libstdc++: Remove "no stronger" assertion in compare exchange [PR102177]

P0418R2 removed some preconditions from std::atomic::compare_exchange_*
but we still enforce them via __glibcxx_assert. This removes those
assertions.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:

	PR c++/102177
	* include/bits/atomic_base.h (__is_valid_cmpexch_failure_order):
	New function to check if a memory order is valid for the failure
	case of compare exchange operations.
	(__atomic_base<I>::compare_exchange_weak): Simplify assertions
	by using __is_valid_cmpexch_failure_order.
	(__atomic_base<I>::compare_exchange_strong): Likewise.
	(__atomic_base<P*>::compare_exchange_weak): Likewise.
	(__atomic_base<P*>::compare_exchange_strong): Likewise.
	(__atomic_impl::compare_exchange_weak): Add assertion.
	(__atomic_impl::compare_exchange_strong): Likewise.
	* include/std/atomic (atomic::compare_exchange_weak): Likewise.
	(atomic::compare_exchange_strong): Likewise.

diff --git a/libstdc++-v3/include/bits/atomic_base.h b/libstdc++-v3/include/bits/atomic_base.h
index 20cf1343c58ece9a29ecb220536d161d0c997396..cbe1da6d12583f4f137909ca1f0f9e8cac196b4a 100644 (file)
--- a/libstdc++-v3/include/bits/atomic_base.h
+++ b/libstdc++-v3/include/bits/atomic_base.h
@@ -121,6 +121,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       | __memory_order_modifier(__m & __memory_order_modifier_mask));
   }
 
+  constexpr bool
+  __is_valid_cmpexch_failure_order(memory_order __m) noexcept
+  {
+    return (__m & __memory_order_mask) != memory_order_release
+       && (__m & __memory_order_mask) != memory_order_acq_rel;
+  }
+
   _GLIBCXX_ALWAYS_INLINE void
   atomic_thread_fence(memory_order __m) noexcept
   { __atomic_thread_fence(int(__m)); }
@@ -511,13 +518,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       compare_exchange_weak(__int_type& __i1, __int_type __i2,
                            memory_order __m1, memory_order __m2) noexcept
       {
-       memory_order __b2 __attribute__ ((__unused__))
-         = __m2 & __memory_order_mask;
-       memory_order __b1 __attribute__ ((__unused__))
-         = __m1 & __memory_order_mask;
-       __glibcxx_assert(__b2 != memory_order_release);
-       __glibcxx_assert(__b2 != memory_order_acq_rel);
-       __glibcxx_assert(__b2 <= __b1);
+       __glibcxx_assert(__is_valid_cmpexch_failure_order(__m2));
 
        return __atomic_compare_exchange_n(&_M_i, &__i1, __i2, 1,
                                           int(__m1), int(__m2));
@@ -528,13 +529,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
                            memory_order __m1,
                            memory_order __m2) volatile noexcept
       {
-       memory_order __b2 __attribute__ ((__unused__))
-         = __m2 & __memory_order_mask;
-       memory_order __b1 __attribute__ ((__unused__))
-         = __m1 & __memory_order_mask;
-       __glibcxx_assert(__b2 != memory_order_release);
-       __glibcxx_assert(__b2 != memory_order_acq_rel);
-       __glibcxx_assert(__b2 <= __b1);
+       __glibcxx_assert(__is_valid_cmpexch_failure_order(__m2));
 
        return __atomic_compare_exchange_n(&_M_i, &__i1, __i2, 1,
                                           int(__m1), int(__m2));
@@ -560,13 +555,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       compare_exchange_strong(__int_type& __i1, __int_type __i2,
                              memory_order __m1, memory_order __m2) noexcept
       {
-       memory_order __b2 __attribute__ ((__unused__))
-         = __m2 & __memory_order_mask;
-       memory_order __b1 __attribute__ ((__unused__))
-         = __m1 & __memory_order_mask;
-       __glibcxx_assert(__b2 != memory_order_release);
-       __glibcxx_assert(__b2 != memory_order_acq_rel);
-       __glibcxx_assert(__b2 <= __b1);
+       __glibcxx_assert(__is_valid_cmpexch_failure_order(__m2));
 
        return __atomic_compare_exchange_n(&_M_i, &__i1, __i2, 0,
                                           int(__m1), int(__m2));
@@ -577,14 +566,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
                              memory_order __m1,
                              memory_order __m2) volatile noexcept
       {
-       memory_order __b2 __attribute__ ((__unused__))
-         = __m2 & __memory_order_mask;
-       memory_order __b1 __attribute__ ((__unused__))
-         = __m1 & __memory_order_mask;
-
-       __glibcxx_assert(__b2 != memory_order_release);
-       __glibcxx_assert(__b2 != memory_order_acq_rel);
-       __glibcxx_assert(__b2 <= __b1);
+       __glibcxx_assert(__is_valid_cmpexch_failure_order(__m2));
 
        return __atomic_compare_exchange_n(&_M_i, &__i1, __i2, 0,
                                           int(__m1), int(__m2));
@@ -869,13 +851,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
                              memory_order __m1,
                              memory_order __m2) noexcept
       {
-       memory_order __b2 __attribute__ ((__unused__))
-         = __m2 & __memory_order_mask;
-       memory_order __b1 __attribute__ ((__unused__))
-         = __m1 & __memory_order_mask;
-       __glibcxx_assert(__b2 != memory_order_release);
-       __glibcxx_assert(__b2 != memory_order_acq_rel);
-       __glibcxx_assert(__b2 <= __b1);
+       __glibcxx_assert(__is_valid_cmpexch_failure_order(__m2));
 
        return __atomic_compare_exchange_n(&_M_p, &__p1, __p2, 0,
                                           int(__m1), int(__m2));
@@ -886,14 +862,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
                              memory_order __m1,
                              memory_order __m2) volatile noexcept
       {
-       memory_order __b2 __attribute__ ((__unused__))
-         = __m2 & __memory_order_mask;
-       memory_order __b1 __attribute__ ((__unused__))
-         = __m1 & __memory_order_mask;
-
-       __glibcxx_assert(__b2 != memory_order_release);
-       __glibcxx_assert(__b2 != memory_order_acq_rel);
-       __glibcxx_assert(__b2 <= __b1);
+       __glibcxx_assert(__is_valid_cmpexch_failure_order(__m2));
 
        return __atomic_compare_exchange_n(&_M_p, &__p1, __p2, 0,
                                           int(__m1), int(__m2));
@@ -996,6 +965,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
                            _Val<_Tp> __desired, memory_order __success,
                            memory_order __failure) noexcept
       {
+       __glibcxx_assert(__is_valid_cmpexch_failure_order(__failure));
+
        return __atomic_compare_exchange(__ptr, std::__addressof(__expected),
                                         std::__addressof(__desired), true,
                                         int(__success), int(__failure));
@@ -1007,6 +978,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
                              _Val<_Tp> __desired, memory_order __success,
                              memory_order __failure) noexcept
       {
+       __glibcxx_assert(__is_valid_cmpexch_failure_order(__failure));
+
        return __atomic_compare_exchange(__ptr, std::__addressof(__expected),
                                         std::__addressof(__desired), false,
                                         int(__success), int(__failure));

diff --git a/libstdc++-v3/include/std/atomic b/libstdc++-v3/include/std/atomic
index 9b1fb15ac4112cf3d2a06aeb4f49b6519a60261e..b395c65d468790e4df9bc5a32017517b20f52cf3 100644 (file)
--- a/libstdc++-v3/include/std/atomic
+++ b/libstdc++-v3/include/std/atomic
@@ -320,6 +320,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       compare_exchange_weak(_Tp& __e, _Tp __i, memory_order __s,
                            memory_order __f) noexcept
       {
+       __glibcxx_assert(__is_valid_cmpexch_failure_order(__f));
+
        return __atomic_compare_exchange(std::__addressof(_M_i),
                                         std::__addressof(__e),
                                         std::__addressof(__i),
@@ -330,6 +332,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       compare_exchange_weak(_Tp& __e, _Tp __i, memory_order __s,
                            memory_order __f) volatile noexcept
       {
+       __glibcxx_assert(__is_valid_cmpexch_failure_order(__f));
+
        return __atomic_compare_exchange(std::__addressof(_M_i),
                                         std::__addressof(__e),
                                         std::__addressof(__i),
@@ -352,6 +356,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       compare_exchange_strong(_Tp& __e, _Tp __i, memory_order __s,
                              memory_order __f) noexcept
       {
+       __glibcxx_assert(__is_valid_cmpexch_failure_order(__f));
+
        return __atomic_compare_exchange(std::__addressof(_M_i),
                                         std::__addressof(__e),
                                         std::__addressof(__i),
@@ -362,6 +368,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       compare_exchange_strong(_Tp& __e, _Tp __i, memory_order __s,
                              memory_order __f) volatile noexcept
       {
+       __glibcxx_assert(__is_valid_cmpexch_failure_order(__f));
+
        return __atomic_compare_exchange(std::__addressof(_M_i),
                                         std::__addressof(__e),
                                         std::__addressof(__i),