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 "DwarfCompileUnit.h"
#include "llvm/Constants.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/Target/Mangler.h"
#include "llvm/Target/TargetData.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/Analysis/DebugInfo.h"
#include "llvm/Analysis/DIBuilder.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringExtras.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> PrintDbgScope("print-dbgscope", cl::Hidden,
     cl::desc("Print DbgScope information for each machine instruction"));

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 absense of debug location information explicit."),
     cl::init(false));

#ifndef NDEBUG
STATISTIC(BlocksWithoutLineNo, "Number of blocks without any line number");
#endif

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 {

//===----------------------------------------------------------------------===//
/// DbgVariable - This class is used to track local variable information.
///
class DbgVariable {
  DIVariable Var;                    // Variable Descriptor.
  DIE *TheDIE;                       // Variable DIE.
  unsigned DotDebugLocOffset;        // Offset in DotDebugLocEntries.
public:
  // AbsVar may be NULL.
  DbgVariable(DIVariable V) : Var(V), TheDIE(0), DotDebugLocOffset(~0U) {}

  // Accessors.
  DIVariable getVariable()           const { return Var; }
  void setDIE(DIE *D)                      { TheDIE = D; }
  DIE *getDIE()                      const { return TheDIE; }
  void setDotDebugLocOffset(unsigned O)    { DotDebugLocOffset = O; }
  unsigned getDotDebugLocOffset()    const { return DotDebugLocOffset; }
  StringRef getName()                const { return Var.getName(); }
  unsigned getTag()                  const { return Var.getTag(); }
  bool variableHasComplexAddress()   const {
    assert(Var.Verify() && "Invalid complex DbgVariable!");
    return Var.hasComplexAddress();
  }
  bool isBlockByrefVariable()        const {
    assert(Var.Verify() && "Invalid complex DbgVariable!");
    return Var.isBlockByrefVariable();
  }
  unsigned getNumAddrElements()      const { 
    assert(Var.Verify() && "Invalid complex DbgVariable!");
    return Var.getNumAddrElements();
  }
  uint64_t getAddrElement(unsigned i) const {
    return Var.getAddrElement(i);
  }
  DIType 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;
    }
    return Ty;
  }
};

//===----------------------------------------------------------------------===//
/// DbgRange - This is used to track range of instructions with identical
/// debug info scope.
///
typedef std::pair<const MachineInstr *, const MachineInstr *> DbgRange;

//===----------------------------------------------------------------------===//
/// DbgScope - This class is used to track scope information.
///
class DbgScope {
  DbgScope *Parent;                   // Parent to this scope.
  DIDescriptor Desc;                  // Debug info descriptor for scope.
  // Location at which this scope is inlined.
  AssertingVH<const MDNode> InlinedAtLocation;
  bool AbstractScope;                 // Abstract Scope
  const MachineInstr *LastInsn;       // Last instruction of this scope.
  const MachineInstr *FirstInsn;      // First instruction of this scope.
  unsigned DFSIn, DFSOut;
  // Scopes defined in scope.  Contents not owned.
  SmallVector<DbgScope *, 4> Scopes;
  // Variables declared in scope.  Contents owned.
  SmallVector<DbgVariable *, 8> Variables;
  SmallVector<DbgRange, 4> Ranges;
  // Private state for dump()
  mutable unsigned IndentLevel;
public:
  DbgScope(DbgScope *P, DIDescriptor D, const MDNode *I = 0)
    : Parent(P), Desc(D), InlinedAtLocation(I), AbstractScope(false),
      LastInsn(0), FirstInsn(0),
      DFSIn(0), DFSOut(0), IndentLevel(0) {}
  virtual ~DbgScope();

  // Accessors.
  DbgScope *getParent()          const { return Parent; }
  void setParent(DbgScope *P)          { Parent = P; }
  DIDescriptor getDesc()         const { return Desc; }
  const MDNode *getInlinedAt()         const { return InlinedAtLocation; }
  const MDNode *getScopeNode()         const { return Desc; }
  const SmallVector<DbgScope *, 4> &getScopes() { return Scopes; }