[PATCH 8/8] atomic: Switch atomic.h to builtin atomics

[Wilco Dijkstra]

Switch to standard builtin atomics by removing the defines for !USE_ATOMIC_COMPILER_BUILTINS.

Passes buildmanyglibc, OK for commit?

---

diff --git a/include/atomic.h b/include/atomic.h
index 98ba808ee9e3bdd30a81d62bacfdeb8333c061d9..690bdabeb4029a1ce7739a13d36f8949f0a46053 100644
--- a/include/atomic.h
+++ b/include/atomic.h
@@ -563,10 +563,6 @@
    C11.  Usually, a function named atomic_OP_MO(args) is equivalent to C11's
    atomic_OP_explicit(args, memory_order_MO); exceptions noted below.  */
 
-/* Each arch can request to use compiler built-ins for C11 atomics.  If it
-   does, all atomics will be based on these.  */
-#if USE_ATOMIC_COMPILER_BUILTINS
-
 /* We require 32b atomic operations; some archs also support 64b atomic
    operations.  */
 void __atomic_link_error (void);
@@ -693,167 +689,6 @@ void __atomic_link_error (void);
   ({ __atomic_check_size((mem));					      \
   __atomic_fetch_xor ((mem), (operand), __ATOMIC_RELEASE); })
 
-#else /* !USE_ATOMIC_COMPILER_BUILTINS  */
-
-/* By default, we assume that read, write, and full barriers are equivalent
-   to acquire, release, and seq_cst barriers.  Archs for which this does not
-   hold have to provide custom definitions of the fences.  */
-# ifndef atomic_thread_fence_acquire
-#  define atomic_thread_fence_acquire() atomic_read_barrier ()
-# endif
-# ifndef atomic_thread_fence_release
-#  define atomic_thread_fence_release() atomic_write_barrier ()
-# endif
-# ifndef atomic_thread_fence_seq_cst
-#  define atomic_thread_fence_seq_cst() atomic_full_barrier ()
-# endif
-
-# ifndef atomic_load_relaxed
-#  define atomic_load_relaxed(mem) \
-   ({ __typeof ((__typeof (*(mem))) *(mem)) __atg100_val;		      \
-   __asm ("" : "=r" (__atg100_val) : "0" (*(mem)));			      \
-   __atg100_val; })
-# endif
-# ifndef atomic_load_acquire
-#  define atomic_load_acquire(mem) \
-   ({ __typeof (*(mem)) __atg101_val = atomic_load_relaxed (mem);	      \
-   atomic_thread_fence_acquire ();					      \
-   __atg101_val; })
-# endif
-
-# ifndef atomic_store_relaxed
-/* XXX Use inline asm here?  */
-#  define atomic_store_relaxed(mem, val) do { *(mem) = (val); } while (0)
-# endif
-# ifndef atomic_store_release
-#  define atomic_store_release(mem, val) \
-   do {									      \
-     atomic_thread_fence_release ();					      \
-     atomic_store_relaxed ((mem), (val));				      \
-   } while (0)
-# endif
-
-/* On failure, this CAS has memory_order_relaxed semantics.  */
-/* XXX This potentially has one branch more than necessary, but archs
-   currently do not define a CAS that returns both the previous value and
-   the success flag.  */
-# ifndef atomic_compare_exchange_weak_acquire
-#  define atomic_compare_exchange_weak_acquire(mem, expected, desired) \
-   ({ typeof (*(expected)) __atg102_expected = *(expected);		      \
-   *(expected) =							      \
-     atomic_compare_and_exchange_val_acq ((mem), (desired), *(expected));     \
-   *(expected) == __atg102_expected; })
-# endif
-# ifndef atomic_compare_exchange_weak_relaxed
-/* XXX Fall back to CAS with acquire MO because archs do not define a weaker
-   CAS.  */
-#  define atomic_compare_exchange_weak_relaxed(mem, expected, desired) \
-   atomic_compare_exchange_weak_acquire ((mem), (expected), (desired))
-# endif
-# ifndef atomic_compare_exchange_weak_release
-#  define atomic_compare_exchange_weak_release(mem, expected, desired) \
-   ({ typeof (*(expected)) __atg103_expected = *(expected);		      \
-   *(expected) =							      \
-     atomic_compare_and_exchange_val_rel ((mem), (desired), *(expected));     \
-   *(expected) == __atg103_expected; })
-# endif
-
-/* XXX Fall back to acquire MO because archs do not define a weaker
-   atomic_exchange.  */
-# ifndef atomic_exchange_relaxed
-#  define atomic_exchange_relaxed(mem, val) \
-   atomic_exchange_acq ((mem), (val))
-# endif
-# ifndef atomic_exchange_acquire
-#  define atomic_exchange_acquire(mem, val) \
-   atomic_exchange_acq ((mem), (val))
-# endif
-# ifndef atomic_exchange_release
-#  define atomic_exchange_release(mem, val) \
-   atomic_exchange_rel ((mem), (val))
-# endif
-
-# ifndef atomic_fetch_add_acquire
-#  define atomic_fetch_add_acquire(mem, operand) \
-   atomic_exchange_and_add_acq ((mem), (operand))
-# endif
-# ifndef atomic_fetch_add_relaxed
-/* XXX Fall back to acquire MO because the MO semantics of
-   atomic_exchange_and_add are not documented; the generic version falls back
-   to atomic_exchange_and_add_acq if atomic_exchange_and_add is not defined,
-   and vice versa.  */
-#  define atomic_fetch_add_relaxed(mem, operand) \
-   atomic_fetch_add_acquire ((mem), (operand))
-# endif
-# ifndef atomic_fetch_add_release
-#  define atomic_fetch_add_release(mem, operand) \
-   atomic_exchange_and_add_rel ((mem), (operand))
-# endif
-# ifndef atomic_fetch_add_acq_rel
-#  define atomic_fetch_add_acq_rel(mem, operand) \
-   ({ atomic_thread_fence_release ();					      \
-   atomic_exchange_and_add_acq ((mem), (operand)); })
-# endif
-
-/* XXX Fall back to acquire MO because archs do not define a weaker
-   atomic_and_val.  */
-# ifndef atomic_fetch_and_relaxed
-#  define atomic_fetch_and_relaxed(mem, operand) \
-   atomic_fetch_and_acquire ((mem), (operand))
-# endif
-/* XXX The default for atomic_and_val has acquire semantics, but this is not
-   documented.  */
-# ifndef atomic_fetch_and_acquire
-#  define atomic_fetch_and_acquire(mem, operand) \
-   atomic_and_val ((mem), (operand))
-# endif
-# ifndef atomic_fetch_and_release
-/* XXX This unnecessarily has acquire MO.  */
-#  define atomic_fetch_and_release(mem, operand) \
-   ({ atomic_thread_fence_release ();					      \
-   atomic_and_val ((mem), (operand)); })
-# endif
-
-/* XXX The default for atomic_or_val has acquire semantics, but this is not
-   documented.  */
-# ifndef atomic_fetch_or_acquire
-#  define atomic_fetch_or_acquire(mem, operand) \
-   atomic_or_val ((mem), (operand))
-# endif
-/* XXX Fall back to acquire MO because archs do not define a weaker
-   atomic_or_val.  */
-# ifndef atomic_fetch_or_relaxed
-#  define atomic_fetch_or_relaxed(mem, operand) \
-   atomic_fetch_or_acquire ((mem), (operand))
-# endif
-/* XXX Contains an unnecessary acquire MO because archs do not define a weaker
-   atomic_or_val.  */
-# ifndef atomic_fetch_or_release
-#  define atomic_fetch_or_release(mem, operand) \
-   ({ atomic_thread_fence_release ();					      \
-   atomic_fetch_or_acquire ((mem), (operand)); })
-# endif
-
-# ifndef atomic_fetch_xor_release
-/* Failing the atomic_compare_exchange_weak_release reloads the value in
-   __atg104_expected, so we need only do the XOR again and retry.  */
-# define atomic_fetch_xor_release(mem, operand) \
-  ({ __typeof (mem) __atg104_memp = (mem);				      \
-     __typeof (*(mem)) __atg104_expected = (*__atg104_memp);		      \
-     __typeof (*(mem)) __atg104_desired;				      \
-     __typeof (*(mem)) __atg104_op = (operand);				      \
-									      \
-     do									      \
-       __atg104_desired = __atg104_expected ^ __atg104_op;		      \
-     while (__glibc_unlikely						      \
-	    (atomic_compare_exchange_weak_release (			      \
-	       __atg104_memp, &__atg104_expected, __atg104_desired)	      \
-	     == 0));							      \
-     __atg104_expected; })
-#endif
-
-#endif /* !USE_ATOMIC_COMPILER_BUILTINS  */
-
 /* This operation does not affect synchronization semantics but can be used
    in the body of a spin loop to potentially improve its efficiency.  */
 #ifndef atomic_spin_nop