[llvm-commits] [llvm] r165739 - in /llvm/trunk: include/llvm/Bitcode/BitstreamReader.h lib/Bitcode/Reader/BitcodeReader.cpp lib/Bitcode/Reader/BitcodeReader.h lib/Bitcode/Writer/BitcodeWriter.cpp test/Bitcode/function-encoding-rel-operands.ll

David Blaikie dblaikie at gmail.com
Mon Oct 15 13:14:00 PDT 2012


On Thu, Oct 11, 2012 at 1:20 PM, Jan Wen Voung <jvoung at google.com> wrote:
> Author: jvoung
> Date: Thu Oct 11 15:20:40 2012
> New Revision: 165739
>
> URL: http://llvm.org/viewvc/llvm-project?rev=165739&view=rev
> Log:
> Change encoding of instruction operands in bitcode binaries to be relative
> to the instruction position.  The old encoding would give an absolute
> ID which counts up within a function, and only resets at the next function.
>
> I.e., Instead of having:
>
> ... = icmp eq i32 n-1, n-2
> br i1 ..., label %bb1, label %bb2
>
> it will now be roughly:
>
> ... = icmp eq i32 1, 2
> br i1 1, label %bb1, label %bb2
>
> This makes it so that ids remain relatively small and can be encoded
> in fewer bits.
>
> With this encoding, forward reference operands will be given
> negative-valued IDs.  Use signed VBRs for the most common case
> of forward references, which is phi instructions.
>
> To retain backward compatibility we bump the bitcode version
> from 0 to 1 to distinguish between the different encodings.
>
> Added:
>     llvm/trunk/test/Bitcode/function-encoding-rel-operands.ll
> Modified:
>     llvm/trunk/include/llvm/Bitcode/BitstreamReader.h
>     llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp
>     llvm/trunk/lib/Bitcode/Reader/BitcodeReader.h
>     llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp
>
> Modified: llvm/trunk/include/llvm/Bitcode/BitstreamReader.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Bitcode/BitstreamReader.h?rev=165739&r1=165738&r2=165739&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/Bitcode/BitstreamReader.h (original)
> +++ llvm/trunk/include/llvm/Bitcode/BitstreamReader.h Thu Oct 11 15:20:40 2012
> @@ -409,7 +409,7 @@
>    }
>
>    /// EnterSubBlock - Having read the ENTER_SUBBLOCK abbrevid, enter
> -  /// the block, and return true if the block is valid.
> +  /// the block, and return true if the block has an error.
>    bool EnterSubBlock(unsigned BlockID, unsigned *NumWordsP = 0) {
>      // Save the current block's state on BlockScope.
>      BlockScope.push_back(Block(CurCodeSize));
>
> Modified: llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp?rev=165739&r1=165738&r2=165739&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp (original)
> +++ llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp Thu Oct 11 15:20:40 2012
> @@ -891,9 +891,9 @@
>    }
>  }
>
> -/// DecodeSignRotatedValue - Decode a signed value stored with the sign bit in
> +/// decodeSignRotatedValue - Decode a signed value stored with the sign bit in
>  /// the LSB for dense VBR encoding.
> -static uint64_t DecodeSignRotatedValue(uint64_t V) {
> +uint64_t BitcodeReader::decodeSignRotatedValue(uint64_t V) {
>    if ((V & 1) == 0)
>      return V >> 1;
>    if (V != 1)
> @@ -943,7 +943,7 @@
>  static APInt ReadWideAPInt(ArrayRef<uint64_t> Vals, unsigned TypeBits) {
>    SmallVector<uint64_t, 8> Words(Vals.size());
>    std::transform(Vals.begin(), Vals.end(), Words.begin(),
> -                 DecodeSignRotatedValue);
> +                 BitcodeReader::decodeSignRotatedValue);
>
>    return APInt(TypeBits, Words);
>  }
> @@ -997,7 +997,7 @@
>      case bitc::CST_CODE_INTEGER:   // INTEGER: [intval]
>        if (!CurTy->isIntegerTy() || Record.empty())
>          return Error("Invalid CST_INTEGER record");
> -      V = ConstantInt::get(CurTy, DecodeSignRotatedValue(Record[0]));
> +      V = ConstantInt::get(CurTy, decodeSignRotatedValue(Record[0]));
>        break;
>      case bitc::CST_CODE_WIDE_INTEGER: {// WIDE_INTEGER: [n x intval]
>        if (!CurTy->isIntegerTy() || Record.empty())
> @@ -1524,13 +1524,22 @@
>      // Read a record.
>      switch (Stream.ReadRecord(Code, Record)) {
>      default: break;  // Default behavior, ignore unknown content.
> -    case bitc::MODULE_CODE_VERSION:  // VERSION: [version#]
> +    case bitc::MODULE_CODE_VERSION: {  // VERSION: [version#]
>        if (Record.size() < 1)
>          return Error("Malformed MODULE_CODE_VERSION");
> -      // Only version #0 is supported so far.
> -      if (Record[0] != 0)
> -        return Error("Unknown bitstream version!");
> +      // Only version #0 and #1 are supported so far.
> +      unsigned module_version = Record[0];
> +      switch (module_version) {
> +        default: return Error("Unknown bitstream version!");
> +        case 0:
> +          UseRelativeIDs = false;
> +          break;
> +        case 1:
> +          UseRelativeIDs = true;
> +          break;
> +      }
>        break;
> +    }
>      case bitc::MODULE_CODE_TRIPLE: {  // TRIPLE: [strchr x N]
>        std::string S;
>        if (ConvertToString(Record, 0, S))
> @@ -1797,13 +1806,6 @@
>      // Read a record.
>      switch (Stream.ReadRecord(Code, Record)) {
>      default: break;  // Default behavior, ignore unknown content.
> -    case bitc::MODULE_CODE_VERSION:  // VERSION: [version#]
> -      if (Record.size() < 1)
> -        return Error("Malformed MODULE_CODE_VERSION");
> -      // Only version #0 is supported so far.
> -      if (Record[0] != 0)
> -        return Error("Unknown bitstream version!");
> -      break;
>      case bitc::MODULE_CODE_TRIPLE: {  // TRIPLE: [strchr x N]
>        std::string S;
>        if (ConvertToString(Record, 0, S))
> @@ -2016,7 +2018,7 @@
>        unsigned OpNum = 0;
>        Value *LHS, *RHS;
>        if (getValueTypePair(Record, OpNum, NextValueNo, LHS) ||
> -          getValue(Record, OpNum, LHS->getType(), RHS) ||
> +          popValue(Record, OpNum, NextValueNo, LHS->getType(), RHS) ||
>            OpNum+1 > Record.size())
>          return Error("Invalid BINOP record");
>
> @@ -2131,8 +2133,8 @@
>        unsigned OpNum = 0;
>        Value *TrueVal, *FalseVal, *Cond;
>        if (getValueTypePair(Record, OpNum, NextValueNo, TrueVal) ||
> -          getValue(Record, OpNum, TrueVal->getType(), FalseVal) ||
> -          getValue(Record, OpNum, Type::getInt1Ty(Context), Cond))
> +          popValue(Record, OpNum, NextValueNo, TrueVal->getType(), FalseVal) ||
> +          popValue(Record, OpNum, NextValueNo, Type::getInt1Ty(Context), Cond))
>          return Error("Invalid SELECT record");
>
>        I = SelectInst::Create(Cond, TrueVal, FalseVal);
> @@ -2146,7 +2148,7 @@
>        unsigned OpNum = 0;
>        Value *TrueVal, *FalseVal, *Cond;
>        if (getValueTypePair(Record, OpNum, NextValueNo, TrueVal) ||
> -          getValue(Record, OpNum, TrueVal->getType(), FalseVal) ||
> +          popValue(Record, OpNum, NextValueNo, TrueVal->getType(), FalseVal) ||
>            getValueTypePair(Record, OpNum, NextValueNo, Cond))
>          return Error("Invalid SELECT record");
>
> @@ -2171,7 +2173,7 @@
>        unsigned OpNum = 0;
>        Value *Vec, *Idx;
>        if (getValueTypePair(Record, OpNum, NextValueNo, Vec) ||
> -          getValue(Record, OpNum, Type::getInt32Ty(Context), Idx))
> +          popValue(Record, OpNum, NextValueNo, Type::getInt32Ty(Context), Idx))
>          return Error("Invalid EXTRACTELT record");
>        I = ExtractElementInst::Create(Vec, Idx);
>        InstructionList.push_back(I);
> @@ -2182,9 +2184,9 @@
>        unsigned OpNum = 0;
>        Value *Vec, *Elt, *Idx;
>        if (getValueTypePair(Record, OpNum, NextValueNo, Vec) ||
> -          getValue(Record, OpNum,
> +          popValue(Record, OpNum, NextValueNo,
>                     cast<VectorType>(Vec->getType())->getElementType(), Elt) ||
> -          getValue(Record, OpNum, Type::getInt32Ty(Context), Idx))
> +          popValue(Record, OpNum, NextValueNo, Type::getInt32Ty(Context), Idx))
>          return Error("Invalid INSERTELT record");
>        I = InsertElementInst::Create(Vec, Elt, Idx);
>        InstructionList.push_back(I);
> @@ -2195,7 +2197,7 @@
>        unsigned OpNum = 0;
>        Value *Vec1, *Vec2, *Mask;
>        if (getValueTypePair(Record, OpNum, NextValueNo, Vec1) ||
> -          getValue(Record, OpNum, Vec1->getType(), Vec2))
> +          popValue(Record, OpNum, NextValueNo, Vec1->getType(), Vec2))
>          return Error("Invalid SHUFFLEVEC record");
>
>        if (getValueTypePair(Record, OpNum, NextValueNo, Mask))
> @@ -2215,7 +2217,7 @@
>        unsigned OpNum = 0;
>        Value *LHS, *RHS;
>        if (getValueTypePair(Record, OpNum, NextValueNo, LHS) ||
> -          getValue(Record, OpNum, LHS->getType(), RHS) ||
> +          popValue(Record, OpNum, NextValueNo, LHS->getType(), RHS) ||
>            OpNum+1 != Record.size())
>          return Error("Invalid CMP record");
>
> @@ -2260,7 +2262,8 @@
>        }
>        else {
>          BasicBlock *FalseDest = getBasicBlock(Record[1]);
> -        Value *Cond = getFnValueByID(Record[2], Type::getInt1Ty(Context));
> +        Value *Cond = getValue(Record, 2, NextValueNo,
> +                               Type::getInt1Ty(Context));
>          if (FalseDest == 0 || Cond == 0)
>            return Error("Invalid BR record");
>          I = BranchInst::Create(TrueDest, FalseDest, Cond);
> @@ -2276,7 +2279,7 @@
>          Type *OpTy = getTypeByID(Record[1]);
>          unsigned ValueBitWidth = cast<IntegerType>(OpTy)->getBitWidth();
>
> -        Value *Cond = getFnValueByID(Record[2], OpTy);
> +        Value *Cond = getValue(Record, 2, NextValueNo, OpTy);
>          BasicBlock *Default = getBasicBlock(Record[3]);
>          if (OpTy == 0 || Cond == 0 || Default == 0)
>            return Error("Invalid SWITCH record");
> @@ -2331,7 +2334,7 @@
>        if (Record.size() < 3 || (Record.size() & 1) == 0)
>          return Error("Invalid SWITCH record");
>        Type *OpTy = getTypeByID(Record[0]);
> -      Value *Cond = getFnValueByID(Record[1], OpTy);
> +      Value *Cond = getValue(Record, 1, NextValueNo, OpTy);
>        BasicBlock *Default = getBasicBlock(Record[2]);
>        if (OpTy == 0 || Cond == 0 || Default == 0)
>          return Error("Invalid SWITCH record");
> @@ -2355,7 +2358,7 @@
>        if (Record.size() < 2)
>          return Error("Invalid INDIRECTBR record");
>        Type *OpTy = getTypeByID(Record[0]);
> -      Value *Address = getFnValueByID(Record[1], OpTy);
> +      Value *Address = getValue(Record, 1, NextValueNo, OpTy);
>        if (OpTy == 0 || Address == 0)
>          return Error("Invalid INDIRECTBR record");
>        unsigned NumDests = Record.size()-2;
> @@ -2397,7 +2400,8 @@
>
>        SmallVector<Value*, 16> Ops;
>        for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i, ++OpNum) {
> -        Ops.push_back(getFnValueByID(Record[OpNum], FTy->getParamType(i)));
> +        Ops.push_back(getValue(Record, OpNum, NextValueNo,
> +                               FTy->getParamType(i)));
>          if (Ops.back() == 0) return Error("Invalid INVOKE record");
>        }
>
> @@ -2444,7 +2448,14 @@
>        InstructionList.push_back(PN);
>
>        for (unsigned i = 0, e = Record.size()-1; i != e; i += 2) {
> -        Value *V = getFnValueByID(Record[1+i], Ty);
> +        Value *V;
> +        // With the new function encoding, it is possible that operands have
> +        // negative IDs (for forward references).  Use a signed VBR
> +        // representation to keep the encoding small.
> +        if (UseRelativeIDs)
> +          V = getValueSigned(Record, 1+i, NextValueNo, Ty);
> +        else
> +          V = getValue(Record, 1+i, NextValueNo, Ty);
>          BasicBlock *BB = getBasicBlock(Record[2+i]);
>          if (!V || !BB) return Error("Invalid PHI record");
>          PN->addIncoming(V, BB);
> @@ -2542,7 +2553,7 @@
>        unsigned OpNum = 0;
>        Value *Val, *Ptr;
>        if (getValueTypePair(Record, OpNum, NextValueNo, Ptr) ||
> -          getValue(Record, OpNum,
> +          popValue(Record, OpNum, NextValueNo,
>                      cast<PointerType>(Ptr->getType())->getElementType(), Val) ||
>            OpNum+2 != Record.size())
>          return Error("Invalid STORE record");
> @@ -2556,7 +2567,7 @@
>        unsigned OpNum = 0;
>        Value *Val, *Ptr;
>        if (getValueTypePair(Record, OpNum, NextValueNo, Ptr) ||
> -          getValue(Record, OpNum,
> +          popValue(Record, OpNum, NextValueNo,
>                      cast<PointerType>(Ptr->getType())->getElementType(), Val) ||
>            OpNum+4 != Record.size())
>          return Error("Invalid STOREATOMIC record");
> @@ -2579,9 +2590,9 @@
>        unsigned OpNum = 0;
>        Value *Ptr, *Cmp, *New;
>        if (getValueTypePair(Record, OpNum, NextValueNo, Ptr) ||
> -          getValue(Record, OpNum,
> +          popValue(Record, OpNum, NextValueNo,
>                      cast<PointerType>(Ptr->getType())->getElementType(), Cmp) ||
> -          getValue(Record, OpNum,
> +          popValue(Record, OpNum, NextValueNo,
>                      cast<PointerType>(Ptr->getType())->getElementType(), New) ||
>            OpNum+3 != Record.size())
>          return Error("Invalid CMPXCHG record");
> @@ -2599,7 +2610,7 @@
>        unsigned OpNum = 0;
>        Value *Ptr, *Val;
>        if (getValueTypePair(Record, OpNum, NextValueNo, Ptr) ||
> -          getValue(Record, OpNum,
> +          popValue(Record, OpNum, NextValueNo,
>                      cast<PointerType>(Ptr->getType())->getElementType(), Val) ||
>            OpNum+4 != Record.size())
>          return Error("Invalid ATOMICRMW record");
> @@ -2653,7 +2664,8 @@
>          if (FTy->getParamType(i)->isLabelTy())
>            Args.push_back(getBasicBlock(Record[OpNum]));
>          else
> -          Args.push_back(getFnValueByID(Record[OpNum], FTy->getParamType(i)));
> +          Args.push_back(getValue(Record, OpNum, NextValueNo,
> +                                  FTy->getParamType(i)));
>          if (Args.back() == 0) return Error("Invalid CALL record");
>        }
>
> @@ -2682,7 +2694,7 @@
>        if (Record.size() < 3)
>          return Error("Invalid VAARG record");
>        Type *OpTy = getTypeByID(Record[0]);
> -      Value *Op = getFnValueByID(Record[1], OpTy);
> +      Value *Op = getValue(Record, 1, NextValueNo, OpTy);
>        Type *ResTy = getTypeByID(Record[2]);
>        if (!OpTy || !Op || !ResTy)
>          return Error("Invalid VAARG record");
>
> Modified: llvm/trunk/lib/Bitcode/Reader/BitcodeReader.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Bitcode/Reader/BitcodeReader.h?rev=165739&r1=165738&r2=165739&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Bitcode/Reader/BitcodeReader.h (original)
> +++ llvm/trunk/lib/Bitcode/Reader/BitcodeReader.h Thu Oct 11 15:20:40 2012
> @@ -179,18 +179,27 @@
>    typedef std::pair<unsigned, GlobalVariable*> BlockAddrRefTy;
>    DenseMap<Function*, std::vector<BlockAddrRefTy> > BlockAddrFwdRefs;
>
> +  /// UseRelativeIDs - Indicates that we are using a new encoding for
> +  /// instrunction operands where most operands in the current
> +  /// FUNCTION_BLOCK are encoded relative to the instruction number,
> +  /// for a more compact encoding.  Some instruction operands are not
> +  /// relative to the instruction ID: basic block numbers, and types.
> +  /// Once the old style function blocks have been phased out, we would
> +  /// not need this flag.
> +  bool UseRelativeIDs;
> +
>  public:
>    explicit BitcodeReader(MemoryBuffer *buffer, LLVMContext &C)
>      : Context(C), TheModule(0), Buffer(buffer), BufferOwned(false),
>        LazyStreamer(0), NextUnreadBit(0), SeenValueSymbolTable(false),
>        ErrorString(0), ValueList(C), MDValueList(C),
> -      SeenFirstFunctionBody(false) {
> +      SeenFirstFunctionBody(false), UseRelativeIDs(false) {
>    }
>    explicit BitcodeReader(DataStreamer *streamer, LLVMContext &C)
>      : Context(C), TheModule(0), Buffer(0), BufferOwned(false),
>        LazyStreamer(streamer), NextUnreadBit(0), SeenValueSymbolTable(false),
>        ErrorString(0), ValueList(C), MDValueList(C),
> -      SeenFirstFunctionBody(false) {
> +      SeenFirstFunctionBody(false), UseRelativeIDs(false) {
>    }
>    ~BitcodeReader() {
>      FreeState();
> @@ -223,6 +232,9 @@
>    /// @brief Cheap mechanism to just extract module triple
>    /// @returns true if an error occurred.
>    bool ParseTriple(std::string &Triple);
> +
> +  static uint64_t decodeSignRotatedValue(uint64_t V);
> +
>  private:
>    Type *getTypeByID(unsigned ID);
>    Value *getFnValueByID(unsigned ID, Type *Ty) {
> @@ -247,6 +259,9 @@
>                          unsigned InstNum, Value *&ResVal) {
>      if (Slot == Record.size()) return true;
>      unsigned ValNo = (unsigned)Record[Slot++];
> +    // Adjust the ValNo, if it was encoded relative to the InstNum.
> +    if (UseRelativeIDs)
> +      ValNo = InstNum - ValNo;
>      if (ValNo < InstNum) {
>        // If this is not a forward reference, just return the value we already
>        // have.
> @@ -255,20 +270,54 @@
>      } else if (Slot == Record.size()) {
>        return true;
>      }
> -
> +
>      unsigned TypeNo = (unsigned)Record[Slot++];
>      ResVal = getFnValueByID(ValNo, getTypeByID(TypeNo));
>      return ResVal == 0;
>    }
> -  bool getValue(SmallVector<uint64_t, 64> &Record, unsigned &Slot,
> -                Type *Ty, Value *&ResVal) {
> -    if (Slot == Record.size()) return true;
> -    unsigned ValNo = (unsigned)Record[Slot++];
> -    ResVal = getFnValueByID(ValNo, Ty);
> +
> +  /// popValue - Read a value out of the specified record from slot 'Slot'.
> +  /// Increment Slot past the number of slots used by the value in the record.
> +  /// Return true if there is an error.
> +  bool popValue(SmallVector<uint64_t, 64> &Record, unsigned &Slot,
> +                unsigned InstNum, Type *Ty, Value *&ResVal) {
> +    if (getValue(Record, Slot, InstNum, Ty, ResVal))
> +      return true;
> +    // All values currently take a single record slot.
> +    ++Slot;
> +    return false;
> +  }
> +
> +  /// getValue -- Like popValue, but does not increment the Slot number.
> +  bool getValue(SmallVector<uint64_t, 64> &Record, unsigned Slot,
> +                unsigned InstNum, Type *Ty, Value *&ResVal) {
> +    ResVal = getValue(Record, Slot, InstNum, Ty);
>      return ResVal == 0;
>    }
>
> -
> +  /// getValue -- Version of getValue that returns ResVal directly,
> +  /// or 0 if there is an error.
> +  Value *getValue(SmallVector<uint64_t, 64> &Record, unsigned Slot,
> +                  unsigned InstNum, Type *Ty) {
> +    if (Slot == Record.size()) return 0;
> +    unsigned ValNo = (unsigned)Record[Slot];
> +    // Adjust the ValNo, if it was encoded relative to the InstNum.
> +    if (UseRelativeIDs)
> +      ValNo = InstNum - ValNo;
> +    return getFnValueByID(ValNo, Ty);
> +  }
> +
> +  /// getValueSigned -- Like getValue, but decodes signed VBRs.
> +  Value *getValueSigned(SmallVector<uint64_t, 64> &Record, unsigned Slot,
> +                        unsigned InstNum, Type *Ty) {
> +    if (Slot == Record.size()) return 0;
> +    unsigned ValNo = (unsigned)decodeSignRotatedValue(Record[Slot]);
> +    // Adjust the ValNo, if it was encoded relative to the InstNum.
> +    if (UseRelativeIDs)
> +      ValNo = InstNum - ValNo;
> +    return getFnValueByID(ValNo, Ty);
> +  }
> +
>    bool ParseModule(bool Resume);
>    bool ParseAttributeBlock();
>    bool ParseTypeTable();
>
> Modified: llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp?rev=165739&r1=165738&r2=165739&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp (original)
> +++ llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp Thu Oct 11 15:20:40 2012
> @@ -41,8 +41,6 @@
>  /// These are manifest constants used by the bitcode writer. They do not need to
>  /// be kept in sync with the reader, but need to be consistent within this file.
>  enum {
> -  CurVersion = 0,
> -
>    // VALUE_SYMTAB_BLOCK abbrev id's.
>    VST_ENTRY_8_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
>    VST_ENTRY_7_ABBREV,
> @@ -722,16 +720,20 @@
>    Stream.ExitBlock();
>  }
>
> +static void emitSignedInt64(SmallVectorImpl<uint64_t> &Vals, uint64_t V) {
> +  if ((int64_t)V >= 0)
> +    Vals.push_back(V << 1);
> +  else
> +    Vals.push_back((-V << 1) | 1);
> +}
> +
>  static void EmitAPInt(SmallVectorImpl<uint64_t> &Vals,
>                        unsigned &Code, unsigned &AbbrevToUse, const APInt &Val,
>                        bool EmitSizeForWideNumbers = false
>                        ) {
>    if (Val.getBitWidth() <= 64) {
>      uint64_t V = Val.getSExtValue();
> -    if ((int64_t)V >= 0)
> -      Vals.push_back(V << 1);
> -    else
> -      Vals.push_back((-V << 1) | 1);
> +    emitSignedInt64(Vals, V);
>      Code = bitc::CST_CODE_INTEGER;
>      AbbrevToUse = CONSTANTS_INTEGER_ABBREV;
>    } else {
> @@ -747,11 +749,7 @@
>
>      const uint64_t *RawWords = Val.getRawData();
>      for (unsigned i = 0; i != NWords; ++i) {
> -      int64_t V = RawWords[i];
> -      if (V >= 0)
> -        Vals.push_back(V << 1);
> -      else
> -        Vals.push_back((-V << 1) | 1);
> +      emitSignedInt64(Vals, RawWords[i]);
>      }
>      Code = bitc::CST_CODE_WIDE_INTEGER;
>    }
> @@ -1025,12 +1023,13 @@
>  ///
>  /// This function adds V's value ID to Vals.  If the value ID is higher than the
>  /// instruction ID, then it is a forward reference, and it also includes the
> -/// type ID.
> +/// type ID.  The value ID that is written is encoded relative to the InstID.
>  static bool PushValueAndType(const Value *V, unsigned InstID,
>                               SmallVector<unsigned, 64> &Vals,
>                               ValueEnumerator &VE) {
>    unsigned ValID = VE.getValueID(V);
> -  Vals.push_back(ValID);
> +  // Make encoding relative to the InstID.
> +  Vals.push_back(InstID - ValID);
>    if (ValID >= InstID) {
>      Vals.push_back(VE.getTypeID(V->getType()));
>      return true;
> @@ -1038,6 +1037,30 @@
>    return false;
>  }
>
> +/// pushValue - Like PushValueAndType, but where the type of the value is
> +/// omitted (perhaps it was already encoded in an earlier operand).
> +static void pushValue(const Value *V, unsigned InstID,
> +                      SmallVector<unsigned, 64> &Vals,
> +                      ValueEnumerator &VE) {
> +  unsigned ValID = VE.getValueID(V);
> +  Vals.push_back(InstID - ValID);
> +}
> +
> +static void pushValue64(const Value *V, unsigned InstID,
> +                        SmallVector<uint64_t, 128> &Vals,
> +                        ValueEnumerator &VE) {
> +  uint64_t ValID = VE.getValueID(V);
> +  Vals.push_back(InstID - ValID);
> +}
> +
> +static void pushValueSigned(const Value *V, unsigned InstID,
> +                            SmallVector<uint64_t, 128> &Vals,
> +                            ValueEnumerator &VE) {
> +  unsigned ValID = VE.getValueID(V);
> +  int64_t diff = ((int32_t)InstID - (int32_t)ValID);
> +  emitSignedInt64(Vals, diff);
> +}
> +
>  /// WriteInstruction - Emit an instruction to the specified stream.
>  static void WriteInstruction(const Instruction &I, unsigned InstID,
>                               ValueEnumerator &VE, BitstreamWriter &Stream,
> @@ -1058,7 +1081,7 @@
>        Code = bitc::FUNC_CODE_INST_BINOP;
>        if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
>          AbbrevToUse = FUNCTION_INST_BINOP_ABBREV;
> -      Vals.push_back(VE.getValueID(I.getOperand(1)));
> +      pushValue(I.getOperand(1), InstID, Vals, VE);
>        Vals.push_back(GetEncodedBinaryOpcode(I.getOpcode()));
>        uint64_t Flags = GetOptimizationFlags(&I);
>        if (Flags != 0) {
> @@ -1096,32 +1119,32 @@
>    case Instruction::Select:
>      Code = bitc::FUNC_CODE_INST_VSELECT;
>      PushValueAndType(I.getOperand(1), InstID, Vals, VE);
> -    Vals.push_back(VE.getValueID(I.getOperand(2)));
> +    pushValue(I.getOperand(2), InstID, Vals, VE);
>      PushValueAndType(I.getOperand(0), InstID, Vals, VE);
>      break;
>    case Instruction::ExtractElement:
>      Code = bitc::FUNC_CODE_INST_EXTRACTELT;
>      PushValueAndType(I.getOperand(0), InstID, Vals, VE);
> -    Vals.push_back(VE.getValueID(I.getOperand(1)));
> +    pushValue(I.getOperand(1), InstID, Vals, VE);
>      break;
>    case Instruction::InsertElement:
>      Code = bitc::FUNC_CODE_INST_INSERTELT;
>      PushValueAndType(I.getOperand(0), InstID, Vals, VE);
> -    Vals.push_back(VE.getValueID(I.getOperand(1)));
> -    Vals.push_back(VE.getValueID(I.getOperand(2)));
> +    pushValue(I.getOperand(1), InstID, Vals, VE);
> +    pushValue(I.getOperand(2), InstID, Vals, VE);
>      break;
>    case Instruction::ShuffleVector:
>      Code = bitc::FUNC_CODE_INST_SHUFFLEVEC;
>      PushValueAndType(I.getOperand(0), InstID, Vals, VE);
> -    Vals.push_back(VE.getValueID(I.getOperand(1)));
> -    Vals.push_back(VE.getValueID(I.getOperand(2)));
> +    pushValue(I.getOperand(1), InstID, Vals, VE);
> +    pushValue(I.getOperand(2), InstID, Vals, VE);
>      break;
>    case Instruction::ICmp:
>    case Instruction::FCmp:
>      // compare returning Int1Ty or vector of Int1Ty
>      Code = bitc::FUNC_CODE_INST_CMP2;
>      PushValueAndType(I.getOperand(0), InstID, Vals, VE);
> -    Vals.push_back(VE.getValueID(I.getOperand(1)));
> +    pushValue(I.getOperand(1), InstID, Vals, VE);
>      Vals.push_back(cast<CmpInst>(I).getPredicate());
>      break;
>
> @@ -1147,7 +1170,7 @@
>        Vals.push_back(VE.getValueID(II.getSuccessor(0)));
>        if (II.isConditional()) {
>          Vals.push_back(VE.getValueID(II.getSuccessor(1)));
> -        Vals.push_back(VE.getValueID(II.getCondition()));
> +        pushValue(II.getCondition(), InstID, Vals, VE);
>        }
>      }
>      break;
> @@ -1164,7 +1187,7 @@
>        Vals64.push_back(SwitchRecordHeader);
>
>        Vals64.push_back(VE.getTypeID(SI.getCondition()->getType()));
> -      Vals64.push_back(VE.getValueID(SI.getCondition()));
> +      pushValue64(SI.getCondition(), InstID, Vals64, VE);
>        Vals64.push_back(VE.getValueID(SI.getDefaultDest()));
>        Vals64.push_back(SI.getNumCases());
>        for (SwitchInst::CaseIt i = SI.case_begin(), e = SI.case_end();
> @@ -1215,7 +1238,9 @@
>    case Instruction::IndirectBr:
>      Code = bitc::FUNC_CODE_INST_INDIRECTBR;
>      Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));
> -    for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
> +    // Encode the address operand as relative, but not the basic blocks.
> +    pushValue(I.getOperand(0), InstID, Vals, VE);
> +    for (unsigned i = 1, e = I.getNumOperands(); i != e; ++i)
>        Vals.push_back(VE.getValueID(I.getOperand(i)));
>      break;
>
> @@ -1234,7 +1259,7 @@
>
>      // Emit value #'s for the fixed parameters.
>      for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
> -      Vals.push_back(VE.getValueID(I.getOperand(i)));  // fixed param.
> +      pushValue(I.getOperand(i), InstID, Vals, VE);  // fixed param.
>
>      // Emit type/value pairs for varargs params.
>      if (FTy->isVarArg()) {
> @@ -1256,12 +1281,19 @@
>    case Instruction::PHI: {
>      const PHINode &PN = cast<PHINode>(I);
>      Code = bitc::FUNC_CODE_INST_PHI;
> -    Vals.push_back(VE.getTypeID(PN.getType()));
> +    // With the newer instruction encoding, forward references could give
> +    // negative valued IDs.  This is most common for PHIs, so we use
> +    // signed VBRs.
> +    SmallVector<uint64_t, 128> Vals64;
> +    Vals64.push_back(VE.getTypeID(PN.getType()));
>      for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
> -      Vals.push_back(VE.getValueID(PN.getIncomingValue(i)));
> -      Vals.push_back(VE.getValueID(PN.getIncomingBlock(i)));
> +      pushValueSigned(PN.getIncomingValue(i), InstID, Vals64, VE);
> +      Vals64.push_back(VE.getValueID(PN.getIncomingBlock(i)));
>      }
> -    break;
> +    // Emit a Vals64 vector and exit.
> +    Stream.EmitRecord(Code, Vals64, AbbrevToUse);
> +    Vals64.clear();
> +    return;
>    }
>
>    case Instruction::LandingPad: {
> @@ -1311,7 +1343,7 @@
>      else
>        Code = bitc::FUNC_CODE_INST_STORE;
>      PushValueAndType(I.getOperand(1), InstID, Vals, VE);  // ptrty + ptr
> -    Vals.push_back(VE.getValueID(I.getOperand(0)));       // val.
> +    pushValue(I.getOperand(0), InstID, Vals, VE);         // val.
>      Vals.push_back(Log2_32(cast<StoreInst>(I).getAlignment())+1);
>      Vals.push_back(cast<StoreInst>(I).isVolatile());
>      if (cast<StoreInst>(I).isAtomic()) {
> @@ -1322,8 +1354,8 @@
>    case Instruction::AtomicCmpXchg:
>      Code = bitc::FUNC_CODE_INST_CMPXCHG;
>      PushValueAndType(I.getOperand(0), InstID, Vals, VE);  // ptrty + ptr
> -    Vals.push_back(VE.getValueID(I.getOperand(1)));       // cmp.
> -    Vals.push_back(VE.getValueID(I.getOperand(2)));       // newval.
> +    pushValue(I.getOperand(1), InstID, Vals, VE);         // cmp.
> +    pushValue(I.getOperand(2), InstID, Vals, VE);         // newval.
>      Vals.push_back(cast<AtomicCmpXchgInst>(I).isVolatile());
>      Vals.push_back(GetEncodedOrdering(
>                       cast<AtomicCmpXchgInst>(I).getOrdering()));
> @@ -1333,7 +1365,7 @@
>    case Instruction::AtomicRMW:
>      Code = bitc::FUNC_CODE_INST_ATOMICRMW;
>      PushValueAndType(I.getOperand(0), InstID, Vals, VE);  // ptrty + ptr
> -    Vals.push_back(VE.getValueID(I.getOperand(1)));       // val.
> +    pushValue(I.getOperand(1), InstID, Vals, VE);         // val.
>      Vals.push_back(GetEncodedRMWOperation(
>                       cast<AtomicRMWInst>(I).getOperation()));
>      Vals.push_back(cast<AtomicRMWInst>(I).isVolatile());
> @@ -1358,8 +1390,13 @@
>      PushValueAndType(CI.getCalledValue(), InstID, Vals, VE);  // Callee
>
>      // Emit value #'s for the fixed parameters.
> -    for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
> -      Vals.push_back(VE.getValueID(CI.getArgOperand(i)));  // fixed param.
> +    for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i) {
> +      // Check for labels (can happen with asm labels).
> +      if (FTy->getParamType(i)->isLabelTy())
> +        Vals.push_back(VE.getValueID(CI.getArgOperand(i)));
> +      else
> +        pushValue(CI.getArgOperand(i), InstID, Vals, VE);  // fixed param.
> +    }
>
>      // Emit type/value pairs for varargs params.
>      if (FTy->isVarArg()) {
> @@ -1372,7 +1409,7 @@
>    case Instruction::VAArg:
>      Code = bitc::FUNC_CODE_INST_VAARG;
>      Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));   // valistty
> -    Vals.push_back(VE.getValueID(I.getOperand(0))); // valist.
> +    pushValue(I.getOperand(0), InstID, Vals, VE); // valist.
>      Vals.push_back(VE.getTypeID(I.getType())); // restype.
>      break;
>    }
> @@ -1514,8 +1551,8 @@
>  // Emit blockinfo, which defines the standard abbreviations etc.
>  static void WriteBlockInfo(const ValueEnumerator &VE, BitstreamWriter &Stream) {
>    // We only want to emit block info records for blocks that have multiple
> -  // instances: CONSTANTS_BLOCK, FUNCTION_BLOCK and VALUE_SYMTAB_BLOCK.  Other
> -  // blocks can defined their abbrevs inline.
> +  // instances: CONSTANTS_BLOCK, FUNCTION_BLOCK and VALUE_SYMTAB_BLOCK.
> +  // Other blocks can defined their abbrevs inline.
>    Stream.EnterBlockInfoBlock(2);
>
>    { // 8-bit fixed-width VST_ENTRY/VST_BBENTRY strings.
> @@ -1773,12 +1810,10 @@
>  static void WriteModule(const Module *M, BitstreamWriter &Stream) {
>    Stream.EnterSubblock(bitc::MODULE_BLOCK_ID, 3);
>
> -  // Emit the version number if it is non-zero.
> -  if (CurVersion) {
> -    SmallVector<unsigned, 1> Vals;
> -    Vals.push_back(CurVersion);
> -    Stream.EmitRecord(bitc::MODULE_CODE_VERSION, Vals);
> -  }
> +  SmallVector<unsigned, 1> Vals;
> +  unsigned CurVersion = 1;
> +  Vals.push_back(CurVersion);
> +  Stream.EmitRecord(bitc::MODULE_CODE_VERSION, Vals);
>
>    // Analyze the module, enumerating globals, functions, etc.
>    ValueEnumerator VE(M);
>
> Added: llvm/trunk/test/Bitcode/function-encoding-rel-operands.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Bitcode/function-encoding-rel-operands.ll?rev=165739&view=auto
> ==============================================================================
> --- llvm/trunk/test/Bitcode/function-encoding-rel-operands.ll (added)
> +++ llvm/trunk/test/Bitcode/function-encoding-rel-operands.ll Thu Oct 11 15:20:40 2012
> @@ -0,0 +1,49 @@
> +; Basic sanity test to check that instruction operands are encoded with
> +; relative IDs.
> +; RUN: llvm-as < %s | llvm-bcanalyzer -dump | FileCheck %s

I'm not sure if this is just me, but this test case is breaking my
CMake build because the test case cannot find llvm-bcanalyzer to run
unless I explicitly build llvm-bcanalyzer before runinng the tests.

Any idea what missing dependency might need to be tweaked to make this work?

- David

> +
> +; CHECK: FUNCTION_BLOCK
> +; CHECK: INST_BINOP {{.*}}op0=1 op1=1
> +; CHECK: INST_BINOP {{.*}}op0=1 op1=1
> +; CHECK: INST_BINOP {{.*}}op0=1 op1=1
> +; CHECK: INST_RET {{.*}}op0=1
> +define i32 @test_int_binops(i32 %a) nounwind {
> +entry:
> +  %0 = add i32 %a, %a
> +  %1 = sub i32 %0, %0
> +  %2 = mul i32 %1, %1
> +  ret i32 %2
> +}
> +
> +
> +; CHECK: FUNCTION_BLOCK
> +; CHECK: INST_CAST {{.*}}op0=1
> +; CHECK: INST_BINOP {{.*}}op0=1 op1=1
> +; CHECK: INST_BINOP {{.*}}op0=1 op1=1
> +; CHECK: INST_BINOP {{.*}}op0=1 op1=1
> +; CHECK: INST_BINOP {{.*}}op0=1 op1=1
> +; CHECK: INST_RET {{.*}}op0=1
> +define double @test_float_binops(i32 %a) nounwind {
> +  %1 = sitofp i32 %a to double
> +  %2 = fadd double %1, %1
> +  %3 = fsub double %2, %2
> +  %4 = fmul double %3, %3
> +  %5 = fdiv double %4, %4
> +  ret double %5
> +}
> +
> +
> +; CHECK: FUNCTION_BLOCK
> +; skip checking operands of INST_INBOUNDS_GEP since that depends on ordering
> +; between literals and the formal parameters.
> +; CHECK: INST_INBOUNDS_GEP {{.*}}
> +; CHECK: INST_LOAD {{.*}}op0=1 {{.*}}
> +; CHECK: INST_CMP2 op0=1 {{.*}}
> +; CHECK: INST_RET {{.*}}op0=1
> +define i1 @test_load(i32 %a, {i32, i32}* %ptr) nounwind {
> +entry:
> +  %0 = getelementptr inbounds {i32, i32}* %ptr, i32 %a, i32 0
> +  %1 = load i32* %0
> +  %2 = icmp eq i32 %1, %a
> +  ret i1 %2
> +}
>
>
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