implement XLAHooks and register it to PyTorch when loaded.

torch_xla/csrc/BUILD

@@ -270,6 +270,7 @@ ptxla_cc_library(
         ":status",
         ":tensor",
         ":version",
+        ":xla_hooks",
         "//torch_xla/csrc/runtime",
         "//torch_xla/csrc/runtime:pjrt_computation_client",
         "//torch_xla/csrc/runtime:metrics",
@@ -374,3 +375,21 @@ cc_library(
         "@com_google_absl//absl/status:statusor",
     ],
 )
+
+ptxla_cc_library(
+    name = "xla_hooks",
+    srcs = [
+        "xla_hooks.cpp",
+    ],
+    hdrs = [
+        "xla_hooks.h",
+    ],
+    deps = [
+        "//torch_xla/csrc:device",
+        "//torch_xla/csrc:tensor", 
+        "//torch_xla/csrc/runtime:computation_client",
+        "//torch_xla/csrc/runtime",
+        "//torch_xla/csrc/runtime:xla_util",
+    ],
+)
+

torch_xla/csrc/xla_hooks.cpp

@@ -0,0 +1,98 @@
+#include "xla_hooks.h"
+
+#include <iostream>
+#include <sstream>
+
+// PyTorch integration headers
+#include <ATen/core/Generator.h>
+#include <ATen/detail/XLAHooksInterface.h>
+#include <c10/core/Device.h>
+#include <c10/core/DeviceType.h>
+#include <c10/util/Exception.h>
+#include <c10/util/Logging.h>
+#include <c10/util/intrusive_ptr.h>
+
+// XLA headers
+#include "torch_xla/csrc/aten_xla_bridge.h"
+#include "torch_xla/csrc/runtime/computation_client.h"
+#include "torch_xla/csrc/runtime/debug_macros.h"
+#include "torch_xla/csrc/runtime/runtime.h"
+#include "xla_backend_impl.h"
+#include "xla_generator.h"
+
+namespace torch_xla::detail {
+
+void XLAHooks::init() const {
+  C10_LOG_API_USAGE_ONCE("aten.init.xla");
+
+  // Initialize XLA backend - this registers XLA functions and sets up
+  // the backend infrastructure
+  torch_xla::InitXlaBackend();
+}
+
+bool XLAHooks::hasXLA() const { return isAvailable(); }
+
+bool XLAHooks::isAvailable() const {
+  try {
+    return deviceCount() > 0;
+  } catch (...) {
+    // If device enumeration fails, XLA is not available
+    return false;
+  }
+}
+
+std::string XLAHooks::showConfig() const {
+  std::ostringstream oss;
+  oss << "XLA Backend Configuration:\n";
+  oss << "  - XLA devices available: " << deviceCount() << "\n";
+  return oss.str();
+}
+
+c10::DeviceIndex XLAHooks::deviceCount() const {
+  auto maybe_client = torch_xla::runtime::GetComputationClient();
+  if (!maybe_client.ok()) {
+    // If runtime client initialization failed, return 0 devices
+    return 0;
+  }
+
+  auto* client = maybe_client.value();
+  return static_cast<c10::DeviceIndex>(client->GetNumDevices());
+}
+
+c10::DeviceIndex XLAHooks::getCurrentDevice() const {
+  return bridge::GetCurrentAtenDevice().index();
+}
+
+bool XLAHooks::hasPrimaryContext(c10::DeviceIndex device_index) const {
+  TORCH_CHECK(false, "hasPrimaryContext is not implemented.");
+}
+
+bool XLAHooks::isPinnedPtr(const void* data) const {
+  TORCH_CHECK(false, "isPinnedPtr is not implemented.");
+}
+
+c10::Allocator* XLAHooks::getPinnedMemoryAllocator() const {
+  TORCH_CHECK(false, "getPinnedMemoryAllocator is not implemented.");
+}
+
+c10::Device XLAHooks::getDeviceFromPtr(void* data) const {
+  TORCH_CHECK(false, "getDeviceFromPtr is not implemented.");
+}
+
+const at::Generator& XLAHooks::getDefaultGenerator(
+    c10::DeviceIndex device_index) const {
+  return at::detail::getDefaultXLAGenerator(device_index);
+}
+
+at::Generator XLAHooks::getNewGenerator(c10::DeviceIndex device_index) const {
+  // Create and return a new XLA generator using the make_generator template
+  // function
+  return at::make_generator<at::XLAGeneratorImpl>(device_index);
+}
+
+}  // namespace torch_xla::detail
+
+// Register XLA hooks with PyTorch on module load
+namespace at {
+REGISTER_XLA_HOOKS(torch_xla::detail::XLAHooks)
+}  // namespace at

torch_xla/csrc/xla_hooks.h

@@ -0,0 +1,42 @@
+#pragma once
+
+#include <string>
+
+// PyTorch integration headers
+#include <ATen/core/Generator.h>
+#include <ATen/detail/XLAHooksInterface.h>
+#include <c10/core/Device.h>
+#include <c10/core/DeviceType.h>
+#include <c10/util/Exception.h>
+
+namespace torch_xla::detail {
+
+// XLA hooks implementation following PyTorch patterns
+struct XLAHooks : public at::XLAHooksInterface {
+  XLAHooks(const at::XLAHooksArgs& args) {}
+
+  // Core accelerator interface methods
+  void init() const override;
+  bool hasXLA() const override;
+  bool isAvailable() const override;
+  bool isBuilt() const override { return true; }
+  std::string showConfig() const override;
+
+  // Device management
+  c10::DeviceIndex deviceCount() const override;
+  c10::DeviceIndex getCurrentDevice() const override;
+  bool hasPrimaryContext(c10::DeviceIndex device_index) const override;
+
+  // Memory management
+  bool isPinnedPtr(const void* data) const override;
+  c10::Allocator* getPinnedMemoryAllocator() const override;
+  c10::Device getDeviceFromPtr(void* data) const override;
+
+  // Generator methods
+  const at::Generator& getDefaultGenerator(
+      c10::DeviceIndex device_index = -1) const override;
+  at::Generator getNewGenerator(
+      c10::DeviceIndex device_index = -1) const override;
+};
+
+}  // namespace torch_xla::detail