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[BOLT][NFCI] Use FileSymbols for local symbol disambiguation #89088

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Jun 20, 2025
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[BOLT][NFCI] Use FileSymbols for local symbol disambiguation #89088

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37 changes: 8 additions & 29 deletions bolt/lib/Rewrite/RewriteInstance.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -780,14 +780,6 @@ void RewriteInstance::discoverFileObjects() {

// For local symbols we want to keep track of associated FILE symbol name for
// disambiguation by combined name.
StringRef FileSymbolName;
bool SeenFileName = false;
struct SymbolRefHash {
size_t operator()(SymbolRef const &S) const {
return std::hash<decltype(DataRefImpl::p)>{}(S.getRawDataRefImpl().p);
}
};
std::unordered_map<SymbolRef, StringRef, SymbolRefHash> SymbolToFileName;
for (const ELFSymbolRef &Symbol : InputFile->symbols()) {
Expected<StringRef> NameOrError = Symbol.getName();
if (NameOrError && NameOrError->starts_with("__asan_init")) {
Expand All @@ -806,21 +798,8 @@ void RewriteInstance::discoverFileObjects() {
if (cantFail(Symbol.getFlags()) & SymbolRef::SF_Undefined)
continue;

if (cantFail(Symbol.getType()) == SymbolRef::ST_File) {
if (cantFail(Symbol.getType()) == SymbolRef::ST_File)
FileSymbols.emplace_back(Symbol);
StringRef Name =
cantFail(std::move(NameOrError), "cannot get symbol name for file");
// Ignore Clang LTO artificial FILE symbol as it is not always generated,
// and this uncertainty is causing havoc in function name matching.
if (Name == "ld-temp.o")
continue;
FileSymbolName = Name;
SeenFileName = true;
continue;
}
if (!FileSymbolName.empty() &&
!(cantFail(Symbol.getFlags()) & SymbolRef::SF_Global))
SymbolToFileName[Symbol] = FileSymbolName;
}

// Sort symbols in the file by value. Ignore symbols from non-allocatable
Expand Down Expand Up @@ -1028,14 +1007,14 @@ void RewriteInstance::discoverFileObjects() {
// The <id> field is used for disambiguation of local symbols since there
// could be identical function names coming from identical file names
// (e.g. from different directories).
std::string AltPrefix;
auto SFI = SymbolToFileName.find(Symbol);
if (SymbolType == SymbolRef::ST_Function && SFI != SymbolToFileName.end())
AltPrefix = Name + "/" + std::string(SFI->second);
auto SFI = llvm::upper_bound(FileSymbols, ELFSymbolRef(Symbol));
if (SymbolType == SymbolRef::ST_Function && SFI != FileSymbols.begin()) {
StringRef FileSymbolName = cantFail(SFI[-1].getName());
if (!FileSymbolName.empty())
AlternativeName = NR.uniquify(Name + "/" + FileSymbolName.str());
}

UniqueName = NR.uniquify(Name);
if (!AltPrefix.empty())
AlternativeName = NR.uniquify(AltPrefix);
}

uint64_t SymbolSize = ELFSymbolRef(Symbol).getSize();
Expand Down Expand Up @@ -1294,7 +1273,7 @@ void RewriteInstance::discoverFileObjects() {
FDE->getAddressRange());
}

BC->setHasSymbolsWithFileName(SeenFileName);
BC->setHasSymbolsWithFileName(FileSymbols.size());

// Now that all the functions were created - adjust their boundaries.
adjustFunctionBoundaries();
Expand Down
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