Improve LegacyPassManager API to correctly report modified status

When calling on-the-fly passes from the legacy pass manager, the modification
status is not reported, which is a problem in case we depend on an acutal
transformation pass, and not only analyse.

Update the Legacy PM API to optionally report the changed status, assert if a
change is detected but this change is lost.

Related to https://reviews.llvm.org/D80916

Differential Revision: https://reviews.llvm.org/D81236

Author: serge-sans-paille

llvm/include/llvm/IR/LegacyPassManagers.h

@@ -330,7 +330,8 @@ class PMDataManager {
   /// through getAnalysis interface.
   virtual void addLowerLevelRequiredPass(Pass *P, Pass *RequiredPass);
 
-  virtual Pass *getOnTheFlyPass(Pass *P, AnalysisID PI, Function &F);
+  virtual std::tuple<Pass *, bool> getOnTheFlyPass(Pass *P, AnalysisID PI,
+                                                   Function &F);
 
   /// Initialize available analysis information.
   void initializeAnalysisInfo() {

llvm/include/llvm/Pass.h

@@ -203,14 +203,17 @@ class Pass {
   template<typename AnalysisType>
   AnalysisType &getAnalysis() const; // Defined in PassAnalysisSupport.h
 
-  template<typename AnalysisType>
-  AnalysisType &getAnalysis(Function &F); // Defined in PassAnalysisSupport.h
+  template <typename AnalysisType>
+  AnalysisType &
+  getAnalysis(Function &F,
+              bool *Changed = nullptr); // Defined in PassAnalysisSupport.h
 
   template<typename AnalysisType>
   AnalysisType &getAnalysisID(AnalysisID PI) const;
 
-  template<typename AnalysisType>
-  AnalysisType &getAnalysisID(AnalysisID PI, Function &F);
+  template <typename AnalysisType>
+  AnalysisType &getAnalysisID(AnalysisID PI, Function &F,
+                              bool *Changed = nullptr);
 };
 
 //===----------------------------------------------------------------------===//

llvm/include/llvm/PassAnalysisSupport.h

@@ -167,7 +167,7 @@ class AnalysisResolver {
   }
 
   /// Find pass that is implementing PI. Initialize pass for Function F.
-  Pass *findImplPass(Pass *P, AnalysisID PI, Function &F);
+  std::tuple<Pass *, bool> findImplPass(Pass *P, AnalysisID PI, Function &F);
 
   void addAnalysisImplsPair(AnalysisID PI, Pass *P) {
     if (findImplPass(PI) == P)
@@ -246,23 +246,30 @@ AnalysisType &Pass::getAnalysisID(AnalysisID PI) const {
 
 /// getAnalysis<AnalysisType>() - This function is used by subclasses to get
 /// to the analysis information that they claim to use by overriding the
-/// getAnalysisUsage function.
-template<typename AnalysisType>
-AnalysisType &Pass::getAnalysis(Function &F) {
+/// getAnalysisUsage function. If as part of the dependencies, an IR
+/// transformation is triggered (e.g. because the analysis requires
+/// BreakCriticalEdges), and Changed is non null, *Changed is updated.
+template <typename AnalysisType>
+AnalysisType &Pass::getAnalysis(Function &F, bool *Changed) {
   assert(Resolver &&"Pass has not been inserted into a PassManager object!");
 
-  return getAnalysisID<AnalysisType>(&AnalysisType::ID, F);
+  return getAnalysisID<AnalysisType>(&AnalysisType::ID, F, Changed);
 }
 
-template<typename AnalysisType>
-AnalysisType &Pass::getAnalysisID(AnalysisID PI, Function &F) {
+template <typename AnalysisType>
+AnalysisType &Pass::getAnalysisID(AnalysisID PI, Function &F, bool *Changed) {
   assert(PI && "getAnalysis for unregistered pass!");
   assert(Resolver && "Pass has not been inserted into a PassManager object!");
   // PI *must* appear in AnalysisImpls.  Because the number of passes used
   // should be a small number, we just do a linear search over a (dense)
   // vector.
-  Pass *ResultPass = Resolver->findImplPass(this, PI, F);
+  Pass *ResultPass;
+  bool LocalChanged;
+  std::tie(ResultPass, LocalChanged) = Resolver->findImplPass(this, PI, F);
+
   assert(ResultPass && "Unable to find requested analysis info");
+  if (Changed)
+    *Changed |= LocalChanged;
 
   // Because the AnalysisType may not be a subclass of pass (for
   // AnalysisGroups), we use getAdjustedAnalysisPointer here to potentially

llvm/lib/IR/LegacyPassManager.cpp

@@ -437,7 +437,8 @@ class MPPassManager : public Pass, public PMDataManager {
   /// Return function pass corresponding to PassInfo PI, that is
   /// required by module pass MP. Instantiate analysis pass, by using
   /// its runOnFunction() for function F.
-  Pass* getOnTheFlyPass(Pass *MP, AnalysisID PI, Function &F) override;
+  std::tuple<Pass *, bool> getOnTheFlyPass(Pass *MP, AnalysisID PI,
+                                           Function &F) override;
 
   StringRef getPassName() const override { return "Module Pass Manager"; }
 
@@ -1290,7 +1291,8 @@ void PMDataManager::addLowerLevelRequiredPass(Pass *P, Pass *RequiredPass) {
   llvm_unreachable("Unable to schedule pass");
 }
 
-Pass *PMDataManager::getOnTheFlyPass(Pass *P, AnalysisID PI, Function &F) {
+std::tuple<Pass *, bool> PMDataManager::getOnTheFlyPass(Pass *P, AnalysisID PI,
+                                                        Function &F) {
   llvm_unreachable("Unable to find on the fly pass");
 }
 
@@ -1307,8 +1309,8 @@ Pass *AnalysisResolver::getAnalysisIfAvailable(AnalysisID ID, bool dir) const {
   return PM.findAnalysisPass(ID, dir);
 }
 
-Pass *AnalysisResolver::findImplPass(Pass *P, AnalysisID AnalysisPI,
-                                     Function &F) {
+std::tuple<Pass *, bool>
+AnalysisResolver::findImplPass(Pass *P, AnalysisID AnalysisPI, Function &F) {
   return PM.getOnTheFlyPass(P, AnalysisPI, F);
 }
 
@@ -1665,16 +1667,17 @@ void MPPassManager::addLowerLevelRequiredPass(Pass *P, Pass *RequiredPass) {
 /// Return function pass corresponding to PassInfo PI, that is
 /// required by module pass MP. Instantiate analysis pass, by using
 /// its runOnFunction() for function F.
-Pass* MPPassManager::getOnTheFlyPass(Pass *MP, AnalysisID PI, Function &F){
+std::tuple<Pass *, bool> MPPassManager::getOnTheFlyPass(Pass *MP, AnalysisID PI,
+                                                        Function &F) {
   FunctionPassManagerImpl *FPP = OnTheFlyManagers[MP];
   assert(FPP && "Unable to find on the fly pass");
 
   FPP->releaseMemoryOnTheFly();
-  FPP->run(F);
-  return ((PMTopLevelManager*)FPP)->findAnalysisPass(PI);
+  bool Changed = FPP->run(F);
+  return std::make_tuple(((PMTopLevelManager *)FPP)->findAnalysisPass(PI),
+                         Changed);
 }
 
-
 //===----------------------------------------------------------------------===//
 // PassManagerImpl implementation