A value number issue
Gary Oblock
gary@amperecomputing.com
Thu Jul 29 07:29:55 GMT 2021
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... ;-(
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?
Thanks, I really appreciate your help even though in this case
I'm still kind of stuck.
Gary
________________________________
From: Richard Biener <richard.guenther@gmail.com>
Sent: Thursday, July 29, 2021 12:12 AM
To: Gary Oblock <gary@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 <gary@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.guenther@gmail.com>
> Sent: Wednesday, July 28, 2021 3:40 AM
> To: Gary Oblock <gary@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 <gary@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.guenther@gmail.com>
> > Sent: Thursday, July 22, 2021 5:18 AM
> > To: Gary Oblock <gary@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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