Revert "Add r159136 back now that pr13124 has been fixed."

This reverts commit r189886.

I found a corner case where this optimization is not valid:

Say we have a "linkonce_odr unnamed_addr" in two translation units:
* In TU 1 this optimization kicks in and makes it hidden.
* In TU 2 it gets const merged with a constant that is *not* unnamed_addr,
  resulting in a non unnamed_addr constant with default visibility.
* The static linker rules for combining visibility them produce a hidden
  symbol, which is incorrect from the point of view of the non unnamed_addr
  constant.

The one place we can do this is when we know that the symbol is not used from
another TU in the same shared object, i.e., during LTO. I will move it there.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189954 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/IPO/GlobalOpt.cpp

@@ -1914,12 +1914,6 @@ bool GlobalOpt::ProcessGlobal(GlobalVariable *GV,
     return true;
   }
 
-  if (GV->hasLinkOnceODRLinkage() && GV->hasUnnamedAddr() && GV->isConstant() &&
-      GV->getVisibility() != GlobalValue::HiddenVisibility) {
-    GV->setVisibility(GlobalValue::HiddenVisibility);
-    return true;
-  }
-
   if (!GV->hasLocalLinkage())
     return false;
 
@@ -1932,7 +1926,6 @@ bool GlobalOpt::ProcessGlobal(GlobalVariable *GV,
   if (!GS.isCompared && !GV->hasUnnamedAddr()) {
     GV->setUnnamedAddr(true);
     NumUnnamed++;
-    return true;
   }
 
   if (GV->isConstant() || !GV->hasInitializer())
@@ -2112,10 +2105,6 @@ bool GlobalOpt::OptimizeFunctions(Module &M) {
       F->eraseFromParent();
       Changed = true;
       ++NumFnDeleted;
-    } else if (F->hasLinkOnceODRLinkage() && F->hasUnnamedAddr() &&
-               F->getVisibility() != GlobalValue::HiddenVisibility) {
-      F->setVisibility(GlobalValue::HiddenVisibility);
-      Changed = true;
     } else if (F->hasLocalLinkage()) {
       if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
           !F->hasAddressTaken()) {