[Bug tree-optimization/103435] [12 Regression] gcc/gimple-ssa-store-merging.c:879:13: runtime error: shift exponent 64 is too large for 64-bit type 'long unsigned int'

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103435

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:9a0152509234c514dcdb34468155459dfd7afacf

commit r10-10659-g9a0152509234c514dcdb34468155459dfd7afacf
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Sat Nov 27 13:00:55 2021 +0100

    bswap: Fix UB in find_bswap_or_nop_finalize [PR103435]

    On gcc.c-torture/execute/pr103376.c in the following code we trigger UB
    in the compiler.  n->range is 8 because it is 64-bit load and rsize is 0
    because it is a bswap sequence with load and known to be 0:
      /* Find real size of result (highest non-zero byte).  */
      if (n->base_addr)
        for (tmpn = n->n, rsize = 0; tmpn; tmpn >>= BITS_PER_MARKER, rsize++);
      else
        rsize = n->range;
    The shifts then shift uint64_t by 64 bits.  For this case mask is 0
    and we want both *cmpxchg and *cmpnop as 0, the operation can be done as
    both nop and bswap and callers will prefer nop.

    2021-11-27  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/103435
            * gimple-ssa-store-merging.c (find_bswap_or_nop_finalize): Avoid UB
if
            n->range - rsize == 8, just clear both *cmpnop and *cmpxchg in that
            case.

    (cherry picked from commit 567d5f3d62fba2a23a9e975f7e7c7b61bb67cf24)