On 06/28/2011 10:38 AM, Koen Kooi wrote: > > Op 28 jun 2011, om 19:36 heeft Darren Hart het volgende geschreven: > >> >> >> On 06/24/2011 04:54 AM, Koen Kooi wrote: >>> Hi, >>> >>> We discussed tune files a bit during last nights TSC meeting and Khem had >>> expressed the need before, so I'd like to get this discussion started by >>> using >>> armv7a as an example. >>> >>> For armv7a capable cores we have the following hardware features: >>> >>> * armv7a instruction set >>> * thumb1 instruction set >>> * thumb2 instruction set >>> * VFP coprocessor >>> * optional NEON coprocessor >>> >>> For the ABI we can choose the following: >>> >>> * softtp without hw support (e.g. no VFP instructions emitted, slow) >>> * softfp with hw support (e.g. VFP and/or NEON instructions emitted, fast) >>> * hardfp, emits VFP and/or NEON instructions, slightly faster than >>> softfp/hw, >>> incompatible with everything else >>> >>> And the extra knobs: >>> >>> * pure thumb1, no arm instructions (limited use) >>> * thumb1/arm interworking >>> * pure thumb2, no arm instructions >>> * thumb2 interworking (not sure if that's actually usefull, thumb2 has >>> complete coverage) >>> >>> In OE .dev we have the following vars: >>> >>> TARGET_FPU: switches between hw float and sw float, no reflection in >>> package arch >>> ARM_FP_ABI: switches between softfp and hardfp, will create 'armv7a' or >>> 'armv7a-hardfp' as package arch >>> ARM_INSTRUCTION_SET: switches between arm and thumb1, no reflection in >>> package arch >>> THUMB_INTERWORK: turns on interworking, no reflection in package arch >>> >>> (side note, oe-core/distroless and meta-yocto/poky don't turn set TARGET_FPU >>> for armv7a and will generate slow code, angstrom does turn it on) >> >> >> oe-core tune-cortexa8.inc doesn't make use of these variables (unlike >> meta-texasinstruments) and does make use of the neon coprocessor, but >> still uses the softfp float-api: >> >> TARGET_CC_ARCH = "-march=armv7-a -mtune=cortex-a8 -mfpu=neon >> -mfloat-abi=softfp -fno-tree-vectorize" > > Don't confuse softfp calling conventions with softfloat! The above will still > emit > vfp and neon instructions if your set TARGET_FPU = hard
Ah. So we would need to add something like: conf/distro/include/angstrom.inc:TARGET_FPU_armv7a ?= "hard" conf/distro/include/angstrom.inc:TARGET_FPU_armv7a-vfp ?= "hard" to something DISTRO specific (poky.conf or similar). It isn't clear to me why this is a distro policy decision instead of part of the tune include or the machine config itself. Can someone elaborate on why this goes where it does? Thanks, -- Darren Hart Intel Open Source Technology Center Yocto Project - Linux Kernel _______________________________________________ Openembedded-core mailing list Openembedded-core@lists.openembedded.org http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-core
