[NewPM] Verify LoopAnalysisResults after a loop pass

All loop passes should preserve all analyses in LoopAnalysisResults. Add
checks for those when the checks are enabled (which is by default with
expensive checks on).

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

This is a reland of https://reviews.llvm.org/D98820 which was reverted
due to unacceptably large compile time regressions in normal debug
builds.

llvm/lib/Transforms/Scalar/LoopPassManager.cpp

@@ -14,6 +14,7 @@
 #include "llvm/Analysis/MemorySSA.h"
 #include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/Support/Debug.h"
 #include "llvm/Support/TimeProfiler.h"
 
 using namespace llvm;
@@ -291,8 +292,17 @@ PreservedAnalyses FunctionToLoopPassAdaptor::run(Function &F,
     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.
+    if (VerifyDomInfo)
+      LAR.DT.verify();
+    if (VerifyLoopInfo)
+      LAR.LI.verify(LAR.DT);
+    if (LAR.MSSA && VerifyMemorySSA)
+      LAR.MSSA->verifyMemorySSA();
+#endif
 
     // If the loop hasn't been deleted, we need to handle invalidation here.
     if (!Updater.skipCurrentLoop())