1 files changed, 39 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/IPO/ElimAvailExtern.cpp b/llvm/lib/Transforms/IPO/ElimAvailExtern.cpp
index e13c00a92e4..0e138cbbc7a 100644
--- a/llvm/lib/Transforms/IPO/ElimAvailExtern.cpp
+++ b/llvm/lib/Transforms/IPO/ElimAvailExtern.cpp
@@ -49,9 +49,46 @@ ModulePass *llvm::createEliminateAvailableExternallyPass() {
   return new EliminateAvailableExternally();
 }
 
+static void convertAliasToDeclaration(GlobalAlias &GA, Module &M) {
+  GlobalValue *GVal = GA.getBaseObject();
+  GlobalValue *NewGV;
+  if (auto *GVar = dyn_cast<GlobalVariable>(GVal)) {
+    GlobalVariable *NewGVar = new GlobalVariable(
+        M, GVar->getType()->getElementType(), GVar->isConstant(),
+        GVar->getLinkage(), /*init*/ nullptr, GA.getName(), GVar,
+        GVar->getThreadLocalMode(), GVar->getType()->getAddressSpace());
+    NewGV = NewGVar;
+    NewGV->copyAttributesFrom(GVar);
+  } else {
+    auto *F = dyn_cast<Function>(GVal);
+    assert(F);
+    Function *NewF = Function::Create(F->getFunctionType(), F->getLinkage(),
+                                      GA.getName(), &M);
+    NewGV = NewF;
+    NewGV->copyAttributesFrom(F);
+  }
+  GA.replaceAllUsesWith(ConstantExpr::getBitCast(NewGV, GA.getType()));
+  GA.eraseFromParent();
+}
+
 bool EliminateAvailableExternally::runOnModule(Module &M) {
   bool Changed = false;
 
+  // Convert any aliases that alias with an available externally
+  // value (which will be turned into declarations later on in this routine)
+  // into declarations themselves. All aliases must be definitions, and
+  // must alias with a definition. So this involves creating a declaration
+  // equivalent to the alias's base object.
+  for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); I != E;) {
+    // Increment the iterator first since we may delete the current alias.
+    GlobalAlias &GA = *(I++);
+    GlobalValue *GVal = GA.getBaseObject();
+    if (!GVal->hasAvailableExternallyLinkage())
+      continue;
+    convertAliasToDeclaration(GA, M);
+    Changed = true;
+  }
+
   // Drop initializers of available externally global variables.
   for (GlobalVariable &GV : M.globals()) {
     if (!GV.hasAvailableExternallyLinkage())
@@ -65,6 +102,7 @@ bool EliminateAvailableExternally::runOnModule(Module &M) {
     GV.removeDeadConstantUsers();
     GV.setLinkage(GlobalValue::ExternalLinkage);
     NumVariables++;
+    Changed = true;
   }
 
   // Drop the bodies of available externally functions.
@@ -76,6 +114,7 @@ bool EliminateAvailableExternally::runOnModule(Module &M) {
       F.deleteBody();
     F.removeDeadConstantUsers();
     NumFunctions++;
+    Changed = true;
   }
 
   return Changed;