GlobalOpt does not treat externally_initialized globals correctly

GlobalOpt currently merges stores into the initialisers of internal,
externally_initialized globals, but should not do so as the value of the global
may change between the initialiser and any code in the module being run.

llvm-svn: 250035

2 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index a4b8408b1bf..46a209f2320 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -1804,7 +1804,7 @@ bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
       GVI = FirstNewGV; // Don't skip the newly produced globals!
       return true;
     }
-  } else if (GS.StoredType == GlobalStatus::StoredOnce) {
+  } else if (GS.StoredType == GlobalStatus::StoredOnce && GS.StoredOnceValue) {
     // If the initial value for the global was an undef value, and if only
     // one other value was stored into it, we can just change the
     // initializer to be the stored value, then delete all stores to the
diff --git a/llvm/lib/Transforms/Utils/GlobalStatus.cpp b/llvm/lib/Transforms/Utils/GlobalStatus.cpp
index 44b7d25d519..3893a752503 100644
--- a/llvm/lib/Transforms/Utils/GlobalStatus.cpp
+++ b/llvm/lib/Transforms/Utils/GlobalStatus.cpp
@@ -49,6 +49,10 @@ bool llvm::isSafeToDestroyConstant(const Constant *C) {
 
 static bool analyzeGlobalAux(const Value *V, GlobalStatus &GS,
                              SmallPtrSetImpl<const PHINode *> &PhiUsers) {
+  if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
+    if (GV->isExternallyInitialized())
+      GS.StoredType = GlobalStatus::StoredOnce;
+
   for (const Use &U : V->uses()) {
     const User *UR = U.getUser();
     if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(UR)) {