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[BOLT] Store FileSymRefs in a multimap

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With aggressive ICF, it's possible to have different local symbols
(under different FILE symbols) to be mapped to the same address.

FileSymRefs only keeps a single SymbolRef per address, which prevents
fragment matching from finding the correct symbol to perform parent
function lookup.

Work around this issue by switching FileSymRefs to a multimap. In
future, uses of FileSymRefs can be replaced with SortedSymbols which
keeps essentially the same information.

Test Plan: added ambiguous_fragment.test

Reviewers: dcci, ayermolo, maksfb, rafaelauler

Reviewed By: rafaelauler

Pull Request: https://github.com/llvm/llvm-project/pull/98992
This commit is contained in:
Amir Ayupov
2024-07-16 22:14:43 -07:00
committed by GitHub
parent f0ac8903ea
commit 3fe50b6dde
5 changed files with 104 additions and 4 deletions
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13
bolt/lib/Rewrite/RewriteInstance.cpp
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@@ -886,7 +886,7 @@ void RewriteInstance::discoverFileObjects() {
if (SymName == "__hot_start" || SymName == "__hot_end")
continue;
FileSymRefs[SymbolAddress] = Symbol;
FileSymRefs.emplace(SymbolAddress, Symbol);
// Skip section symbols that will be registered by disassemblePLT().
if (SymbolType == SymbolRef::ST_Debug) {
@@ -1052,7 +1052,9 @@ void RewriteInstance::discoverFileObjects() {
// Remove the symbol from FileSymRefs so that we can skip it from
// in the future.
auto SI = FileSymRefs.find(SymbolAddress);
auto SI = llvm::find_if(
llvm::make_range(FileSymRefs.equal_range(SymbolAddress)),
[&](auto SymIt) { return SymIt.second == Symbol; });
assert(SI != FileSymRefs.end() && "symbol expected to be present");
assert(SI->second == Symbol && "wrong symbol found");
FileSymRefs.erase(SI);
@@ -1260,6 +1262,7 @@ void RewriteInstance::discoverFileObjects() {
registerFragments();
FileSymbols.clear();
FileSymRefs.clear();
discoverBOLTReserved();
}
@@ -1433,7 +1436,11 @@ void RewriteInstance::registerFragments() {
const uint64_t Address = BF->getAddress();
// Get fragment's own symbol
const auto SymIt = FileSymRefs.find(Address);
const auto SymIt = llvm::find_if(
llvm::make_range(FileSymRefs.equal_range(Address)), [&](auto SI) {
StringRef Name = cantFail(SI.second.getName());
return Name.contains(ParentName);
});
if (SymIt == FileSymRefs.end()) {
BC->errs()
<< "BOLT-ERROR: symbol lookup failed for function at address 0x"