Refs #10765: Improve performance on if/else chains

Author: web-flow

lib/programmemory.cpp

@@ -194,6 +194,8 @@ void ProgramMemory::erase_if(const std::function<bool(const ExprIdToken&)>& pred
 {
     if (mValues->empty())
         return;
+    if (!hasModifiableVars)
+        return;
 
     // TODO: how to delay until we actuallly modify?
     copyOnWrite();
@@ -234,13 +236,15 @@ void ProgramMemory::replace(ProgramMemory pm, bool skipUnknown)
 
     copyOnWrite();
 
+    hasModifiableVars = false;
     for (auto&& p : (*pm.mValues)) {
         if (skipUnknown) {
             auto it = mValues->find(p.first);
             if (it != mValues->end() && it->second.isUninitValue())
                 continue;
         }
         (*mValues)[p.first] = std::move(p.second);
+        hasModifiableVars |= p.first.tok->varId() > 0;
     }
 }
 

lib/programmemory.h

@@ -158,6 +158,7 @@ struct CPPCHECKLIB ProgramMemory {
     Map::iterator find(nonneg int exprid);
 
     std::shared_ptr<Map> mValues;
+    bool hasModifiableVars = false;
 };
 
 struct ProgramMemoryState {