[ThinLTO] Look through aliases when computing hash keys

Without this, we don't consider types used by aliasees in our cache key.
This caused issues when using the same cache for thin-linking the same
TU with different sets of virtual call candidates for a virtual call
inside of a constructor. That's sort of a mouthful. :)

Differential Revision: https://reviews.llvm.org/D55060

llvm-svn: 348216

1 files changed, 8 insertions, 2 deletions

diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index f4840db..c1d3cad 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -221,8 +221,14 @@ void llvm::computeLTOCacheKey(
   // Imported functions may introduce new uses of type identifier resolutions,
   // so we need to collect their used resolutions as well.
   for (auto &ImpM : ImportList)
-    for (auto &ImpF : ImpM.second)
-      AddUsedThings(Index.findSummaryInModule(ImpF, ImpM.first()));
+    for (auto &ImpF : ImpM.second) {
+      GlobalValueSummary *S = Index.findSummaryInModule(ImpF, ImpM.first());
+      AddUsedThings(S);
+      // If this is an alias, we also care about any types/etc. that the aliasee
+      // may reference.
+      if (auto *AS = dyn_cast_or_null<AliasSummary>(S))
+        AddUsedThings(AS->getBaseObject());
+    }
 
   auto AddTypeIdSummary = [&](StringRef TId, const TypeIdSummary &S) {
     AddString(TId);