[Bug target/105549] aarch64: Wrong va_arg alignment handling with packed bitfields and alignment

cvs-commit at gcc dot gnu.org gcc-bugzilla@gcc.gnu.org
Wed Jan 25 14:28:07 GMT 2023


--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Christophe Lyon


commit r12-9067-gf593bfa059fbd2c145d8dd2bae4860959e9e55fe
Author: Christophe Lyon <christophe.lyon@arm.com>
Date:   Tue Jun 14 21:08:33 2022 +0000

    aarch64: fix warning emission for ABI break since GCC 9.1

    While looking at PR 105549, which is about fixing the ABI break
    introduced in GCC 9.1 in parameter alignment with bit-fields, we
    noticed that the GCC 9.1 warning is not emitted in all the cases where
    it should be.  This patch fixes that and the next patch in the series
    fixes the GCC 9.1 break.

    We split this into two patches since patch #2 introduces a new ABI
    break starting with GCC 13.1.  This way, patch #1 can be back-ported
    to release branches if needed to fix the GCC 9.1 warning issue.

    The main idea is to add a new global boolean that indicates whether
    we're expanding the start of a function, so that aarch64_layout_arg
    can emit warnings for callees as well as callers.  This removes the
    need for aarch64_function_arg_boundary to warn (with its incomplete
    information).  However, in the first patch there are still cases where
    we emit warnings were we should not; this is fixed in patch #2 where
    we can distinguish between GCC 9.1 and GCC.13.1 ABI breaks properly.

    The fix in aarch64_function_arg_boundary (replacing & with &&) looks
    like an oversight of a previous commit in this area which changed
    'abi_break' from a boolean to an integer.

    We also take the opportunity to fix the comment above
    aarch64_function_arg_alignment since the value of the abi_break
    parameter was changed in a previous commit, no longer matching the

    2022-11-28  Christophe Lyon  <christophe.lyon@arm.com>
                Richard Sandiford  <richard.sandiford@arm.com>


            * config/aarch64/aarch64.cc (aarch64_function_arg_alignment): Fix
            (aarch64_layout_arg): Factorize warning conditions.
            (aarch64_function_arg_boundary): Fix typo.
            * function.cc (currently_expanding_function_start): New variable.
            (expand_function_start): Handle
            * function.h (currently_expanding_function_start): Declare.


            * gcc.target/aarch64/bitfield-abi-warning-align16-O2.c: New test.
            * gcc.target/aarch64/bitfield-abi-warning-align16-O2-extra.c: New
            * gcc.target/aarch64/bitfield-abi-warning-align32-O2.c: New test.
            * gcc.target/aarch64/bitfield-abi-warning-align32-O2-extra.c: New
            * gcc.target/aarch64/bitfield-abi-warning-align8-O2.c: New test.
            * gcc.target/aarch64/bitfield-abi-warning.h: New test.
            * g++.target/aarch64/bitfield-abi-warning-align16-O2.C: New test.
            * g++.target/aarch64/bitfield-abi-warning-align16-O2-extra.C: New
            * g++.target/aarch64/bitfield-abi-warning-align32-O2.C: New test.
            * g++.target/aarch64/bitfield-abi-warning-align32-O2-extra.C: New
            * g++.target/aarch64/bitfield-abi-warning-align8-O2.C: New test.
            * g++.target/aarch64/bitfield-abi-warning.h: New test.

    (cherry picked from commit 3df1a115be22caeab3ffe7afb12e71adb54ff132)

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