On Wed, Jul 20, 2016 at 5:33 PM, Jim Wilson jim.wilson@linaro.org wrote:
On Wed, Jul 20, 2016 at 2:14 PM, Jeffrey Walton noloader@gmail.com wrote:
I'm having trouble with ARMv8/Aarch64. One is an early Mustang server
ARMv8 implies 32-bit code (aarch32). Aaarch64 implies 64-bit code. These are two different compilers, with two different sets of command line options.
Thanks Jim. According to ARM, ARMv8 is 64-bit (http://www.arm.com/products/processors/armv8-architecture.php). Maybe I'm parsing the page incorrectly?
(Note that I'm aware of Aarch32 execution environments on Aarch64. I'm not trying for that test case at the moment).
$ g++ -DDEBUG -g3 -O0 -mfpu=neon-fp-armv8 -fPIC -pipe -c cryptlib.cpp g++: error: unrecognized command line option ‘-mfpu=neon-fp-armv8’ GNUmakefile:753: recipe for target 'cryptlib.o' failed-mfpu=neon-fp-armv8 is an arm (32-bit) compiler option. The aarch64 (64-bit) compiler will not accept it.
Because FP and Neon support is optional in the 32-bit arm architecture, there are compiler options to enable fp and/or neon support. Usually FP support is enabled by default for a linux distro, but the neon support usually is not, and you can enable neon by using this -mcpu=neon-fp-armv8 option if running 32-bit code on an ARMv8 architecture part.
OK, thanks. So is neon-fp-armv8 an Aarch32 execution environment option?
Meanwhile, the aarch64 spec requires FP and ASIMD instruction support in the linux ABI, so there are no options to enable them, they are on by default.
Yeah, I was clear on asimd being ARM-64's equivalent to NEON and it was enabled by default.
If you really want to disable them, you can do so by using a -march= option, e.g. -march=aarch64+fp+simd enables them, and -march=aarch64+nofp+nosimd disables them. However, if you disable fp support,
Oh, NO. We want to test under them. Sorry about the confusion.
you will break the ABI, and your code may not compile or run, so don't do that unless perhaps you have an embedded target, and have your own OS build and your own ABI. or no code that uses FP You can also enable/.disable crc (crypto) support this way, but a better way is to use a -mcpu= option, and let gcc figure out if the target has crc instructions.
See the aarch64 compiler docs here https://gcc.gnu.org/onlinedocs/gcc/AArch64-Options.html#AArch64-Options
So it looks like the course of action is to simply remove it from http://github.com/weidai11/cryptopp/blob/master/cryptest.sh#L874 . (It was added recently because of the ML recommendation).
These ARM options are awful. I spent the better part of a day trying to untangle the option combinations to ensure we are getting good test coverage in a test script. I'd give my left arm device for a compiler that provides -march=native or -mfpu=native and gets it right.
Jeff