Index: llvm/trunk/include/llvm/Analysis/AliasAnalysis.h
===================================================================
--- llvm/trunk/include/llvm/Analysis/AliasAnalysis.h
+++ llvm/trunk/include/llvm/Analysis/AliasAnalysis.h
@@ -1096,6 +1096,12 @@
 /// This manager effectively wraps the AnalysisManager for registering alias
 /// analyses. When you register your alias analysis with this manager, it will
 /// ensure the analysis itself is registered with its AnalysisManager.
+///
+/// The result of this analysis is only invalidated if one of the particular
+/// aggregated AA results end up being invalidated. This removes the need to
+/// explicitly preserve the results of `AAManager`. Note that analyses should no
+/// longer be registered once the `AAManager` is run.
+
 class AAManager : public AnalysisInfoMixin<AAManager> {
 public:
   using Result = AAResults;
Index: llvm/trunk/lib/Analysis/AliasAnalysis.cpp
===================================================================
--- llvm/trunk/lib/Analysis/AliasAnalysis.cpp
+++ llvm/trunk/lib/Analysis/AliasAnalysis.cpp
@@ -79,12 +79,10 @@
 
 bool AAResults::invalidate(Function &F, const PreservedAnalyses &PA,
                            FunctionAnalysisManager::Invalidator &Inv) {
-  // Check if the AA manager itself has been invalidated.
-  auto PAC = PA.getChecker<AAManager>();
-  if (!PAC.preserved() && !PAC.preservedSet<AllAnalysesOn<Function>>())
-    return true; // The manager needs to be blown away, clear everything.
-
-  // Check all of the dependencies registered.
+  // AAResults preserves the AAManager by default, due to the stateless nature
+  // of AliasAnalysis. There is no need to check whether it has been preserved
+  // explicitly. However, we still need to check if any of the dependencies end
+  // up being invalidated, and invalidate ourselves in that case.
   for (AnalysisKey *ID : AADeps)
     if (Inv.invalidate(ID, F, PA))
       return true;
Index: llvm/trunk/test/Analysis/MemoryDependenceAnalysis/invalidation.ll
===================================================================
--- llvm/trunk/test/Analysis/MemoryDependenceAnalysis/invalidation.ll
+++ llvm/trunk/test/Analysis/MemoryDependenceAnalysis/invalidation.ll
@@ -1,17 +1,16 @@
 ; Test that memdep gets invalidated when the analyses it depends on are
 ; invalidated.
 ;
-; Check AA specifically.
+; Check AA. AA is stateless, there's nothing to invalidate.
 ; RUN: opt -disable-output -debug-pass-manager -aa-pipeline='basic-aa' %s 2>&1 \
 ; RUN:     -passes='require<memdep>,invalidate<aa>,gvn' \
 ; RUN:     | FileCheck %s --check-prefix=CHECK-AA-INVALIDATE
 ; CHECK-AA-INVALIDATE: Running pass: RequireAnalysisPass
 ; CHECK-AA-INVALIDATE: Running analysis: MemoryDependenceAnalysis
 ; CHECK-AA-INVALIDATE: Running pass: InvalidateAnalysisPass
-; CHECK-AA-INVALIDATE: Invalidating analysis: AAManager
-; CHECK-AA-INVALIDATE: Invalidating analysis: MemoryDependenceAnalysis
+; CHECK-NOT-AA-INVALIDATE: Invalidating analysis: MemoryDependenceAnalysis
 ; CHECK-AA-INVALIDATE: Running pass: GVN
-; CHECK-AA-INVALIDATE: Running analysis: MemoryDependenceAnalysis
+; CHECK-NOT-AA-INVALIDATE: Running analysis: MemoryDependenceAnalysis
 ;
 ; Check domtree specifically.
 ; RUN: opt -disable-output -debug-pass-manager %s 2>&1 \
Index: llvm/trunk/test/Other/new-pass-manager.ll
===================================================================
--- llvm/trunk/test/Other/new-pass-manager.ll
+++ llvm/trunk/test/Other/new-pass-manager.ll
@@ -355,13 +355,11 @@
 ; CHECK-AA-MODULE-INVALIDATE: Running analysis: AAManager
 ; CHECK-AA-MODULE-INVALIDATE: Finished llvm::Function pass manager run
 ; CHECK-AA-MODULE-INVALIDATE: Running pass: InvalidateAnalysisPass
-; CHECK-AA-MODULE-INVALIDATE: Invalidating analysis: AAManager
 ; CHECK-AA-MODULE-INVALIDATE: Invalidating analysis: GlobalsAA
 ; CHECK-AA-MODULE-INVALIDATE: Running pass: RequireAnalysisPass
 ; CHECK-AA-MODULE-INVALIDATE: Running analysis: GlobalsAA
 ; CHECK-AA-MODULE-INVALIDATE: Starting llvm::Function pass manager run
 ; CHECK-AA-MODULE-INVALIDATE: Running pass: AAEvaluator
-; CHECK-AA-MODULE-INVALIDATE: Running analysis: AAManager
 ; CHECK-AA-MODULE-INVALIDATE: Finished llvm::Function pass manager run
 ; CHECK-AA-MODULE-INVALIDATE: Finished llvm::Module pass manager run
 
Index: llvm/trunk/unittests/Transforms/Scalar/LoopPassManagerTest.cpp
===================================================================
--- llvm/trunk/unittests/Transforms/Scalar/LoopPassManagerTest.cpp
+++ llvm/trunk/unittests/Transforms/Scalar/LoopPassManagerTest.cpp
@@ -572,7 +572,6 @@
   // invalidation and running.
   EXPECT_CALL(MFPHandle, run(HasName("f"), _))
       .WillOnce(Return(getLoopPassPreservedAnalyses()));
-  EXPECT_CALL(MLAHandle, invalidate(_, _, _)).Times(3);
   EXPECT_CALL(MLAHandle, run(HasName("loop.0.0"), _, _));
   EXPECT_CALL(MLAHandle, run(HasName("loop.0.1"), _, _));
   EXPECT_CALL(MLAHandle, run(HasName("loop.0"), _, _));