On Thu, Jul 29, 2021 at 9:29 AM Gary Oblock <g...@amperecomputing.com> wrote:
>
> Richard,
>
> I didn't find a use of _975 with that type...
>
> A small test case is easier said than done. It's mcf
> and I pulled a copy out of SPEC for my unit tests (we have
> a SPEC license) and that passes. However, when I compile it
> in the SPEC framework, it fails. Otherwise, I'd have used
> creduce to make a really tiny test case a couple of weeks
> ago... ;-(
Does it pass if you cut&paste the exact command SPEC uses
in its build directory?
>
> In RTL a trick I used to use in the bad old days when I did one off VLIW
> schedulers, was to instrument the bit that assigns the RTL's id
> number and put a trap there to catch the creation of an interesting
> bit of RTL. Does that kind of trick work with SSA variable creation?
Well, I'm usually debugging cc1 then and conditionally break on
the return from make_ssa_name_fn if t->base.u.version == the SSA version
or for any GC allocated entity at the return of ggc_internal_alloc and the
corresponding address of the object.
> Thanks, I really appreciate your help even though in this case
> I'm still kind of stuck.
>
> Gary
>
> ________________________________
> From: Richard Biener <richard.guent...@gmail.com>
> Sent: Thursday, July 29, 2021 12:12 AM
> To: Gary Oblock <g...@amperecomputing.com>
> Cc: gcc@gcc.gnu.org <gcc@gcc.gnu.org>
> Subject: Re: A value number issue
>
> [EXTERNAL EMAIL NOTICE: This email originated from an external sender. Please
> be mindful of safe email handling and proprietary information protection
> practices.]
>
>
> On Wed, Jul 28, 2021 at 11:03 PM Gary Oblock <g...@amperecomputing.com> wrote:
> >
> > Richard,
> >
> > Here is more on the actual failure.
> >
> > From the pre pass dump:
> >
> > :
> > Inserted _975 = (struct node.reorg.reorder *) dedangled_865;
> > Replaced bea_43->tail with _975 in dedangled_864 = bea_43->tail;
> >
> >
> >
> > EMERGENCY DUMP:
> >
> > void master.constprop ()
> > {
> > :
> > unsigned long _974;
> > struct node.reorg.reorder * _975;
> >
> > :
> > <bb 36> [local count: 4422246]:
> > _58 = MEM[(int64_t *)&net + 608B];
> > _59 = _58 + 1;
> > MEM[(int64_t *)&net + 608B] = _59;
> > dedangled_865 = bea_43->tail;
> > dedangled_863 = bea_43->head;
> > _975 = (struct node.reorg.reorder *) dedangled_865;
> > dedangled_864 = bea_43->tail;
> > dedangled_866 = bea_43->head;
> > if (red_cost_of_bea_42 > 0)
> > goto <bb 166>; [59.00%]
> > else
> > goto <bb 37>; [41.00%]
> > :
> > ----------
> > In tree-ssa-sccvn.c at about line 6000 or so there is
> > this sequence:
> >
> > if (!useless_type_conversion_p (TREE_TYPE (lhs),
> > TREE_TYPE (sprime)))
> > {
> > /* We preserve conversions to but not from function or method
> > types. This asymmetry makes it necessary to re-instantiate
> > conversions here. */
> > if (POINTER_TYPE_P (TREE_TYPE (lhs))
> > && FUNC_OR_METHOD_TYPE_P (TREE_TYPE (TREE_TYPE (lhs))))
> > sprime = fold_convert (TREE_TYPE (lhs), sprime);
> > else
> > gcc_unreachable ();
> > }
> >
> > We reach the gcc_unreachable because:
> >
> > lhs = dedangled_864, TREE_TYPE(lhs) = unsigned long
> > sprime = _975, TREE_TYPE(sprime) = struct node.reorg.reorder *
> >
> > I've got to ask why does the _975 have that type?
>
> Because the value was used with that type?
>
> > The ssa var dedangled_865 is an unsigned long.
> > If I knew why this happens then, hopefully, I can adjust
> > the GIMPLE I create to avoid this situation...
> >
> > Question, would have including all references to denangled_865
> > in the pre pass dump helped you answer this? By the way, I couldn't
> > find a spot where dedangled_865 or any of its phi related uses
> > (a use of x where x <- phi<... denanged_865..> and so on recursively)
> > was converted to struct node.reorg.reorder *.
>
> So what did you change in GCC? If you did not change value-numbering
> then you can reduce the testcase down and extract a GIMPLE frontend
> testcase for VN (use -fdump-tree-all-gimple and massage the GIMPLE
> dumped before the FRE/PRE pass that causes the issue)
>
> > Gary
> >
> >
> > ________________________________
> > From: Richard Biener <richard.guent...@gmail.com>
> > Sent: Wednesday, July 28, 2021 3:40 AM
> > To: Gary Oblock <g...@amperecomputing.com>
> > Cc: gcc@gcc.gnu.org <gcc@gcc.gnu.org>
> > Subject: Re: A value number issue
> >
> > [EXTERNAL EMAIL NOTICE: This email originated from an external sender.
> > Please be mindful of safe email handling and proprietary information
> > protection practices.]
> >
> >
> > On Fri, Jul 23, 2021 at 3:40 AM Gary Oblock <g...@amperecomputing.com>
> > wrote:
> > >
> > > Richard,
> > >
> > > OK, all that I've gotten so far out of the dump file is
> > > that the name of "_920" is just something sccvn concocted
> > > and wasn't something I accidentally caused.
> > >
> > > That still leaves me with the question of what is going on.
> > >
> > > Here's all the interesting bits of the dumpfile concerning
> > > dedangled_864:
> > >
> > > :
> > > dedangled_865 = *bea_43 + 64
> > > dedangled_863 = *bea_43 + 128
> > > dedangled_864 = *bea_43 + 64
> > > dedangled_866 = *bea_43 + 128
> > > dedangled_867 = dedangled_863
> > > dedangled_867 = dedangled_865
> > > dedangled_868 = dedangled_864
> > > dedangled_868 = dedangled_866
> > > :
> > > Equivalence classes for indirect node id 160 "dedangled_865": pointer 84,
> > > location 0
> > > Equivalence classes for indirect node id 161 "dedangled_863": pointer 85,
> > > location 0
> > > Equivalence classes for indirect node id 162 "dedangled_864": pointer 86,
> > > location 0
> > > :
> > > dedangled_865 = { ESCAPED NONLOCAL }
> > > dedangled_863 = { ESCAPED NONLOCAL }
> > > dedangled_864 = { ESCAPED NONLOCAL }
> > > dedangled_866 = { ESCAPED NONLOCAL }
> > > dedangled_867 = { ESCAPED NONLOCAL }
> > > dedangled_868 = { ESCAPED NONLOCAL }
> > > :
> > > Value numbering store MEM[(int64_t *)&net + 608B] to _59
> > > Setting value number of .MEM_123 to .MEM_123 (changed)
> > > Value numbering stmt = dedangled_865 = bea_43->tail;
> > > Setting value number of dedangled_865 to dedangled_865 (changed)
> > > Making available beyond BB36 dedangled_865 for value dedangled_865
> > > Value numbering stmt = dedangled_863 = bea_43->head;
> > > Setting value number of dedangled_863 to dedangled_863 (changed)
> > > Making available beyond BB36 dedangled_863 for value dedangled_863
> > > Value numbering stmt = dedangled_864 = bea_43->tail;
> > > Inserting name _920 for expression (struct node.reorg.reorder *)
> > > dedangled_865
> >
> > this means that the earlier dedangled_865 = bea_43->tail; somehow did not
> > produce a value that was considered OK but it was close enough so VN
> > remembers the expression (struct node.reorg.reorder *) dedangled_865
> > as known result, using _920 as value. _920 should be then inserted during
> > elimination.
> >
> > I'm not sure what your actual problem is - you can see in eliminate_stmt
> > how we deal with such values:
> >
> > /* If there is no existing usable leader but SCCVN thinks
> > it has an expression it wants to use as replacement,
> > insert that. */
> > tree val = VN_INFO (lhs)->valnum;
> > vn_ssa_aux_t vn_info;
> > if (val != VN_TOP
> > && TREE_CODE (val) == SSA_NAME
> > && (vn_info = VN_INFO (val), true)
> > && vn_info->needs_insertion
> > && vn_info->expr != NULL
> > && (sprime = eliminate_insert (b, gsi, val)) != NULL_TREE)
> > eliminate_push_avail (b, sprime);
> >
> >
> > > Setting value number of dedangled_864 to _920 (changed)
> > > Making available beyond BB36 dedangled_864 for value _920
> > > Value numbering stmt = dedangled_866 = bea_43->head;
> > > :
> > > Value numbering stmt = dedangled_868 = PHI <dedangled_864(166),
> > > dedangled_866(37)>
> > > Setting value number of dedangled_868 to dedangled_868 (changed)
> > > :
> > > Setting value number of dedangled_363 to _920 (changed)
> > > dedangled_864 is available for _920
> > > Value numbering stmt = _896 = dedangled_363 == dedangled_873;
> > > dedangled_864 is available for _920
> > > (the last line repeats many times)
> > > :
> > > Value numbering stmt = _881 = dedangled_363 == dedangled_875;
> > > dedangled_864 is available for _920
> > > (the last line repeats many times)
> > > :
> > > Value numbering stmt = _880 = _881 & _891;
> > > dedangled_864 is available for _920
> > > dedangled_864 is available for _920
> > > dedangled_864 is available for _920
> > > dedangled_864 is available for _920
> > > :
> > > Setting value number of dedangled_313 to _920 (changed)
> > > dedangled_864 is available for _920
> > > Value numbering stmt = _904 = dedangled_313 == dedangled_873;
> > > dedangled_864 is available for _920
> > > (the last line repeats many times)
> > > :
> > > Value numbering stmt = _442 = _11 & _904;
> > > dedangled_864 is available for _920
> > > Match-and-simplified _11 & _904 to _904
> > > :
> > > Value numbering stmt = if (_442 != 0)
> > > dedangled_864 is available for _920
> > > :
> > > Making available beyond BB36 dedangled_863 for value dedangled_863
> > > Value numbering stmt = dedangled_864 = bea_43->tail;
> > > Setting value number of dedangled_864 to _920
> > > Making available beyond BB36 dedangled_864 for value _920
> > > Value numbering stmt = dedangled_866 = bea_43->head;
> > > :
> > > Making available beyond BB38 dedangled_867 for value dedangled_867
> > > Value numbering stmt = dedangled_868 = PHI <dedangled_864(166),
> > > dedangled_866(37)>
> > > Setting value number of dedangled_868 to dedangled_868
> > > :
> > > Setting value number of dedangled_363 to _920
> > > dedangled_864 is available for _920
> > > Value numbering stmt = _896 = dedangled_363 == dedangled_873;
> > > dedangled_864 is available for _920
> > > (the last line repeats many times)
> > > :
> > > Value numbering stmt = _881 = dedangled_363 == dedangled_875;
> > > dedangled_864 is available for _920
> > > (the last line repeats many times)
> > > :
> > > (a bunch more of the "dedangled_864 is available for _920")
> > > :
> > > exp_gen[36] := { red_cost_of_bea_42 (0019), bea_43 (0020),
> > > {mem_ref<608B>,addr_expr<&net>}@.MEM_99 (0027), {plus_expr,_58,1} (0028),
> > > {component_ref<tail>,mem_ref<0B>,bea_43}@.MEM_387 (0408),
> > > {component_ref<head>,mem_ref<0B>,bea_43}@.MEM_387 (0407) }
> > > phi_gen[36] := { }
> > > tmp_gen[36] := { _58 (0027), _59 (0028), dedangled_865 (0408),
> > > dedangled_863 (0407), dedangled_864 (0448), dedangled_866 (0229) }
> > > avail_out[36] := { xchange_449(D) (0232), arcs_1 (0003), stop_arcs_2
> > > (0004), _4 (0006), _5 (0007), i_646 (0340), _7 (0008), _8 (0009), _9
> > > (0010), i_10 (0011), _212 (0112), xchange_900 (0431), end_arc_385 (0180),
> > > _14 (0013), _19 (0015), field_arry_addr_112 (0045), i_665 (0352),
> > > next_666 (0353), _163 (0081), next_218 (0113), _173 (0083), _178 (0086),
> > > _179 (0087), _176 (0084), end_arc_443 (0226), end_arc_444 (0227),
> > > end_arc_445 (0228), _222 (0238), _223 (0115), _224 (0116), _225 (0117),
> > > _226 (0118), _227 (0119), _228 (0120), _229 (0121), _231 (0123), _21
> > > (0016), red_cost_of_bea_42 (0019), bea_43 (0020), i_649 (0343), _45
> > > (0021), _46 (0022), _47 (0023), _58 (0027), _59 (0028), dedangled_865
> > > (0408), dedangled_863 (0407), dedangled_864 (0448), dedangled_866 (0229) }
> > > exp_gen[37] := { }
> > > phi_gen[37] := { }
> > > tmp_gen[37] := { }
> > > avail_out[37] := { xchange_449(D) (0232), arcs_1 (0003), stop_arcs_2
> > > (0004), _4 (0006), _5 (0007), i_646 (0340), _7 (0008), _8 (0009), _9
> > > (0010), i_10 (0011), _212 (0112), xchange_900 (0431), end_arc_385 (0180),
> > > _14 (0013), _19 (0015), field_arry_addr_112 (0045), i_665 (0352),
> > > next_666 (0353), _163 (0081), next_218 (0113), _173 (0083), _178 (0086),
> > > _179 (0087), _176 (0084), end_arc_443 (0226), end_arc_444 (0227),
> > > end_arc_445 (0228), _222 (0238), _223 (0115), _224 (0116), _225 (0117),
> > > _226 (0118), _227 (0119), _228 (0120), _229 (0121), _231 (0123), _21
> > > (0016), red_cost_of_bea_42 (0019), bea_43 (0020), i_649 (0343), _45
> > > (0021), _46 (0022), _47 (0023), _58 (0027), _59 (0028), dedangled_865
> > > (0408), dedangled_863 (0407), dedangled_864 (0448), dedangled_866 (0229) }
> > > exp_gen[38] := { dedangled_867 (0409), dedangled_868 (0410) }
> > > phi_gen[38] := { dedangled_867 (0409), dedangled_868 (0410) }
> > > tmp_gen[38] := { }
> > > avail_out[38] := { xchange_449(D) (0232), arcs_1 (0003), stop_arcs_2
> > > (0004), _4 (0006), _5 (0007), i_646 (0340), _7 (0008), _8 (0009), _9
> > > (0010), i_10 (0011), _212 (0112), xchange_900 (0431), end_arc_385 (0180),
> > > _14 (0013), _19 (0015), field_arry_addr_112 (0045), i_665 (0352),
> > > next_666 (0353), _163 (0081), next_218 (0113), _173 (0083), _178 (0086),
> > > _179 (0087), _176 (0084), end_arc_443 (0226), end_arc_444 (0227),
> > > end_arc_445 (0228), _222 (0238), _223 (0115), _224 (0116), _225 (0117),
> > > _226 (0118), _227 (0119), _228 (0120), _229 (0121), _231 (0123), _21
> > > (0016), red_cost_of_bea_42 (0019), bea_43 (0020), i_649 (0343), _45
> > > (0021), _46 (0022), _47 (0023), _58 (0027), _59 (0028), dedangled_865
> > > (0408), dedangled_863 (0407), dedangled_864 (0448), dedangled_866 (0229),
> > > dedangled_867 (0409), dedangled_868 (0410) }
> > > (a presence in the avail_out for rest until it reaches a point where is
> > > in none of them)
> > > :
> > > ANTIC_OUT[166] := { {mem_ref<0B>,addr_expr<&opt>}@.MEM_104(D) (0112),
> > > bea_43 (0020), dedangled_863 (0407), dedangled_864 (0448) }
> > > [changed] ANTIC_IN[166] := { {mem_ref<0B>,addr_expr<&opt>}@.MEM_104(D)
> > > (0112), bea_43 (0020), dedangled_863 (0407), dedangled_864 (0448) }
> > > S[166] := { {mem_ref<0B>,addr_expr<&opt>}@.MEM_104(D) (0112), bea_43
> > > (0020), dedangled_863 (0407), dedangled_864 (0448) }
> > > :
> > > PA_OUT[36] := { stop_arcs_2 (0004), _4 (0006),
> > > {mem_ref<0B>,addr_expr<&opt>}@.MEM_104(D) (0112), xchange_900 (0431),
> > > {mem_ref<0B>,addr_expr<&opt_basket>}@.MEM_104(D) (0015),
> > > {mem_ref<0B>,addr_expr<&full_group_end_arc>}@.MEM_104(D) (0083),
> > > end_arc_445 (0228), {mem_ref<0B>,addr_expr<&perm_p>}@.MEM_104(D) (0016),
> > > red_cost_of_bea_42 (0019), bea_43 (0020), dedangled_865 (0408),
> > > dedangled_863 (0407), dedangled_864 (0448), dedangled_866 (0229),
> > > {mem_ref<616B>,addr_expr<&net>}@.MEM_99 (0442), {plus_expr,_913,1}
> > > (0438),
> > > {component_ref<orientation>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0258),
> > > {component_ref<flow>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0274),
> > > {component_ref<pred>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0265),
> > > {component_ref<depth>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0049),
> > > {component_ref<basic_arc>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0299), {component_ref<feas_tol>,mem_ref<0B>,addr_expr<&net>}@.MEM_387
> > > (0222), {abs_expr,red_cost_of_bea_42} (0134),
> > > {component_ref<potential>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0306),
> > > {component_ref<child>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0312),
> > > {component_ref<sibling>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0327),
> > > {component_ref<sibling_prev>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0339), {pointer_plus_expr,field_arry_addr_581,-8} (0921),
> > > {bit_xor_expr,xchange_900,1} (0923),
> > > {pointer_plus_expr,field_arry_addr_591,-8} (0924),
> > > {pointer_plus_expr,field_arry_addr_601,-8} (0926) }
> > > :
> > > Replaced bea_43->tail with _975 in dedangled_864 = bea_43->tail;
> > > :
> > > long int pretmp_859;
> > > struct node * * field_addr_860;
> > > struct node * field_val_temp_861;
> > > unsigned long dedangled_863;
> > > unsigned long dedangled_864;
> > > unsigned long dedangled_865;
> > > unsigned long dedangled_866;
> > > :
> > > <bb 36> [local count: 4422246]:
> > > _58 = MEM[(int64_t *)&net + 608B];
> > > _59 = _58 + 1;
> > > MEM[(int64_t *)&net + 608B] = _59;
> > > dedangled_865 = bea_43->tail;
> > > dedangled_863 = bea_43->head;
> > > _975 = (struct node.reorg.reorder *) dedangled_865;
> > > dedangled_864 = bea_43->tail;
> > > dedangled_866 = bea_43->head;
> > > if (red_cost_of_bea_42 > 0)
> > > goto <bb 166>; [59.00%]
> > > else
> > > goto <bb 37>; [41.00%]
> > >
> > > <bb 166> [local count: 2609125]:
> > > goto <bb 38>; [100.00%]
> > >
> > > <bb 37> [local count: 1813121]:
> > >
> > > <bb 38> [local count: 4422246]:
> > > # dedangled_867 = PHI <dedangled_863(166), dedangled_865(37)>
> > > # dedangled_868 = PHI <dedangled_864(166), dedangled_866(37)>
> > > if (dedangled_867 != dedangled_868)
> > > goto <bb 126>; [89.00%]
> > > else
> > > goto <bb 55>; [11.00%]
> > > =================================================
> > > I was pretty arbitrary here about what I extracted from the
> > > dump file but it's 33MB in size.
> > >
> > > I'm still thinking it's something dumb that I did
> > > when I created "dedangled_864" but I can't spot it from
> > > the dump. Does anyone have any ideas? Note, before I
> > > looked at the dump I at least had a half-baked idea
> > > of what to try but now this leaves me without a clue
> > > as to what to do (I'm going to read up on the original
> > > algorithm.)
> > >
> > > Thanks,
> > >
> > > GaryRichard,
> > >
> > > OK, all that I've gotten so far out of the dump file is
> > > that the name of "_920" is just something sccvn concocted
> > > and wasn't something I accidentaly caused.
> > >
> > > That still leaves me with the question of what is going on.
> > >
> > > Here's all the interesting bits of the dumpfile concerning
> > > dedangled_864:
> > >
> > > :
> > > dedangled_865 = *bea_43 + 64
> > > dedangled_863 = *bea_43 + 128
> > > dedangled_864 = *bea_43 + 64
> > > dedangled_866 = *bea_43 + 128
> > > dedangled_867 = dedangled_863
> > > dedangled_867 = dedangled_865
> > > dedangled_868 = dedangled_864
> > > dedangled_868 = dedangled_866
> > > :
> > > Equivalence classes for indirect node id 160 "dedangled_865": pointer 84,
> > > location 0
> > > Equivalence classes for indirect node id 161 "dedangled_863": pointer 85,
> > > location 0
> > > Equivalence classes for indirect node id 162 "dedangled_864": pointer 86,
> > > location 0
> > > :
> > > dedangled_865 = { ESCAPED NONLOCAL }
> > > dedangled_863 = { ESCAPED NONLOCAL }
> > > dedangled_864 = { ESCAPED NONLOCAL }
> > > dedangled_866 = { ESCAPED NONLOCAL }
> > > dedangled_867 = { ESCAPED NONLOCAL }
> > > dedangled_868 = { ESCAPED NONLOCAL }
> > > :
> > > Value numbering store MEM[(int64_t *)&net + 608B] to _59
> > > Setting value number of .MEM_123 to .MEM_123 (changed)
> > > Value numbering stmt = dedangled_865 = bea_43->tail;
> > > Setting value number of dedangled_865 to dedangled_865 (changed)
> > > Making available beyond BB36 dedangled_865 for value dedangled_865
> > > Value numbering stmt = dedangled_863 = bea_43->head;
> > > Setting value number of dedangled_863 to dedangled_863 (changed)
> > > Making available beyond BB36 dedangled_863 for value dedangled_863
> > > Value numbering stmt = dedangled_864 = bea_43->tail;
> > > Inserting name _920 for expression (struct node.reorg.reorder *)
> > > dedangled_865
> > > Setting value number of dedangled_864 to _920 (changed)
> > > Making available beyond BB36 dedangled_864 for value _920
> > > Value numbering stmt = dedangled_866 = bea_43->head;
> > > :
> > > Value numbering stmt = dedangled_868 = PHI <dedangled_864(166),
> > > dedangled_866(37)>
> > > Setting value number of dedangled_868 to dedangled_868 (changed)
> > > :
> > > Setting value number of dedangled_363 to _920 (changed)
> > > dedangled_864 is available for _920
> > > Value numbering stmt = _896 = dedangled_363 == dedangled_873;
> > > dedangled_864 is available for _920
> > > (the last line repeats many times)
> > > :
> > > Value numbering stmt = _881 = dedangled_363 == dedangled_875;
> > > dedangled_864 is available for _920
> > > (the last line repeats many times)
> > > :
> > > Value numbering stmt = _880 = _881 & _891;
> > > dedangled_864 is available for _920
> > > dedangled_864 is available for _920
> > > dedangled_864 is available for _920
> > > dedangled_864 is available for _920
> > > :
> > > Setting value number of dedangled_313 to _920 (changed)
> > > dedangled_864 is available for _920
> > > Value numbering stmt = _904 = dedangled_313 == dedangled_873;
> > > dedangled_864 is available for _920
> > > (the last line repeats many times)
> > > :
> > > Value numbering stmt = _442 = _11 & _904;
> > > dedangled_864 is available for _920
> > > Match-and-simplified _11 & _904 to _904
> > > :
> > > Value numbering stmt = if (_442 != 0)
> > > dedangled_864 is available for _920
> > > :
> > > Making available beyond BB36 dedangled_863 for value dedangled_863
> > > Value numbering stmt = dedangled_864 = bea_43->tail;
> > > Setting value number of dedangled_864 to _920
> > > Making available beyond BB36 dedangled_864 for value _920
> > > Value numbering stmt = dedangled_866 = bea_43->head;
> > > :
> > > Making available beyond BB38 dedangled_867 for value dedangled_867
> > > Value numbering stmt = dedangled_868 = PHI <dedangled_864(166),
> > > dedangled_866(37)>
> > > Setting value number of dedangled_868 to dedangled_868
> > > :
> > > Setting value number of dedangled_363 to _920
> > > dedangled_864 is available for _920
> > > Value numbering stmt = _896 = dedangled_363 == dedangled_873;
> > > dedangled_864 is available for _920
> > > (the last line repeats many times)
> > > :
> > > Value numbering stmt = _881 = dedangled_363 == dedangled_875;
> > > dedangled_864 is available for _920
> > > (the last line repeats many times)
> > > :
> > > (a bunch more of the "dedangled_864 is available for _920")
> > > :
> > > exp_gen[36] := { red_cost_of_bea_42 (0019), bea_43 (0020),
> > > {mem_ref<608B>,addr_expr<&net>}@.MEM_99 (0027), {plus_expr,_58,1} (0028),
> > > {component_ref<tail>,mem_ref<0B>,bea_43}@.MEM_387 (0408),
> > > {component_ref<head>,mem_ref<0B>,bea_43}@.MEM_387 (0407) }
> > > phi_gen[36] := { }
> > > tmp_gen[36] := { _58 (0027), _59 (0028), dedangled_865 (0408),
> > > dedangled_863 (0407), dedangled_864 (0448), dedangled_866 (0229) }
> > > avail_out[36] := { xchange_449(D) (0232), arcs_1 (0003), stop_arcs_2
> > > (0004), _4 (0006), _5 (0007), i_646 (0340), _7 (0008), _8 (0009), _9
> > > (0010), i_10 (0011), _212 (0112), xchange_900 (0431), end_arc_385 (0180),
> > > _14 (0013), _19 (0015), field_arry_addr_112 (0045), i_665 (0352),
> > > next_666 (0353), _163 (0081), next_218 (0113), _173 (0083), _178 (0086),
> > > _179 (0087), _176 (0084), end_arc_443 (0226), end_arc_444 (0227),
> > > end_arc_445 (0228), _222 (0238), _223 (0115), _224 (0116), _225 (0117),
> > > _226 (0118), _227 (0119), _228 (0120), _229 (0121), _231 (0123), _21
> > > (0016), red_cost_of_bea_42 (0019), bea_43 (0020), i_649 (0343), _45
> > > (0021), _46 (0022), _47 (0023), _58 (0027), _59 (0028), dedangled_865
> > > (0408), dedangled_863 (0407), dedangled_864 (0448), dedangled_866 (0229) }
> > > exp_gen[37] := { }
> > > phi_gen[37] := { }
> > > tmp_gen[37] := { }
> > > avail_out[37] := { xchange_449(D) (0232), arcs_1 (0003), stop_arcs_2
> > > (0004), _4 (0006), _5 (0007), i_646 (0340), _7 (0008), _8 (0009), _9
> > > (0010), i_10 (0011), _212 (0112), xchange_900 (0431), end_arc_385 (0180),
> > > _14 (0013), _19 (0015), field_arry_addr_112 (0045), i_665 (0352),
> > > next_666 (0353), _163 (0081), next_218 (0113), _173 (0083), _178 (0086),
> > > _179 (0087), _176 (0084), end_arc_443 (0226), end_arc_444 (0227),
> > > end_arc_445 (0228), _222 (0238), _223 (0115), _224 (0116), _225 (0117),
> > > _226 (0118), _227 (0119), _228 (0120), _229 (0121), _231 (0123), _21
> > > (0016), red_cost_of_bea_42 (0019), bea_43 (0020), i_649 (0343), _45
> > > (0021), _46 (0022), _47 (0023), _58 (0027), _59 (0028), dedangled_865
> > > (0408), dedangled_863 (0407), dedangled_864 (0448), dedangled_866 (0229) }
> > > exp_gen[38] := { dedangled_867 (0409), dedangled_868 (0410) }
> > > phi_gen[38] := { dedangled_867 (0409), dedangled_868 (0410) }
> > > tmp_gen[38] := { }
> > > avail_out[38] := { xchange_449(D) (0232), arcs_1 (0003), stop_arcs_2
> > > (0004), _4 (0006), _5 (0007), i_646 (0340), _7 (0008), _8 (0009), _9
> > > (0010), i_10 (0011), _212 (0112), xchange_900 (0431), end_arc_385 (0180),
> > > _14 (0013), _19 (0015), field_arry_addr_112 (0045), i_665 (0352),
> > > next_666 (0353), _163 (0081), next_218 (0113), _173 (0083), _178 (0086),
> > > _179 (0087), _176 (0084), end_arc_443 (0226), end_arc_444 (0227),
> > > end_arc_445 (0228), _222 (0238), _223 (0115), _224 (0116), _225 (0117),
> > > _226 (0118), _227 (0119), _228 (0120), _229 (0121), _231 (0123), _21
> > > (0016), red_cost_of_bea_42 (0019), bea_43 (0020), i_649 (0343), _45
> > > (0021), _46 (0022), _47 (0023), _58 (0027), _59 (0028), dedangled_865
> > > (0408), dedangled_863 (0407), dedangled_864 (0448), dedangled_866 (0229),
> > > dedangled_867 (0409), dedangled_868 (0410) }
> > > (a presence in the avail_out for rest until it reaches a point where is
> > > in none of them)
> > > :
> > > ANTIC_OUT[166] := { {mem_ref<0B>,addr_expr<&opt>}@.MEM_104(D) (0112),
> > > bea_43 (0020), dedangled_863 (0407), dedangled_864 (0448) }
> > > [changed] ANTIC_IN[166] := { {mem_ref<0B>,addr_expr<&opt>}@.MEM_104(D)
> > > (0112), bea_43 (0020), dedangled_863 (0407), dedangled_864 (0448) }
> > > S[166] := { {mem_ref<0B>,addr_expr<&opt>}@.MEM_104(D) (0112), bea_43
> > > (0020), dedangled_863 (0407), dedangled_864 (0448) }
> > > :
> > > PA_OUT[36] := { stop_arcs_2 (0004), _4 (0006),
> > > {mem_ref<0B>,addr_expr<&opt>}@.MEM_104(D) (0112), xchange_900 (0431),
> > > {mem_ref<0B>,addr_expr<&opt_basket>}@.MEM_104(D) (0015),
> > > {mem_ref<0B>,addr_expr<&full_group_end_arc>}@.MEM_104(D) (0083),
> > > end_arc_445 (0228), {mem_ref<0B>,addr_expr<&perm_p>}@.MEM_104(D) (0016),
> > > red_cost_of_bea_42 (0019), bea_43 (0020), dedangled_865 (0408),
> > > dedangled_863 (0407), dedangled_864 (0448), dedangled_866 (0229),
> > > {mem_ref<616B>,addr_expr<&net>}@.MEM_99 (0442), {plus_expr,_913,1}
> > > (0438),
> > > {component_ref<orientation>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0258),
> > > {component_ref<flow>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0274),
> > > {component_ref<pred>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0265),
> > > {component_ref<depth>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0049),
> > > {component_ref<basic_arc>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0299), {component_ref<feas_tol>,mem_ref<0B>,addr_expr<&net>}@.MEM_387
> > > (0222), {abs_expr,red_cost_of_bea_42} (0134),
> > > {component_ref<potential>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0306),
> > > {component_ref<child>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0312),
> > > {component_ref<sibling>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0327),
> > > {component_ref<sibling_prev>,mem_ref<0B>,addr_expr<&_reorg_base_var_node.reorg.reorder>}@.MEM_387
> > > (0339), {pointer_plus_expr,field_arry_addr_581,-8} (0921),
> > > {bit_xor_expr,xchange_900,1} (0923),
> > > {pointer_plus_expr,field_arry_addr_591,-8} (0924),
> > > {pointer_plus_expr,field_arry_addr_601,-8} (0926) }
> > > :
> > > Replaced bea_43->tail with _975 in dedangled_864 = bea_43->tail;
> > > :
> > > long int pretmp_859;
> > > struct node * * field_addr_860;
> > > struct node * field_val_temp_861;
> > > unsigned long dedangled_863;
> > > unsigned long dedangled_864;
> > > unsigned long dedangled_865;
> > > unsigned long dedangled_866;
> > > :
> > > <bb 36> [local count: 4422246]:
> > > _58 = MEM[(int64_t *)&net + 608B];
> > > _59 = _58 + 1;
> > > MEM[(int64_t *)&net + 608B] = _59;
> > > dedangled_865 = bea_43->tail;
> > > dedangled_863 = bea_43->head;
> > > _975 = (struct node.reorg.reorder *) dedangled_865;
> > > dedangled_864 = bea_43->tail;
> > > dedangled_866 = bea_43->head;
> > > if (red_cost_of_bea_42 > 0)
> > > goto <bb 166>; [59.00%]
> > > else
> > > goto <bb 37>; [41.00%]
> > >
> > > <bb 166> [local count: 2609125]:
> > > goto <bb 38>; [100.00%]
> > >
> > > <bb 37> [local count: 1813121]:
> > >
> > > <bb 38> [local count: 4422246]:
> > > # dedangled_867 = PHI <dedangled_863(166), dedangled_865(37)>
> > > # dedangled_868 = PHI <dedangled_864(166), dedangled_866(37)>
> > > if (dedangled_867 != dedangled_868)
> > > goto <bb 126>; [89.00%]
> > > else
> > > goto <bb 55>; [11.00%]
> > > =================================================
> > > I was pretty arbitrary here about what I extracted from the
> > > dump file but it's 33MB in size.
> > >
> > > I'm still thinking it's something dumb that I did
> > > when I created "dedangled_864" but I can't spot it from
> > > the dump. Does anyone have any ideas? Note, before I
> > > looked at the dump I at least had a half-baked idea
> > > of what to try but now this leaves me without a clue
> > > as to what to do (I'm going to read up on the original
> > > algorithm.)
> > >
> > > Thanks,
> > >
> > > Gary
> > >
> > > ________________________________
> > > From: Richard Biener <richard.guent...@gmail.com>
> > > Sent: Thursday, July 22, 2021 5:18 AM
> > > To: Gary Oblock <g...@amperecomputing.com>
> > > Cc: gcc@gcc.gnu.org <gcc@gcc.gnu.org>
> > > Subject: Re: A value number issue
> > >
> > > [EXTERNAL EMAIL NOTICE: This email originated from an external sender.
> > > Please be mindful of safe email handling and proprietary information
> > > protection practices.]
> > >
> > >
> > > On Thu, Jul 22, 2021 at 8:06 AM Gary Oblock via Gcc <gcc@gcc.gnu.org>
> > > wrote:
> > > >
> > > > I seem to be having a problem with the pre pass.
> > > >
> > > > When eliminate_dom_walker::eliminate_stmt is called with
> > > > the gsi to "dedangled_864 = bea_43->tail;" which in turn
> > > > calls eliminate_dom_walker::eliminate_avail op of dedangled_864.
> > > > This gives VN_INFO (lhs)->valnum of _920. The _920 is not
> > > > associated with any SSA variable in the function and I don't
> > > > see how it got associated with dedangled_864. This is not
> > > > a theoretical issue because it causes an error (the gcc_unreachable
> > > > in eliminate_stmt is called.)
> > >
> > > But you show below the definition of _920 so I don't quite understand
> > > your question. You can follow VNs reasoning in the -details dump.
> > >
> > > >
> > > > Here is how _920 (in function main) is used.
> > > >
> > > > _920 = arcnew_916->head;
> > > > _921 = MEM[(struct node.reorg.reorder *)_920].firstin;
> > > > MEM[(struct node.reorg.reorder *)_920].firstin = arcnew_916;
> > > >
> > > > Here is how dedangled_864 is used:
> > > >
> > > > <bb 63> [local count: 2609125]:
> > > > dedangled_863 = bea_43->head;
> > > > dedangled_864 = bea_43->tail;
> > > > goto <bb 65>; [100.00%]
> > > >
> > > > <bb 64> [local count: 1813121]:
> > > > dedangled_865 = bea_43->tail;
> > > > dedangled_866 = bea_43->head;
> > > >
> > > > <bb 65> [local count: 4422246]:
> > > > # dedangled_867 = PHI <dedangled_863(63), dedangled_865(64)>
> > > > # dedangled_868 = PHI <dedangled_864(63), dedangled_866(64)>
> > > > delta_461 = 1;
> > > > goto <bb 82>; [100.00%]
> > > >
> > > > Note, dedangled_868 is used in an ever widening net of
> > > > phis and operations. Also, the other similar statements
> > > >
> > > > dedangled_863 = bea_43->head;
> > > > dedangled_865 = bea_43->tail;
> > > > dedangled_866 = bea_43->head;
> > > >
> > > > don't seem to be malformed.
> > > >
> > > > I tried using a watchpoint to see what was happening but that turned
> > > > out to be not productive in that it was tripping on something
> > > > unrelated even if I set it at the start of the pre pass.
> > > >
> > > > I'm assuming that some of my code is malformed in some
> > > > subtle way and I was wondering it anybody had any ideas?
> > > > I say subtle because this was all working on a slightly different
> > > > version of gcc without the code of some other Ampere optimizations
> > > > in the mix (I disabled those optimizations and things still failed.)
> > > >
> > > > Note, if you guys don't have any ideas the next approach is adding
> > > > tons of brute force instrumentation and special purpose sanity
> > > > checking to the value numbering routine... please help me avoid that.
> > > >
> > > > Thanks,
> > > >
> > > > Gary
> > > >
> > > >
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