On Wed, Sep 23, 2026 at 6:04 AM Wilco Dijkstra <[email protected]> wrote:
>
> Hi Andrea,
>
> > I think we should warn if someone passes both `-mcmodel=large
> > -moutline-atomics` to the command line. I noticed
> > aarch64_flag_outline_atomics is initialized to 2 so I think
> > `aarch64_flag_outline_atomics == 1` or
> > opts_set->x_aarch64_flag_outline_atomics will be the check there.
>
> Sure, something like this? Not sure what OPT_ value to use, but the outline
> atomics one seemed most relevant.
>
> Cheers,
> Wilco
>
>
> v3: Add warning
>
> Outline atomics is not designed to be used with -mcmodel=large, so disable
> it automatically if the large code model is used. Warn if the option was
> enabled on the command-line. Update documentation.
>
> gcc:
> PR target/112465
> * config/aarch64/aarch64.cc (aarch64_override_options_after_change_1):
> Turn off outline atomics with -mcmodel=large.
> * doc/invoke.texi (-mcmodel=large): Update description.
>
> ---
>
> diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
> index
> f9d906f449f27906f8cf0b4b4edee898cb795e15..b176f0474b19f91ac496d986b6b24f8a09923420
> 100644
> --- a/gcc/config/aarch64/aarch64.cc
> +++ b/gcc/config/aarch64/aarch64.cc
> @@ -19987,6 +19987,15 @@ aarch64_override_options_after_change_1 (struct
> gcc_options *opts)
> intermediary step for the former. */
> if (flag_mlow_precision_sqrt)
> flag_mrecip_low_precision_sqrt = true;
> +
> + /* Turn off outline atomics with -mcmodel=large. */
> + if (aarch64_cmodel == AARCH64_CMODEL_LARGE)
> + {
> + if (!TARGET_LSE && opts->x_aarch64_flag_outline_atomics == 1)
> + warning (OPT_moutline_atomics,
> + "%<-mcmodel=large%> implies %<-mno-outline-atomics%>");
> + opts->x_aarch64_flag_outline_atomics = 0;
Ok.
> + }
> }
>
> /* 'Unpack' up the internal tuning structs and update the options
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index
> 498a3608151e8641ee1495b548ca38182efbe3eb..edc29aaec0f9aa0f6b717277f2559035507ce43a
> 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -21495,10 +21495,10 @@ dynamically linked. This is the default code model.
>
> @opindex mcmodel=large
> @item -mcmodel=large
> -Generate code for the large code model. This makes no assumptions about
> -addresses and sizes of sections. Programs can be statically linked only.
> The
> -@option{-mcmodel=large} option is incompatible with @option{-mabi=ilp32},
> -@option{-fpic} and @option{-fPIC}.
> +Generate code for the large code model. This allows large .bss and .data
> +sections, however .text and .rodata must still be < 2GiB in total.
> +The @option{-moutline-atomics} is turned off by default. Static linking
> +with small/tiny model object files is not supported.
>
> @item -mtp=@var{name}
> @opindex mtp
>
