[PATCH v2 6/6] math: Disable exception check for soft-fp routine with compiler-rt
H.J. Lu
hjl.tools@gmail.com
Fri Mar 13 16:46:16 GMT 2026
On Fri, Mar 13, 2026 at 7:21 AM Adhemerval Zanella Netto
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 25/02/26 22:03, H.J. Lu wrote:
> > On Thu, Feb 26, 2026 at 2:32 AM Adhemerval Zanella
> > <adhemerval.zanella@linaro.org> wrote:
> >>
> >> The compiler-rt does not support throwing floating-point exceptions
> >> for math builtin (__addtf3, __multf3, __divtf3, etc.) [1][2][3].
> >> So disable the check when compiler-rt is used instead of libgcc.
> >
> > I think we check capability instead of HAVE_COMPILER_RT_RUNTIME.
>
> I think we can not easily check capability for a runtime only behavior,
> there is no indication in compiler pre-defined flags or similar to
> indicate this behavior.
Since this issue is specific to soft-fp exception, I think we should add
a macro for soft-fp exception capability and xfail these tests when
compiler-rt is used.
> Even compiler-rt documentation is not explicit clear about floating
> point exceptions for soft-fp implementations.
>
>
> >
> >> Checked on x86_64-linux-gnu and aarch64-linux-gnu with clang.
> >>
> >> [1] https://github.com/llvm/llvm-project/issues/59924
> >> [2] https://github.com/llvm/llvm-project/issues/60141
> >> [3] https://github.com/llvm/llvm-project/issues/172499
> >> ---
> >> config.h.in | 3 +++
> >> configure | 4 +++
> >> configure.ac | 3 +++
> >> sysdeps/aarch64/math-tests-exceptions.h | 34 +++++++++++++++++++++++++
> >> sysdeps/x86_64/math-tests-exceptions.h | 33 ++++++++++++++++++++++++
> >> 5 files changed, 77 insertions(+)
> >> create mode 100644 sysdeps/aarch64/math-tests-exceptions.h
> >> create mode 100644 sysdeps/x86_64/math-tests-exceptions.h
> >>
> >> diff --git a/config.h.in b/config.h.in
> >> index 125532ec6b..215b223e12 100644
> >> --- a/config.h.in
> >> +++ b/config.h.in
> >> @@ -231,6 +231,9 @@
> >> /* Define to 1 if compiler runtime provides __sfp_handle_exceptions */
> >> #undef HAVE_SFP_HANDLE_EXCEPTIONS
> >>
> >> +/* Define to 1 if compiler uses compiler-rt instead of libgcc. */
> >> +#undef HAVE_COMPILER_RT_RUNTIME
> >> +
> >> /*
> >> */
> >>
> >> diff --git a/configure b/configure
> >> index d156912063..4ccf5600d7 100755
> >> --- a/configure
> >> +++ b/configure
> >> @@ -9398,6 +9398,10 @@ esac
> >> fi
> >> { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_cv_runtime_library" >&5
> >> printf "%s\n" "$libc_cv_runtime_library" >&6; }
> >> +if test $libc_cv_runtime_library = compiler-rt; then
> >> + printf "%s\n" "#define HAVE_COMPILER_RT_RUNTIME 1" >>confdefs.h
> >> +
> >> +fi
> >> config_vars="$config_vars
> >> libgcc-name = $libc_cv_libgcc"
> >> config_vars="$config_vars
> >> diff --git a/configure.ac b/configure.ac
> >> index 776695486a..9ced9ec0f5 100644
> >> --- a/configure.ac
> >> +++ b/configure.ac
> >> @@ -2152,6 +2152,9 @@ AC_CACHE_CHECK([for the usable compiler runtime library], [libc_cv_runtime_libra
> >> ;;
> >> *) AC_MSG_FAILURE([non supported compiler runtime library]) ;;
> >> esac])
> >> +if test $libc_cv_runtime_library = compiler-rt; then
> >> + AC_DEFINE([HAVE_COMPILER_RT_RUNTIME])
> >> +fi
> >> LIBC_CONFIG_VAR([libgcc-name], [$libc_cv_libgcc])
> >> LIBC_CONFIG_VAR([libgcc_eh-name], [$libc_cv_libgcc_eh])
> >>
> >> diff --git a/sysdeps/aarch64/math-tests-exceptions.h b/sysdeps/aarch64/math-tests-exceptions.h
> >> new file mode 100644
> >> index 0000000000..dc824c25a5
> >> --- /dev/null
> >> +++ b/sysdeps/aarch64/math-tests-exceptions.h
> >> @@ -0,0 +1,34 @@
> >> +/* Configuration for math tests: support for exceptions. AArch64 version.
> >> + Copyright (C) 2026 Free Software Foundation, Inc.
> >> + This file is part of the GNU C Library.
> >> +
> >> + The GNU C Library is free software; you can redistribute it and/or
> >> + modify it under the terms of the GNU Lesser General Public
> >> + License as published by the Free Software Foundation; either
> >> + version 2.1 of the License, or (at your option) any later version.
> >> +
> >> + The GNU C Library is distributed in the hope that it will be useful,
> >> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> >> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> >> + Lesser General Public License for more details.
> >> +
> >> + You should have received a copy of the GNU Lesser General Public
> >> + License along with the GNU C Library; if not, see
> >> + <https://www.gnu.org/licenses/>. */
> >> +
> >> +#ifndef _MATH_TESTS_EXCEPTIONS_H
> >> +#define _MATH_TESTS_EXCEPTIONS_H 1
> >> +
> >> +#define EXCEPTION_TESTS_float 1
> >> +#define EXCEPTION_TESTS_double 1
> >> +/* compiler-rt does not support floating-point exceptions for the
> >> + long double / __float128 math builtins. */
> >> +#ifdef HAVE_COMPILER_RT_RUNTIME
> >> +# define EXCEPTION_TESTS_long_double 0
> >> +# define EXCEPTION_TESTS_float128 0
> >> +#else
> >> +# define EXCEPTION_TESTS_long_double 1
> >> +# define EXCEPTION_TESTS_float128 1
> >> +#endif
> >> +
> >> +#endif /* math-tests-exceptions.h. */
> >> diff --git a/sysdeps/x86_64/math-tests-exceptions.h b/sysdeps/x86_64/math-tests-exceptions.h
> >> new file mode 100644
> >> index 0000000000..fa60397b79
> >> --- /dev/null
> >> +++ b/sysdeps/x86_64/math-tests-exceptions.h
> >> @@ -0,0 +1,33 @@
> >> +/* Configuration for math tests: support for exceptions. x86_64 version.
> >> + Copyright (C) 2026 Free Software Foundation, Inc.
> >> + This file is part of the GNU C Library.
> >> +
> >> + The GNU C Library is free software; you can redistribute it and/or
> >> + modify it under the terms of the GNU Lesser General Public
> >> + License as published by the Free Software Foundation; either
> >> + version 2.1 of the License, or (at your option) any later version.
> >> +
> >> + The GNU C Library is distributed in the hope that it will be useful,
> >> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> >> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> >> + Lesser General Public License for more details.
> >> +
> >> + You should have received a copy of the GNU Lesser General Public
> >> + License along with the GNU C Library; if not, see
> >> + <https://www.gnu.org/licenses/>. */
> >> +
> >> +#ifndef _MATH_TESTS_EXCEPTIONS_H
> >> +#define _MATH_TESTS_EXCEPTIONS_H 1
> >> +
> >> +#define EXCEPTION_TESTS_float 1
> >> +#define EXCEPTION_TESTS_double 1
> >> +#define EXCEPTION_TESTS_long_double 1
> >> +/* compiler-rt does not support floating-point exceptions for the
> >> + _float128 math builtins. */
> >> +#ifdef HAVE_COMPILER_RT_RUNTIME
> >> +# define EXCEPTION_TESTS_float128 0
> >> +#else
> >> +# define EXCEPTION_TESTS_float128 1
> >> +#endif
> >> +
> >> +#endif /* math-tests-exceptions.h. */
> >> --
> >> 2.43.0
> >>
> >
> >
>
--
H.J.
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