Hi Malvika,
> > Hi Konstantin, > > I installed the clang version 4.0.1 to check for the issue you were facing > with -O2 compilation. I was able to compile with -O2 and -O0 > optimization without any errors. Please see the exact command I used and the > following output for your reference: > > $ clang -O2 -target bpf -I /usr/include/aarch64-linux-gnu/ -c t1.c > $ clang -O0 -target bpf -I /usr/include/aarch64-linux-gnu/ -c t1.c > $ clang -v > clang version 4.0.1-10 (tags/RELEASE_401/final) > Target: aarch64-unknown-linux-gnu > Thread model: posix > InstalledDir: /usr/bin > Found candidate GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/6 > Found candidate GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/6.4.0 > Found candidate GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/7 > Found candidate GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/7.3.0 > Found candidate GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/8 > Found candidate GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/8.0.1 > Found candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/6 > Found candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/6.4.0 > Found candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/7 > Found candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/7.3.0 > Found candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/8 > Found candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/8.0.1 > Selected GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/7.3.0 > Candidate multilib: .;@m64 > Selected multilib: .;@m64 > > I hope this was helpful to you. Sorry for delay. I tried with clang 6.0, but still seeing same issue. Digging a bit more, I think the culprit is here: #ifdef __GNUC__ # if __GNUC__ >= 2 # define __bswap_16(x) \ (__extension__ \ ({ unsigned short int __v, __x = (unsigned short int) (x); \ if (__builtin_constant_p (__x)) \ <------ evaluates to FALSE !!! __v = __bswap_constant_16 (__x); \ else \ __asm__ ("rorw $8, %w0" \ : "=r" (__v) \ : "0" (__x) \ : "cc"); \ __v; })) # else /* This is better than nothing. */ # define __bswap_16(x) \ (__extension__ \ ({ unsigned short int __x = (unsigned short int) (x); \ __bswap_constant_16 (__x); })) # endif #else static __inline unsigned short int __bswap_16 (unsigned short int __bsx) { return __bswap_constant_16 (__bsx); } #endif Seems that gcc and clang implements __builtin_constant_p in a different way. Let say, the following function: int bbb1(void) {uint16_t x=0; return__bswap_constant_16(x);} when compiled with gcc would return 1, while when compiled with clang - 0. Adding 'const' to definition of 'x' cures the problem for clang. I don't know why there is no 'const' in original __bswap_16() macro. To overcome that problem, I used: clang -O2 -U__GNUC__ -target bpf -c t1.c Another possible option - define our own analogs for buitin hton*(). Konstantin > Best Regards, > Malvika Gupta > > > -----Original Message----- > From: Malvika Gupta > Sent: Wednesday, September 5, 2018 4:43 PM > To: Ananyev, Konstantin <konstantin.anan...@intel.com> > Cc: dev@dpdk.org; Gavin Hu (Arm Technology China) <gavin...@arm.com>; > Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>; > Brian Brooks <brian.bro...@arm.com>; nd <n...@arm.com> > Subject: RE: [PATCH] test/bpf: use hton instead of __builtin_bswap > > Hi Ananyev, > > I used clang version 6.0.0. Please see the following output for your > reference. > > $ clang -v > clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final) > Target: aarch64-unknown-linux-gnu > Thread model: posix > InstalledDir: /usr/bin > Found candidate GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/6 > Found candidate GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/6.4.0 > Found candidate GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/7 > Found candidate GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/7.3.0 > Found candidate GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/8 > Found candidate GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/8.0.1 > Found candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/6 Found > candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/6.4.0 > Found candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/7 Found > candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/7.3.0 > Found candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/8 Found > candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/8.0.1 > Selected GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/7.3.0 > Candidate multilib: .;@m64 > Selected multilib: .;@m64 > > Also, the code compiles with both -O2 and -O0 for me. > > I hope this was helpful > Best, > Malvika > > -----Original Message----- > From: Ananyev, Konstantin <konstantin.anan...@intel.com> > Sent: Tuesday, September 4, 2018 8:56 AM > To: Malvika Gupta <malvika.gu...@arm.com> > Cc: dev@dpdk.org; Gavin Hu (Arm Technology China) <gavin...@arm.com>; > Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>; > Brian Brooks <brian.bro...@arm.com>; nd <n...@arm.com> > Subject: RE: [PATCH] test/bpf: use hton instead of __builtin_bswap > > Hi, > > > > > Convert host machine endianness to networking endianness for > > comparison of incoming packets with BPF filter > > > > > > Signed-off-by: Malvika Gupta <malvika.gu...@arm.com> > > Reviewed-by: Gavin Hu <gavin...@arm.com> > > Reviewed-by: Brian Brooks <brian.bro...@arm.com> > > Suggested-by: Brian Brooks <brian.bro...@arm.com> > > --- > > test/bpf/t1.c | 7 ++++--- > > test/bpf/t3.c | 3 ++- > > 2 files changed, 6 insertions(+), 4 deletions(-) > > > > diff --git a/test/bpf/t1.c b/test/bpf/t1.c index 60f9434ab..7943fcf34 > > 100644 > > --- a/test/bpf/t1.c > > +++ b/test/bpf/t1.c > > @@ -28,24 +28,25 @@ > > #include <net/ethernet.h> > > #include <netinet/ip.h> > > #include <netinet/udp.h> > > +#include <arpa/inet.h> > > > > uint64_t > > entry(void *pkt) > > { > > struct ether_header *ether_header = (void *)pkt; > > > > - if (ether_header->ether_type != __builtin_bswap16(0x0800)) > > + if (ether_header->ether_type != htons(0x0800)) > > Which version of clang do you use? > With my one I get: > $ clang -O2 -target bpf -c t1.c > t1.c:37:34: error: couldn't allocate output register for constraint 'r' > if (ether_header->ether_type != ntohs(0x0800)) > ^ > /usr/include/netinet/in.h:402:21: note: expanded from macro 'ntohs' > # define ntohs(x) __bswap_16 (x) > ^ > /usr/include/bits/byteswap-16.h:31:14: note: expanded from macro '__bswap_16' > __asm__ ("rorw $8, %w0" > > With '-O0' it compiles ok. > > $ clang -v > clang version 4.0.1 (tags/RELEASE_401/final) > Target: x86_64-unknown-linux-gnu > Thread model: posix > InstalledDir: /usr/bin > Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/7 > Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/7 > Selected GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/7 > Candidate multilib: .;@m64 > Candidate multilib: 32;@m32 > Selected multilib: .;@m64 > > Konstantin > > > return 0; > > > > struct iphdr *iphdr = (void *)(ether_header + 1); > > if (iphdr->protocol != 17 || (iphdr->frag_off & 0x1ffff) != 0 || > > - iphdr->daddr != __builtin_bswap32(0x1020304)) > > + iphdr->daddr != htonl(0x1020304)) > > return 0; > > > > int hlen = iphdr->ihl * 4; > > struct udphdr *udphdr = (void *)iphdr + hlen; > > > > - if (udphdr->dest != __builtin_bswap16(5000)) > > + if (udphdr->dest != htons(5000)) > > return 0; > > > > return 1; > > diff --git a/test/bpf/t3.c b/test/bpf/t3.c index 531b9cb8c..24298b7c7 > > 100644 > > --- a/test/bpf/t3.c > > +++ b/test/bpf/t3.c > > @@ -17,6 +17,7 @@ > > #include <net/ethernet.h> > > #include <rte_config.h> > > #include "mbuf.h" > > +#include <arpa/inet.h> > > > > extern void rte_pktmbuf_dump(FILE *, const struct rte_mbuf *, > > unsigned int); > > > > @@ -29,7 +30,7 @@ entry(const void *pkt) > > mb = pkt; > > eth = rte_pktmbuf_mtod(mb, const struct ether_header *); > > > > - if (eth->ether_type == __builtin_bswap16(ETHERTYPE_ARP)) > > + if (eth->ether_type == htons(ETHERTYPE_ARP)) > > rte_pktmbuf_dump(stdout, mb, 64); > > > > return 1; > > -- > > 2.17.1