Enable jitting with a known memory size.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@49924 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 560 insertions, 6 deletions

diff --git a/include/llvm/ExecutionEngine/JITMemoryManager.h b/include/llvm/ExecutionEngine/JITMemoryManager.h
index 0977d5640f..53900f45ef 100644
--- a/include/llvm/ExecutionEngine/JITMemoryManager.h
+++ b/include/llvm/ExecutionEngine/JITMemoryManager.h
@@ -26,8 +26,9 @@ namespace llvm {
 class JITMemoryManager {
 protected:
   bool HasGOT;
+  bool SizeRequired;
 public:
-  JITMemoryManager() : HasGOT(false) {}
+  JITMemoryManager() : HasGOT(false), SizeRequired(false) {}
   virtual ~JITMemoryManager();
   
   /// CreateDefaultMemManager - This is used to create the default
@@ -53,6 +54,12 @@ public:
   /// return a pointer to its base.
   virtual unsigned char *getGOTBase() const = 0;
   
+  /// RequireSize - If the memory manager requires to know the size of the
+  /// objects to be emitted
+  bool RequiresSize() const {
+    return SizeRequired;
+  }
+
   //===--------------------------------------------------------------------===//
   // Main Allocation Functions
   //===--------------------------------------------------------------------===//
diff --git a/lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp b/lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp
index 230ae54224..691c6fc620 100644
--- a/lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp
+++ b/lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp
@@ -634,3 +634,472 @@ unsigned char* JITDwarfEmitter::EmitEHFrame(const Function* Personality,
   
   return StartEHPtr;
 }
+
+unsigned JITDwarfEmitter::GetDwarfTableSize(MachineFunction& F, 
+                                         MachineCodeEmitter& mce,
+                                         unsigned char* StartFunction,
+                                         unsigned char* EndFunction) {
+  const TargetMachine& TM = F.getTarget();
+  TD = TM.getTargetData();
+  needsIndirectEncoding = TM.getTargetAsmInfo()->getNeedsIndirectEncoding();
+  stackGrowthDirection = TM.getFrameInfo()->getStackGrowthDirection();
+  RI = TM.getRegisterInfo();
+  MCE = &mce;
+  unsigned FinalSize = 0;
+  
+  FinalSize += GetExceptionTableSize(&F);
+      
+  const std::vector<Function *> Personalities = MMI->getPersonalities();
+  FinalSize += GetCommonEHFrameSize(Personalities[MMI->getPersonalityIndex()]);
+
+  FinalSize += GetEHFrameSize(Personalities[MMI->getPersonalityIndex()], StartFunction);
+  
+  return FinalSize;
+}
+
+/// AddAlignment - Add the specified alignment.
+static void AddAlignment(unsigned& FinalSize, unsigned Alignment) {
+  if (Alignment == 0) Alignment = 1;
+  FinalSize = (FinalSize + Alignment - 1) & ~(Alignment - 1);
+}
+  
+
+/// SizeULEB128Bytes - Gives the size of the ULEB128.
+static unsigned SizeULEB128Bytes(unsigned Value) {
+  unsigned FinalSize = 0;
+  do {
+    Value >>= 7;
+    ++FinalSize;
+  } while (Value);
+  return FinalSize;
+}
+  
+/// SizeSLEB128Bytes - Gives the size of the SLEB128.
+static unsigned SizeSLEB128Bytes(int Value) {
+  int Sign = Value >> (8 * sizeof(Value) - 1);
+  bool IsMore;
+  unsigned FinalSize = 0;
+
+  do {
+    unsigned char Byte = Value & 0x7f;
+    Value >>= 7;
+    IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
+    ++FinalSize;
+  } while (IsMore);
+  
+  return FinalSize;
+}
+
+/// SizeString - Gives the size of the string.
+static unsigned SizeString(const std::string &String) {
+  return String.size() + 1;
+}
+
+unsigned JITDwarfEmitter::GetEHFrameSize(const Function* Personality,
+                                         unsigned char* StartFunction) { 
+  unsigned PointerSize = TD->getPointerSize();
+  unsigned FinalSize = 0;
+  // EH frame header.
+  FinalSize += PointerSize;
+  // FDE CIE Offset
+  FinalSize += 3 * PointerSize;
+  // If there is a personality and landing pads then point to the language
+  // specific data area in the exception table.
+  if (MMI->getPersonalityIndex()) {
+    FinalSize += SizeULEB128Bytes(4);     
+    FinalSize += PointerSize;
+  } else {
+    FinalSize += SizeULEB128Bytes(0);
+  }
+      
+  // Indicate locations of function specific  callee saved registers in
+  // frame.
+  FinalSize += GetFrameMovesSize((intptr_t)StartFunction, MMI->getFrameMoves());
+      
+  AddAlignment(FinalSize, 4);
+  
+  // Double zeroes for the unwind runtime
+  FinalSize += 2 * PointerSize;
+
+  return FinalSize;
+}
+
+unsigned JITDwarfEmitter::GetCommonEHFrameSize(const Function* Personality) {
+
+  unsigned PointerSize = TD->getPointerSize();
+  int stackGrowth = stackGrowthDirection == TargetFrameInfo::StackGrowsUp ?
+          PointerSize : -PointerSize;
+  unsigned FinalSize = 0; 
+  // EH Common Frame header
+  FinalSize += PointerSize;
+  FinalSize += 4;
+  FinalSize += 1;
+  FinalSize += SizeString(Personality ? "zPLR" : "zR");
+  FinalSize += SizeULEB128Bytes(1);
+  FinalSize += SizeSLEB128Bytes(stackGrowth);
+  FinalSize += 1;
+  
+  if (Personality) {
+    FinalSize += SizeULEB128Bytes(7);
+    
+    // Encoding
+    FinalSize+= 1;
+    //Personality
+    FinalSize += PointerSize;
+    
+    FinalSize += SizeULEB128Bytes(dwarf::DW_EH_PE_pcrel);
+    FinalSize += SizeULEB128Bytes(dwarf::DW_EH_PE_pcrel);
+      
+  } else {
+    FinalSize += SizeULEB128Bytes(1);
+    FinalSize += SizeULEB128Bytes(dwarf::DW_EH_PE_pcrel);
+  }
+
+  std::vector<MachineMove> Moves;
+  RI->getInitialFrameState(Moves);
+  FinalSize += GetFrameMovesSize(0, Moves);
+  AddAlignment(FinalSize, 4);
+  return FinalSize;
+}
+
+unsigned
+JITDwarfEmitter::GetFrameMovesSize(intptr_t BaseLabelPtr,
+                                   const std::vector<MachineMove> &Moves) {
+  unsigned PointerSize = TD->getPointerSize();
+  int stackGrowth = stackGrowthDirection == TargetFrameInfo::StackGrowsUp ?
+          PointerSize : -PointerSize;
+  bool IsLocal = BaseLabelPtr;
+  unsigned FinalSize = 0; 
+
+  for (unsigned i = 0, N = Moves.size(); i < N; ++i) {
+    const MachineMove &Move = Moves[i];
+    unsigned LabelID = Move.getLabelID();
+    
+    if (LabelID) {
+      LabelID = MMI->MappedLabel(LabelID);
+    
+      // Throw out move if the label is invalid.
+      if (!LabelID) continue;
+    }
+    
+    intptr_t LabelPtr = 0;
+    if (LabelID) LabelPtr = MCE->getLabelAddress(LabelID);
+
+    const MachineLocation &Dst = Move.getDestination();
+    const MachineLocation &Src = Move.getSource();
+    
+    // Advance row if new location.
+    if (BaseLabelPtr && LabelID && (BaseLabelPtr != LabelPtr || !IsLocal)) {
+      FinalSize++;
+      FinalSize += PointerSize;
+      BaseLabelPtr = LabelPtr;
+      IsLocal = true;
+    }
+    
+    // If advancing cfa.
+    if (Dst.isRegister() && Dst.getRegister() == MachineLocation::VirtualFP) {
+      if (!Src.isRegister()) {
+        if (Src.getRegister() == MachineLocation::VirtualFP) {
+          ++FinalSize;
+        } else {
+          ++FinalSize;
+          FinalSize +=
+            SizeULEB128Bytes(RI->getDwarfRegNum(Src.getRegister(), true));
+        }
+        
+        int Offset = -Src.getOffset();
+        
+        FinalSize += SizeULEB128Bytes(Offset);
+      } else {
+        assert(0 && "Machine move no supported yet.");
+      }
+    } else if (Src.isRegister() &&
+      Src.getRegister() == MachineLocation::VirtualFP) {
+      if (Dst.isRegister()) {
+        ++FinalSize; 
+        FinalSize +=
+          SizeULEB128Bytes(RI->getDwarfRegNum(Dst.getRegister(), true));
+      } else {
+        assert(0 && "Machine move no supported yet.");
+      }
+    } else {
+      unsigned Reg = RI->getDwarfRegNum(Src.getRegister(), true);
+      int Offset = Dst.getOffset() / stackGrowth;
+      
+      if (Offset < 0) {
+        ++FinalSize;
+        FinalSize += SizeULEB128Bytes(Reg);
+        FinalSize += SizeSLEB128Bytes(Offset);
+      } else if (Reg < 64) {
+        ++FinalSize;
+        FinalSize += SizeULEB128Bytes(Offset);
+      } else {
+        ++FinalSize;
+        FinalSize += SizeULEB128Bytes(Reg);
+        FinalSize += SizeULEB128Bytes(Offset);
+      }
+    }
+  }
+  return FinalSize;
+}
+
+unsigned JITDwarfEmitter::GetExceptionTableSize(MachineFunction* MF) {
+  unsigned FinalSize = 0;
+
+  // Map all labels and get rid of any dead landing pads.
+  MMI->TidyLandingPads();
+
+  const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
+  const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
+  const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
+  if (PadInfos.empty()) return 0;
+
+  // Sort the landing pads in order of their type ids.  This is used to fold
+  // duplicate actions.
+  SmallVector<const LandingPadInfo *, 64> LandingPads;
+  LandingPads.reserve(PadInfos.size());
+  for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
+    LandingPads.push_back(&PadInfos[i]);
+  std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
+
+  // Negative type ids index into FilterIds, positive type ids index into
+  // TypeInfos.  The value written for a positive type id is just the type
+  // id itself.  For a negative type id, however, the value written is the
+  // (negative) byte offset of the corresponding FilterIds entry.  The byte
+  // offset is usually equal to the type id, because the FilterIds entries
+  // are written using a variable width encoding which outputs one byte per
+  // entry as long as the value written is not too large, but can differ.
+  // This kind of complication does not occur for positive type ids because
+  // type infos are output using a fixed width encoding.
+  // FilterOffsets[i] holds the byte offset corresponding to FilterIds[i].
+  SmallVector<int, 16> FilterOffsets;
+  FilterOffsets.reserve(FilterIds.size());
+  int Offset = -1;
+  for(std::vector<unsigned>::const_iterator I = FilterIds.begin(),
+    E = FilterIds.end(); I != E; ++I) {
+    FilterOffsets.push_back(Offset);
+    Offset -= AsmPrinter::SizeULEB128(*I);
+  }
+
+  // Compute the actions table and gather the first action index for each
+  // landing pad site.
+  SmallVector<ActionEntry, 32> Actions;
+  SmallVector<unsigned, 64> FirstActions;
+  FirstActions.reserve(LandingPads.size());
+
+  int FirstAction = 0;
+  unsigned SizeActions = 0;
+  for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
+    const LandingPadInfo *LP = LandingPads[i];
+    const std::vector<int> &TypeIds = LP->TypeIds;
+    const unsigned NumShared = i ? SharedTypeIds(LP, LandingPads[i-1]) : 0;
+    unsigned SizeSiteActions = 0;
+
+    if (NumShared < TypeIds.size()) {
+      unsigned SizeAction = 0;
+      ActionEntry *PrevAction = 0;
+
+      if (NumShared) {
+        const unsigned SizePrevIds = LandingPads[i-1]->TypeIds.size();
+        assert(Actions.size());
+        PrevAction = &Actions.back();
+        SizeAction = AsmPrinter::SizeSLEB128(PrevAction->NextAction) +
+          AsmPrinter::SizeSLEB128(PrevAction->ValueForTypeID);
+        for (unsigned j = NumShared; j != SizePrevIds; ++j) {
+          SizeAction -= AsmPrinter::SizeSLEB128(PrevAction->ValueForTypeID);
+          SizeAction += -PrevAction->NextAction;
+          PrevAction = PrevAction->Previous;
+        }
+      }
+
+      // Compute the actions.
+      for (unsigned I = NumShared, M = TypeIds.size(); I != M; ++I) {
+        int TypeID = TypeIds[I];
+        assert(-1-TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
+        int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
+        unsigned SizeTypeID = AsmPrinter::SizeSLEB128(ValueForTypeID);
+
+        int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
+        SizeAction = SizeTypeID + AsmPrinter::SizeSLEB128(NextAction);
+        SizeSiteActions += SizeAction;
+
+        ActionEntry Action = {ValueForTypeID, NextAction, PrevAction};
+        Actions.push_back(Action);
+
+        PrevAction = &Actions.back();
+      }
+
+      // Record the first action of the landing pad site.
+      FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
+    } // else identical - re-use previous FirstAction
+
+    FirstActions.push_back(FirstAction);
+
+    // Compute this sites contribution to size.
+    SizeActions += SizeSiteActions;
+  }
+
+  // Compute the call-site table.  Entries must be ordered by address.
+  SmallVector<CallSiteEntry, 64> CallSites;
+
+  RangeMapType PadMap;
+  for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
+    const LandingPadInfo *LandingPad = LandingPads[i];
+    for (unsigned j=0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
+      unsigned BeginLabel = LandingPad->BeginLabels[j];
+      assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
+      PadRange P = { i, j };
+      PadMap[BeginLabel] = P;
+    }
+  }
+
+  bool MayThrow = false;
+  unsigned LastLabel = 0;
+  for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
+        I != E; ++I) {
+    for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
+          MI != E; ++MI) {
+      if (MI->getOpcode() != TargetInstrInfo::LABEL) {
+        MayThrow |= MI->getDesc().isCall();
+        continue;
+      }
+
+      unsigned BeginLabel = MI->getOperand(0).getImm();
+      assert(BeginLabel && "Invalid label!");
+
+      if (BeginLabel == LastLabel)
+        MayThrow = false;
+
+      RangeMapType::iterator L = PadMap.find(BeginLabel);
+
+      if (L == PadMap.end())
+        continue;
+
+      PadRange P = L->second;
+      const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
+
+      assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
+              "Inconsistent landing pad map!");
+
+      // If some instruction between the previous try-range and this one may
+      // throw, create a call-site entry with no landing pad for the region
+      // between the try-ranges.
+      if (MayThrow) {
+        CallSiteEntry Site = {LastLabel, BeginLabel, 0, 0};
+        CallSites.push_back(Site);
+      }
+
+      LastLabel = LandingPad->EndLabels[P.RangeIndex];
+      CallSiteEntry Site = {BeginLabel, LastLabel,
+        LandingPad->LandingPadLabel, FirstActions[P.PadIndex]};
+
+      assert(Site.BeginLabel && Site.EndLabel && Site.PadLabel &&
+              "Invalid landing pad!");
+
+      // Try to merge with the previous call-site.
+      if (CallSites.size()) {
+        CallSiteEntry &Prev = CallSites[CallSites.size()-1];
+        if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
+          // Extend the range of the previous entry.
+          Prev.EndLabel = Site.EndLabel;
+          continue;
+        }
+      }
+
+      // Otherwise, create a new call-site.
+      CallSites.push_back(Site);
+    }
+  }
+  // If some instruction between the previous try-range and the end of the
+  // function may throw, create a call-site entry with no landing pad for the
+  // region following the try-range.
+  if (MayThrow) {
+    CallSiteEntry Site = {LastLabel, 0, 0, 0};
+    CallSites.push_back(Site);
+  }
+
+  // Final tallies.
+  unsigned SizeSites = CallSites.size() * (sizeof(int32_t) + // Site start.
+                                            sizeof(int32_t) + // Site length.
+                                            sizeof(int32_t)); // Landing pad.
+  for (unsigned i = 0, e = CallSites.size(); i < e; ++i)
+    SizeSites += AsmPrinter::SizeULEB128(CallSites[i].Action);
+
+  unsigned SizeTypes = TypeInfos.size() * TD->getPointerSize();
+
+  unsigned TypeOffset = sizeof(int8_t) + // Call site format
+                        // Call-site table length
+                        AsmPrinter::SizeULEB128(SizeSites) + 
+                        SizeSites + SizeActions + SizeTypes;
+
+  unsigned TotalSize = sizeof(int8_t) + // LPStart format
+                       sizeof(int8_t) + // TType format
+                       AsmPrinter::SizeULEB128(TypeOffset) + // TType base offset
+                       TypeOffset;
+
+  unsigned SizeAlign = (4 - TotalSize) & 3;
+
+  // Begin the exception table.
+  AddAlignment(FinalSize, 4);
+  for (unsigned i = 0; i != SizeAlign; ++i) {
+    ++FinalSize;
+  }
+  
+  unsigned PointerSize = TD->getPointerSize();
+
+  // Emit the header.
+  ++FinalSize;
+  // Asm->EOL("LPStart format (DW_EH_PE_omit)");
+  ++FinalSize;
+  // Asm->EOL("TType format (DW_EH_PE_absptr)");
+  ++FinalSize;
+  // Asm->EOL("TType base offset");
+  ++FinalSize;
+  // Asm->EOL("Call site format (DW_EH_PE_udata4)");
+  ++FinalSize;
+  // Asm->EOL("Call-site table length");
+
+  // Emit the landing pad site information.
+  for (unsigned i = 0; i < CallSites.size(); ++i) {
+    CallSiteEntry &S = CallSites[i];
+
+    // Asm->EOL("Region start");
+    FinalSize += PointerSize;
+    
+    //Asm->EOL("Region length");
+    FinalSize += PointerSize;
+
+    // Asm->EOL("Landing pad");
+    FinalSize += PointerSize;
+
+    FinalSize += SizeULEB128Bytes(S.Action);
+    // Asm->EOL("Action");
+  }
+
+  // Emit the actions.
+  for (unsigned I = 0, N = Actions.size(); I != N; ++I) {
+    ActionEntry &Action = Actions[I];
+
+    //Asm->EOL("TypeInfo index");
+    FinalSize += SizeSLEB128Bytes(Action.ValueForTypeID);
+    //Asm->EOL("Next action");
+    FinalSize += SizeSLEB128Bytes(Action.NextAction);
+  }
+
+  // Emit the type ids.
+  for (unsigned M = TypeInfos.size(); M; --M) {
+    // Asm->EOL("TypeInfo");
+    FinalSize += PointerSize;
+  }
+
+  // Emit the filter typeids.
+  for (unsigned j = 0, M = FilterIds.size(); j < M; ++j) {
+    unsigned TypeID = FilterIds[j];
+    FinalSize += SizeULEB128Bytes(TypeID);
+    //Asm->EOL("Filter TypeInfo index");
+  }
+  
+  AddAlignment(FinalSize, 4);
+
+  return FinalSize;
+}
diff --git a/lib/ExecutionEngine/JIT/JITDwarfEmitter.h b/lib/ExecutionEngine/JIT/JITDwarfEmitter.h
index 72c9b45b3b..cbe409ef90 100644
--- a/lib/ExecutionEngine/JIT/JITDwarfEmitter.h
+++ b/lib/ExecutionEngine/JIT/JITDwarfEmitter.h
@@ -35,9 +35,6 @@ class JITDwarfEmitter {
   bool needsIndirectEncoding;
   bool stackGrowthDirection;
   
-public:
-  JITDwarfEmitter(JIT& jit);
-
   unsigned char* EmitExceptionTable(MachineFunction* MF,
                                     unsigned char* StartFunction, 
                                     unsigned char* EndFunction);
@@ -53,17 +50,37 @@ public:
                              unsigned char* EndFunction,
                              unsigned char* ExceptionTable);
     
+  unsigned GetExceptionTableSize(MachineFunction* MF);
+  
+  unsigned GetFrameMovesSize(intptr_t BaseLabelPtr, 
+                             const std::vector<MachineMove> &Moves);
+    
+  unsigned GetCommonEHFrameSize(const Function* Personality);
 
+  unsigned GetEHFrameSize(const Function* Personality, 
+                          unsigned char* StartFunction); 
+    
+public:
+  
+  JITDwarfEmitter(JIT& jit);
+  
   unsigned char* EmitDwarfTable(MachineFunction& F, 
                                 MachineCodeEmitter& MCE,
                                 unsigned char* StartFunction,
                                 unsigned char* EndFunction);
   
+  
+  unsigned GetDwarfTableSize(MachineFunction& F, 
+                             MachineCodeEmitter& MCE,
+                             unsigned char* StartFunction,
+                             unsigned char* EndFunction);
+
   void setModuleInfo(MachineModuleInfo* Info) {
     MMI = Info;
   }
 };
 
+
 } // end namespace llvm
 
 #endif // LLVM_EXECUTION_ENGINE_JIT_DWARFEMITTER_H
diff --git a/lib/ExecutionEngine/JIT/JITEmitter.cpp b/lib/ExecutionEngine/JIT/JITEmitter.cpp
index 1a0bb26fbe..06daec69da 100644
--- a/lib/ExecutionEngine/JIT/JITEmitter.cpp
+++ b/lib/ExecutionEngine/JIT/JITEmitter.cpp
@@ -32,6 +32,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/MutexGuard.h"
 #include "llvm/System/Disassembler.h"
+#include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/ADT/Statistic.h"
 #include <algorithm>
 using namespace llvm;
@@ -597,9 +598,65 @@ void *JITEmitter::getPointerToGVLazyPtr(GlobalValue *V, void *Reference,
   return Resolver.getGlobalValueLazyPtr(V, GVAddress);
 }
 
+static unsigned GetConstantPoolSizeInBytes(MachineConstantPool *MCP) {
+  const std::vector<MachineConstantPoolEntry> &Constants = MCP->getConstants();
+  if (Constants.empty()) return 0;
+
+  MachineConstantPoolEntry CPE = Constants.back();
+  unsigned Size = CPE.Offset;
+  const Type *Ty = CPE.isMachineConstantPoolEntry()
+    ? CPE.Val.MachineCPVal->getType() : CPE.Val.ConstVal->getType();
+  Size += TheJIT->getTargetData()->getABITypeSize(Ty);
+  return Size;
+}
+
+static unsigned GetJumpTableSizeInBytes(MachineJumpTableInfo *MJTI) {
+  const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
+  if (JT.empty()) return 0;
+  
+  unsigned NumEntries = 0;
+  for (unsigned i = 0, e = JT.size(); i != e; ++i)
+    NumEntries += JT[i].MBBs.size();
+
+  unsigned EntrySize = MJTI->getEntrySize();
+
+  return NumEntries * EntrySize;
+}
+
+static void AddAlignment(uintptr_t& Size, unsigned Alignment) {
+  if (Alignment == 0) Alignment = 1;
+  Size = (Size + Alignment - 1) & (Alignment - 1);
+}
 
 void JITEmitter::startFunction(MachineFunction &F) {
-  uintptr_t ActualSize;
+  uintptr_t ActualSize = 0;
+  if (MemMgr->RequiresSize()) {
+    const TargetInstrInfo* TII = F.getTarget().getInstrInfo();
+    MachineJumpTableInfo *MJTI = F.getJumpTableInfo();
+    MachineConstantPool *MCP = F.getConstantPool();
+    
+    // Ensure the constant pool/jump table info is at least 4-byte aligned.
+    AddAlignment(ActualSize, 16);
+    
+    // Add the alignment of the constant pool
+    AddAlignment(ActualSize, 1 << MCP->getConstantPoolAlignment());
+
+    // Add the constant pool size
+    ActualSize += GetConstantPoolSizeInBytes(MCP);
+
+    // Add the aligment of the jump table info
+    AddAlignment(ActualSize, MJTI->getAlignment());
+
+    // Add the jump table size
+    ActualSize += GetJumpTableSizeInBytes(MJTI);
+    
+    // Add the alignment for the function
+    AddAlignment(ActualSize, std::max(F.getFunction()->getAlignment(), 8U));
+
+    // Add the function size
+    ActualSize += TII->GetFunctionSizeInBytes(F);
+  }
+
   BufferBegin = CurBufferPtr = MemMgr->startFunctionBody(F.getFunction(),
                                                          ActualSize);
   BufferEnd = BufferBegin+ActualSize;
@@ -714,10 +771,14 @@ bool JITEmitter::finishFunction(MachineFunction &F) {
          << sys::disassembleBuffer(FnStart, FnEnd-FnStart, (uintptr_t)FnStart);
 #endif
   if (ExceptionHandling) {
-    uintptr_t ActualSize;
+    uintptr_t ActualSize = 0;
     SavedBufferBegin = BufferBegin;
     SavedBufferEnd = BufferEnd;
     SavedCurBufferPtr = CurBufferPtr;
+    
+    if (MemMgr->RequiresSize()) {
+      ActualSize = DE->GetDwarfTableSize(F, *this, FnStart, FnEnd);
+    }
 
     BufferBegin = CurBufferPtr = MemMgr->startExceptionTable(F.getFunction(),
                                                              ActualSize);