Enable EliminateAvailableExternally pass in the LTO pipeline.

Summary:
For LTO we need to enable this pass in the LTO pipeline,
as it is skipped during the "-flto -c" compile step (when PrepareForLTO is
set).

Reviewers: rnk

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11919

llvm-svn: 244622

llvm/lib/Transforms/IPO/PassManagerBuilder.cpp

@@ -556,6 +556,9 @@ void PassManagerBuilder::addLateLTOOptimizationPasses(
   // Delete basic blocks, which optimization passes may have killed.
   PM.add(createCFGSimplificationPass());
 
+  // Drop bodies of available externally objects to improve GlobalDCE.
+  PM.add(createEliminateAvailableExternallyPass());
+
   // Now that we have optimized the program, discard unreachable functions.
   PM.add(createGlobalDCEPass());