libstdc++-v3/ChangeLog:
* acinclude.m4 (GLIBCXX_ENABLE_LOCK_POLICY): Add comment about
checking for CAS on correct word size.
ac_save_CXXFLAGS="$CXXFLAGS"
dnl Why do we care about 2-byte CAS on targets with 4-byte _Atomic_word?!
+ dnl Why don't we check 8-byte CAS for sparc64, where _Atomic_word is long?!
+ dnl New targets should only check for CAS for the _Atomic_word type.
AC_TRY_COMPILE([
#if ! defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2
# error "No 2-byte compare-and-swap"