[gcc r15-4115] vect: Add more dump messages for VLA SLP permutation [PR116583]

[Richard Sandiford via Gcc-cvs]

https://gcc.gnu.org/g:03299164830e19405b35a5fa862e248df4ea01e2

commit r15-4115-g03299164830e19405b35a5fa862e248df4ea01e2
Author: Richard Sandiford <richard.sandif...@arm.com>
Date:   Mon Oct 7 13:03:05 2024 +0100

    vect: Add more dump messages for VLA SLP permutation [PR116583]
    
    Taking the !repeating_p route for VLA vectors causes analysis
    to fail, but it wasn't clear from the dump files when this
    had happened, and which node caused it.
    
    gcc/
            PR tree-optimization/116583
            * tree-vect-slp.cc (vectorizable_slp_permutation_1): Add more
            dump messages.

Diff:
---
 gcc/tree-vect-slp.cc | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index a5cd596fd285..849863c15057 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -10333,10 +10333,22 @@ vectorizable_slp_permutation_1 (vec_info *vinfo, 
gimple_stmt_iterator *gsi,
         instead of relying on the pattern described above.  */
       if (!nunits.is_constant (&npatterns)
          || !TYPE_VECTOR_SUBPARTS (op_vectype).is_constant ())
-       return -1;
+       {
+         if (dump_p)
+           dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
+                            "unsupported permutation %p on variable-length"
+                            " vectors\n", (void *) node);
+         return -1;
+       }
       nelts_per_pattern = ncopies = 1;
       if (linfo && !LOOP_VINFO_VECT_FACTOR (linfo).is_constant (&ncopies))
-       return -1;
+       {
+         if (dump_p)
+           dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
+                            "unsupported permutation %p for variable VF\n",
+                            (void *) node);
+         return -1;
+       }
       pack_p = false;
       unpack_factor = 1;
     }