Disallow aliases to available_externally.

They are as much trouble as aliases to declarations. They are requiring
the code generator to define a symbol with the same value as another
symbol, but the second symbol is undefined.

If representing this is important for some optimization, we could add
support for available_externally aliases. They would be *required* to
point to a declaration (or available_externally definition).

llvm-svn: 254170

1 files changed, 0 insertions, 37 deletions

diff --git a/llvm/lib/Transforms/IPO/ElimAvailExtern.cpp b/llvm/lib/Transforms/IPO/ElimAvailExtern.cpp
index 0e138cbbc7a..af313a6b001 100644
--- a/llvm/lib/Transforms/IPO/ElimAvailExtern.cpp
+++ b/llvm/lib/Transforms/IPO/ElimAvailExtern.cpp
@@ -49,46 +49,9 @@ 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())