On Wed, Jun 17, 2026 at 6:03 AM Alfie Richards <[email protected]> wrote:
>
>
> Hi All,
>
> This is a fix for preserve_none to make it fall back to AAPCS when there are
> variadic arguments.
>
> This aligns it with the ABI clang uses and defacto defines.
>
> Reg tested and bootstrapped for aarch64-linux-gnu.
>
> Okay for master and later backbort to GCC 16?
Yes and Yes.
>
> KR,
> Alfie
>
> -- >8 --
>
> PR target/125838
>
> gcc/ChangeLog:
>
> * config/aarch64/aarch64.cc (aarch64_fntype_abi): Fall back to
> AAPCS for preserve_none variadic calls.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/aarch64/preserve_none_5.c: Update to use AAPCS.
> ---
> gcc/config/aarch64/aarch64.cc | 4 +-
> .../gcc.target/aarch64/preserve_none_5.c | 64 ++++++++++++-------
> 2 files changed, 43 insertions(+), 25 deletions(-)
>
> diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
> index 42e56512c61..b6c464ebc9b 100644
> --- a/gcc/config/aarch64/aarch64.cc
> +++ b/gcc/config/aarch64/aarch64.cc
> @@ -2591,7 +2591,9 @@ aarch64_fntype_abi (const_tree fntype)
> if (lookup_attribute ("aarch64_vector_pcs", TYPE_ATTRIBUTES (fntype)))
> return aarch64_simd_abi ();
>
> - if (lookup_attribute ("preserve_none", TYPE_ATTRIBUTES (fntype)))
> + /* Fall back to AAPCS for variadic functions. */
> + if (lookup_attribute ("preserve_none", TYPE_ATTRIBUTES (fntype))
> + && !stdarg_p (fntype))
> return aarch64_preserve_none_abi ();
>
> if (aarch64_returns_value_in_sve_regs_p (fntype)
> diff --git a/gcc/testsuite/gcc.target/aarch64/preserve_none_5.c
> b/gcc/testsuite/gcc.target/aarch64/preserve_none_5.c
> index d11bf10a898..80bd949a893 100644
> --- a/gcc/testsuite/gcc.target/aarch64/preserve_none_5.c
> +++ b/gcc/testsuite/gcc.target/aarch64/preserve_none_5.c
> @@ -6,35 +6,51 @@
> #include <stdarg.h>
> int foo [[gnu::preserve_none]] (...);
>
> -/* Check the pcs argument order is correct. Should be x20-28, x0-7, x10-14,
> x9, x15 and that the return arg is x0 */
> +/* Check preserve_none falls back to AAPCS for variadic functions. */
>
> /*
> ** bar:
> ** ...
> -** mov w15, 23
> -** mov w9, 22
> -** mov w14, 21
> -** mov w13, 20
> -** mov w12, 19
> -** mov w11, 18
> -** mov w10, 17
> -** mov w7, 16
> -** mov w6, 15
> -** mov w5, 14
> -** mov w4, 13
> -** mov w3, 12
> -** mov w2, 11
> -** mov w1, 10
> +** mov w0, 23
> +** mov w7, 7
> +** mov w6, 6
> +** mov w5, 5
> +** mov w4, 4
> +** mov w3, 3
> +** mov w2, 2
> +** mov w1, 1
> +** str w0, \[sp, 120\]
> +** mov w0, 22
> +** str w0, \[sp, 112\]
> +** mov w0, 21
> +** str w0, \[sp, 104\]
> +** mov w0, 20
> +** str w0, \[sp, 96\]
> +** mov w0, 19
> +** str w0, \[sp, 88\]
> +** mov w0, 18
> +** str w0, \[sp, 80\]
> +** mov w0, 17
> +** str w0, \[sp, 72\]
> +** mov w0, 16
> +** str w0, \[sp, 64\]
> +** mov w0, 15
> +** str w0, \[sp, 56\]
> +** mov w0, 14
> +** str w0, \[sp, 48\]
> +** mov w0, 13
> +** str w0, \[sp, 40\]
> +** mov w0, 12
> +** str w0, \[sp, 32\]
> +** mov w0, 11
> +** str w0, \[sp, 24\]
> +** mov w0, 10
> +** str w0, \[sp, 16\]
> ** mov w0, 9
> -** mov w28, 8
> -** mov w27, 7
> -** mov w26, 6
> -** mov w25, 5
> -** mov w24, 4
> -** mov w23, 3
> -** mov w22, 2
> -** mov w21, 1
> -** mov w20, 0
> +** str w0, \[sp, 8\]
> +** mov w0, 8
> +** str w0, \[sp\]
> +** mov w0, 0
> ** bl foo
> ** add w0, w0, 1
> ** ...
> --
> 2.34.1
>
>
> --
> Alfie Richards
