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Subject: [Bug target/94177] TLS global-dynamic model clobbers function
 parameter on AIX
Date: Fri, 28 May 2021 20:49:24 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94177

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by David Edelsohn
<dje@gcc.gnu.org>:

https://gcc.gnu.org/g:0be51abf080f1d7515e3777dd5e5a983b47573a8

commit r11-8481-g0be51abf080f1d7515e3777dd5e5a983b47573a8
Author: David Edelsohn <dje.gcc@gmail.com>
Date:   Fri Apr 30 14:27:46 2021 -0400

    aix: TLS precompute register parameters (PR 94177)

    AIX uses a compiler-managed TOC for global data, including TLS symbols.
    The GCC TOC implementation manages the TOC entries through the constant
pool.

    TLS symbols sometimes require a function call to obtain the TLS base
    pointer.  The arguments to the TLS call can conflict with arguments to
    a normal function call if the TLS symbol is an argument in the normal c=
all.
    GCC specifically checks for this situation and precomputes the TLS
    arguments, but the mechanism to check for this requirement utilizes
    legitimate_constant_p().  The necessary result of legitimate_constant_p=
()
    for correct TOC behavior and for correct TLS argument behavior is in
    conflict.

    This patch adds a new target hook precompute_tls_p() to decide if an
    argument should be precomputed regardless of the result from
    legitmate_constant_p().

    gcc/ChangeLog:

            PR target/94177
            * calls.c (precompute_register_parameters): Additionally test
            targetm.precompute_tls_p to pre-compute argument.
            * config/rs6000/aix.h (TARGET_PRECOMPUTE_TLS_P): Define.
            * config/rs6000/rs6000.c (rs6000_aix_precompute_tls_p): New.
            * target.def (precompute_tls_p): New.
            * doc/tm.texi.in (TARGET_PRECOMPUTE_TLS_P): Add hook documentat=
ion.
            * doc/tm.texi: Regenerated.

            (cherry-picked from commit
a21b399708175f6fc0ac723a0cebc127da421c60)=