Test for the presence of GCC atomic builtins at configure time. If not found,
disable building LLVM in thread-safe mode and print a nice warning.
Regenerate configure for these changes.
llvm-svn: 72075
diff --git a/llvm/autoconf/configure.ac b/llvm/autoconf/configure.ac
index cb217a5..56853e9 100644
--- a/llvm/autoconf/configure.ac
+++ b/llvm/autoconf/configure.ac
@@ -372,7 +372,6 @@
default) AC_SUBST(ENABLE_THREADS,[1]) ;;
*) AC_MSG_ERROR([Invalid setting for --enable-threads. Use "yes" or "no"]) ;;
esac
-AC_DEFINE_UNQUOTED([ENABLE_THREADS],$ENABLE_THREADS,[Define if threads enabled])
dnl Allow building without position independent code
AC_ARG_ENABLE(pic,
@@ -897,6 +896,26 @@
fi
fi
+dnl atomic builtins are required for threading support.
+if test "$ENABLE_THREADS" -eq 1 ; then
+ AC_MSG_CHECKING(for GCC atomic builtins)
+ AC_LINK_IFELSE(
+ AC_LANG_SOURCE(
+ [[int main() {
+ volatile unsigned long val = 1;
+ __sync_synchronize();
+ __sync_val_compare_and_swap(&val, 1, 0);
+ return 0;
+ }
+ ]]),
+ AC_MSG_RESULT(yes),
+ AC_MSG_RESULT(no)
+ AC_SUBST(ENABLE_THREADS, [0])
+ AC_MSG_WARN([Threading support disabled because atomic builtins are missing]))
+fi
+
+AC_DEFINE_UNQUOTED([ENABLE_THREADS],$ENABLE_THREADS,[Define if threads enabled])
+
dnl===-----------------------------------------------------------------------===
dnl===
dnl=== SECTION 9: Additional checks, variables, etc.