Hello there,
Coming back from Asia I've been putting a lot of thought about how we can make sure we spend our engineering cycles on the work that is most valuable to the current Linaro members, and part of that means reassessing assumptions that we've carried since our foundation.
The first point I want to raise is Thumb-2, the alternative ISA described by ARM like this:
For performance optimised code Thumb-2 technology uses 31 percent less memory to reduce system cost, while providing up to 38 percent higher performance than existing high density code, which can be used to prolong battery-life or to enrich the product feature set. Thumb-2 technology is featured in the processor, and in all ARMv7 architecture-based processors.
We've from the beginning set Thumb-2 in our standard configuration across platforms, but outside of Ubuntu, I think we're unique in that. So the questions I have are:
- Do we know how much better Thumb-2 actually is, in practice? It's easy for us to confirm this on Android; what do the numbers and feel of the system tell us?
- What are the downsides to using Thumb-2 in general? Do we have anecdotes or threads that talk about bad experiences or blockers in the transition?
- If it's so great, how could we lead a wide-ranging transition to Thumb2 becoming the standard ISA for modern v7 applications, including Android, Yocto and anything else relevant that runs on a Cortex A?
Thanks,