[ThinLTO/WPD] Fix index-based WPD for available_externally vtables
Summary:
Clang does not add type metadata to available_externally vtables. When
choosing a summary to look at for virtual function definitions, make
sure we skip summaries for any available externally vtables as they will
not describe any virtual function functions, which are only summarized
in the presence of type metadata on the vtable def. Simply look for the
corresponding strong def's summary.
Also add handling for same-named local vtables with the same GUID
because of same-named files without enough distinguishing path.
In that case we return a conservative result with no devirtualization.
Reviewers: pcc, davidxl, evgeny777
Subscribers: mehdi_amini, inglorion, hiraditya, steven_wu, dexonsmith, arphaman, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69452
diff --git a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
index f0cf558..d7c7504 100644
--- a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
+++ b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
@@ -841,17 +841,35 @@
std::vector<ValueInfo> &TargetsForSlot, const TypeIdCompatibleVtableInfo TIdInfo,
uint64_t ByteOffset) {
for (const TypeIdOffsetVtableInfo P : TIdInfo) {
- // VTable initializer should have only one summary, or all copies must be
- // linkonce/weak ODR.
+ // Ensure that we have at most one external linkage vtable initializer.
assert(P.VTableVI.getSummaryList().size() == 1 ||
- llvm::all_of(
+ llvm::count_if(
P.VTableVI.getSummaryList(),
[&](const std::unique_ptr<GlobalValueSummary> &Summary) {
- return GlobalValue::isLinkOnceODRLinkage(Summary->linkage()) ||
- GlobalValue::isWeakODRLinkage(Summary->linkage());
- }));
- const auto *VS = cast<GlobalVarSummary>(P.VTableVI.getSummaryList()[0].get());
- if (!P.VTableVI.getSummaryList()[0]->isLive())
+ return GlobalValue::isExternalLinkage(Summary->linkage());
+ }) <= 1);
+ // Find the first non-available_externally linkage vtable initializer.
+ // We can have multiple available_externally, linkonce_odr and weak_odr
+ // vtable initializers, however we want to skip available_externally as they
+ // do not have type metadata attached, and therefore the summary will not
+ // contain any vtable functions.
+ //
+ // Also, handle the case of same-named local Vtables with the same path
+ // and therefore the same GUID. This can happen if there isn't enough
+ // distinguishing path when compiling the source file. In that case we
+ // conservatively return false early.
+ const GlobalVarSummary *VS = nullptr;
+ bool LocalFound = false;
+ for (auto &S : P.VTableVI.getSummaryList()) {
+ if (GlobalValue::isLocalLinkage(S->linkage())) {
+ if (LocalFound)
+ return false;
+ LocalFound = true;
+ }
+ if (!GlobalValue::isAvailableExternallyLinkage(S->linkage()))
+ VS = cast<GlobalVarSummary>(S.get());
+ }
+ if (!VS->isLive())
continue;
for (auto VTP : VS->vTableFuncs()) {
if (VTP.VTableOffset != P.AddressPointOffset + ByteOffset)