PCCounts has a lot of counters which were related to the information collected by JM. Apart from the the BASE_INTERP counter, no other counter are updated. This counter is only used by the PCCounts friend API, but it might be useful to reuse this code for implementing the Code Coverage recent project, as highlighted in Bug 1176880 prototype.

Comment on attachment 8641688 [details] [diff] [review] Remove unused JM-related PCCounts counters. Review of attachment 8641688 [details] [diff] [review]: ----------------------------------------------------------------- ::: js/src/jsopcode.cpp @@ +173,5 @@ > bool printed = false; > + double val = script->getPCCounts(pc).numExec(); > + if (val) { > + if (printed) > + Sprint(sp, ", "); While re-reading my patch, I notice that this printed flag is useless now. I'll remove it before landing.

As the counter is now part of the PCCounts structure, we should no longer make any copy of the counter, otherwise the numExec() function will return a reference to a temporary returned copy, and not to the original PCCounts content.