DwarfDebug.cpp

//===-- llvm/CodeGen/DwarfDebug.cpp - Dwarf Debug Framework ---------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains support for writing dwarf debug info into asm files.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "dwarfdebug"
#include "DwarfDebug.h"
#include "DIE.h"
#include "DwarfAccelTable.h"
#include "DwarfCompileUnit.h"
#include "llvm/Constants.h"
#include "llvm/DebugInfo.h"
#include "llvm/DIBuilder.h"
#include "llvm/Module.h"
#include "llvm/Instructions.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/DataLayout.h"
#include "llvm/Target/TargetFrameLowering.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ValueHandle.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Support/Timer.h"
#include "llvm/Support/Path.h"
using namespace llvm;

static cl::opt<bool> DisableDebugInfoPrinting("disable-debug-info-print",
                                              cl::Hidden,
     cl::desc("Disable debug info printing"));

static cl::opt<bool> UnknownLocations("use-unknown-locations", cl::Hidden,
     cl::desc("Make an absence of debug location information explicit."),
     cl::init(false));

namespace {
  enum DefaultOnOff {
    Default, Enable, Disable
  };
}

static cl::opt<DefaultOnOff> DwarfAccelTables("dwarf-accel-tables", cl::Hidden,
     cl::desc("Output prototype dwarf accelerator tables."),
     cl::values(
                clEnumVal(Default, "Default for platform"),
                clEnumVal(Enable, "Enabled"),
                clEnumVal(Disable, "Disabled"),
                clEnumValEnd),
     cl::init(Default));

static cl::opt<DefaultOnOff> DarwinGDBCompat("darwin-gdb-compat", cl::Hidden,
     cl::desc("Compatibility with Darwin gdb."),
     cl::values(
                clEnumVal(Default, "Default for platform"),
                clEnumVal(Enable, "Enabled"),
                clEnumVal(Disable, "Disabled"),
                clEnumValEnd),
     cl::init(Default));

namespace {
  const char *DWARFGroupName = "DWARF Emission";
  const char *DbgTimerName = "DWARF Debug Writer";
} // end anonymous namespace

//===----------------------------------------------------------------------===//

/// Configuration values for initial hash set sizes (log2).
///
static const unsigned InitAbbreviationsSetSize = 9; // log2(512)

namespace llvm {

DIType DbgVariable::getType() const {
  DIType Ty = Var.getType();
  // FIXME: isBlockByrefVariable should be reformulated in terms of complex
  // addresses instead.
  if (Var.isBlockByrefVariable()) {
    /* Byref variables, in Blocks, are declared by the programmer as
       "SomeType VarName;", but the compiler creates a
       __Block_byref_x_VarName struct, and gives the variable VarName
       either the struct, or a pointer to the struct, as its type.  This
       is necessary for various behind-the-scenes things the compiler
       needs to do with by-reference variables in blocks.
       
       However, as far as the original *programmer* is concerned, the
       variable should still have type 'SomeType', as originally declared.
       
       The following function dives into the __Block_byref_x_VarName
       struct to find the original type of the variable.  This will be
       passed back to the code generating the type for the Debug
       Information Entry for the variable 'VarName'.  'VarName' will then
       have the original type 'SomeType' in its debug information.
       
       The original type 'SomeType' will be the type of the field named
       'VarName' inside the __Block_byref_x_VarName struct.
       
       NOTE: In order for this to not completely fail on the debugger
       side, the Debug Information Entry for the variable VarName needs to
       have a DW_AT_location that tells the debugger how to unwind through
       the pointers and __Block_byref_x_VarName struct to find the actual
       value of the variable.  The function addBlockByrefType does this.  */
    DIType subType = Ty;
    unsigned tag = Ty.getTag();
    
    if (tag == dwarf::DW_TAG_pointer_type) {
      DIDerivedType DTy = DIDerivedType(Ty);
      subType = DTy.getTypeDerivedFrom();
    }
    
    DICompositeType blockStruct = DICompositeType(subType);
    DIArray Elements = blockStruct.getTypeArray();
    
    for (unsigned i = 0, N = Elements.getNumElements(); i < N; ++i) {
      DIDescriptor Element = Elements.getElement(i);
      DIDerivedType DT = DIDerivedType(Element);
      if (getName() == DT.getName())
        return (DT.getTypeDerivedFrom());
    }
  }
  return Ty;
}

} // end llvm namespace

DwarfDebug::DwarfDebug(AsmPrinter *A, Module *M)
  : Asm(A), MMI(Asm->MMI), FirstCU(0),
    AbbreviationsSet(InitAbbreviationsSetSize),
    SourceIdMap(DIEValueAllocator), StringPool(DIEValueAllocator),
    PrevLabel(NULL) {
  NextStringPoolNumber = 0;

  DwarfInfoSectionSym = DwarfAbbrevSectionSym = 0;
  DwarfStrSectionSym = TextSectionSym = 0;
  DwarfDebugRangeSectionSym = DwarfDebugLocSectionSym = 0;
  FunctionBeginSym = FunctionEndSym = 0;

  // Turn on accelerator tables and older gdb compatibility
  // for Darwin.
  bool isDarwin = Triple(M->getTargetTriple()).isOSDarwin();
  if (DarwinGDBCompat == Default) {
    if (isDarwin)
      isDarwinGDBCompat = true;
    else
      isDarwinGDBCompat = false;
  } else
    isDarwinGDBCompat = DarwinGDBCompat == Enable ? true : false;

  if (DwarfAccelTables == Default) {
    if (isDarwin)
      hasDwarfAccelTables = true;
    else
      hasDwarfAccelTables = false;
  } else
    hasDwarfAccelTables = DwarfAccelTables == Enable ? true : false;

  {
    NamedRegionTimer T(DbgTimerName, DWARFGroupName, TimePassesIsEnabled);
    beginModule(M);
  }
}
DwarfDebug::~DwarfDebug() {
}

/// EmitSectionSym - Switch to the specified MCSection and emit an assembler
/// temporary label to it if SymbolStem is specified.
static MCSymbol *EmitSectionSym(AsmPrinter *Asm, const MCSection *Section,
                                const char *SymbolStem = 0) {
  Asm->OutStreamer.SwitchSection(Section);
  if (!SymbolStem) return 0;

  MCSymbol *TmpSym = Asm->GetTempSymbol(SymbolStem);
  Asm->OutStreamer.EmitLabel(TmpSym);
  return TmpSym;
}

MCSymbol *DwarfDebug::getStringPool() {
  return Asm->GetTempSymbol("section_str");
}