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Change parent hashing algorithm to be non-recursive and elaborate

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greatly on many comments in the code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187742 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eric Christopher 2013-08-05 21:40:57 +00:00
parent 5a328054f3
commit b30347e64e
1 changed files with 32 additions and 20 deletions
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52
lib/CodeGen/AsmPrinter/DwarfDebug.cpp
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@ -962,7 +962,7 @@ void DwarfDebug::collectDeadVariables() {
DeleteContainerSeconds(DeadFnScopeMap);
}
// Type Signature computation code.
// Type Signature [7.27] computation code.
typedef ArrayRef<uint8_t> HashValue;
/// \brief Grabs the string in whichever attribute is passed in and returns
@ -1012,36 +1012,48 @@ static void addULEB128ToHash(MD5 &Hash, uint64_t Value) {
/// \brief Including \p Parent adds the context of Parent to \p Hash.
static void addParentContextToHash(MD5 &Hash, DIE *Parent) {
unsigned Tag = Parent->getTag();
DEBUG(dbgs() << "Adding parent context to hash...\n");
// For each surrounding type or namespace...
if (Tag != dwarf::DW_TAG_namespace && Tag != dwarf::DW_TAG_class_type &&
Tag != dwarf::DW_TAG_structure_type)
return;
// ... beginning with the outermost such construct...
if (Parent->getParent() != NULL)
addParentContextToHash(Hash, Parent->getParent());
// [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();
}
// Append the letter "C" to the sequence.
addULEB128ToHash(Hash, 'C');
// 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;
// Followed by the DWARF tag of the construct.
addULEB128ToHash(Hash, Parent->getTag());
// ... Append the letter "C" to the sequence...
addULEB128ToHash(Hash, 'C');
// Then the name, taken from the DW_AT_name attribute.
StringRef Name = getDIEStringAttr(Parent, dwarf::DW_AT_name);
if (!Name.empty())
addStringToHash(Hash, Name);
// ... 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.
/// 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.
// 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);