From 4d53d6d104c990fb5c2626ddab37a693b6d4f749 Mon Sep 17 00:00:00 2001
From: Simon Dardis <simon.dardis@mips.com>
Date: Fri, 22 Dec 2017 20:31:07 +0000
Subject: Reland "[mips][compiler-rt] Provide 64bit atomic add and sub"

r318733 introduced a build failure for native MIPS32 systems for xray due
to the lack of __sync_fetch_and_add / __syn_fetch_and_sub support. This patch
extends the existing support providing atomics so that xray can be
successfully built.

The initial patch was reverted in r321292, as I suspected it may have caused the
buildbot failure. Another patch in the updates the bot fetched caused the test
failures which was reverted.

Reviewers: atanasyan, dberris

Differential Revision: https://reviews.llvm.org/D40385


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@321383 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/sanitizer_common/sanitizer_atomic_clang_mips.h | 118 +++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 lib/sanitizer_common/sanitizer_atomic_clang_mips.h

(limited to 'lib/sanitizer_common/sanitizer_atomic_clang_mips.h')

diff --git a/lib/sanitizer_common/sanitizer_atomic_clang_mips.h b/lib/sanitizer_common/sanitizer_atomic_clang_mips.h
new file mode 100644
index 000000000..c64e6e542
--- /dev/null
+++ b/lib/sanitizer_common/sanitizer_atomic_clang_mips.h
@@ -0,0 +1,118 @@
+//===-- sanitizer_atomic_clang_mips.h ---------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of ThreadSanitizer/AddressSanitizer runtime.
+// Not intended for direct inclusion. Include sanitizer_atomic.h.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SANITIZER_ATOMIC_CLANG_MIPS_H
+#define SANITIZER_ATOMIC_CLANG_MIPS_H
+
+namespace __sanitizer {
+
+// MIPS32 does not support atomics > 4 bytes. To address this lack of
+// functionality, the sanitizer library provides helper methods which use an
+// internal spin lock mechanism to emulate atomic oprations when the size is
+// 8 bytes.
+static void __spin_lock(volatile int *lock) {
+  while (__sync_lock_test_and_set(lock, 1))
+    while (*lock) {
+    }
+}
+
+static void __spin_unlock(volatile int *lock) { __sync_lock_release(lock); }
+
+// Make sure the lock is on its own cache line to prevent false sharing.
+// Put it inside a struct that is aligned and padded to the typical MIPS
+// cacheline which is 32 bytes.
+static struct {
+  int lock;
+  char pad[32 - sizeof(int)];
+} __attribute__((aligned(32))) lock = {0, {0}};
+
+template <>
+INLINE atomic_uint64_t::Type atomic_fetch_add(volatile atomic_uint64_t *ptr,
+                                              atomic_uint64_t::Type val,
+                                              memory_order mo) {
+  DCHECK(mo &
+         (memory_order_relaxed | memory_order_releasae | memory_order_seq_cst));
+  DCHECK(!((uptr)ptr % sizeof(*ptr)));
+
+  atomic_uint64_t::Type ret;
+
+  __spin_lock(&lock.lock);
+  ret = *(const_cast<atomic_uint64_t::Type volatile *>(&ptr->val_dont_use));
+  ptr->val_dont_use = ret + val;
+  __spin_unlock(&lock.lock);
+
+  return ret;
+}
+
+template <>
+INLINE atomic_uint64_t::Type atomic_fetch_sub(volatile atomic_uint64_t *ptr,
+                                              atomic_uint64_t::Type val,
+                                              memory_order mo) {
+  return atomic_fetch_add(ptr, -val, mo);
+}
+
+template <>
+INLINE bool atomic_compare_exchange_strong(volatile atomic_uint64_t *ptr,
+                                           atomic_uint64_t::Type *cmp,
+                                           atomic_uint64_t::Type xchg,
+                                           memory_order mo) {
+  DCHECK(mo &
+         (memory_order_relaxed | memory_order_releasae | memory_order_seq_cst));
+  DCHECK(!((uptr)ptr % sizeof(*ptr)));
+
+  typedef atomic_uint64_t::Type Type;
+  Type cmpv = *cmp;
+  Type prev;
+  bool ret = false;
+
+  __spin_lock(&lock.lock);
+  prev = *(const_cast<Type volatile *>(&ptr->val_dont_use));
+  if (prev == cmpv) {
+    ret = true;
+    ptr->val_dont_use = xchg;
+  }
+  __spin_unlock(&lock.lock);
+
+  return ret;
+}
+
+template <>
+INLINE atomic_uint64_t::Type atomic_load(const volatile atomic_uint64_t *ptr,
+                                         memory_order mo) {
+  DCHECK(mo &
+         (memory_order_relaxed | memory_order_releasae | memory_order_seq_cst));
+  DCHECK(!((uptr)ptr % sizeof(*ptr)));
+
+  atomic_uint64_t::Type zero = 0;
+  volatile atomic_uint64_t *Newptr =
+      const_cast<volatile atomic_uint64_t *>(ptr);
+  return atomic_fetch_add(Newptr, zero, mo);
+}
+
+template <>
+INLINE void atomic_store(volatile atomic_uint64_t *ptr, atomic_uint64_t::Type v,
+                         memory_order mo) {
+  DCHECK(mo &
+         (memory_order_relaxed | memory_order_releasae | memory_order_seq_cst));
+  DCHECK(!((uptr)ptr % sizeof(*ptr)));
+
+  __spin_lock(&lock.lock);
+  ptr->val_dont_use = v;
+  __spin_unlock(&lock.lock);
+}
+
+}  // namespace __sanitizer
+
+#endif  // SANITIZER_ATOMIC_CLANG_MIPS_H
+
-- 
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