On 14/01/2017 02:22, Leo wrote:
> #include "arm_neon.h"
> #include <stdio.h>
>
> typedef union {
> float16_t m1;
> unsigned short m2;
> } MYUNION;
>
> int main(void)
> {
> MYUNION U1;
> U1.m1 = 5;
> printf("m2 = 0x%x \n",U1.m2);
> return 0;
> }
What representation for (float16_t)5 were you expecting?
Giving the code a spin...
$ arm-linux-gnueabihf-gcc foo.c
In file included from foo.c:1:0:
/tmp/gcc-linaro-5.3-2016.02/lib/gcc/arm-linux-gnueabihf/5.3.1/include/arm_neon.h:31:2:
error: #error You must enable NEON instructions (e.g. -mfloat-abi=softfp -mfpu=neon) to use arm_neon.h
#error You must enable NEON instructions (e.g. -mfloat-abi=softfp -mfpu=neon) to use arm_neon.h
^
foo.c:5:8: error: unknown type name 'float16_t'
float16_t m1;
^
$ arm-linux-gnueabihf-gcc -mfloat-abi=softfp -mfpu=neon foo.c
In file included from /tmp/gcc-linaro-5.3-2016.02/arm-linux-gnueabihf/libc/usr/include/features.h:389:0,
from /tmp/gcc-linaro-5.3-2016.02/arm-linux-gnueabihf/libc/usr/include/stdint.h:25,
from /tmp/gcc-linaro-5.3-2016.02/lib/gcc/arm-linux-gnueabihf/5.3.1/include/stdint.h:9,
from /tmp/gcc-linaro-5.3-2016.02/lib/gcc/arm-linux-gnueabihf/5.3.1/include/arm_neon.h:38,
from foo.c:1:
/tmp/gcc-linaro-5.3-2016.02/arm-linux-gnueabihf/libc/usr/include/gnu/stubs.h:7:29:
fatal error: gnu/stubs-soft.h: No such file or directory
compilation terminated.
Hmmm, looks like my toolchain doesn't support float16_t
https://gcc.gnu.org/onlinedocs/gcc/Half-Precision.html
Let's try __fp16
typedef union {
__fp16 m1;
unsigned short m2;
} MYUNION;
$ arm-linux-gnueabihf-gcc -S -O2 -mfp16-format=alternative foo.c
main:
movw r0, #:lower16:.LC0
push {r3, lr}
mov r1, #17664
movt r0, #:upper16:.LC0
bl printf
movs r0, #0
pop {r3, pc}
NB: I'm targeting armv7-a, while you're targeting armv8-a
(I missed the [aarch64] tag in the Subject. It's a good idea to repeat
important information in the body.)
Sending anyway FWIW.
Regards.
