[Bug middle-end/126446] [13/14/15/16/17 Regression] X86-64: ICE at -O1 -mavx2 during RTL pass: vregs since r12-2085

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126446

--- Comment #9 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <[email protected]>:

https://gcc.gnu.org/g:a7ba10ac1e027349a655ee4572abf34c1b9c1db1

commit r17-2796-ga7ba10ac1e027349a655ee4572abf34c1b9c1db1
Author: Jakub Jelinek <[email protected]>
Date:   Wed Jul 29 23:34:54 2026 +0200

    isel: Fix ICE on out of bounds vector elt access [PR126446]

    The isel pass has a check for out of bounds constant index before
    optimizing into .VEC_SET, but it does it using
          // if index is a constant, then check the bounds
          poly_uint64 idx_poly;
          if (poly_int_tree_p (idx, &idx_poly))
            {
              poly_uint64 nelts = TYPE_VECTOR_SUBPARTS (TREE_TYPE (view_op0));
              if (known_gt (idx_poly, nelts))
                return false;
            }
    In the testcase below, idx is INTEGER_CST with long long type and
    negative value, that doesn't fit into poly_uint64, so we happily convert
    it into .VEC_SET.

    Furthermore, the known_gt check looks wrong, already idx_poly known_eq
    to nelts is too large and out of bounds for .VEC_SET.

    This patch fixes that by punting if !poly_int_tree_p (idx, &idx_poly)
    and poly_int_tree_p (idx), so when it is INTEGER_CST or POLY_INT_CST
    which doesn't fit into poly_uint64 (so likely negative), and
    uses known_ge instead of known_gt.

    2026-07-29  Jakub Jelinek  <[email protected]>

            PR target/126446
            * gimple-isel.cc (gimple_expand_vec_set_extract_expr): Punt if
            idx doesn't fit into poly_uint64 but is poly_int_tree_p.  Use
            known_ge rather than known_gt for out of bounds check.  Formatting
            fixes.

    Reviewed-by: Richard Biener <[email protected]>