[LLVMdev] Power/Energy Awareness in LLVM

[Sean Silva]

On Mon, Apr 15, 2013 at 12:28 PM, Ghassan Shobaki <ghassan_shobaki at yahoo.com
> wrote:

>
> Thank you for the link! It is not clear though what -Oe actually
> implements. Does it simply optimize for speed as suggested by Chris or it
> does other things?
>

There is no -Oe


> Generally speaking, speed correlates well with low energy, because
> completing the task in fewer cycles means consuming less energy unless the
> speed optimization causes the energy per cycle to be significantly higher.
> In theory, some compiler and hardware optimizations such as
> instruction-level parallelism (ILP), speculative execution and pre-fetching
> increase the energy consumption per cycle. If the same speed can be
> achieved using less energy per cycle by controlling such optimizations, the
> total energy consumption will be less. Some of these optimizations may be
> controlled by the compiler. Also, the switching energy from one instruction
> to another depends on the instruction order. So, in theory, if there are
> multiple instruction orders that give the same speed, the order that
> minimizes the switching energy will consume less overall energy. There is
> some academic research on this with simulation data, but I am not aware of
> any actual implementation in a production compiler that proves actual
> energy reduction. Has anyone ever implemented and experimented with such
> optimizations in LLVM?
>
>
I'm not aware of any such work.

-- Sean Silva
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130415/e7ba3b10/attachment.html>