> The thing I'm saying is that you're turning a test that was `if (addr < LIMIT)` into `if (addr != 0 && addr < LIMIT)`, which is not nothing. And it's on EVERY

> The thing I'm saying is that you're turning a test that was `if (addr < LIMIT)` into `if (addr != 0 && addr < LIMIT)`, which is not nothing. And it's on EVERY memory access. But that's not what I'm saying. I'm saying every memory access would become: addr = addr - START_OFFSET (eg, 0x1000) if (addr < LIMIT) { do stuff } There's just an extra sub in there. And you can definitely optimize that, same as any other bounds check optimization. Which the runtime is already tasked with doing since all your loads are already (wasm_address + host_array_buffer_ptr). If that add is free, the early sub likely is, too. They fall into the same category here. But you can also make it completely free by just ensuring there's a dead zone before the host array buffer location, such that anything in the range 0x0-0x1000 (or whatever) just lands before the array buffer's start location which has been mmap'd to trap. Then you don't need any changes at all.