[llvm] r188028 - Move hash computation code into a separate class and file.

David Blaikie dblaikie at gmail.com
Sat Aug 10 13:42:50 PDT 2013


On Thu, Aug 8, 2013 at 4:45 PM, Eric Christopher <echristo at gmail.com> wrote:

> Author: echristo
> Date: Thu Aug  8 18:45:55 2013
> New Revision: 188028
>
> URL: http://llvm.org/viewvc/llvm-project?rev=188028&view=rev
> Log:
> Move hash computation code into a separate class and file.
>
> No functional change intended.
>
> Added:
>     llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.cpp
>     llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.h
> Modified:
>     llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>
> Added: llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.cpp?rev=188028&view=auto
>
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.cpp (added)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.cpp Thu Aug  8 18:45:55 2013
> @@ -0,0 +1,136 @@
> +//===-- llvm/CodeGen/DIEHash.cpp - Dwarf Hashing 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 DWARF4 hashing of DIEs.
> +//
>
> +//===----------------------------------------------------------------------===//
> +
> +#define DEBUG_TYPE "dwarfdebug"
> +
> +#include "DIE.h"
> +#include "DIEHash.h"
> +#include "DwarfCompileUnit.h"
> +#include "llvm/ADT/ArrayRef.h"
> +#include "llvm/ADT/StringRef.h"
> +#include "llvm/Support/Debug.h"
> +#include "llvm/Support/Dwarf.h"
> +#include "llvm/Support/Endian.h"
> +#include "llvm/Support/MD5.h"
> +#include "llvm/Support/raw_ostream.h"
> +
> +using namespace llvm;
> +
> +/// \brief Grabs the string in whichever attribute is passed in and
> returns
> +/// a reference to it.
> +static StringRef getDIEStringAttr(DIE *Die, uint16_t Attr) {
> +  const SmallVectorImpl<DIEValue *> &Values = Die->getValues();
> +  const DIEAbbrev &Abbrevs = Die->getAbbrev();
> +
> +  // Iterate through all the attributes until we find the one we're
> +  // looking for, if we can't find it return an empty string.
> +  for (size_t i = 0; i < Values.size(); ++i) {
> +    if (Abbrevs.getData()[i].getAttribute() == Attr) {
> +      DIEValue *V = Values[i];
> +      assert(isa<DIEString>(V) && "String requested. Not a string.");
>

cast already asserts when !isa - so this assert is unnecessary


> +      DIEString *S = cast<DIEString>(V);
> +      return S->getString();
> +    }
> +  }
> +  return StringRef("");
> +}
> +
> +/// \brief Adds the string in \p Str to the hash. This also hashes
> +/// a trailing NULL with the string.
> +void DIEHash::addString(StringRef Str) {
> +  DEBUG(dbgs() << "Adding string " << Str << " to hash.\n");
> +  Hash.update(Str);
> +  Hash.update(makeArrayRef((uint8_t)'\0'));
> +}
> +
> +// FIXME: The LEB128 routines are copied and only slightly modified out of
> +// LEB128.h.
> +
> +/// \brief Adds the unsigned in \p Value to the hash encoded as a ULEB128.
> +void DIEHash::addULEB128(uint64_t Value) {
> +  DEBUG(dbgs() << "Adding ULEB128 " << Value << " to hash.\n");
> +  do {
> +    uint8_t Byte = Value & 0x7f;
> +    Value >>= 7;
> +    if (Value != 0)
> +      Byte |= 0x80; // Mark this byte to show that more bytes will follow.
> +    Hash.update(Byte);
> +  } while (Value != 0);
> +}
> +
> +/// \brief Including \p Parent adds the context of Parent to the hash..
> +void DIEHash::addParentContext(DIE *Parent) {
> +
> +  DEBUG(dbgs() << "Adding parent context to hash...\n");
> +
> +  // [7.27.2] For each surrounding type or namespace beginning with the
> +  // outermost such construct...
> +  SmallVector<DIE *, 1> Parents;
> +  while (Parent->getTag() != dwarf::DW_TAG_compile_unit) {
> +    Parents.push_back(Parent);
> +    Parent = Parent->getParent();
> +  }
> +
> +  // Reverse iterate over our list to go from the outermost construct to
> the
> +  // innermost.
> +  for (SmallVectorImpl<DIE *>::reverse_iterator I = Parents.rbegin(),
> +                                                E = Parents.rend();
> +       I != E; ++I) {
> +    DIE *Die = *I;
> +
> +    // ... Append the letter "C" to the sequence...
> +    addULEB128('C');
> +
> +    // ... Followed by the DWARF tag of the construct...
> +    addULEB128(Die->getTag());
> +
> +    // ... Then the name, taken from the DW_AT_name attribute.
> +    StringRef Name = getDIEStringAttr(Die, dwarf::DW_AT_name);
> +    DEBUG(dbgs() << "... adding context: " << Name << "\n");
> +    if (!Name.empty())
> +      addString(Name);
> +  }
> +}
> +
> +/// This is based on the type signature computation given in section 7.27
> of the
> +/// DWARF4 standard. It is the md5 hash of a flattened description of the
> DIE
> +/// with
> +/// the exception that we are hashing only the context and the name of
> the type.
> +uint64_t DIEHash::computeDIEODRSignature(DIE *Die) {
> +
> +  // Add the contexts to the hash. We won't be computing the ODR hash for
> +  // function local types so it's safe to use the generic context hashing
> +  // algorithm here.
> +  // FIXME: If we figure out how to account for linkage in some way we
> could
> +  // actually do this with a slight modification to the parent hash
> algorithm.
> +  DIE *Parent = Die->getParent();
> +  if (Parent)
> +    addParentContext(Parent);
> +
> +  // Add the current DIE information.
> +
> +  // Add the DWARF tag of the DIE.
> +  addULEB128(Die->getTag());
> +
> +  // Add the name of the type to the hash.
> +  addString(getDIEStringAttr(Die, dwarf::DW_AT_name));
> +
> +  // Now get the result.
> +  MD5::MD5Result Result;
> +  Hash.final(Result);
> +
> +  // ... take the least significant 8 bytes and return those. Our MD5
> +  // implementation always returns its results in little endian, swap
> bytes
> +  // appropriately.
> +  return *reinterpret_cast<support::ulittle64_t *>(Result + 8);
> +}
>
> Added: llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.h?rev=188028&view=auto
>
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.h (added)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.h Thu Aug  8 18:45:55 2013
> @@ -0,0 +1,46 @@
> +//===-- llvm/CodeGen/DIEHash.h - Dwarf Hashing Framework -------*- C++
> -*--===//
> +//
> +//                     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 DWARF4 hashing of DIEs.
> +//
>
> +//===----------------------------------------------------------------------===//
> +
> +#include "llvm/Support/MD5.h"
> +
> +namespace llvm {
> +
> +class CompileUnit;
> +
> +/// \brief An object containing the capability of hashing and adding hash
> +/// attributes onto a DIE.
> +class DIEHash {
> +public:
> +  /// \brief Initializes. The hash is default initialized.
> +  DIEHash() {}
>

You could leave this ctor implicit. Though I'm not sure about this whole
class as an abstraction - it has one stateless function. Why isn't that
just a free function?


> +
> +  /// \brief Computes the ODR signature
> +  uint64_t computeDIEODRSignature(DIE *Die);

+
> +  // Helper routines to process parts of a DIE.
> + private:
> +  /// \brief Adds the parent context of \param Die to the hash.
> +  void addParentContext(DIE *Die);
> +
> +  // Routines that add DIEValues to the hash.
> +private:
> +  /// \brief Encodes and adds \param Value to the hash as a ULEB128.
> +  void addULEB128(uint64_t Value);
> +
> +  /// \brief Adds \param Str to the hash and includes a NULL byte.
> +  void addString(StringRef Str);
> +
> +private:
> +  MD5 Hash;
> +};
> +}
>
> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=188028&r1=188027&r2=188028&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Thu Aug  8 18:45:55
> 2013
> @@ -14,6 +14,7 @@
>  #define DEBUG_TYPE "dwarfdebug"
>  #include "DwarfDebug.h"
>  #include "DIE.h"
> +#include "DIEHash.h"
>  #include "DwarfAccelTable.h"
>  #include "DwarfCompileUnit.h"
>  #include "llvm/ADT/STLExtras.h"
> @@ -962,8 +963,7 @@ void DwarfDebug::collectDeadVariables()
>    DeleteContainerSeconds(DeadFnScopeMap);
>  }
>
> -// Type Signature [7.27] computation code.
> -typedef ArrayRef<uint8_t> HashValue;
> +// Type Signature [7.27] and ODR Hash code.
>
>  /// \brief Grabs the string in whichever attribute is passed in and
> returns
>  /// a reference to it. Returns "" if the attribute doesn't exist.
> @@ -976,100 +976,6 @@ static StringRef getDIEStringAttr(DIE *D
>    return StringRef("");
>  }
>
> -/// \brief Adds the string in \p Str to the hash in \p Hash. This also
> hashes
> -/// a trailing NULL with the string.
> -static void addStringToHash(MD5 &Hash, StringRef Str) {
> -  DEBUG(dbgs() << "Adding string " << Str << " to hash.\n");
> -  Hash.update(Str);
> -  Hash.update(makeArrayRef((uint8_t)'\0'));
> -}
> -
> -// FIXME: These are copied and only slightly modified out of LEB128.h.
> -
> -/// \brief Adds the unsigned in \p N to the hash in \p Hash. This also
> encodes
> -/// the unsigned as a ULEB128.
> -static void addULEB128ToHash(MD5 &Hash, uint64_t Value) {
> -  DEBUG(dbgs() << "Adding ULEB128 " << Value << " to hash.\n");
> -  do {
> -    uint8_t Byte = Value & 0x7f;
> -    Value >>= 7;
> -    if (Value != 0)
> -      Byte |= 0x80; // Mark this byte to show that more bytes will follow.
> -    Hash.update(Byte);
> -  } while (Value != 0);
> -}
> -
> -/// \brief Including \p Parent adds the context of Parent to \p Hash.
> -static void addParentContextToHash(MD5 &Hash, DIE *Parent) {
> -
> -  DEBUG(dbgs() << "Adding parent context to hash...\n");
> -
> -  // [7.27.2] For each surrounding type or namespace beginning with the
> -  // outermost such construct...
> -  SmallVector<DIE *, 1> Parents;
> -  while (Parent->getTag() != dwarf::DW_TAG_compile_unit) {
> -    Parents.push_back(Parent);
> -    Parent = Parent->getParent();
> -  }
> -
> -  // Reverse iterate over our list to go from the outermost construct to
> the
> -  // innermost.
> -  for (SmallVectorImpl<DIE *>::reverse_iterator I = Parents.rbegin(),
> -                                                E = Parents.rend();
> -       I != E; ++I) {
> -    DIE *Die = *I;
> -
> -    // ... Append the letter "C" to the sequence...
> -    addULEB128ToHash(Hash, 'C');
> -
> -    // ... Followed by the DWARF tag of the construct...
> -    addULEB128ToHash(Hash, Die->getTag());
> -
> -    // ... Then the name, taken from the DW_AT_name attribute.
> -    StringRef Name = getDIEStringAttr(Die, dwarf::DW_AT_name);
> -    DEBUG(dbgs() << "... adding context: " << Name << "\n");
> -    if (!Name.empty())
> -      addStringToHash(Hash, Name);
> -  }
> -}
> -
> -/// This is based on the type signature computation given in section 7.27
> of the
> -/// DWARF4 standard. It is the md5 hash of a flattened description of the
> DIE with
> -/// the exception that we are hashing only the context and the name of
> the type.
> -static void addDIEODRSignature(MD5 &Hash, CompileUnit *CU, DIE *Die) {
> -
> -  // Add the contexts to the hash. We won't be computing the ODR hash for
> -  // function local types so it's safe to use the generic context hashing
> -  // algorithm here.
> -  // FIXME: If we figure out how to account for linkage in some way we
> could
> -  // actually do this with a slight modification to the parent hash
> algorithm.
> -  DIE *Parent = Die->getParent();
> -  if (Parent)
> -    addParentContextToHash(Hash, Parent);
> -
> -  // Add the current DIE information.
> -
> -  // Add the DWARF tag of the DIE.
> -  addULEB128ToHash(Hash, Die->getTag());
> -
> -  // Add the name of the type to the hash.
> -  addStringToHash(Hash, getDIEStringAttr(Die, dwarf::DW_AT_name));
> -
> -  // Now get the result.
> -  MD5::MD5Result Result;
> -  Hash.final(Result);
> -
> -  // ... take the least significant 8 bytes and store those as the
> attribute.
> -  // Our MD5 implementation always returns its results in little endian,
> swap
> -  // bytes appropriately.
> -  uint64_t Signature = *reinterpret_cast<support::ulittle64_t *>(Result +
> 8);
> -
> -  // FIXME: This should be added onto the type unit, not the type, but
> this
> -  // works as an intermediate stage.
> -  CU->addUInt(Die, dwarf::DW_AT_GNU_odr_signature, dwarf::DW_FORM_data8,
> -              Signature);
> -}
> -
>  /// Return true if the current DIE is contained within an anonymous
> namespace.
>  static bool isContainedInAnonNamespace(DIE *Die) {
>    DIE *Parent = Die->getParent();
> @@ -1090,7 +996,7 @@ static bool shouldAddODRHash(CompileUnit
>    return CU->getLanguage() == dwarf::DW_LANG_C_plus_plus &&
>           getDIEStringAttr(Die, dwarf::DW_AT_name) != "" &&
>           !isContainedInAnonNamespace(Die);
> - }
> +}
>
>  void DwarfDebug::finalizeModuleInfo() {
>    // Collect info for variables that were optimized out.
> @@ -1111,12 +1017,16 @@ void DwarfDebug::finalizeModuleInfo() {
>    // out type.
>    // FIXME: Do type splitting.
>    for (unsigned i = 0, e = TypeUnits.size(); i != e; ++i) {
> -    MD5 Hash;
>      DIE *Die = TypeUnits[i];
> +    DIEHash Hash;
>      // If we've requested ODR hashes and it's applicable for an ODR hash
> then
>      // add the ODR signature now.
> +    // FIXME: This should be added onto the type unit, not the type, but
> this
> +    // works as an intermediate stage.
>      if (GenerateODRHash && shouldAddODRHash(CUMap.begin()->second, Die))
> -      addDIEODRSignature(Hash, CUMap.begin()->second, Die);
> +      CUMap.begin()->second->addUInt(Die, dwarf::DW_AT_GNU_odr_signature,
> +                                     dwarf::DW_FORM_data8,
> +                                     Hash.computeDIEODRSignature(Die));
>    }
>
>     // Compute DIE offsets and sizes.
>
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20130810/c621a520/attachment.html>


More information about the llvm-commits mailing list