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,
--
Christian Robottom Reis, Engineering VP
Brazil (GMT-3) | [+55] 16 9112 6430 | [+1] 612 216 4935
Linaro.org: Open Source Software for ARM SoCs
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