diff options
Diffstat (limited to 'libstdc++-v3/acinclude.m4')
| -rw-r--r-- | libstdc++-v3/acinclude.m4 | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4 index 349566466ac..c160a1a3366 100644 --- a/libstdc++-v3/acinclude.m4 +++ b/libstdc++-v3/acinclude.m4 @@ -1967,6 +1967,69 @@ AC_DEFUN([GLIBCXX_ENABLE_PCH], [ dnl +dnl Check for atomic builtins. +dnl See: +dnl http://gcc.gnu.org/onlinedocs/gcc/Atomic-Builtins.html#Atomic-Builtins +dnl +dnl This checks to see if the host supports the compiler-generated +dnl builtins for atomic operations. Note, this is intended to be an +dnl all-or-nothing switch, so all the atomic operations that are used +dnl should be checked. +dnl +dnl Note: +dnl libgomp and libgfortran do this with a link test, instead of an asm test. +dnl see: CHECK_SYNC_FETCH_AND_ADD +dnl +dnl Defines: +dnl _GLIBCXX_ATOMIC_BUILTINS if the compiler on this target supports atomics. +dnl +AC_DEFUN([GLIBCXX_ENABLE_ATOMIC_BUILTINS], [ + AC_MSG_CHECKING([for atomic builtins]) + AC_LANG_SAVE + AC_LANG_CPLUSPLUS + + # Fake what AC_TRY_COMPILE does. XXX Look at redoing this new-style. + cat > conftest.$ac_ext << EOF +[#]line __oline__ "configure" +int main() +{ + // NB: _Atomic_word not necessarily int. + typedef int atomic_type; + atomic_type c1; + atomic_type c2; + const atomic_type c3(0); + if (__sync_fetch_and_add(&c1, c2) == c3) + { + // Do something. + } + return 0; +} +EOF + old_CXXFLAGS="$CXXFLAGS" + CXXFLAGS="$CXXFLAGS -S" + if AC_TRY_EVAL(ac_compile); then + if grep __sync_fetch_and_add conftest.s >/dev/null 2>&1 ; then + enable_atomic_builtins=no + else + AC_DEFINE(_GLIBCXX_ATOMIC_BUILTINS, 1, + [Define if builtin atomic operations are supported on this host.]) + enable_atomic_builtins=yes + atomicity_dir=cpu/generic/atomicity_builtins + fi + fi + CXXFLAGS="$old_CXXFLAGS" + rm -f conftest* + + # Now, if still generic, set to mutex. + if test $atomicity_dir = "cpu/generic" ; then + atomicity_dir=cpu/generic/atomicity_mutex + fi + AC_LANG_RESTORE + AC_MSG_RESULT($enable_atomic_builtins) +]) + + +dnl dnl Check for exception handling support. If an explicit enable/disable dnl sjlj exceptions is given, we don't have to detect. Otherwise the dnl target may or may not support call frame exceptions. |