[SYCL] Implement accessor default constructor (#6940)

This patch implements SYCL 2020 accessor default constructor

sycl/include/sycl/accessor.hpp

@@ -1182,6 +1182,15 @@ class __SYCL_SPECIAL_CLASS __SYCL_TYPE(accessor) accessor :
       return reinterpret_cast<PtrType>(AccessorBaseHost::getPtr());
   }
 
+public:
+  accessor()
+      : AccessorBaseHost(
+            /*Offset=*/{0, 0, 0}, /*AccessRange=*/{0, 0, 0},
+            /*MemoryRange=*/{0, 0, 0},
+            /*AccessMode=*/getAdjustedMode({}),
+            /*SYCLMemObject=*/nullptr, /*Dims=*/0, /*ElemSize=*/0,
+            /*OffsetInBytes=*/0, /*IsSubBuffer=*/false, /*PropertyList=*/{}){};
+
 #endif // __SYCL_DEVICE_ONLY__
 
 private:
@@ -1937,7 +1946,7 @@ class __SYCL_SPECIAL_CLASS __SYCL_TYPE(accessor) accessor :
   size_t byte_size() const noexcept { return size() * sizeof(DataT); }
 
   size_t max_size() const noexcept {
-    return (std::numeric_limits<difference_type>::max)();
+    return empty() ? 0 : (std::numeric_limits<difference_type>::max)();
   }
 
   bool empty() const noexcept { return size() == 0; }

sycl/source/detail/scheduler/commands.cpp

@@ -2001,6 +2001,8 @@ static pi_result SetKernelParamsAndLaunch(
       break;
     case kernel_param_kind_t::kind_accessor: {
       Requirement *Req = (Requirement *)(Arg.MPtr);
+      if (Req->MAccessRange == range<3>({0, 0, 0}))
+        break;
       if (getMemAllocationFunc == nullptr)
         throw sycl::exception(make_error_code(errc::kernel_argument),
                               "placeholder accessor must be bound by calling "

sycl/test/basic_tests/accessor/accessor_default_ctor.cpp

@@ -0,0 +1,19 @@
+// RUN: %clangxx -fsycl -fsycl-targets=%sycl_triple %s -o %t.out
+
+#include <sycl/sycl.hpp>
+
+int main() {
+  sycl::accessor<int, 0, sycl::access::mode::read_write, sycl::target::device>
+      B;
+  assert(B.empty());
+  assert(B.size() == 0);
+  assert(B.max_size() == 0);
+  assert(B.byte_size() == 0);
+  // The return values of get_pointer() and get_multi_ptr() are unspecified.
+  assert(B.get_pointer() == nullptr);
+  // TODO: uncomment check with get_multi_ptr() when SYCL 2020 mupti_ptr feature
+  // will be merged
+  // assert(B.get_multi_ptr() == nullptr);
+
+  return 0;
+}

sycl/unittests/scheduler/AccessorDefaultCtor.cpp

@@ -0,0 +1,42 @@
+#include "SchedulerTest.hpp"
+#include "SchedulerTestUtils.hpp"
+#include <detail/handler_impl.hpp>
+
+#include <helpers/PiMock.hpp>
+#include <helpers/ScopedEnvVar.hpp>
+#include <helpers/TestKernel.hpp>
+
+#include <vector>
+
+using namespace sycl;
+
+TEST_F(SchedulerTest, AccDefaultCtorDoesntAffectDepGraph) {
+  unittest::PiMock Mock;
+  platform Plt = Mock.getPlatform();
+
+  queue QueueDev(context(Plt), default_selector_v);
+  MockScheduler MS;
+
+  detail::QueueImplPtr QueueDevImpl = detail::getSyclObjImpl(QueueDev);
+
+  std::vector<detail::Command *> ToEnqueue;
+
+  MockHandlerCustomFinalize MockCGH(QueueDevImpl, false);
+
+  sycl::accessor<int, 0, sycl::access::mode::read_write, sycl::target::device>
+      B;
+
+  MockCGH.single_task<class acc_with_zero_dim>([=]() {
+    int size = B.size();
+    (void)size;
+  });
+
+  std::unique_ptr<sycl::detail::CG> CmdGroup = MockCGH.finalize();
+
+  detail::Command *NewCmd =
+      MS.addCG(std::move(CmdGroup), QueueDevImpl, ToEnqueue);
+
+  // if MDeps is empty, accessor built from default ctor does not affect
+  // dependency graph in accordance with SYCL 2020
+  EXPECT_TRUE(NewCmd->MDeps.empty());
+}

sycl/unittests/scheduler/CMakeLists.txt

@@ -23,4 +23,5 @@ add_sycl_unittest(SchedulerTests OBJECT
     InOrderQueueSyncCheck.cpp
     RunOnHostIntelCG.cpp
     EnqueueWithDependsOnDeps.cpp
+    AccessorDefaultCtor.cpp
 )

sycl/unittests/scheduler/EnqueueWithDependsOnDeps.cpp

@@ -8,7 +8,6 @@
 
 #include "SchedulerTest.hpp"
 #include "SchedulerTestUtils.hpp"
-#include <detail/handler_impl.hpp>
 
 #include <helpers/PiMock.hpp>
 #include <helpers/ScopedEnvVar.hpp>
@@ -19,48 +18,13 @@
 using namespace sycl;
 using EventImplPtr = std::shared_ptr<detail::event_impl>;
 
-namespace DependsOnTest {
-class MockHandlerCustom : public MockHandler {
-public:
-  MockHandlerCustom(std::shared_ptr<sycl::detail::queue_impl> Queue,
-                    bool IsHost)
-      : MockHandler(Queue, IsHost) {}
-
-  std::unique_ptr<sycl::detail::CG> finalize() {
-    std::unique_ptr<sycl::detail::CG> CommandGroup;
-    switch (getType()) {
-    case sycl::detail::CG::Kernel: {
-      CommandGroup.reset(new sycl::detail::CGExecKernel(
-          getNDRDesc(), std::move(getHostKernel()), getKernel(),
-          std::move(MImpl->MKernelBundle), getArgsStorage(), getAccStorage(),
-          getSharedPtrStorage(), getRequirements(), getEvents(), getArgs(),
-          getKernelName(), getOSModuleHandle(), getStreamStorage(),
-          MImpl->MAuxiliaryResources, getCGType(), getCodeLoc()));
-      break;
-    }
-    case sycl::detail::CG::CodeplayHostTask: {
-      CommandGroup.reset(new detail::CGHostTask(
-          std::move(getHostTask()), getQueue(), getQueue()->getContextImplPtr(),
-          getArgs(), getArgsStorage(), getAccStorage(), getSharedPtrStorage(),
-          getRequirements(), getEvents(), getCGType(), getCodeLoc()));
-      break;
-    }
-    default:
-      throw sycl::runtime_error("Unhandled type of command group",
-                                PI_ERROR_INVALID_OPERATION);
-    }
-
-    return CommandGroup;
-  }
-};
-} // namespace DependsOnTest
 detail::Command *AddTaskCG(bool IsHost, MockScheduler &MS,
                            detail::QueueImplPtr DevQueue,
                            const std::vector<EventImplPtr> &Events) {
   std::vector<detail::Command *> ToEnqueue;
 
   // Emulating processing of command group function
-  DependsOnTest::MockHandlerCustom MockCGH(DevQueue, false);
+  MockHandlerCustomFinalize MockCGH(DevQueue, false);
 
   for (auto EventImpl : Events)
     MockCGH.depends_on(detail::createSyclObjFromImpl<event>(EventImpl));

sycl/unittests/scheduler/SchedulerTestUtils.hpp

@@ -10,6 +10,7 @@
 #include <detail/queue_impl.hpp>
 #include <detail/scheduler/commands.hpp>
 #include <detail/scheduler/scheduler.hpp>
+#include <detail/handler_impl.hpp>
 #include <detail/stream_impl.hpp>
 #include <sycl/detail/cl.h>
 
@@ -270,4 +271,38 @@ class MockHandler : public sycl::handler {
 
     return nullptr;
   }
-};
+};
+
+class MockHandlerCustomFinalize : public MockHandler {
+public:
+  MockHandlerCustomFinalize(std::shared_ptr<sycl::detail::queue_impl> Queue,
+                            bool IsHost)
+      : MockHandler(Queue, IsHost) {}
+
+  std::unique_ptr<sycl::detail::CG> finalize() {
+    std::unique_ptr<sycl::detail::CG> CommandGroup;
+    switch (getType()) {
+    case sycl::detail::CG::Kernel: {
+      CommandGroup.reset(new sycl::detail::CGExecKernel(
+          getNDRDesc(), std::move(getHostKernel()), getKernel(),
+          std::move(MImpl->MKernelBundle), getArgsStorage(), getAccStorage(),
+          getSharedPtrStorage(), getRequirements(), getEvents(), getArgs(),
+          getKernelName(), getOSModuleHandle(), getStreamStorage(),
+          MImpl->MAuxiliaryResources, getCGType(), getCodeLoc()));
+      break;
+    }
+    case sycl::detail::CG::CodeplayHostTask: {
+      CommandGroup.reset(new sycl::detail::CGHostTask(
+          std::move(getHostTask()), getQueue(), getQueue()->getContextImplPtr(),
+          getArgs(), getArgsStorage(), getAccStorage(), getSharedPtrStorage(),
+          getRequirements(), getEvents(), getCGType(), getCodeLoc()));
+      break;
+    }
+    default:
+      throw sycl::runtime_error("Unhandled type of command group",
+                                PI_ERROR_INVALID_OPERATION);
+    }
+
+    return CommandGroup;
+  }
+};