[Bug middle-end/106495] New: [13 Regression] Build fails gcc/tree-ssa-threadbackward.cc:22: gcc/vec.h:890:19: error: array subscript 4294967294 is above array bounds of 'basic_block_def* [1]' [-Werror=array-bounds]

[Bug middle-end/106495] New: [13 Regression] Build fails gcc/tree-ssa-threadbackward.cc:22: gcc/vec.h:890:19: error: array subscript 4294967294 is above array bounds of 'basic_block_def* [1]' [-Werror=array-bounds]

[slyfox at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106495

            Bug ID: 106495
           Summary: [13 Regression] Build fails
                    gcc/tree-ssa-threadbackward.cc:22: gcc/vec.h:890:19:
                    error: array subscript 4294967294 is above array
                    bounds of 'basic_block_def* [1]'
                    [-Werror=array-bounds]
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: slyfox at gcc dot gnu.org
                CC: rguenth at gcc dot gnu.org
  Target Milestone: ---
              Host: i686-unknown-linux-gnu
            Target: i686-unknown-linux-gnu

This week's snapshot fails to build due to -Werror on i686-unknown-linux-gnu
as:

configure flags: --prefix=/<<NIX>>/gcc-13.0.0
--with-gmp-include=/<<NIX>>/gmp-with-cxx-stage3-6.2.1-dev/include
--with-gmp-lib=/<<NIX>>/gmp-with-cxx-stage3-6.2.1/lib
--with-mpfr-include=/<<NIX>>/mpfr-stage3-4.1.0-dev/include
--with-mpfr-lib=/<<NIX>>/mpfr-stage3-4.1.0/lib
--with-mpc=/<<NIX>>/libmpc-stage3-1.2.1 --with-libelf=/<<NIX>>/libelf-0.8.13
--with-native-system-header-dir=/<<NIX>>/glibc-2.35-163-dev/include
--with-build-sysroot=/ --program-prefix= --enable-lto --disable-libstdcxx-pch
--without-included-gettext --with-system-zlib --enable-static
--enable-languages=c\,c++ --disable-multilib --enable-plugin
--with-isl=/<<NIX>>/isl-stage3-0.20 --with-arch=i686
--build=i686-unknown-linux-gnu --host=i686-unknown-linux-gnu
--target=i686-unknown-linux-gnu

/build/build/./prev-gcc/xg++ -B/build/build/./prev-gcc/
-B/nix/store/n7mwmdj0lp1p5dih5irc2ibpzrbmdcaf-gcc-13.0.0/i686-unknown-linux-gnu/bin/
-nostdinc++ -B/build/build/prev-i686-unknown-linux-gnu/libstdc++-v3/src/.libs
-B/build/build/prev-i686-unknown-linux-gnu/libstdc++-v3/libsupc++/.libs 
-I/build/build/prev-i686-unknown-linux-gnu/libstdc++-v3/include/i686-unknown-linux-gnu
 -I/build/build/prev-i686-unknown-linux-gnu/libstdc++-v3/include 
-I/build/gcc-13-20220731/libstdc++-v3/libsupc++
-L/build/build/prev-i686-unknown-linux-gnu/libstdc++-v3/src/.libs
-L/build/build/prev-i686-unknown-linux-gnu/libstdc++-v3/libsupc++/.libs 
-fno-PIE -c   -O2
-I/nix/store/iwn78y2lccsmribf58z84nqkb6prsxg8-glibc-2.35-163-dev/include
-B/nix/store/p3w78y574wiwy8zg8mh3vg5mw4ddlqjh-glibc-2.35-163/lib/ -idirafter
/nix/store/iwn78y2lccsmribf58z84nqkb6prsxg8-glibc-2.35-163-dev/include
-idirafter
/nix/store/n5k6i1bs84fyb8p5191mzjzb89qd0h6s-bootstrap-tools/lib/gcc/i686-unknown-linux-gnu/8.3.0/include-fixed
-Wl,-rpath,/nix/store/sj99b1mb1wg0dq0aih6vnmn8flshzf5d-gcc-13.0.0-lib/lib
-Wl,-L/nix/store/p3w78y574wiwy8zg8mh3vg5mw4ddlqjh-glibc-2.35-163/lib -Wl,-rpath
-Wl,/nix/store/p3w78y574wiwy8zg8mh3vg5mw4ddlqjh-glibc-2.35-163/lib
-Wl,-dynamic-linker=/nix/store/p3w78y574wiwy8zg8mh3vg5mw4ddlqjh-glibc-2.35-163/lib/ld-linux.so.2
-fno-checking -gtoggle -DIN_GCC     -fno-exceptions -fno-rtti
-fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings
-Wcast-qual -Wmissing-format-attribute -Woverloaded-virtual -pedantic
-Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -Werror -fno-common
 -DHAVE_CONFIG_H -I. -I. -I../../gcc-13-20220731/gcc
-I../../gcc-13-20220731/gcc/. -I../../gcc-13-20220731/gcc/../include
-I../../gcc-13-20220731/gcc/../libcpp/include
-I../../gcc-13-20220731/gcc/../libcody
-I/nix/store/1iwmdhhdxyxv5dyaj61qb1vbyammbb7z-gmp-with-cxx-stage3-6.2.1-dev/include
-I/nix/store/py5l6yngaiw6zdz5rml85nxvxs32hs0x-mpfr-stage3-4.1.0-dev/include
-I/nix/store/bqrl2cd92fb6hnxfs9m1yrx1yxn2qydk-libmpc-stage3-1.2.1/include 
-I../../gcc-13-20220731/gcc/../libdecnumber
-I../../gcc-13-20220731/gcc/../libdecnumber/bid -I../libdecnumber
-I../../gcc-13-20220731/gcc/../libbacktrace
-I/nix/store/whk7v7bwhrmpgi3am9r8gmwl9k2h86m3-isl-stage3-0.20/include  -o
tree-ssa-threadbackward.o -MT tree-ssa-threadbackward.o -MMD -MP -MF
./.deps/tree-ssa-threadbackward.TPo
../../gcc-13-20220731/gcc/tree-ssa-threadbackward.cc

In file included from ../../gcc-13-20220731/gcc/hash-table.h:248,
                 from ../../gcc-13-20220731/gcc/coretypes.h:486,
                 from ../../gcc-13-20220731/gcc/tree-ssa-threadbackward.cc:22:
In member function 'T& vec<T, A, vl_embed>::operator[](unsigned int) [with T =
basic_block_def*; A = va_heap]',
    inlined from 'const T& vec<T>::operator[](unsigned int) const [with T =
basic_block_def*]' at ../../gcc-13-20220731/gcc/vec.h:1486:20,
    inlined from 'bool back_threader_profitability::profitable_path_p(const
vec<basic_block_def*>&, tree, edge, bool*)' at
../../gcc-13-20220731/gcc/tree-ssa-threadbackward.cc:781:37:
../../gcc-13-20220731/gcc/vec.h:890:19: error: array subscript 4294967294 is
above array bounds of 'basic_block_def* [1]' [-Werror=array-bounds]
  890 |   return m_vecdata[ix];
      |          ~~~~~~~~~^
../../gcc-13-20220731/gcc/vec.h: In member function 'bool
back_threader_profitability::profitable_path_p(const vec<basic_block_def*>&,
tree, edge, bool*)':
../../gcc-13-20220731/gcc/vec.h:635:5: note: while referencing
'vec<basic_block_def*, va_heap, vl_embed>::m_vecdata'
  635 |   T m_vecdata[1];
      |     ^~~~~~~~~
cc1plus: all warnings being treated as errors
make[3]: *** [Makefile:1146: tree-ssa-threadbackward.o] Error 1

Could be a side-effect of r13-1891 ?

[Bug middle-end/106495] [13 Regression] Build fails gcc/tree-ssa-threadbackward.cc:22: gcc/vec.h:890:19: error: array subscript 4294967294 is above array bounds of 'basic_block_def* [1]' [-Werror=array-bounds]

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106495

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |iains at gcc dot gnu.org

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 106496 has been marked as a duplicate of this bug. ***

[Bug middle-end/106495] [13 Regression] Build fails gcc/tree-ssa-threadbackward.cc:22: gcc/vec.h:890:19: error: array subscript 4294967294 is above array bounds of 'basic_block_def* [1]' [-Werror=array-bounds]

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106495

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2022-08-01
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED
   Target Milestone|---                         |13.0
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
I will have a looksee.

[Bug middle-end/106495] [13 Regression] Build fails gcc/tree-ssa-threadbackward.cc:22: gcc/vec.h:890:19: error: array subscript 4294967294 is above array bounds of 'basic_block_def* [1]' [-Werror=array-bounds]

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106495

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
OK, so it's indeed an isolated path we warn on:

<bb 111> [local count: 2735590]:
_46 = global_options.x_param_max_fsm_thread_path_insns;
if (_46 <= n_insns_157)
  goto <bb 113>; [34.00%]
else
  goto <bb 116>; [66.00%]

<bb 116> [local count: 1805491]:
n_insns_346 = ASSERT_EXPR <n_insns_157, n_insns_157 < _46>;
_233 = m_path_340->m_vec;
if (_233 != 0B)
  goto <bb 119>; [70.00%]
else
  goto <bb 175>; [30.00%]

<bb 175> [local count: 541647]:
_379 = ASSERT_EXPR <_233, _233 == 0B>;

<bb 117> [local count: 541647]:
_286 = MEM[(struct vec *)0B].m_vecpfx.m_num;
_381 = ASSERT_EXPR <0B, 0B != 0B>;
if (_286 != 4294967295)
  goto <bb 120>; [0.00%]
else
  goto <bb 118>; [100.00%]

<bb 118> [local count: 541647]:
_391 = ASSERT_EXPR <4294967294, 4294967294 < _286>;
_290 = MEM <struct vec> [(struct basic_block_def * const
&)_381].m_vecdata[4294967294];
goto <bb 122>; [100.00%]

[Bug middle-end/106495] [13 Regression] Build fails gcc/tree-ssa-threadbackward.cc:22: gcc/vec.h:890:19: error: array subscript 4294967294 is above array bounds of 'basic_block_def* [1]' [-Werror=array-bounds]

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106495

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
  if (_233 != 0B)
    goto <bb 113>; [70.00%]
  else
    goto <bb 111>; [30.00%]
;;    succ:       113 [70.0% (guessed)]  count:1263844 (estimated locally)
(TRUE_VALUE,EXECUTABLE)
;;                111 [30.0% (guessed)]  count:541647 (estimated locally)
(FALSE_VALUE,EXECUTABLE)

;;   basic block 111, loop depth 0, count 541647 (estimated locally), maybe hot
;;    prev block 110, next block 112, flags: (NEW, REACHABLE, VISITED)
;;    pred:       110 [30.0% (guessed)]  count:541647 (estimated locally)
(FALSE_VALUE,EXECUTABLE)
  _286 = MEM[(struct vec *)0B].m_vecpfx.m_num;

so a NULL pointer check is not enough to make the NULL case cold.

threadfull1 exposes the path, vrp1 warns on it (it seems VRP1 at least no
longer performs any threading itself).

Before threadfull1 we have

;;   basic block 114, loop depth 0, count 1805491 (estimated locally), maybe
hot
;;    prev block 112, next block 115, flags: (NEW, REACHABLE, VISITED)
;;    pred:       108 [66.0% (guessed)]  count:1805489 (estimated locally)
(FALSE_VALUE,EXECUTABLE)
  _233 = m_path_142(D)->m_vec;
  if (_233 != 0B)
    goto <bb 115>; [70.00%]
  else
    goto <bb 116>; [30.00%]
;;    succ:       115 [70.0% (guessed)]  count:1263844 (estimated locally)
(TRUE_VALUE,EXECUTABLE)
;;                116 [30.0% (guessed)]  count:541647 (estimated locally)
(FALSE_VALUE,EXECUTABLE)

;;   basic block 115, loop depth 0, count 1263844 (estimated locally), maybe
hot
;;    prev block 114, next block 116, flags: (NEW, REACHABLE, VISITED)
;;    pred:       114 [70.0% (guessed)]  count:1263844 (estimated locally)
(TRUE_VALUE,EXECUTABLE)
  _234 = MEM[(const struct vec *)_233].m_vecpfx.m_num;
;;    succ:       116 [always]  count:1263844 (estimated locally)
(FALLTHRU,EXECUTABLE)

;;   basic block 116, loop depth 0, count 1805491 (estimated locally), maybe
hot
;;    prev block 115, next block 117, flags: (NEW, REACHABLE, VISITED)
;;    pred:       114 [30.0% (guessed)]  count:541647 (estimated locally)
(FALSE_VALUE,EXECUTABLE)
;;                115 [always]  count:1263844 (estimated locally)
(FALLTHRU,EXECUTABLE)
  # iftmp.22_235 = PHI <0(114), _234(115)>
  _51 = iftmp.22_235 + 4294967294;
  _232 = _233->m_vecpfx.m_num;
  if (_51 >= _232)
    goto <bb 117>; [0.00%]
  else
    goto <bb 118>; [100.00%]
;;    succ:       117 [never]  count:0 (precise) (TRUE_VALUE,EXECUTABLE)
;;                118 [always]  count:1805491 (estimated locally)
(FALSE_VALUE,EXECUTABLE)

;;   basic block 117, loop depth 0, count 0 (precise), probably never executed
;;    prev block 116, next block 118, flags: (NEW, REACHABLE, VISITED)
;;    pred:       116 [never]  count:0 (precise) (TRUE_VALUE,EXECUTABLE)
  vec<basic_block_def*, va_heap,
vl_embed>::_ZN3vecIP15basic_block_def7va_heap8vl_embedEixEj.part.0 ();
;;    succ:

;;   basic block 118, loop depth 0, count 1805491 (estimated locally), maybe
hot
;;    prev block 117, next block 119, flags: (NEW, REACHABLE, VISITED)
;;    pred:       116 [always]  count:1805491 (estimated locally)
(FALSE_VALUE,EXECUTABLE)
  _52 = MEM <struct vec> [(struct basic_block_def * const
&)_233].m_vecdata[_51];

I can't see from the dumps what threadfull1 does but I think it must somehow
just key on

  # iftmp.22_235 = PHI <0(114), _234(115)>
  _51 = iftmp.22_235 + 4294967294;
  _232 = _233->m_vecpfx.m_num;
  if (_51 >= _232)
    goto <bb 117>; [0.00%]

simplifying 4294967294 >= _232 on the edge from 114?  But maybe the
wrong-doing already starts earlier, but disabling ethread doesn't hide the
diagnostic.

[Bug middle-end/106495] [13 Regression] Build fails gcc/tree-ssa-threadbackward.cc:22: gcc/vec.h:890:19: error: array subscript 4294967294 is above array bounds of 'basic_block_def* [1]' [-Werror=array-bounds]

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106495

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 53395
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53395&action=edit
preprocessed source, trimmed at tail

preprocessed source for i686-pc-linux-gnu, reproduce with

./cc1plus -fpreprocessed tree-ssa-threadbackward.ii -quiet -dumpbase
tree-ssa-threadbackward.cc -dumpbase-ext .cc -mtune=generic -march=pentiumpro
-g -gtoggle -O2 -Wextra -Wall -Wno-narrowing -Wwrite-strings -Wcast-qual
-Wsuggest-attribute=format -Woverloaded-virtual=2 -Wpedantic -Wno-long-long
-Wno-variadic-macros -Wno-overlength-strings -Werror -version -fno-PIE
-fno-checking -fno-exceptions -fno-rtti -fasynchronous-unwind-tables
-fno-common -o tree-ssa-threadbackward.s

[Bug middle-end/106495] [13 Regression] Build fails gcc/tree-ssa-threadbackward.cc:22: gcc/vec.h:890:19: error: array subscript 4294967294 is above array bounds of 'basic_block_def* [1]' [-Werror=array-bounds]

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106495

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #53395|0                           |1
        is obsolete|                            |

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 53396
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53396&action=edit
more reduced profitable_path_p

More reduced, the actual function is now simply

bool
back_threader_profitability::profitable_path_p (const vec<basic_block> &m_path,
      tree ,
      edge ,
      bool *)
{
  if (m_path.length () <= 1)
      return false;

  gimple *stmt = get_gimple_control_stmt (m_path[0]);
  estimate_num_insns (stmt, &eni_size_weights);

  edge entry = find_edge (m_path[m_path.length () - 1],
                          m_path[m_path.length () - 2]);
  if (probably_never_executed_edge_p ((cfun + 0), entry))
    return false;
  return true;
}

[Bug middle-end/106495] [13 Regression] Build fails gcc/tree-ssa-threadbackward.cc:22: gcc/vec.h:890:19: error: array subscript 4294967294 is above array bounds of 'basic_block_def* [1]' [-Werror=array-bounds]

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106495

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aldyh at gcc dot gnu.org

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
So in this case we have

(gdb) p *path->m_vec->m_vecdata[0]
$106 = {e = <edge 0xf4819a40 (5 -> 7)>, type = EDGE_COPY_SRC_BLOCK}
(gdb) p *path->m_vec->m_vecdata[1]
$107 = {e = <edge 0xf48199a0 (7 -> 9)>, type = EDGE_COPY_SRC_BLOCK}
(gdb) p *path->m_vec->m_vecdata[2]
$108 = {e = <edge 0xf48197e0 (9 -> 10)>, type = EDGE_NO_COPY_SRC_BLOCK}

and the last edge (9 -> 10) is known to be never executed:

<bb 9> [local count: 435262723]:
_3 = MEM <struct vec> [(struct basic_block_def * const &)_21].m_vecdata[_2];
_4 = iftmp.22_23 + 4294967295;
if (_4 >= _20)
  goto <bb 10>; [0.00%]

we've isolated a quite "unlikely" combo here.  We could go for generalizing
the earlier patch, disqualifying the path if any of the edges involved.

Note that profitable_path_p only gets to see 5->7->9, strangely not the
final ->10?  It look like only maybe_register_path () via find_taken_edge
will ask profitable_path_p _again_ (but with taken_edge now set)!?

So the "cheapest" way to tackle this particular case is look at taken_edge
in profitable_path_p.

[Bug middle-end/106495] [13 Regression] Build fails gcc/tree-ssa-threadbackward.cc:22: gcc/vec.h:890:19: error: array subscript 4294967294 is above array bounds of 'basic_block_def* [1]' [-Werror=array-bounds]

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106495

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 53397
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53397&action=edit
patch

I'm testing this.

[Bug middle-end/106495] [13 Regression] Build fails gcc/tree-ssa-threadbackward.cc:22: gcc/vec.h:890:19: error: array subscript 4294967294 is above array bounds of 'basic_block_def* [1]' [-Werror=array-bounds]

[aldyh at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106495

--- Comment #9 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #7)
> So in this case we have
> 
> (gdb) p *path->m_vec->m_vecdata[0]
> $106 = {e = <edge 0xf4819a40 (5 -> 7)>, type = EDGE_COPY_SRC_BLOCK}
> (gdb) p *path->m_vec->m_vecdata[1]
> $107 = {e = <edge 0xf48199a0 (7 -> 9)>, type = EDGE_COPY_SRC_BLOCK}
> (gdb) p *path->m_vec->m_vecdata[2]
> $108 = {e = <edge 0xf48197e0 (9 -> 10)>, type = EDGE_NO_COPY_SRC_BLOCK}
> 
> and the last edge (9 -> 10) is known to be never executed:
> 
> <bb 9> [local count: 435262723]:
> _3 = MEM <struct vec> [(struct basic_block_def * const &)_21].m_vecdata[_2];
> _4 = iftmp.22_23 + 4294967295;
> if (_4 >= _20)
>   goto <bb 10>; [0.00%]
> 
> we've isolated a quite "unlikely" combo here.  We could go for generalizing
> the earlier patch, disqualifying the path if any of the edges involved.
> 
> Note that profitable_path_p only gets to see 5->7->9, strangely not the
> final ->10?  It look like only maybe_register_path () via find_taken_edge
> will ask profitable_path_p _again_ (but with taken_edge now set)!?

profitable_path_p gets called during path discovery (find_paths_to_names), so
we don't have complete info.  The idea is that if a path so far is
unprofitable, no sense looking further in that particular direction.  In
reality Jeff and I ran into a testcase where a partial path was not profitable,
but a path with some extra blocks was.  There's a PR somewhere for it, but it
happened so infrequent, that this heuristic was good enough.

> 
> So the "cheapest" way to tackle this particular case is look at taken_edge
> in profitable_path_p.

I would've prefered putting everything in your previous patch, since it would
be shared between both threaders, though I suppose the forward threader is
slowly dying ;-).

[Bug middle-end/106495] [13 Regression] Build fails gcc/tree-ssa-threadbackward.cc:22: gcc/vec.h:890:19: error: array subscript 4294967294 is above array bounds of 'basic_block_def* [1]' [-Werror=array-bounds]

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106495

--- Comment #10 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:b9da686470d1c23929eefb401280ad8ba17e2a58

commit r13-1924-gb9da686470d1c23929eefb401280ad8ba17e2a58
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Aug 1 14:59:08 2022 +0200

    tree-optimization/106495 - avoid threading to possibly never executed edge

    The following builds upon the logic of the PR105679 fix by avoiding
    to thread to a known edge that is predicted as probably never executed.

            PR tree-optimization/106495
            * tree-ssa-threadbackward.cc
            (back_threader_profitability::profitable_path_p): If known_edge
            is probably never executed avoid threading.

[Bug middle-end/106495] [13 Regression] Build fails gcc/tree-ssa-threadbackward.cc:22: gcc/vec.h:890:19: error: array subscript 4294967294 is above array bounds of 'basic_block_def* [1]' [-Werror=array-bounds]

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106495

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #11 from Richard Biener <rguenth at gcc dot gnu.org> ---
Should be fixed.