GH #34: Disable the PassInfo cache assertions to make the cache effec…

…tive in builds with assertions enabld

Since the PassInfo cache does a regular, uncached, slow lookup for the
asserted condition, it's not very effective *cough* when assertions are
enabled. Since disabling these assertions gives quite a nice perf boost
and it's not really worse than the patch we had previously, let's just
do that.

lib/IR/LegacyPassManager.cpp

@@ -726,9 +726,6 @@ const PassInfo *PMTopLevelManager::findAnalysisPassInfo(AnalysisID AID) const {
   const PassInfo *&PI = AnalysisPassInfos[AID];
   if (!PI)
     PI = PassRegistry::getPassRegistry()->getPassInfo(AID);
-  else
-    assert(PI == PassRegistry::getPassRegistry()->getPassInfo(AID) &&
-           "The pass info pointer changed for an analysis ID!");
 
   return PI;
 }