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Subject: [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'
Date: Sat, 27 Nov 2021 12:01:41 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103435

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:567d5f3d62fba2a23a9e975f7e7c7b61bb67cf24

commit r12-5557-g567d5f3d62fba2a23a9e975f7e7c7b61bb67cf24
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 =3D n->n, rsize =3D 0; tmpn; tmpn >>=3D BITS_PER_MARKER, =
rsize++);
      else
        rsize =3D 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): Avoi=
d UB
if
            n->range - rsize =3D=3D 8, just clear both *cmpnop and *cmpxchg=
 in that
            case.=