Move createReversePostOrderFunctionAttrsPass right after the inliner is done

[mehdi_amini]

Summary

This is where it was originally, until LoopVersioningLICM was
inserted before in r259986, I don't believe it was on purpose.

[chandlerc]

This was clearly a mistake. We have tests for this that you can probable just add some CHECK lines too to get coverage. See test/Other/pass-pipelines.ll

[ashutosh.nema]

Thanks for pointing Mehdi, this change looks OK.

[mehdi_amini]

r268252

lib/Transforms/IPO/PassManagerBuilder.cpp

void PassManagerBuilder::populateModulePassManager(
   }
   if (!DisableUnitAtATime)
     MPM.add(createPostOrderFunctionAttrsLegacyPass());
   if (OptLevel > 2)
     MPM.add(createArgumentPromotionPass()); // Scalarize uninlined fn args
 
   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.
   if (PrepareForThinLTO) {
     // Reduce the size of the IR as much as possible.
     MPM.add(createGlobalOptimizerPass());
     // Rename anon function to be able to export them in the summary.
     MPM.add(createNameAnonFunctionPass());
     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
   // size. By placing it just after inlining other optimizations which runs 
   // later might get benefit of no-alias assumption in clone loop. 
   if (UseLoopVersioningLICM) {
     MPM.add(createLoopVersioningLICMPass());    // Do LoopVersioningLICM
     MPM.add(createLICMPass());                  // Hoist loop invariants
   }
 
-  if (!DisableUnitAtATime)
-    MPM.add(createReversePostOrderFunctionAttrsPass());
-
   if (!DisableUnitAtATime && OptLevel > 1 && !PrepareForLTO)
     // 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
     // are unreferenced they will be removed by GlobalDCE later, so
     // this only impacts referenced available externally globals.
     // Eventually they will be suppressed during codegen, but eliminating
     // here enables more opportunity for GlobalDCE as it may make