> > Hi Konstantin,
> >
> > At time of upstreaming the patch, I had compiled it on Cortex-A72 and it
> had worked with the -I parameter.
>
> Just curious what is memory ordering on your box (BE/LE)?
The memory ordering on my machine was little endian
> > But when tried building it on
> > x86-64, I encountered the error that you were facing. From my
> > understanding of this problem, this is a portability issue. As you pointed
> out, gcc and clang implement __builtin_constant_p in a different way on x86
> but that may not be true for ARM.
> >
> > In such a case, to enable compilation on x86, we may want to write
> > specific hton and ntoh functions. But this would become a tedious task
> > because, in future, to enable compilation on other architectures besides
> x86 and ARM, we may have to repeat this process of writing analogs for each
> architecture.
>
> Don't see why we need it done for each arch.
> Obviously all is needed is BE and LE version.
>
> > I think the best solution in the current scenario would be to use the
> > -U parameter to enable compilation on
> > x86 and later decide if we want to write a new patch with analogs for
> builtin hton() and ntoh().
>
> I suppose -U__GNUC__ is ok.
> If you decide to go that way, please update appropriate comments in *.c.
I will update the comments in the .c files and submit the patch again.
Thanks,
Malvika
> Konstantin
>
> >
> > Best,
> > Malvika
> >
> > -----Original Message-----
> > From: Ananyev, Konstantin <konstantin.anan...@intel.com>
> > Sent: Friday, October 19, 2018 7:17 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>; nd
> <n...@arm.com>
> > Subject: RE: [PATCH] test/bpf: use hton instead of __builtin_bswap
> >
> >
> > 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
