remove inlined functions for faster compilation

lib/Transforms/IPO/PassManagerBuilder.cpp

@@ -475,10 +475,14 @@ void PassManagerBuilder::populateModulePassManager(
   // Start of CallGraph SCC passes.
   if (!DisableUnitAtATime)
     MPM.add(createPruneEHPass()); // Remove dead EH info
+
+  bool RunInliner = false;
   if (Inliner) {
     MPM.add(Inliner);
     Inliner = nullptr;
+    RunInliner = true;    
   }
+
   if (!DisableUnitAtATime)
     MPM.add(createPostOrderFunctionAttrsLegacyPass());
   if (OptLevel > 2)
@@ -492,6 +496,17 @@ void PassManagerBuilder::populateModulePassManager(
   // we must insert a no-op module pass to reset the pass manager.
   MPM.add(createBarrierNoopPass());
 
+  // The inliner performs some kind of dead code elimination as it goes,
+  // but there are cases that are not really caught by it. We might
+  // at some point consider teaching the inliner about them, but it
+  // is OK for now to run GlobalOpt + GlobalDCE in tandem as their
+  // benefits generally outweight the cost, making the whole pipeline
+  // faster. See PR34652.
+  if (RunInliner) {
+    MPM.add(createGlobalOptimizerPass());
+    MPM.add(createGlobalDCEPass());
+  }
+
   if (!DisableUnitAtATime && OptLevel > 1 && !PrepareForLTO &&
       !PrepareForThinLTO)
     // Remove avail extern fns and globals definitions if we aren't