Call verifyPreservedAnalysis in LoopPass even if loop is deleted

[meheff]

Summary

Unconditionally call verifyPreservedAnalysis after each loop pass. Previously this function was not called in the case where the loop was eliminated (such as if the loop is fully unrolled). However, we want to call verifyPreservedAnalysis in this case because preserved analysis such as LoopInfo may have been modified.

lib/Analysis/LoopPass.cpp

for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
         // is a function pass and it's really expensive to verify every
         // loop in the function every time. That level of checking can be
         // enabled with the -verify-loop-info option.
         {
           TimeRegion PassTimer(getPassTimer(LI));
           CurrentLoop->verifyLoop();
         }
 
-        // Then call the regular verifyAnalysis functions.
-        verifyPreservedAnalysis(P);
-
         F.getContext().yield();
       }
 
+      verifyPreservedAnalysis(P);
+
       removeNotPreservedAnalysis(P);
       recordAvailableAnalysis(P);
       removeDeadPasses(P,
                        skipThisLoop ? "<deleted>" :
                                       CurrentLoop->getHeader()->getName(),
                        ON_LOOP_MSG);
 
       if (skipThisLoop)