Ops Review

[Allison Randal]

Geoffrey Broadwell wrote:
> 
> One somewhat non-obvious point here -- as the primitive operation for
> profiling, retrieving the current time with high resolution should be as
> fast an operation as possible.  In addition, it should preferably take
> near-constant time, so care should be taken to avoid any operations that
> may vary in run time.
> 
> My assumption was that the fastest possible thing in PIR was a JITable
> op -- is that not still the case?

In theory, PIR subroutines can be JIT'd too. In practice, the majority 
of ops are not currently JIT'd.

Either way, JIT-ability shouldn't be the primary concern in choosing 
whether to make something an op. The primary question is whether the 
functionality is so common and/or low-level that it should be part of 
the fundamental "built-in" instructions of the virtual machine.

Allison