LPPassManager. Implement preparePassManager() hook.

llvm-svn: 34975

llvm/include/llvm/Analysis/LoopPass.h

@@ -45,6 +45,14 @@ class LoopPass : public Pass {
   // loop nest is completely different.
   virtual bool doFinalization() { return false; }
 
+  // Check if this pass is suitable for the current LPPassManager, if
+  // available. This pass P is not suitable for a LPPassManager if P
+  // is not preserving higher level analysis info used by other
+  // LPPassManager passes. In such case, pop LPPassManager from the
+  // stack. This will force assignPassManager() to create new
+  // LPPassManger as expected.
+  void preparePassManager(PMStack &PMS);
+
   /// Assign pass manager to manager this pass
   virtual void assignPassManager(PMStack &PMS,
 				 PassManagerType PMT = PMT_LoopPassManager);

llvm/lib/Analysis/LoopPass.cpp

@@ -129,6 +129,31 @@ bool LPPassManager::runOnFunction(Function &F) {
 //===----------------------------------------------------------------------===//
 // LoopPass
 
+// Check if this pass is suitable for the current LPPassManager, if
+// available. This pass P is not suitable for a LPPassManager if P
+// is not preserving higher level analysis info used by other
+// LPPassManager passes. In such case, pop LPPassManager from the
+// stack. This will force assignPassManager() to create new
+// LPPassManger as expected.
+void LoopPass::preparePassManager(PMStack &PMS) {
+
+  // Find LPPassManager 
+  while (!PMS.empty()) {
+    if (PMS.top()->getPassManagerType() > PMT_LoopPassManager)
+      PMS.pop();
+    else;
+    break;
+  }
+
+  LPPassManager *LPPM = dynamic_cast<LPPassManager *>(PMS.top());
+
+  // If this pass is destroying high level information that is used
+  // by other passes that are managed by LPM then do not insert
+  // this pass in current LPM. Use new LPPassManager.
+  if (LPPM && !LPPM->preserveHigherLevelAnalysis(this)) 
+    PMS.pop();
+}
+
 /// Assign pass manager to manage this pass.
 void LoopPass::assignPassManager(PMStack &PMS,
                                  PassManagerType PreferredType) {