If it's writing code into memory, and you're going to compile it and rewrite the jump when it's done, isn't the part where the current code is writing in W mode

If it's writing code into memory, and you're going to compile it and rewrite the jump when it's done, isn't the part where the current code is writing in W mode already? The process would be: 1. compile the code when you fault on the basic block exit. 2. mark that basic block executable. 3. Optionally only after return or other jump: mark the jumping basic block as writable, patch the jump, then mark it as executable. In this case, there would be three changes, JS JITs are doing this a lot more often than Dolphin is. They often have more than one level of JIT in addition to an interpreter; so they will end up doing this dance more than once per basic block. Until I see at least some microbenchmarks and concrete estimates, I don't think I'll worry too much about this. Though it is unfortunate to have to modify all of this code.