1 files changed, 52 insertions, 10 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index e8e1e50c9b9..a0052f605d7 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -58,6 +58,11 @@ static cl::opt<bool> UnknownLocations(
     cl::desc("Make an absence of debug location information explicit."),
     cl::init(false));
 
+static cl::opt<bool>
+GenerateODRHash("generate-odr-hash", cl::Hidden,
+                cl::desc("Add an ODR hash to external type DIEs."),
+                cl::init(false));
+
 static cl::opt<bool> GenerateCUHash("generate-cu-hash", cl::Hidden,
                                     cl::desc("Add the CU hash as the dwo_id."),
                                     cl::init(false));
@@ -1014,6 +1019,41 @@ void DwarfDebug::collectDeadVariables() {
   }
 }
 
+// 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.
+static StringRef getDIEStringAttr(DIE *Die, unsigned Attr) {
+  DIEValue *V = Die->findAttribute(Attr);
+
+  if (DIEString *S = dyn_cast_or_null<DIEString>(V))
+    return S->getString();
+
+  return StringRef("");
+}
+
+/// Return true if the current DIE is contained within an anonymous namespace.
+static bool isContainedInAnonNamespace(DIE *Die) {
+  DIE *Parent = Die->getParent();
+
+  while (Parent) {
+    if (Parent->getTag() == dwarf::DW_TAG_namespace &&
+        getDIEStringAttr(Parent, dwarf::DW_AT_name) == "")
+      return true;
+    Parent = Parent->getParent();
+  }
+
+  return false;
+}
+
+/// Test if the current CU language is C++ and that we have
+/// a named type that is not contained in an anonymous namespace.
+static bool shouldAddODRHash(DwarfTypeUnit *CU, DIE *Die) {
+  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.
   collectDeadVariables();
@@ -3001,8 +3041,8 @@ void DwarfDebug::emitDebugStrDWO() {
                          OffSec, StrSym);
 }
 
-void DwarfDebug::addDwarfTypeUnitType(uint16_t Language, StringRef Identifier,
-                                      DIE *RefDie, DICompositeType CTy) {
+void DwarfDebug::addDwarfTypeUnitType(uint16_t Language, DIE *RefDie,
+                                      DICompositeType CTy) {
   const DwarfTypeUnit *&TU = DwarfTypeUnits[CTy];
   if (!TU) {
     DIE *UnitDie = new DIE(dwarf::DW_TAG_type_unit);
@@ -3017,14 +3057,16 @@ void DwarfDebug::addDwarfTypeUnitType(uint16_t Language, StringRef Identifier,
 
     DIE *Die = NewTU->createTypeDIE(CTy);
 
-    MD5 Hash;
-    Hash.update(Identifier);
-    // ... take the least significant 8 bytes and return those. Our MD5
-    // implementation always returns its results in little endian, swap bytes
-    // appropriately.
-    MD5::MD5Result Result;
-    Hash.final(Result);
-    uint64_t Signature = *reinterpret_cast<uint64_t *>(Result + 8);
+    if (GenerateODRHash && shouldAddODRHash(NewTU, Die))
+      NewTU->addUInt(UnitDie, dwarf::DW_AT_GNU_odr_signature,
+                     dwarf::DW_FORM_data8,
+                     DIEHash().computeDIEODRSignature(*Die));
+    // FIXME: This won't handle circularly referential structures, as the DIE
+    // may have references to other DIEs still under construction and missing
+    // their signature. Hashing should walk through the signatures to their
+    // referenced type, or possibly walk the precomputed hashes of related types
+    // at the end.
+    uint64_t Signature = DIEHash().computeTypeSignature(*Die);
     NewTU->setTypeSignature(Signature);
     NewTU->setType(Die);