Re: [PATCH 1/2] testsuite: Add and use thread_fence effective-target

[Christophe Lyon <christophe.lyon@linaro.org>]

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On Sun, 10 Sept 2023 at 21:31, Christophe Lyon <christophe.lyon@linaro.org>
wrote:

> Some targets like arm-eabi with newlib and default settings rely on
> __sync_synchronize() to ensure synchronization.  Newlib does not
> implement it by default, to make users aware they have to take special
> care.
>
> This makes a few tests fail to link.
>
> This patch adds a new thread_fence effective target (similar to the
> corresponding one in libstdc++ testsuite), and uses it in the tests
> that need it, making them UNSUPPORTED instead of FAIL and UNRESOLVED.
>
> 2023-09-10  Christophe Lyon  <christophe.lyon@linaro.org>
>
>         gcc/
>         * doc/sourcebuild.texi (Other attributes): Document thread_fence
>         effective-target.
>
>         gcc/testsuite/
>         * g++.dg/init/array54.C: Require thread_fence.
>         * gcc.dg/c2x-nullptr-1.c: Likewise.
>         * gcc.dg/pr103721-2.c: Likewise.
>         * lib/target-supports.exp (check_effective_target_thread_fence):
>         New.
> ---
>  gcc/doc/sourcebuild.texi              |  4 ++++
>  gcc/testsuite/g++.dg/init/array54.C   |  1 +
>  gcc/testsuite/gcc.dg/c2x-nullptr-1.c  |  1 +
>  gcc/testsuite/gcc.dg/pr103721-2.c     |  1 +
>  gcc/testsuite/lib/target-supports.exp | 12 ++++++++++++
>  5 files changed, 19 insertions(+)
>
> diff --git a/gcc/doc/sourcebuild.texi b/gcc/doc/sourcebuild.texi
> index 1a78b3c1abb..a5f61c29f3b 100644
> --- a/gcc/doc/sourcebuild.texi
> +++ b/gcc/doc/sourcebuild.texi
> @@ -2860,6 +2860,10 @@ Compiler has been configured to support link-time
> optimization (LTO).
>  Compiler and linker support link-time optimization relocatable linking
>  with @option{-r} and @option{-flto} options.
>
> +@item thread_fence
> +Target implements @code{__atomic_thread_fence} without relying on
> +non-implemented @code{__sync_synchronize()}.
> +
>  @item naked_functions
>  Target supports the @code{naked} function attribute.
>
> diff --git a/gcc/testsuite/g++.dg/init/array54.C
> b/gcc/testsuite/g++.dg/init/array54.C
> index f6be350ba72..5241e451d6d 100644
> --- a/gcc/testsuite/g++.dg/init/array54.C
> +++ b/gcc/testsuite/g++.dg/init/array54.C
> @@ -1,5 +1,6 @@
>  // PR c++/90947
>  // { dg-do run { target c++11 } }
> +// { dg-require-effective-target thread_fence }
>
>  #include <atomic>
>
> diff --git a/gcc/testsuite/gcc.dg/c2x-nullptr-1.c
> b/gcc/testsuite/gcc.dg/c2x-nullptr-1.c
> index 4e440234d52..97a31c27409 100644
> --- a/gcc/testsuite/gcc.dg/c2x-nullptr-1.c
> +++ b/gcc/testsuite/gcc.dg/c2x-nullptr-1.c
> @@ -1,5 +1,6 @@
>  /* Test valid usage of C23 nullptr.  */
>  /* { dg-do run } */
> +// { dg-require-effective-target thread_fence }
>  /* { dg-options "-std=c2x -pedantic-errors -Wall -Wextra
> -Wno-unused-variable" } */
>
>  #include <stdarg.h>
> diff --git a/gcc/testsuite/gcc.dg/pr103721-2.c
> b/gcc/testsuite/gcc.dg/pr103721-2.c
> index aefa1f0f147..e059b1cfc2d 100644
> --- a/gcc/testsuite/gcc.dg/pr103721-2.c
> +++ b/gcc/testsuite/gcc.dg/pr103721-2.c
> @@ -1,4 +1,5 @@
>  // { dg-do run }
> +// { dg-require-effective-target thread_fence }
>  // { dg-options "-O2" }
>
>  extern void abort ();
> diff --git a/gcc/testsuite/lib/target-supports.exp
> b/gcc/testsuite/lib/target-supports.exp
> index d353cc0aaf0..7ac9e7530cc 100644
> --- a/gcc/testsuite/lib/target-supports.exp
> +++ b/gcc/testsuite/lib/target-supports.exp
> @@ -9107,6 +9107,18 @@ proc check_effective_target_sync_char_short { } {
>              || [check_effective_target_mips_llsc] }}]
>  }
>
> +# Return 1 if thread_fence does not rely on __sync_synchronize
> +# library function
> +
> +proc check_effective_target_thread_fence {} {
> +    return [check_no_compiler_messages thread_fence executable {
> +       int main () {
> +           __atomic_thread_fence (__ATOMIC_SEQ_CST);
> +           return 0;
> +       }
> +    } ""]
> +}
> +
>  # Return 1 if the target uses a ColdFire FPU.
>
>  proc check_effective_target_coldfire_fpu { } {
> --
> 2.34.1
>
>