diff options
Diffstat (limited to 'libstdc++-v3/acinclude.m4')
| -rw-r--r-- | libstdc++-v3/acinclude.m4 | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4 index 988c532c4e2..8129373e9dd 100644 --- a/libstdc++-v3/acinclude.m4 +++ b/libstdc++-v3/acinclude.m4 @@ -5471,6 +5471,31 @@ AC_DEFUN([GLIBCXX_ZONEINFO_DIR], [ fi ]) +dnl +dnl Check whether lock tables can be aligned to avoid false sharing. +dnl +dnl Defines: +dnl _GLIBCXX_CAN_ALIGNAS_DESTRUCTIVE_SIZE if objects with static storage +dnl duration can be aligned to std::hardware_destructive_interference_size. +dnl +AC_DEFUN([GLIBCXX_CHECK_ALIGNAS_CACHELINE], [ + AC_LANG_SAVE + AC_LANG_CPLUSPLUS + + AC_MSG_CHECKING([whether static objects can be aligned to the cacheline size]) + AC_TRY_COMPILE(, [struct alignas(__GCC_DESTRUCTIVE_SIZE) Aligned { }; + alignas(Aligned) static char buf[sizeof(Aligned) * 16]; + ], [ac_alignas_cacheline=yes], [ac_alignas_cacheline=no]) + if test "$ac_alignas_cacheline" = yes; then + AC_DEFINE_UNQUOTED(_GLIBCXX_CAN_ALIGNAS_DESTRUCTIVE_SIZE, 1, + [Define if global objects can be aligned to + std::hardware_destructive_interference_size.]) + fi + AC_MSG_RESULT($ac_alignas_cacheline) + + AC_LANG_RESTORE +]) + # Macros from the top-level gcc directory. m4_include([../config/gc++filt.m4]) m4_include([../config/tls.m4]) |