Thanks dlewin555. I understand that it's possible to use hard float. Some Android or arm Ubuntu version are using it.
But for the default Angstrom (this the BeagleBone Black is delivered with). How can we check the hard float is not used ? I guess I could rebuild Anstrong using hard float but I am wondering why the default build doesn't use it ? I trust the Angstrom builder. It should have better knowledge than me. So if he preferred not to use the hard float it should have a good reason and I would like to know it. Regards Le lundi 28 octobre 2013 15:44:08 UTC+1, dlewin555 a écrit : > > As I think this a sane question (ie : everyone should ask himself/herself > this ) I answer you that : > > - the BBB is based on the AM335x > - This last is itself is based on Cortex A8 > > Therefore if you dig into the A8 arm documentation CortexA_ProgGuide.pdf > that you can easily download from Arm website ( free account is required) > you'll see : > > > >> If your target platform supports hardware floating-point or NEON, specify >> this to ensure that >> the compiler can make use of these instructions. For a Cortex-A5 target, >> you would specify >> –mfpu=neon-vfpv4. >> -mfloat-abi=<name> >> This option specifies the floating-point ABI to use. Values for <name> >> are: >> soft causes GCC to generate code containing calls to the software >> floating-point >> library for floating-point operations. >> softfp enables GCC to generate code containing hardware floating-point >> instructions, >> but still uses the software floating-point linkage. > > > .... > > >> hard enables GCC to generate code containing hardware floating-point >> instructions >> and uses FPU-specific hardware floating-point linkage. >> The default depends on the target configuration. You must compile your >> entire program with the >> same ABI, and link with a compatible set of libraries. >> Table 19-1 shows a few examples of code generation for floating-point >> operations. >> 19.1.5 armcc optimization options >> The armcc compiler enables you to compile your C and C++ code. It is an >> optimizing compiler >> with a range of command-line options to enable you to control the level >> of optimization. >> The command line option gives a choice of optimization levels, as >> follows: >> • -Ospace. This option instructs the compiler to perform optimizations to >> reduce image size >> at the expense of a possible increase in execution time. >> • -Otime. This option instructs the compiler to perform optimizations to >> reduce execution >> time at the expense of a possible increase in image size. >> • -O0. Turns off most optimizations. It gives the best possible debug >> view and the lowest >> level of optimization. >> • -O1. Removes unused inline functions and unused static functions. Turns >> off optimizations >> that seriously degrade the debug view. If used with --debug, this option >> gives a satisfactory >> debug view with good code density. >> • -O2 (default). High optimization. If used with --debug, the debug view >> might be less >> satisfactory because the mapping of object code to source code is not >> always clear. >> • -O3. performs the same optimizations as -O2 however the balance between >> space and time >> optimizations in the generated code is more heavily weighted towards >> space or time >> compared with -O2. That is: >> — -O3 -Otime aims to produce faster code than -O2 -Otime, at the risk of >> increasing your image size >> — -O3 -Ospace aims to produce smaller code than -O2 -Ospace, but >> performance might >> be degraded. >> Table 19-1 Floating-point code generation >> -mfpu -mfloat-abi Resultant code >> Any value soft Floating-point emulation using software floating-point >> library >> vfpv3 softfp VFPv3 floating-point code >> vfpv3-d16 softfp VFPv3 floating-point code >> neon hard VFPv3 and Advanced SIMD code, where the floating-point and >> SIMD types use the hardware FP registers > > > So in clear, as far as you use neon option (which is hardwired in the BBB) > you need to define the hardfloat as well . > > Hope this will help > > > Le samedi 26 octobre 2013 01:27:24 UTC+2, [email protected] a écrit : > >> Hello, >> >> After trying to cross-compile with the hard float library without >> success, I finally use the soft float library and it work. >> >> I would like to check if the cause is really the hard float. >> >> I'm using the default Angstrom distribution. Does it use soft float and >> how to check that ? >> >> If Angstrom distribution doesn't use hard float, why ? >> >> Regards >> > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
