[Bug middle-end/99619] New: fails to infer local-dynamic TLS model from hidden visibility

[Bug middle-end/99619] New: fails to infer local-dynamic TLS model from hidden visibility

[amonakov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99619

            Bug ID: 99619
           Summary: fails to infer local-dynamic TLS model from hidden
                    visibility
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amonakov at gcc dot gnu.org
  Target Milestone: ---

Thread-local variables with hidden visibility don't need to use the
"general-dynamic" TLS model: they can use "local-dynamic" model, which is more
efficient when more than one variable is accessed. This is documented in "ELF
handling for thread-local storage".

Testcase:

__attribute__((visibility("hidden")))
extern __thread int a, b;

int f()
{
    return a + b;
}

clang -O2 -fpic emits:
f:
        .cfi_startproc
        push    rax
        .cfi_def_cfa_offset 16
        lea     rdi, [rip + a@TLSLD]
        call    __tls_get_addr@PLT
        mov     rcx, rax
        mov     eax, dword ptr [rax + b@DTPOFF]
        add     eax, dword ptr [rcx + a@DTPOFF]
        pop     rcx
        .cfi_def_cfa_offset 8
        ret

gcc -O2 -fpic emits:
f:
        .cfi_startproc
        push    rbx
        .cfi_def_cfa_offset 16
        .cfi_offset 3, -16
        data16  lea rdi, a@tlsgd[rip]
        .value  0x6666
        rex64
        call    __tls_get_addr@PLT
        mov     rbx, rax
        data16  lea rdi, b@tlsgd[rip]
        .value  0x6666
        rex64
        call    __tls_get_addr@PLT
        mov     eax, DWORD PTR [rax]
        add     eax, DWORD PTR [rbx]
        pop     rbx
        .cfi_def_cfa_offset 8
        ret

[Bug middle-end/99619] fails to infer local-dynamic TLS model from hidden visibility

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99619

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement

[Bug middle-end/99619] fails to infer local-dynamic TLS model from hidden visibility

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99619

--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Alexander Monakov <amonakov@gcc.gnu.org>:

https://gcc.gnu.org/g:1d561e1851c466a4952081caef17747781609b00

commit r13-3416-g1d561e1851c466a4952081caef17747781609b00
Author: Artem Klimov <jakmobius@gmail.com>
Date:   Wed Jul 6 17:02:01 2022 +0300

    ipa-visibility: Optimize TLS access [PR99619]

    Fix PR99619, which asks to optimize TLS model based on visibility.
    The fix is implemented as an IPA optimization: this allows to take
    optimized visibility status into account (as well as avoid modifying
    all language frontends).

    2022-04-17  Artem Klimov  <jakmobius@gmail.com>

    gcc/ChangeLog:

            PR middle-end/99619
            * ipa-visibility.cc (function_and_variable_visibility): Promote
            TLS access model afer visibility optimizations.
            * varasm.cc (have_optimized_refs): New helper.
            (optimize_dyn_tls_for_decl_p): New helper. Use it ...
            (decl_default_tls_model): ... here in place of 'optimize' check.

    gcc/testsuite/ChangeLog:

            PR middle-end/99619
            * gcc.dg/tls/vis-attr-gd.c: New test.
            * gcc.dg/tls/vis-attr-hidden-gd.c: New test.
            * gcc.dg/tls/vis-attr-hidden.c: New test.
            * gcc.dg/tls/vis-flag-hidden-gd.c: New test.
            * gcc.dg/tls/vis-flag-hidden.c: New test.
            * gcc.dg/tls/vis-pragma-hidden-gd.c: New test.
            * gcc.dg/tls/vis-pragma-hidden.c: New test.

    Co-Authored-By:  Alexander Monakov  <amonakov@gcc.gnu.org>
    Signed-off-by: Artem Klimov <jakmobius@gmail.com>

[Bug middle-end/99619] fails to infer local-dynamic TLS model from hidden visibility

[amonakov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99619

Alexander Monakov <amonakov at gcc dot gnu.org> changed:

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

--- Comment #2 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
Fixed for gcc-13.