1 files changed, 136 insertions, 0 deletions
diff --git a/lib/CodeGen/AsmPrinter/DIEHash.cpp b/lib/CodeGen/AsmPrinter/DIEHash.cpp
new file mode 100644
index 0000000..81ea20a
--- /dev/null
+++ b/lib/CodeGen/AsmPrinter/DIEHash.cpp
@@ -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.");
+      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);
+}