[Bug jit/95314] New: Sharing a local reference to a global variable in multiple functions results in location references block not in block tree

[Bug jit/95314] New: Sharing a local reference to a global variable in multiple functions results in location references block not in block tree

[bouanto at zoho dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95314

            Bug ID: 95314
           Summary: Sharing a local reference to a global variable in
                    multiple functions results in location references
                    block not in block tree
           Product: gcc
           Version: 10.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: jit
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: bouanto at zoho dot com
  Target Milestone: ---

Hi.
If a create, in a function, a reference (with gcc_jit_lvalue_get_address) to a
global and reuse this local reference in another function, it gives the
following error:

libgccjit.so: error: location references block not in block tree
…
during IPA pass: *free_lang_data
libgccjit.so: error: verify_gimple failed
0x7f83924b35c9 verify_gimple_in_cfg(function*, bool)
        ../../gcc-10.1.0/gcc/tree-cfg.c:5462
0x7f839236a819 execute_function_todo
        ../../gcc-10.1.0/gcc/passes.c:1985
0x7f839236add7 do_per_function
        ../../gcc-10.1.0/gcc/passes.c:1647
0x7f839236b06b do_per_function
        ../../gcc-10.1.0/gcc/passes.c:2050
0x7f839236b06b execute_todo
        ../../gcc-10.1.0/gcc/passes.c:2039

I can try to make an example to reproduce this issue if needed.

Is that the expected behavior or should libgccjit gives a proper error?

(Recreating the reference in every function fix this issue.)

Thanks.

[Bug jit/95314] Sharing a local reference to a global variable in multiple functions results in location references block not in block tree

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95314

--- Comment #1 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Thanks for reporting it; this sounds like a bug.

Please can you use attach a reproducer (e.g. using
gcc_jit_context_dump_reproducer_to_file).

Looking at the backtrace, it looks like a bad interaction with inlining, FWIW.

[Bug jit/95314] Sharing a local reference to a global variable in multiple functions results in location references block not in block tree

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95314

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

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

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Generally, most of the trees (with some exceptions) aren't shareable and
shouldn't be used by multiple different functions.  During gimplifications the
function body is unshared, but not sure what the JIT FE does exactly.

[Bug jit/95314] Sharing a local reference to a global variable in multiple functions results in location references block not in block tree

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95314

--- Comment #3 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Thanks Jakub, that sounds like the problem: I'm creating a tree per
playback::rvalue (m_inner), and I need to unshare them.

[Bug jit/95314] Sharing a local reference to a global variable in multiple functions results in location references block not in block tree

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95314

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
unshare_expr can handle that.

[Bug jit/95314] Sharing a local reference to a global variable in multiple functions results in location references block not in block tree

[bouanto at zoho dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95314

--- Comment #5 from bouanto at zoho dot com ---
The reproducer generates a file where the function create_code only contains
this:

  /* Replay of API calls for ctxt_0x7f8079128680.  */

So, no code is actually generated and thus, does not reproduce this issue.

[Bug jit/95314] Sharing a local reference to a global variable in multiple functions results in location references block not in block tree

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95314

--- Comment #6 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Sorry about that; thanks for trying.  I think I can figure out a reproducer,
and will try tomorrow.

[Bug jit/95314] Sharing a local reference to a global variable in multiple functions results in location references block not in block tree

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95314

--- Comment #7 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Created attachment 48615
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48615&action=edit
Non-reproducing attempt at a reproducer

I attempted to reproduce this, but was unsuccessful.  I'm attaching what I have
so far (for gcc/testsuite/jit.dg), but annoyingly this runs successfully.

[Bug jit/95314] Sharing a local reference to a global variable in multiple functions results in location references block not in block tree

[bouanto at zoho dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95314

--- Comment #8 from bouanto at zoho dot com ---
Created attachment 48617
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48617&action=edit
Small example to reproduce the bug

[Bug jit/95314] Sharing a local reference to a global variable in multiple functions results in location references block not in block tree

[bouanto at zoho dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95314

--- Comment #9 from bouanto at zoho dot com ---
Actually, it seems I was wrong on the conditions to reproduce this issue.
I managed to create a small example to reproduce the issue.
I attached it to the bug report.

[Bug jit/95314] Sharing a local reference to a global variable in multiple functions results in location references block not in block tree

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95314

David Malcolm <dmalcolm at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2020-05-27

--- Comment #10 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Thanks; I'm seeing the crash with your reproducer.

[Bug jit/95314] Sharing a local reference to a global variable in multiple functions results in location references block not in block tree

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95314

--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by David Malcolm <dmalcolm@gcc.gnu.org>:

https://gcc.gnu.org/g:c98bd673ef93836f03491201f1c63929ea429cd6

commit r11-668-gc98bd673ef93836f03491201f1c63929ea429cd6
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Wed May 27 09:44:07 2020 -0400

    jit: use deep unsharing of trees [PR 95314]

    PR jit/95314 reports a internal error inside verify_gimple, which
    turned out to be due to reusing the result of
    gcc_jit_lvalue_get_address in several functions, leading to tree nodes
    shared between multiple function bodies.

    This patch fixes the issue by adopting the "Deep unsharing" strategy
    described in the comment in gimplify.c preceding mostly_copy_tree_r:
    to mark all of the jit "frontend"'s expression tree nodes with
    TREE_VISITED, and to set LANG_HOOKS_DEEP_UNSHARING, so that "they are
    unshared on the first reference within functions when the regular
    unsharing algorithm runs".

    gcc/jit/ChangeLog:
            PR jit/95314
            * dummy-frontend.c (LANG_HOOKS_DEEP_UNSHARING): Define to be true.
            * jit-playback.h (gcc::jit::playback::rvalue): Mark tree node with
            TREE_VISITED.

    gcc/testsuite/ChangeLog:
            PR jit/95314
            * jit.dg/all-non-failing-tests.h: Add test-pr95314-rvalue-reuse.c.
            * jit.dg/test-pr95314-rvalue-reuse.c: New test.

[Bug jit/95314] Sharing a local reference to a global variable in multiple functions results in location references block not in block tree

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95314

David Malcolm <dmalcolm at gcc dot gnu.org> changed:

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

--- Comment #12 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Should be fixed by the above commit.