[Bug target/94177] TLS global-dynamic model clobbers function parameter on AIX

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94177

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by David Edelsohn <dje@gcc.gnu.org>:

https://gcc.gnu.org/g:a21b399708175f6fc0ac723a0cebc127da421c60

commit r12-165-ga21b399708175f6fc0ac723a0cebc127da421c60
Author: David Edelsohn <dje.gcc@gmail.com>
Date:   Sun Apr 11 19:41:26 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 call.
    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 documentation.
            * doc/tm.texi: Regenerated.