Re: [dpdk-dev] DPDK compilation on arm is failing in Travis

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

> >
> >  Thomas Monjalon <thomas@monjalon.net> writes:
> >
> >
> >
> >  The compilation of the master branch is failing for aarch64:
> >
> >  https://travis-ci.com/DPDK/dpdk
> >
> > The log is so much verbose that I am not able to understand what
> >
> > is really wrong.
> >
> > Please help to diagnose and fix, thanks.
> >
> >
> >
> > A discussion about this:
> >
> >
> >
> > http://mails.dpdk.org/archives/dev/2019-June/134012.html
> >
> >
> >
> > I see the error now.
> >
> > It is printing the full log after the error, so I missed the error
> >
> > at the top.
> >
> >
> >
> > I've read your comment about a possible error with the patch
> >
> > removing weak functions but neither me nor Bruce were able to
> > reproduce
> >
> > it.
> >
> >  What is the condition to see this compiler warning?
> >
> >
> >
> > It is only on ARM, and only when the neon intrinsics are in use.
> >
> > I am not able to reproduce it from the tip of master.
> >
> >
> >
> > I am using:
> >
> > gcc (Ubuntu 8.3.0-6ubuntu1~18.04) 8.3.0
> >
> >
> >
> > From the log on Travis, looks like the compiler is:
> >
> > gcc (Ubuntu 5.4.0-6ubuntu1~16.04.11) 5.4.0 20160609
> >
> >
> >
> > Is this the issue?
> >
> >
> >
> > Why are we seeing the error now?
> >
> > I tested with gcc-5 (Ubuntu/Linaro 5.5.0-12ubuntu1) 5.5.0 20171010, it
> works fine. I cannot get hold of 5.4.0. Not sure if needs to be supported.
> >
> > Are there any issues in upgrading to 7 or 8?
> >
> > I have tested it on my ubuntu 16.04 vm on commit
> > 8cb511bb94ad92a76990f175cac76bb13d51daba
> > (head of master seems to be failing for other reasons on my vm).
> > I tested the following gcc versions:
> >
> > gcc 5.5.0 "cc (Ubuntu 5.5.0-12ubuntu1~16.04) 5.5.0 20171010"
> > gcc 7.4.0 "cc (Ubuntu 7.4.0-1ubuntu1~16.04~ppa1) 7.4.0"
> > gcc 8.1.0 "cc (Ubuntu 8.1.0-5ubuntu1~16.04) 8.1.0"
> >
> > All tested versions failed on the exact same error shown in travis. I
> > don't know if the compiler is at fault here. Maybe Aaron's patch is a viable
> option?
> >
> >  The issue is the vector lane setting code looks like:
> >
> >
> >
> >    lval = lane_set(scalar, rval, lane id)
> >
> >
> >
> > In this case, 'rval' is being used before it is ever set, but it
> >
> > really could be just 0 for the first lane setting code.  Thereafter,
> >
> > we use the old value of input as the rval, but each time a different lane is
> set.
> >
> >
> >
> > It would be nice if there were an intrinsic that formatted correctly
> >
> > from the start (something we could call like lval =
> >
> > lane_set_from_array(scalar_array)).
> >
> > [Honnappa] This exists already. ‘vdupq_n_s32’ can be used. Can you try the
> following?
> 
> Well, it isn't exactly that.  You are setting all lanes from a scalar.
Yes, you are correct, it sets all the lanes. I am not sure on how this will affect the performance.

> I'd rather be able to say:
> 
>    input0 = vdupq_nn_s32(&parms[0]);
>    input1 = vdupq_nn_s32(&parms[4]);
> 
> Something like that, which lets us delete all the rest of the lane-set code.  But
> it seems it doesn't exist.
> 
> Regardless, I think either patch should work (either using the 'all lanes'
> setting you have or the static variable).  I have no preference on it - it's up to
> you (or someone else) to say which is preferred.  I guess your version could be
> preferable since there's no static to need to "explain" :)
I think we can go ahead with your patch with using a temporary vector for the first set, as it does not introduce any change to the code and hence performance should not get affected.

But, I do not understand why you have added 'static'. Also, changing 'ZEROVAL' to 'tmp' or something similar will be better.

> 
> > honnag01@qc2400f-1:~/dpdk$ git diff
> >
> > diff --git a/lib/librte_acl/acl_run_neon.h
> > b/lib/librte_acl/acl_run_neon.h
> >
> > index 01b9766d8..b3196cd12 100644
> >
> > --- a/lib/librte_acl/acl_run_neon.h
> >
> > +++ b/lib/librte_acl/acl_run_neon.h
> >
> > @@ -181,8 +181,8 @@ search_neon_8(const struct rte_acl_ctx *ctx, const
> > uint8_t **data,
> >
> >
> >
> >         while (flows.started > 0) {
> >
> >                 /* Gather 4 bytes of input data for each stream. */
> >
> > -               input0 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 0), input0, 0);
> >
> > -               input1 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 4), input1, 0);
> >
> > +               input0 = vdupq_n_s32(GET_NEXT_4BYTES(parms, 0));
> >
> > +               input1 = vdupq_n_s32(GET_NEXT_4BYTES(parms, 4));
> >
> >
> >
> >                 input0 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 1),
> > input0, 1);
> >
> >                 input1 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 5),
> > input1, 1);
> >
> > @@ -242,7 +242,7 @@ search_neon_4(const struct rte_acl_ctx *ctx, const
> > uint8_t **data,
> >
> >
> >
> >         while (flows.started > 0) {
> >
> >                 /* Gather 4 bytes of input data for each stream. */
> >
> > -               input = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 0), input, 0);
> >
> > +               input = vdupq_n_s32(GET_NEXT_4BYTES(parms, 0));
> >
> >                 input = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 1),
> > input, 1);
> >
> >                 input = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 2),
> > input, 2);
> >
> >                                                 input =
> > vsetq_lane_s32(GET_NEXT_4BYTES(parms, 3), input, 3);
> >
> >
> >
> >  Then 'input' would never appear as an rval before it was set.
> >
> >
> >
> > I thought Jerin Jacob (CC'd) would have some opinion on the right fix.
> >
> > There are three 'fixes' I know exist - one is to squelch the warning
> >
> > (but I don't like it because it could hide future code that introduces
> >
> > this), one is to create a static and use assignment, one is to replace
> >
> > the first call and pass in a 0'd lane for the first one.
> >
> >
> >
> > Actually, I think I have a patch that could work to not introduce an
> >
> > assignment, but squelch the warning.  Something like the following
> > (not
> >
> > tested).
> >
> >
> >
> > ---
> >
> >
> >
> > diff --git a/lib/librte_acl/acl_run_neon.h
> >
> > b/lib/librte_acl/acl_run_neon.h index 01b9766d8..37c984fef 100644
> >
> > --- a/lib/librte_acl/acl_run_neon.h
> >
> > +++ b/lib/librte_acl/acl_run_neon.h
> >
> > @@ -165,6 +165,7 @@ search_neon_8(const struct rte_acl_ctx *ctx, const
> >
> > uint8_t **data,
> >
> >     uint64_t index_array[8];
> >
> >     struct completion cmplt[8];
> >
> >     struct parms parms[8];
> >
> > +   static int32x4_t ZEROVAL;
> >
> >     int32x4_t input0, input1;
> >
> >
> >
> >     acl_set_flow(&flows, cmplt, RTE_DIM(cmplt), data, results, @@ -
> >
> > 181,8 +182,8 @@ search_neon_8(const struct rte_acl_ctx *ctx, const
> >
> > uint8_t **data,
> >
> >
> >
> >     while (flows.started > 0) {
> >
> >             /* Gather 4 bytes of input data for each stream. */
> >
> > -           input0 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 0), input0,
> >
> > 0);
> >
> > -           input1 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 4), input1,
> >
> > 0);
> >
> > +           input0 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 0),
> >
> > ZEROVAL, 0);
> >
> > +           input1 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 4),
> >
> > ZEROVAL, 0);
> >
> >
> >
> >             input0 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 1), input0,
> >
> > 1);
> >
> >              input1 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 5),
> > input1,
> >
> > 1); @@
> >
> >  -227,6 +228,7 @@ search_neon_4(const struct rte_acl_ctx *ctx, const
> >
> > uint8_t **data,
> >
> >     uint64_t index_array[4];
> >
> >     struct completion cmplt[4];
> >
> >     struct parms parms[4];
> >
> > +   static int32x4_t ZEROVAL;
> >
> >     int32x4_t input;
> >
> >
> >
> >     acl_set_flow(&flows, cmplt, RTE_DIM(cmplt), data, results, @@ -
> >
> > 242,7 +244,7 @@ search_neon_4(const struct rte_acl_ctx *ctx, const
> >
> > uint8_t **data,
> >
> >
> >
> >     while (flows.started > 0) {
> >
> >             /* Gather 4 bytes of input data for each stream. */
> >
> > -           input = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 0), input, 0);
> >
> > +           input = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 0),
> >
> > ZEROVAL, 0);
> >
> >             input = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 1), input,
> > 1);
> >
> >             input = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 2), input,
> > 2);
> >
> >             input = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 3), input,
> > 3);
> >
> > --
> >
> > 2.21.0