avoid progress-related hot spot in ValueFlowPassRunner::run() [skip ci]

Author: firewave

lib/valueflow.cpp

@@ -7219,8 +7219,12 @@ struct ValueFlowPassRunner {
             const std::size_t passnum = state.settings.vfOptions.maxIterations - n + 1;
             const std::string passnum_s = std::to_string(passnum);
             if (std::any_of(passes.begin(), passes.end(), [&](const ValuePtr<ValueFlowPass>& pass) {
-                ProgressReporter progressReporter(state.errorLogger, state.settings.reportProgress, state.tokenlist.getSourceFilePath(), std::string("ValueFlow::") + pass->name() + (' ' + passnum_s));
-                return run(pass, passnum);
+                const std::string passnum = std::to_string(state.settings.vfOptions.maxIterations - n + 1);
+                // the string concatination is a hot spot in TestIO::testScanfArgument and TestIO::testPrintfArgumentVariables
+                const bool doProgress = state.settings.reportProgress >= 0;
+                std::string stage = doProgress ? std::string("ValueFlow::") + pass->name() + (' ' + passnum) : "";
+                ProgressReporter progressReporter(state.errorLogger, state.settings.reportProgress >= 0, state.tokenlist.getSourceFilePath(), std::move(stage));
+                return run(pass);
             }))
                 return true;
             --n;