Ops Review
Allison Randal
allison at parrot.org
Tue Jan 20 22:22:46 UTC 2009
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
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