https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104475
--- Comment #4 from Andrew Macleod <amacleod at redhat dot com> ---
(In reply to Aldy Hernandez from comment #3)
> This isn't the threader but VRP/ranger.
>
> What happens is that the threader isolates the path, making it easier for
> VRP to see the equivalence, and then CCP4 folds the constant into the
> problematic call. This is from the .ccp4 pass:
>
> Folding statement: __atomic_or_fetch_4 (pretmp_29, 64, 0);
> Folded into: __atomic_or_fetch_4 (184B, 64, 0);
>
> In VRP2 the ranger is folding:
>
> Folding statement: pretmp_29 = &MEM[(struct __atomic_base *)_1 + 184B]._M_i;
> Folded into: pretmp_29 = 184B;
>
> The ranger is determining that _1 is 0 because it has determined that since
> _2 is 0 on the 2->3 edge, so is _1, as m_mutex is the first field of _1:
>
> =========== BB 2 ============
> Imports: _1
> Exports: _1 _2
> _2 : _1(I)
> <bb 2> [local count: 1073741824]:
> _1 = this_10(D)->d;
> _2 = &_1->m_mutex;
> MEM[(struct __as_base &)&lock] ={v} {CLOBBER};
> if (_2 != 0B)
> goto <bb 5>; [90.00%]
> else
> goto <bb 3>; [10.00%]
>
> 2->5 (T) _1 : struct QFutureInterfaceBasePrivate * [1B, +INF]
> 2->5 (T) _2 : struct QMutex * [1B, +INF]
> 2->3 (F) _1 : struct QFutureInterfaceBasePrivate * [0B, 0B]
> 2->3 (F) _2 : struct QMutex * [0B, 0B]
>
> Andrew, how/where is that we relate _1 and _2 here? I can't seem to find it.
>
> My gut feeling is that special casing anything in the ranger for this is
> wrong.
Its via op1_range for OP_ADDR:
--param=ranger-debug=tracegori shows:
2120 GORI outgoing_edge for _1 on edge 2->3
2121 GORI compute op 1 (_2) at if (_2 != 0B)
GORI LHS =bool [0, 0]
GORI Computes _2 = struct QMutex * [0B, 0B] intersect Known range
: struct QMutex * VARYING
GORI TRUE : (2121) produces (_2) struct QMutex * [0B, 0B]
2122 GORI compute op 1 (_1) at _2 = &_1->m_mutex;
GORI LHS =struct QMutex * [0B, 0B]
GORI Computes _1 = struct QFutureInterfaceBasePrivate * [0B, 0B]
intersect Known range : struct QFutureInterfaceBasePrivate * VARYING
GORI TRUE : (2122) produces (_1) struct QFutureInterfaceBasePrivate
* [0B, 0B]
GORI TRUE : (2120) outgoing_edge (_1) struct
QFutureInterfaceBasePrivate * [0B, 0B]
so with _2 == 0, the 2122 trace element is solving for _1 in
_2 = &_1->m_mutex
[0,0] = &_1->m_mutex
is it possible for _1 to be anything other than 0 in this case? If so we need
to adjust range-ops
