libstdc++: Add "futex" and "gthreads" effective-target keywords

This adds a new "futex" effective-target keyword that can be used to
selectively enable/disable tests based on _GLIBCXX_HAVE_LINUX_FUTEX,
instead of checking for that macro in the code.

It also adds "gthreads" as another one, to make the result of the
dg-require-gthreads directive usable in target selectors.

With these new keywords two tests that are currently only run for linux
can also be run for targets using gthr-single.h (e.g. AIX single-thread
multilib, and targets without a gthreads implementation).

libstdc++-v3/ChangeLog:

	* testsuite/18_support/96817.cc: Use new effective-target
	keywords to select supported targets more effectively.
	* testsuite/30_threads/call_once/66146.cc: Likewise.
	* testsuite/lib/libstdc++.exp (check_effective_target_futex):
	Define new proc.
	(check_effective_target_gthreads): Define new proc to replace
	dg-require-gthreads.

3 files changed, 41 insertions, 8 deletions

diff --git a/libstdc++-v3/testsuite/18_support/96817.cc b/libstdc++-v3/testsuite/18_support/96817.cc
index 4591a72..7f35f03 100644
--- a/libstdc++-v3/testsuite/18_support/96817.cc
+++ b/libstdc++-v3/testsuite/18_support/96817.cc
@@ -15,19 +15,18 @@
 // with this library; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
-// { dg-options "-pthread"  }
-// { dg-do run { target *-*-linux-gnu } }
-// { dg-require-effective-target pthread }
+// { dg-do run }
+// { dg-additional-options "-pthread" { target pthread } }
+
+// Static init cannot detect recursion for gthreads targets without futexes
+// (and the futex case can only detect it if __libc_single_threaded==true).
+// { dg-skip-if "unsupported" { gthreads && { ! futex } } }
 
 // PR libstdc++/96817
 
 #include <exception>
 #include <stdlib.h>
 
-#ifndef _GLIBCXX_HAVE_LINUX_FUTEX
-# error "This test requries futex support in the library"
-#endif
-
 int init()
 {
 #if __has_include(<sys/single_threaded.h>)
diff --git a/libstdc++-v3/testsuite/30_threads/call_once/66146.cc b/libstdc++-v3/testsuite/30_threads/call_once/66146.cc
index b1ca0eb..a9c9948 100644
--- a/libstdc++-v3/testsuite/30_threads/call_once/66146.cc
+++ b/libstdc++-v3/testsuite/30_threads/call_once/66146.cc
@@ -16,9 +16,11 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
-// { dg-skip-if "" { pthread && { ! *-*-*linux* } } }
 // { dg-additional-options "-pthread" { target pthread } }
 
+// Currently std::call_once is broken for gthreads targets without futexes:
+// { dg-skip-if "see PR 66146" { gthreads && { ! futex } } }
+
 #include <mutex>
 #include <cstdlib>
 #include <testsuite_hooks.h>
diff --git a/libstdc++-v3/testsuite/lib/libstdc++.exp b/libstdc++-v3/testsuite/lib/libstdc++.exp
index fc1e8f2..9ba4ced 100644
--- a/libstdc++-v3/testsuite/lib/libstdc++.exp
+++ b/libstdc++-v3/testsuite/lib/libstdc++.exp
@@ -1613,6 +1613,38 @@ proc check_effective_target_tbb-backend { } {
     }]
 }
 
+# Return 1 if futex syscall is available
+proc check_effective_target_futex { } {
+    return [check_v3_target_prop_cached et_futex {
+	# Set up and compile a C++ test program that depends on tbb
+	set src futex[pid].cc
+	set exe futex[pid].x
+
+	set f [open $src "w"]
+	puts $f "#include <bits/c++config.h>"
+	puts $f "#if ! _GLIBCXX_HAVE_LINUX_FUTEX"
+	puts $f "#  error No futex syscall available"
+	puts $f "#endif"
+	close $f
+
+	set lines [v3_target_compile $src /dev/null preprocess ""]
+	file delete $src
+
+	if [string match "" $lines] {
+	    # No error message, preprocessing succeeded.
+	    verbose "check_v3_futex: `1'" 2
+	    return 1
+	}
+	verbose "check_v3_futex: `0'" 2
+	return 0
+    }]
+}
+
+# Return 1 if futex syscall is available
+proc check_effective_target_gthreads { } {
+    return [check_v3_target_gthreads_timed]
+}
+
 set additional_prunes ""
 
 if { [info exists env(GCC_RUNTEST_PARALLELIZE_DIR)] \