> On Mar 30, 2016, at 3:46 PM, Phil Blundell <p...@pbcl.net> wrote: > > On Wed, 2016-03-30 at 11:53 -0700, Andre McCurdy wrote: >> Either way it shouldn't be a concern for the CPU tuning files. >> Building Thumb2 for an armv8a CPU is really just an extension of >> "optimise for size" and we don't include -Os, -O2, etc options in the >> CPU tuning files. > > Yes, agreed. In principle there's no reason that the compiler couldn't > choose between A32 and T32 instruction sets dynamically for each > compilation unit (or each function) according to which it thinks would > give the better result. And from the user's point of view, the outcome > should be equivalent apart from minor performance differences.
yes I think thumb2 on aarch32 may be controlled via a global configuration metadata like distro feature or some such. > >>>> For most cores from Cortex A9 onwards NEON and VFP are optional, so >>>> hardcoded assumptions won't work. > >> Nothing very concrete. The ARM Cortex-A Series Programmer’s Guide for >> ARMv8-A mentions: >> >> "Both floating-point and NEON are required in all standard ARMv8 >> implementations. However, implementations targeting specialized >> markets may support the following combinations: >> >> - No NEON or floating-point. >> - Full floating-point and SIMD support with exception trapping. >> - Full floating-point and SIMD support without exception trapping. > > Is there any evidence that anyone is actually building ARMv8-A (as > opposed to -R or -M) cores that lack VFP and/or NEON? Unless there is a > fairly clear indication that such cores do exist and are likely to be > used with OE, I think we should not complicate the tuning files with > support for such things. Anybody who wants them can always add > appropriate tunes later, either in oe-core or in their own layer. > agreed. > p. > >
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