AArch64: Add support for AArch64 atomic operations

This patch adds support for AArch64 atomic operations. Some
of the stubs use the lightweight store/load exclusive.

Change-Id: Iaf704d048b2dc15bf08cf8e4f0c3ea9f2052fe13
Signed-off-by: Serban Constantinescu <serban.constantinescu@arm.com>

diff --git a/libc/private/bionic_atomic_aarch64.h b/libc/private/bionic_atomic_aarch64.h
new file mode 100644 (file)
index 0000000..c5a9e2e
--- /dev/null
+++ b/libc/private/bionic_atomic_aarch64.h
@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifndef BIONIC_ATOMIC_AARCH64_H
+#define BIONIC_ATOMIC_AARCH64_H
+
+/* For ARMv8, we can use the 'dmb' instruction directly */
+__ATOMIC_INLINE__ void __bionic_memory_barrier(void) {
+  __asm__ __volatile__ ( "dmb ish" : : : "memory" );
+}
+
+/* Compare-and-swap, without any explicit barriers. Note that this function
+ * returns 0 on success, and 1 on failure. The opposite convention is typically
+ * used on other platforms.
+ */
+__ATOMIC_INLINE__ int __bionic_cmpxchg(int32_t old_value, int32_t new_value, volatile int32_t* ptr) {
+  int32_t tmp, oldval;
+  __asm__ __volatile__ (
+      "// atomic_cmpxchg\n"
+      "1:  ldaxr %w1, [%3]\n"
+      "    cmp %w1, %w4\n"
+      "    b.ne 2f\n"
+      "    stlxr %w0, %w5, [%3]\n"
+      "    cbnz  %w0, 1b\n"
+      "2:"
+      : "=&r" (tmp), "=&r" (oldval), "+o"(*ptr)
+      : "r" (ptr), "Ir" (old_value), "r" (new_value)
+      : "cc");
+  return oldval != old_value;
+}
+
+/* Swap, without any explicit barriers.  */
+__ATOMIC_INLINE__ int32_t __bionic_swap(int32_t new_value, volatile int32_t* ptr) {
+  int32_t prev, status;
+  __asm__ __volatile__ (
+      "// atomic_swap\n"
+      "1:  ldxr %w0, [%3]\n"
+      "    stxr %w1, %w4, [%3]\n"
+      "    cbnz %w1, 1b\n"
+      : "=&r" (prev), "=&r" (status), "+o" (*ptr)
+      : "r" (ptr), "r" (new_value)
+      : "cc");
+  return prev;
+}
+
+/* Atomic decrement, without explicit barriers.  */
+__ATOMIC_INLINE__ int32_t __bionic_atomic_dec(volatile int32_t* ptr) {
+  int32_t prev, tmp, status;
+  __asm__ __volatile__ (
+      "1:  ldxr %w0, [%4]\n"
+      "    sub %w1, %w0, #1\n"
+      "    stxr %w2, %w1, [%4]\n"
+      "    cbnz %w2, 1b"
+      : "=&r" (prev), "=&r" (tmp), "=&r" (status), "+m"(*ptr)
+      : "r" (ptr)
+      : "cc");
+  return prev;
+}
+
+#endif /* BIONIC_ATOMICS_AARCH64_H */

diff --git a/libc/private/bionic_atomic_inline.h b/libc/private/bionic_atomic_inline.h
index 4936fe1..2bb1128 100644 (file)
--- a/libc/private/bionic_atomic_inline.h
+++ b/libc/private/bionic_atomic_inline.h
@@ -44,7 +44,9 @@ extern "C" {
  */
 #define  __ATOMIC_INLINE__  static __inline__ __attribute__((always_inline))
 
-#ifdef __arm__
+#if defined(__aarch64__)
+#  include "bionic_atomic_aarch64.h"
+#elif defined(__arm__)
 #  include "bionic_atomic_arm.h"
 #elif defined(__i386__)
 #  include "bionic_atomic_x86.h"