[LegacyPassManager] Remove analysis P from AnUsageMap before deleting it in schedulePass.

[craig.topper]

Summary

If we deem the analysis pass useless and delete it, we need to make sure we remove it from AnUsageMap. Otherwise we might allocate another pass in the freed memory. This will cause us to reuse the AnalysisUsage from the original pass instead of the new one.

Fixes PR38511

[craig.topper]

Ping

[chandlerc]

This seems like a fine patch... But can we add a test that hits this? Feel free to submit w/ test case though, the code here seems trivial.

llvm/trunk/lib/IR/LegacyPassManager.cpp

void PMTopLevelManager::schedulePass(Pass *P) {
   // Give pass a chance to prepare the stage.
   P->preparePassManager(activeStack);
 
   // If P is an analysis pass and it is available then do not
   // generate the analysis again. Stale analysis info should not be
   // available at this point.
   const PassInfo *PI = findAnalysisPassInfo(P->getPassID());
   if (PI && PI->isAnalysis() && findAnalysisPass(P->getPassID())) {
+    // Remove any cached AnalysisUsage information.
+    AnUsageMap.erase(P);
     delete P;
     return;
   }
 
   AnalysisUsage *AnUsage = findAnalysisUsage(P);
 
   bool checkAnalysis = true;
   while (checkAnalysis) {