Revert r313157 "ThinLTO: Correctly follow aliasee references when dead stripping."

This broke Chromium's CFI build; see crbug.com/765004.

> We were previously handling aliases during dead stripping by adding
> the aliased global's "original name" GUID to the worklist. This will
> lead to incorrect behaviour if the global has local linkage because
> the original name GUID will not correspond to the global's GUID in
> the summary.
>
> Because an alias is just another name for the global that it
> references, there is no need to mark the referenced global as used,
> or to follow references from any other copies of the global. So all
> we need to do is to follow references from the aliasee's summary
> instead of the alias.
>
> Differential Revision: https://reviews.llvm.org/D37789

llvm-svn: 313222

1 files changed, 8 insertions, 5 deletions

diff --git a/llvm/lib/Transforms/IPO/FunctionImport.cpp b/llvm/lib/Transforms/IPO/FunctionImport.cpp
index b043687f898..da763b18d4d 100644
--- a/llvm/lib/Transforms/IPO/FunctionImport.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionImport.cpp
@@ -488,14 +488,17 @@ void llvm::computeDeadSymbols(
   while (!Worklist.empty()) {
     auto VI = Worklist.pop_back_val();
     for (auto &Summary : VI.getSummaryList()) {
-      GlobalValueSummary *Base = Summary.get();
-      if (auto *AS = dyn_cast<AliasSummary>(Base))
-        Base = &AS->getAliasee();
-      for (auto Ref : Base->refs())
+      for (auto Ref : Summary->refs())
         visit(Ref);
-      if (auto *FS = dyn_cast<FunctionSummary>(Base))
+      if (auto *FS = dyn_cast<FunctionSummary>(Summary.get()))
         for (auto Call : FS->calls())
           visit(Call.first);
+      if (auto *AS = dyn_cast<AliasSummary>(Summary.get())) {
+        auto AliaseeGUID = AS->getAliasee().getOriginalName();
+        ValueInfo AliaseeVI = Index.getValueInfo(AliaseeGUID);
+        if (AliaseeVI)
+          visit(AliaseeVI);
+      }
     }
   }
   Index.setWithGlobalValueDeadStripping();