[NewPM] Verify LoopAnalysisResults after a loop pass

[aeubanks]

Summary

All loop passes should preserve all analyses in LoopAnalysisResults. Add
checks for those.

Note that due to PR44815, we don't check LAR's ScalarEvolution.
Apparently calling SE.verify() can change its results.

[asbirlea]

Seems reasonable to verify MSSA unconditionally at this point but if the debug build becomes too overloaded, it can be put under the VerifyMemorySSA flag, like in other loop passes.

llvm/lib/Transforms/Scalar/LoopPassManager.cpp

#endif
     }
 
     // Do not pass deleted Loop into the instrumentation.
     if (Updater.skipCurrentLoop())
       PI.runAfterPassInvalidated<Loop>(*Pass, PassPA);
     else
       PI.runAfterPass<Loop>(*Pass, *L, PassPA);
 
-    // FIXME: We should verify the set of analyses relevant to Loop passes
-    // are preserved.
+#ifndef NDEBUG
+    // LoopAnalysisResults should always be valid.
+    // Note that we don't LAR.SE.verify() because that can change observed SE
+    // queries. See PR44815.
+    LAR.DT.verify();
+    LAR.LI.verify(LAR.DT);
+    if (LAR.MSSA)
+      LAR.MSSA->verifyMemorySSA();
+#endif
 
     // If the loop hasn't been deleted, we need to handle invalidation here.
     if (!Updater.skipCurrentLoop())
       // We know that the loop pass couldn't have invalidated any other
       // loop's analyses (that's the contract of a loop pass), so directly
       // handle the loop analysis manager's invalidation here.
       LAM.invalidate(*L, PassPA);