[PATCH v2 1/2] testsuite: Add dg-require-atomic-cmpxchg-word

[Hans-Peter Nilsson <hp@axis.com>]

> From: Hans-Peter Nilsson <hp@axis.com>
> Date: Wed, 4 Oct 2023 17:15:28 +0200

> New version coming up.

Using pointer-sized int instead of int,
__atomic_compare_exchange instead of __atomic_exchange,
renamed to atomic-cmpxchg-word from atomic-exchange, and
updating a comment that already seemed reasonably well
placed.

Tested as with v1 1/2.

Ok to commit?

-- >8 --
Some targets (armv6-m) support inline atomic load and store,
i.e. dg-require-thread-fence matches, but not atomic operations like
compare and exchange.

This directive can be used to replace uses of dg-require-thread-fence
where an atomic operation is actually used.

	* testsuite/lib/dg-options.exp (dg-require-atomic-cmpxchg-word):
	New proc.
	* testsuite/lib/libstdc++.exp (check_v3_target_atomic_cmpxchg_word):
	Ditto.
---
 libstdc++-v3/testsuite/lib/dg-options.exp |  9 ++++++
 libstdc++-v3/testsuite/lib/libstdc++.exp  | 37 +++++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/libstdc++-v3/testsuite/lib/dg-options.exp b/libstdc++-v3/testsuite/lib/dg-options.exp
index 84ad0c65330b..850442b6b7c1 100644
--- a/libstdc++-v3/testsuite/lib/dg-options.exp
+++ b/libstdc++-v3/testsuite/lib/dg-options.exp
@@ -133,6 +133,15 @@ proc dg-require-thread-fence { args } {
     return
 }
 
+proc dg-require-atomic-cmpxchg-word { args } {
+    if { ![ check_v3_target_atomic_cmpxchg_word ] } {
+	upvar dg-do-what dg-do-what
+	set dg-do-what [list [lindex ${dg-do-what} 0] "N" "P"]
+	return
+    }
+    return
+}
+
 proc dg-require-atomic-builtins { args } {
     if { ![ check_v3_target_atomic_builtins ] } {
 	upvar dg-do-what dg-do-what
diff --git a/libstdc++-v3/testsuite/lib/libstdc++.exp b/libstdc++-v3/testsuite/lib/libstdc++.exp
index 608056e5068e..4bedb36dc6f9 100644
--- a/libstdc++-v3/testsuite/lib/libstdc++.exp
+++ b/libstdc++-v3/testsuite/lib/libstdc++.exp
@@ -1221,6 +1221,43 @@ proc check_v3_target_thread_fence { } {
     }]
 }
 
+proc check_v3_target_atomic_cmpxchg_word { } {
+    return [check_v3_target_prop_cached et_atomic_cmpxchg_word {
+	global cxxflags
+	global DEFAULT_CXXFLAGS
+
+	# Set up and link a C++11 test program that depends on
+	# atomic-compare-exchange being available for a pointer-sized
+	# integer.  It should be sufficient as gcc can derive all
+	# other operations when a target implements this operation.
+	set src atomic_cmpxchg_word[pid].cc
+
+	set f [open $src "w"]
+	puts $f "
+	__UINTPTR_TYPE__ i, j, k;
+	int main() {
+	__atomic_compare_exchange (&i, &j, &k, 1, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
+	return 0;
+	}"
+	close $f
+
+	set cxxflags_saved $cxxflags
+	set cxxflags "$cxxflags $DEFAULT_CXXFLAGS -Werror -std=gnu++11"
+
+	set lines [v3_target_compile $src /dev/null executable ""]
+	set cxxflags $cxxflags_saved
+	file delete $src
+
+	if [string match "" $lines] {
+	    # No error message, linking succeeded.
+	    return 1
+	} else {
+	    verbose "check_v3_target_atomic_cmpxchg_word: compilation failed" 2
+	    return 0
+	}
+    }]
+}
+
 # Return 1 if atomics_bool and atomic_int are always lock-free, 0 otherwise.
 proc check_v3_target_atomic_builtins { } {
     return [check_v3_target_prop_cached et_atomic_builtins {
-- 
2.30.2