Re: [dpdk-dev] pmdinfogen issues: cross compilation for ARM fails with older host compiler

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

On Fri, Nov 11, 2016 at 10:34:39AM +0000, Hemant Agrawal wrote:
> Hi Neil,
>                Pmdinfogen compiles with host compiler. It usages rte_byteorder.h of the target platform.
> However, if the host compiler is older than 4.8, it will be an issue during cross compilation for some platforms.
> e.g. if we are compiling on x86 host for ARM, x86 host compiler will not understand the arm asm instructions.
> 
> /* fix missing __builtin_bswap16 for gcc older then 4.8 */
> #if !(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8))
> static inline uint16_t rte_arch_bswap16(uint16_t _x)
> {
>                register uint16_t x = _x;
>                asm volatile ("rev16 %0,%1"
>                                     : "=r" (x)
>                                     : "r" (x)
>                                     );
>                return x;
> }
> #endif
> 
> One easy solution is that we add compiler platform check in this code section of rte_byteorder.h
> e.g
> #if !(defined __arm__ || defined __aarch64__)
> static inline uint16_t rte_arch_bswap16(uint16_t _x)
> {
>                return (_x >> 8) | ((_x << 8) & 0xff00);
> }
> #else ….
> 
> Is there a better way to fix it?

IMO, It is a HOST build infrastructure issue. If a host app is using the
dpdk service then it should compile and link against HOST target(in this
specific case, build/x86_64-native-linuxapp-gcc). I think, introducing the
HOSTTARGET kind of scheme is a clean solution.

/Jerin