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 regards, Koen _______________________________________________ Openembedded-core mailing list Openembedded-core@lists.openembedded.org http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-core
