC.TheTarget->createTargetMachine(
 149       BC.TripleName, "", "", TargetOptions(), std::nullopt));
 150   std::unique_ptr<AsmPrinter> MAP(
 151       BC.TheTarget->createAsmPrinter(*TM, std::move(AsmStreamer)));
 152
 153   StringRef FunctionName = BF.getOneName();
 154   OS << "  .globl " << FunctionName << '\n';
 155   OS << "  .type " << FunctionName << ", %function\n";
 156   OS << FunctionName << ":\n";
 157
 158   // FDATA for the entry point
 159   if (uint64_t EntryExecCount = BF.getKnownExecutionCount())
 160     OS << "# FDATA: 0 [unknown] 0 "
 161        << "1 " << FunctionName << " 0 "
 162        << "0 " << EntryExecCount << '\n';
 163
 164   // Binary data references from the function.
 165   std::unordered_set<const BinaryData *> BDReferences;
 166   // Function references from the function (to avoid constructing call graph).
 167   std::unordered_set<const MCSymbol *> CallReferences;
 168
 169   MAP->OutStreamer->emitCFIStartProc(/*IsSimple=*/false);
 170   for (const BinaryBasicBlock *BB : BF.getLayout().blocks()) {
 171     OS << BB->getName() << ": \n";
 172
 173     const std::string BranchLabel = Twine(BB->getName(), "_br").str();
 174     const MCInst *LastInst = BB->getLastNonPseudoInstr();
 175
 176     for (const MCInst &Instr : *BB) {
 177       // Dump pseudo instructions (CFI)
 178       if (BC.MIB->isPseudo(Instr)) {
 179         if (BC.MIB->isCFI(Instr))
 180           dumpCFI(BF, Instr, *MAP.get());
 181         continue;
 182       }
 183
 184       // Analyze symbol references (data, functions) from the instruction.
 185       bool IsCall = BC.MIB->isCall(Instr);
 186       for (const MCOperand &Operand : MCPlus::primeOperands(Instr)) {
 187         if (Operand.isExpr() &&
 188             Operand.getExpr()->getKind() == MCExpr::SymbolRef) {
 189           std::pair<const MCSymbol *, uint64_t> TSI =
 190               BC.MIB->getTargetSymbolInfo(Operand.getExpr());
 191           const MCSymbol *Symbol = TSI.first;
 192           if (IsCall)
 193             CallReferences.insert(Symbol);
 194           else if (const BinaryData *BD =
 195                        BC.getBinaryDataByName(Symbol->getName()))
 196             BDReferences.insert(BD);
 197         }
 198       }
 199
 200       if (&Instr == LastInst && (BB->succ_size() || IsCall))
 201         OS << BranchLabel << ":\n";
 202
 203       BC.InstPrinter->printInst(&Instr, 0, "", *BC.STI, OS);
 204       OS << '\n';
 205     }
 206
 207     // Dump profile data in FDATA format (as parsed by link_fdata).
 208     for (const BinaryBasicBlock *Succ : BB->successors()) {
 209       const BinaryBasicBlock::BinaryBranchInfo BI = BB->getBranchInfo(*Succ);
 210       if (!BI.MispredictedCount && !BI.Count)
 211         continue;
 212
 213       OS << "# FDATA: 1 " << FunctionName << " #" << BranchLabel << "# "
 214          << "1 " << FunctionName << " #" << Succ->getName() << "# "
 215          << BI.MispredictedCount << " " << BI.Count << '\n';
 216     }
 217
 218     OS << '\n';
 219   }
 220   MAP->OutStreamer->emitCFIEndProc();
 221
 222   OS << ".size " << FunctionName << ", .-" << FunctionName << '\n';
 223
 224   const BinarySection *LastSection = BF.getOriginSection();
 225   // Print stubs for all target functions.
 226   for (const MCSymbol *CalleeSymb : CallReferences)
 227     dumpTargetFunctionStub(OS, BC, CalleeSymb, LastSection);
 228
 229   OS << "# Jump tables\n";
 230   // Print all jump tables.
 231   for (auto &JTI : BF.jumpTables())
 232     dumpJumpTableSymbols(OS, JTI.second, *MAP.get(), LastSection);
 233
 234   OS << "# BinaryData\n";
 235   // Print data references.
 236   for (const BinaryData *BD : BDReferences)
 237     dumpBinaryDataSymbols(OS, BD, LastSection);
 238 }
 239
 240 void AsmDumpPass::runOnFunctions(BinaryContext &BC) {
 241   for (const auto &BFIt : BC.getBinaryFunctions())
 242     dumpFunction(BFIt.second);
 243 }
 244
 245 } // namespace bolt
 246 } // namespace llvm