Re: PING^2 [PATCH] rs6000: Fix an assertion in update_target_cost_per_stmt [PR103702]

[Richard Biener <richard.guenther@gmail.com>]

On Wed, Jan 26, 2022 at 3:15 AM Kewen.Lin via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Gentle ping:
>
> https://gcc.gnu.org/pipermail/gcc-patches/2021-December/587309.html

OK.

Thanks,
Richard.

> BR,
> Kewen
>
> > on 2021/12/23 上午10:06, Kewen.Lin via Gcc-patches wrote:
> >> Hi,
> >>
> >> This patch is to fix one wrong assertion which is too aggressive.
> >> Vectorizer can do vec_construct costing for the vector type which
> >> only has one unit.  For the failed case, the passed-in vector type
> >> is "vector(1) int", though it doesn't end up with any construction
> >> eventually.  We have to handle this kind of input in function
> >> rs6000_cost_data::update_target_cost_per_stmt.
> >>
> >> Bootstrapped and regtested on powerpc64le-linux-gnu P9 and
> >> powerpc64-linux-gnu P8.
> >>
> >> Is it ok for trunk?
> >>
> >> BR,
> >> Kewen
> >> -----
> >> gcc/ChangeLog:
> >>
> >>      PR target/103702
> >>      * config/rs6000/rs6000.c
> >>      (rs6000_cost_data::update_target_cost_per_stmt): Fix one wrong
> >>      assertion with early return.
> >>
> >> gcc/testsuite/ChangeLog:
> >>
> >>      PR target/103702
> >>      * gcc.target/powerpc/pr103702.c: New test.
> >> ---
> >>  gcc/config/rs6000/rs6000.c                  |  7 ++++--
> >>  gcc/testsuite/gcc.target/powerpc/pr103702.c | 24 +++++++++++++++++++++
> >>  2 files changed, 29 insertions(+), 2 deletions(-)
> >>  create mode 100644 gcc/testsuite/gcc.target/powerpc/pr103702.c
> >>
> >> diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
> >> index 0b09713b2f5..37f07fe5358 100644
> >> --- a/gcc/config/rs6000/rs6000.c
> >> +++ b/gcc/config/rs6000/rs6000.c
> >> @@ -5461,8 +5461,11 @@ rs6000_cost_data::update_target_cost_per_stmt (vect_cost_for_stmt kind,
> >>      {
> >>        tree vectype = STMT_VINFO_VECTYPE (stmt_info);
> >>        unsigned int nunits = vect_nunits_for_cost (vectype);
> >> -      /* We don't expect strided/elementwise loads for just 1 nunit.  */
> >> -      gcc_assert (nunits > 1);
> >> +      /* As PR103702 shows, it's possible that vectorizer wants to do
> >> +         costings for only one unit here, it's no need to do any
> >> +         penalization for it, so simply early return here.  */
> >> +      if (nunits == 1)
> >> +        return;
> >>        /* i386 port adopts nunits * stmt_cost as the penalized cost
> >>           for this kind of penalization, we used to follow it but
> >>           found it could result in an unreliable body cost especially
> >> diff --git a/gcc/testsuite/gcc.target/powerpc/pr103702.c b/gcc/testsuite/gcc.target/powerpc/pr103702.c
> >> new file mode 100644
> >> index 00000000000..585946fd64b
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.target/powerpc/pr103702.c
> >> @@ -0,0 +1,24 @@
> >> +/* We don't have one powerpc.*_ok for Power6, use altivec_ok conservatively.  */
> >> +/* { dg-require-effective-target powerpc_altivec_ok } */
> >> +/* { dg-options "-mdejagnu-cpu=power6 -O2 -ftree-loop-vectorize -fno-tree-scev-cprop" } */
> >> +
> >> +/* Verify there is no ICE.  */
> >> +
> >> +unsigned short a, e;
> >> +int *b, *d;
> >> +int c;
> >> +extern int fn2 ();
> >> +void
> >> +fn1 ()
> >> +{
> >> +  void *f;
> >> +  for (;;)
> >> +    {
> >> +      fn2 ();
> >> +      b = f;
> >> +      e = 0;
> >> +      for (; e < a; ++e)
> >> +    b[e] = d[e * c];
> >> +    }
> >> +}
> >> +
> >> --
> >> 2.27.0
> >>
>