Make the queue backend discoverable in sycl_core.

     - Rename SyclQueueManager to SyclRTManager
     - Minor stylistic changes:
          -- reorder functions alphabetically.
	  -- Move all enums into separate file.
     - Add C API to get backend from queue,
       and also add a way to check if a queue is the current queue.
     - Update sycl_core to match C API.

Author: Diptorup Deb

Diff for: backends/include/dppl_sycl_device_interface.h

@@ -28,31 +28,14 @@
 #pragma once
 
 #include "dppl_data_types.h"
+#include "dppl_sycl_enum_types.h"
 #include "dppl_sycl_types.h"
 #include "Support/DllExport.h"
 #include "Support/ExternC.h"
 #include "Support/MemOwnershipAttrs.h"
 
 DPPL_C_EXTERN_C_BEGIN
 
-/*!
- * @brief Redefinition of Sycl's device_type so that we do not have to include
- * sycl.hpp here and in the Python bindings.
- *
- */
-enum DPPLSyclDeviceType
-{
-    DPPL_CPU         = 1 << 0,
-    DPPL_GPU         = 1 << 1,
-    DPPL_ACCELERATOR = 1 << 2,
-    DPPL_CUSTOM      = 1 << 3,
-    DPPL_AUTOMATIC   = 1 << 4,
-    DPPL_HOST_DEVICE = 1 << 5,
-    DPPL_ALL         = 1 << 6
-    // IMP: before adding new values here look at DPPLSyclBEType enum. The
-    // values should not overlap.
-};
-
 /*!
  * @brief Prints out some of the info::deivice attributes for the device.
  *

Diff for: backends/include/dppl_sycl_enum_types.h

@@ -0,0 +1,90 @@
+//===--- dppl_sycl_enum_types.h - DPPL-SYCL interface ---*---C++ -----*----===//
+//
+//               Python Data Parallel Processing Library (PyDPPL)
+//
+// Copyright 2020 Intel Corporation
+//
+// 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.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header defines DPPL specficif enum types that wrap corresponding Sycl
+/// enum classes. These enums are defined primarily so that Python extensions
+/// that use DPPL do not have to include Sycl headers directly.
+///
+//===----------------------------------------------------------------------===//
+
+#pragma once
+
+#include "Support/ExternC.h"
+
+DPPL_C_EXTERN_C_BEGIN
+
+/*!
+ * @brief Redefinition of DPC++-specific Sycl backend types.
+ *
+ */
+enum DPPLSyclBEType
+{
+    DPPL_UNKNOWN_BACKEND = 0x0,
+    DPPL_OPENCL          = 1 << 16,
+    DPPL_HOST            = 1 << 15,
+    DPPL_LEVEL_ZERO      = 1 << 14,
+    DPPL_CUDA            = 1 << 13
+};
+
+/*!
+ * @brief DPPL device types that are equivalent to Sycl's device_type.
+ *
+ */
+enum DPPLSyclDeviceType
+{
+    DPPL_CPU         = 1 << 0,
+    DPPL_GPU         = 1 << 1,
+    DPPL_ACCELERATOR = 1 << 2,
+    DPPL_CUSTOM      = 1 << 3,
+    DPPL_AUTOMATIC   = 1 << 4,
+    DPPL_HOST_DEVICE = 1 << 5,
+    DPPL_ALL         = 1 << 6
+    // IMP: before adding new values here look at DPPLSyclBEType enum. The
+    // values should not overlap.
+};
+
+/*!
+ * @brief Supported types for kernel arguments to be passed to a Sycl kernel
+ * using DPPL.
+ *
+ * \todo Add support for sycl::buffer
+ *
+ */
+typedef enum
+{
+    DPPL_CHAR,
+    DPPL_SIGNED_CHAR,
+    DPPL_UNSIGNED_CHAR,
+    DPPL_SHORT,
+    DPPL_INT,
+    DPPL_UNSIGNED_INT,
+    DPPL_LONG,
+    DPPL_UNSIGNED_LONG,
+    DPPL_LONG_LONG,
+    DPPL_UNSIGNED_LONG_LONG,
+    DPPL_SIZE_T,
+    DPPL_FLOAT,
+    DPPL_DOUBLE,
+    DPPL_LONG_DOUBLE,
+    DPPL_VOID_PTR
+} DPPLKernelArgType;
+
+DPPL_C_EXTERN_C_END

Diff for: backends/include/dppl_sycl_platform_interface.h

@@ -26,26 +26,13 @@
 #pragma once
 
 #include "dppl_data_types.h"
+#include "dppl_sycl_enum_types.h"
 #include "Support/DllExport.h"
 #include "Support/ExternC.h"
 #include "Support/MemOwnershipAttrs.h"
 
 DPPL_C_EXTERN_C_BEGIN
 
-/*!
- * @brief Redefinition of DPC++'s backend types. We have this wrapper so that
- * the sycl header is not exposed to Python extensions.
- *
- */
-enum DPPLSyclBEType
-{
-    DPPL_UNKNOWN_BACKEND = 0x0,
-    DPPL_OPENCL          = 1 << 16,
-    DPPL_HOST            = 1 << 15,
-    DPPL_LEVEL_ZERO      = 1 << 14,
-    DPPL_CUDA            = 1 << 13
-};
-
 /*!
  * @brief Returns the number of sycl::platform available on the system.
  *

Diff for: backends/include/dppl_sycl_queue_interface.h

@@ -28,6 +28,7 @@
 #pragma once
 
 #include "dppl_data_types.h"
+#include "dppl_sycl_enum_types.h"
 #include "dppl_sycl_types.h"
 #include "Support/DllExport.h"
 #include "Support/ExternC.h"
@@ -36,37 +37,21 @@
 DPPL_C_EXTERN_C_BEGIN
 
 /*!
- * @brief Supported types for kernel arguments to be passed to a Sycl kernel.
- *
- * \todo Add support for sycl::buffer
+ * @brief Delete the pointer after casting it to sycl::queue.
  *
+ * @param    QRef           A DPPLSyclQueueRef pointer that gets deleted.
  */
-typedef enum
-{
-    DPPL_CHAR,
-    DPPL_SIGNED_CHAR,
-    DPPL_UNSIGNED_CHAR,
-    DPPL_SHORT,
-    DPPL_INT,
-    DPPL_UNSIGNED_INT,
-    DPPL_LONG,
-    DPPL_UNSIGNED_LONG,
-    DPPL_LONG_LONG,
-    DPPL_UNSIGNED_LONG_LONG,
-    DPPL_SIZE_T,
-    DPPL_FLOAT,
-    DPPL_DOUBLE,
-    DPPL_LONG_DOUBLE,
-    DPPL_VOID_PTR
-} DPPLKernelArgType;
+DPPL_API
+void DPPLQueue_Delete (__dppl_take DPPLSyclQueueRef QRef);
 
 /*!
- * @brief Delete the pointer after casting it to sycl::queue.
+ * @brief Returns the Sycl backend for the provided sycl::queue.
  *
- * @param    QRef           A DPPLSyclQueueRef pointer that gets deleted.
+ * @param    QRef           An opaque pointer to the sycl queue.
+ * @return   A enum DPPLSyclBEType corresponding to the backed for the queue.
  */
 DPPL_API
-void DPPLQueue_Delete (__dppl_take DPPLSyclQueueRef QRef);
+enum DPPLSyclBEType DPPLQueue_GetBackend (__dppl_keep DPPLSyclQueueRef QRef);
 
 /*!
  * @brief Returns the Sycl context for the queue.

Diff for: backends/include/dppl_sycl_queue_manager.h

@@ -91,6 +91,17 @@ DPPL_API
 size_t DPPLQueueMgr_GetNumQueues (enum DPPLSyclBEType BETy,
                                   enum DPPLSyclDeviceType DeviceTy);
 
+/*!
+ * @brief Returns True if the passed in queue and the current queue are the
+ * same, else returns False.
+ *
+ * @param    QRef           An opaque pointer to a sycl::queue.
+ * @return   True or False depending on whether the QRef argument is the same as
+ * the currently activated queue.
+ */
+DPPL_API
+bool DPPLQueueMgr_IsCurrentQueue (__dppl_keep const DPPLSyclQueueRef QRef);
+
 /*!
 * @brief Set the default DPPL queue to the sycl::queue for the given backend
 * and device type combination.

Diff for: backends/include/dppl_sycl_types.h

@@ -25,6 +25,10 @@
 
 #pragma once
 
+#include "Support/ExternC.h"
+
+DPPL_C_EXTERN_C_BEGIN
+
 /*!
  * @brief Opaque pointer to a sycl::context
  *
@@ -74,3 +78,5 @@ typedef struct DPPLOpaqueSyclQueue *DPPLSyclQueueRef;
  * @see sycl::usm
  */
 typedef struct DPPLOpaqueSyclUSM *DPPLSyclUSMRef;
+
+DPPL_C_EXTERN_C_END

Diff for: backends/source/dppl_sycl_queue_interface.cpp

@@ -25,6 +25,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "dppl_sycl_queue_interface.h"
+#include "dppl_sycl_context_interface.h"
 #include "Support/CBindingWrapping.h"
 
 #include <CL/sycl.hpp>                /* SYCL headers   */
@@ -117,6 +118,13 @@ void DPPLQueue_Delete (__dppl_take DPPLSyclQueueRef QRef)
     delete unwrap(QRef);
 }
 
+enum DPPLSyclBEType DPPLQueue_GetBackend (__dppl_keep DPPLSyclQueueRef QRef)
+{
+    auto Q = unwrap(QRef);
+    auto C = Q->get_context();
+    return DPPLContext_GetBackend(wrap(&C));
+}
+
 __dppl_give DPPLSyclDeviceRef
 DPPLQueue_GetDevice (__dppl_keep const DPPLSyclQueueRef QRef)
 {

Diff for: backends/source/dppl_sycl_queue_manager.cpp

@@ -121,6 +121,8 @@ class QMgrHelper
     static __dppl_give DPPLSyclQueueRef
     getCurrentQueue ();
 
+    static bool isCurrentQueue (__dppl_keep const DPPLSyclQueueRef QRef);
+
     static void
     setAsDefaultQueue (enum DPPLSyclBEType BETy,
                        enum DPPLSyclDeviceType DeviceTy,
@@ -144,13 +146,14 @@ class QMgrHelper
  */
 DPPLSyclQueueRef QMgrHelper::getCurrentQueue ()
 {
-    if(get_active_queues().empty()) {
+    auto activated_q = get_active_queues();
+    if(activated_q.empty()) {
         // \todo handle error
         std::cerr << "No currently active queues.\n";
         return nullptr;
     }
-    auto last = QMgrHelper::get_active_queues().size() - 1;
-    return wrap(new queue(QMgrHelper::get_active_queues()[last]));
+    auto last = activated_q.size() - 1;
+    return wrap(new queue(activated_q[last]));
 }
 
 /*!
@@ -212,6 +215,28 @@ QMgrHelper::getQueue (enum DPPLSyclBEType BETy,
     return wrap(QRef);
 }
 
+/*!
+ * Compares the context and device of the current queue to the context and
+ * device of the queue passed as input. Return true if both queues have the
+ * same context and device.
+ */
+bool QMgrHelper::isCurrentQueue (__dppl_keep const DPPLSyclQueueRef QRef)
+{
+    auto activated_q = get_active_queues();
+    if(activated_q.empty()) {
+        // \todo handle error
+        std::cerr << "No currently active queues.\n";
+        return false;
+    }
+    auto last = activated_q.size() - 1;
+    auto currQ = activated_q[last];
+    auto currCtx = currQ.get_context();
+    auto currD = currQ.get_device();
+    auto InD = unwrap(QRef)->get_device();
+    auto InCtx = unwrap(QRef)->get_context();
+    return (currCtx == InCtx && currD == InD);
+}
+
 /*!
  * Changes the first entry into the stack, i.e., the default queue to a new
  * sycl::queue corresponding to the device type and device number.
@@ -420,6 +445,13 @@ DPPLSyclQueueRef DPPLQueueMgr_GetQueue (enum DPPLSyclBEType BETy,
     return QMgrHelper::getQueue(BETy, DeviceTy, DNum);
 }
 
+/*!
+
+* */
+bool DPPLQueueMgr_IsCurrentQueue (__dppl_keep const DPPLSyclQueueRef QRef)
+{
+    return QMgrHelper::isCurrentQueue(QRef);
+}
 /*!
  * The function sets the global queue, i.e., the sycl::queue object at
  * QMgrHelper::active_queues[0] vector to the sycl::queue corresponding to the