[Bug rtl-optimization/7061] Access of bytes in struct parameters

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=7061

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Roger Sayle <sayle@gcc.gnu.org>:

https://gcc.gnu.org/g:1ad584d538d349db13cfa8440222d91d5e9aff3f

commit r13-859-g1ad584d538d349db13cfa8440222d91d5e9aff3f
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Mon May 30 21:32:58 2022 +0100

    Allow SCmode and DImode to be tieable with TARGET_64BIT on x86_64.

    This patch is a form of insurance policy in case my patch for PR 7061 runs
    into problems on non-x86 targets; the middle-end can add an extra check
    that the backend is happy placing SCmode and DImode values in the same
    register, before creating a SUBREG.  Unfortunately, ix86_modes_tieable_p
    currently claims this is not allowed(?), even though the default target
    hook for modes_tieable_p is to always return true [i.e. false can be
    used to specifically prohibit bad combinations], and the x86_64 ABI
    passes SCmode values in DImode registers!.  This makes the backend's
    modes_tiable_p hook a little more forgiving, and additionally enables
    interconversion between SCmode and V2SFmode, and between DCmode and
    VD2Fmode, which opens interesting opporutunities in the future.

    2022-05-30  Roger Sayle  <roger@nextmovesoftware.com>

    gcc/ChangeLog
            * config/i386/i386.cc (ix86_modes_tieable_p): Allow SCmode to be
            tieable with DImode on TARGET_64BIT, and SCmode tieable with
            V2SFmode, and DCmode with V2DFmode.