Index: lib/Transforms/IPO/FunctionAttrs.cpp
===================================================================
--- lib/Transforms/IPO/FunctionAttrs.cpp
+++ lib/Transforms/IPO/FunctionAttrs.cpp
@@ -1153,6 +1153,7 @@
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.setPreservesCFG();
     AU.addRequired<CallGraphWrapperPass>();
+    AU.addPreserved<CallGraphWrapperPass>();
   }
 };
 }
Index: lib/Transforms/IPO/PassManagerBuilder.cpp
===================================================================
--- lib/Transforms/IPO/PassManagerBuilder.cpp
+++ lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -242,11 +242,6 @@
   MPM.add(createTailCallEliminationPass()); // Eliminate tail calls
   MPM.add(createCFGSimplificationPass());     // Merge & remove BBs
   MPM.add(createReassociatePass());           // Reassociate expressions
-  if (PrepareForThinLTO) {
-    MPM.add(createAggressiveDCEPass());        // Delete dead instructions
-    addInstructionCombiningPass(MPM);          // Combine silly seq's
-    return;
-  }
   // Rotate Loop - disable header duplication at -Oz
   MPM.add(createLoopRotatePass(SizeLevel == 2 ? 0 : -1));
   MPM.add(createLICMPass());                  // Hoist loop invariants
@@ -399,6 +394,14 @@
 
   addFunctionSimplificationPasses(MPM);
 
+  // FIXME: This is a HACK! The inliner pass above implicitly creates a CGSCC
+  // pass manager that we are specifically trying to avoid. To prevent this
+  // we must insert a no-op module pass to reset the pass manager.
+  MPM.add(createBarrierNoopPass());
+
+  if (!DisableUnitAtATime)
+    MPM.add(createReversePostOrderFunctionAttrsPass());
+
   // If we are planning to perform ThinLTO later, let's not bloat the code with
   // unrolling/vectorization/... now. We'll first run the inliner + CGSCC passes
   // during ThinLTO and perform the rest of the optimizations afterward.
@@ -410,11 +413,6 @@
     return;
   }
 
-  // FIXME: This is a HACK! The inliner pass above implicitly creates a CGSCC
-  // pass manager that we are specifically trying to avoid. To prevent this
-  // we must insert a no-op module pass to reset the pass manager.
-  MPM.add(createBarrierNoopPass());
-
   // Scheduling LoopVersioningLICM when inlining is over, because after that
   // we may see more accurate aliasing. Reason to run this late is that too
   // early versioning may prevent further inlining due to increase of code
@@ -425,10 +423,7 @@
     MPM.add(createLICMPass());                  // Hoist loop invariants
   }
 
-  if (!DisableUnitAtATime)
-    MPM.add(createReversePostOrderFunctionAttrsPass());
-
-  if (!DisableUnitAtATime && OptLevel > 1 && !PrepareForLTO)
+  if (!DisableUnitAtATime && OptLevel > 1)
     // Remove avail extern fns and globals definitions if we aren't
     // compiling an object file for later LTO. For LTO we want to preserve
     // these so they are eligible for inlining at link-time. Note if they
@@ -440,15 +435,9 @@
     // and saves running remaining passes on the eliminated functions.
     MPM.add(createEliminateAvailableExternallyPass());
 
-  if (PerformThinLTO) {
-    // Remove dead fns and globals. Removing unreferenced functions could lead
-    // to more opportunities for globalopt.
-    MPM.add(createGlobalDCEPass());
+  if (PerformThinLTO)
+    // Remove dead fns and globals.
     MPM.add(createGlobalOptimizerPass());
-    // Remove dead fns and globals after globalopt.
-    MPM.add(createGlobalDCEPass());
-    addFunctionSimplificationPasses(MPM);
-  }
 
   if (EnableNonLTOGlobalsModRef)
     // We add a fresh GlobalsModRef run at this point. This is particularly