[PATCH v4 07/10] vect: Verify that GET_MODE_NUNITS is a multiple of 2.

[Michael Collison]

While working on autovectorizing for the RISCV port I encountered an issue
where can_duplicate_and_interleave_p assumes that GET_MODE_NUNITS is a
evenly divisible by two. The RISC-V target has vector modes (e.g. VNx1DImode),
where GET_MODE_NUNITS is equal to one.

Tested on RISCV and x86_64-linux-gnu. Okay?

2023-03-09  Michael Collison  <colli...@rivosinc.com>

        * tree-vect-slp.cc (can_duplicate_and_interleave_p):
        Check that GET_MODE_NUNITS is a multiple of 2.
---
 gcc/tree-vect-slp.cc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index d73deaecce0..a64fe454e19 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -423,10 +423,13 @@ can_duplicate_and_interleave_p (vec_info *vinfo, unsigned 
int count,
            (GET_MODE_BITSIZE (int_mode), 1);
          tree vector_type
            = get_vectype_for_scalar_type (vinfo, int_type, count);
+         poly_int64 half_nelts;
          if (vector_type
              && VECTOR_MODE_P (TYPE_MODE (vector_type))
              && known_eq (GET_MODE_SIZE (TYPE_MODE (vector_type)),
-                          GET_MODE_SIZE (base_vector_mode)))
+                          GET_MODE_SIZE (base_vector_mode))
+             && multiple_p (GET_MODE_NUNITS (TYPE_MODE (vector_type)),
+                            2, &half_nelts))
            {
              /* Try fusing consecutive sequences of COUNT / NVECTORS elements
                 together into elements of type INT_TYPE and using the result
@@ -434,7 +437,7 @@ can_duplicate_and_interleave_p (vec_info *vinfo, unsigned 
int count,
              poly_uint64 nelts = GET_MODE_NUNITS (TYPE_MODE (vector_type));
              vec_perm_builder sel1 (nelts, 2, 3);
              vec_perm_builder sel2 (nelts, 2, 3);
-             poly_int64 half_nelts = exact_div (nelts, 2);
+
              for (unsigned int i = 0; i < 3; ++i)
                {
                  sel1.quick_push (i);
-- 
2.34.1