Merge System into Support.

[oota-llvm.git] / lib / Support / RWMutex.cpp

diff --git a/lib/Support/RWMutex.cpp b/lib/Support/RWMutex.cpp
new file mode 100644 (file)
index 0000000..fc02f9c
--- /dev/null
+++ b/lib/Support/RWMutex.cpp
@@ -0,0 +1,157 @@
+//===- RWMutex.cpp - Reader/Writer Mutual Exclusion Lock --------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the llvm::sys::RWMutex class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Config/config.h"
+#include "llvm/Support/RWMutex.h"
+#include <cstring>
+
+//===----------------------------------------------------------------------===//
+//=== WARNING: Implementation here must contain only TRULY operating system
+//===          independent code.
+//===----------------------------------------------------------------------===//
+
+#if !defined(ENABLE_THREADS) || ENABLE_THREADS == 0
+// Define all methods as no-ops if threading is explicitly disabled
+namespace llvm {
+using namespace sys;
+RWMutexImpl::RWMutexImpl() { }
+RWMutexImpl::~RWMutexImpl() { }
+bool RWMutexImpl::reader_acquire() { return true; }
+bool RWMutexImpl::reader_release() { return true; }
+bool RWMutexImpl::writer_acquire() { return true; }
+bool RWMutexImpl::writer_release() { return true; }
+}
+#else
+
+#if defined(HAVE_PTHREAD_H) && defined(HAVE_PTHREAD_RWLOCK_INIT)
+
+#include <cassert>
+#include <pthread.h>
+#include <stdlib.h>
+
+namespace llvm {
+using namespace sys;
+
+
+// This variable is useful for situations where the pthread library has been
+// compiled with weak linkage for its interface symbols. This allows the
+// threading support to be turned off by simply not linking against -lpthread.
+// In that situation, the value of pthread_mutex_init will be 0 and
+// consequently pthread_enabled will be false. In such situations, all the
+// pthread operations become no-ops and the functions all return false. If
+// pthread_rwlock_init does have an address, then rwlock support is enabled.
+// Note: all LLVM tools will link against -lpthread if its available since it
+//       is configured into the LIBS variable.
+// Note: this line of code generates a warning if pthread_rwlock_init is not
+//       declared with weak linkage. It's safe to ignore the warning.
+static const bool pthread_enabled = true;
+
+// Construct a RWMutex using pthread calls
+RWMutexImpl::RWMutexImpl()
+  : data_(0)
+{
+  if (pthread_enabled)
+  {
+    // Declare the pthread_rwlock data structures
+    pthread_rwlock_t* rwlock =
+      static_cast<pthread_rwlock_t*>(malloc(sizeof(pthread_rwlock_t)));
+
+#ifdef __APPLE__
+    // Workaround a bug/mis-feature in Darwin's pthread_rwlock_init.
+    bzero(rwlock, sizeof(pthread_rwlock_t));
+#endif
+
+    // Initialize the rwlock
+    int errorcode = pthread_rwlock_init(rwlock, NULL);
+    (void)errorcode;
+    assert(errorcode == 0);
+
+    // Assign the data member
+    data_ = rwlock;
+  }
+}
+
+// Destruct a RWMutex
+RWMutexImpl::~RWMutexImpl()
+{
+  if (pthread_enabled)
+  {
+    pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
+    assert(rwlock != 0);
+    pthread_rwlock_destroy(rwlock);
+    free(rwlock);
+  }
+}
+
+bool
+RWMutexImpl::reader_acquire()
+{
+  if (pthread_enabled)
+  {
+    pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
+    assert(rwlock != 0);
+
+    int errorcode = pthread_rwlock_rdlock(rwlock);
+    return errorcode == 0;
+  } else return false;
+}
+
+bool
+RWMutexImpl::reader_release()
+{
+  if (pthread_enabled)
+  {
+    pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
+    assert(rwlock != 0);
+
+    int errorcode = pthread_rwlock_unlock(rwlock);
+    return errorcode == 0;
+  } else return false;
+}
+
+bool
+RWMutexImpl::writer_acquire()
+{
+  if (pthread_enabled)
+  {
+    pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
+    assert(rwlock != 0);
+
+    int errorcode = pthread_rwlock_wrlock(rwlock);
+    return errorcode == 0;
+  } else return false;
+}
+
+bool
+RWMutexImpl::writer_release()
+{
+  if (pthread_enabled)
+  {
+    pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
+    assert(rwlock != 0);
+
+    int errorcode = pthread_rwlock_unlock(rwlock);
+    return errorcode == 0;
+  } else return false;
+}
+
+}
+
+#elif defined(LLVM_ON_UNIX)
+#include "Unix/RWMutex.inc"
+#elif defined( LLVM_ON_WIN32)
+#include "Windows/RWMutex.inc"
+#else
+#warning Neither LLVM_ON_UNIX nor LLVM_ON_WIN32 was set in System/Mutex.cpp
+#endif
+#endif