[llvm] [OFFLOAD] Add plugin with support for Intel oneAPI Level Zero (PR #158900)

[Alex Duran via llvm-commits]

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@@ -0,0 +1,657 @@
+//===--- Level Zero Target RTL Implementation -----------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// GenericKernel implementation for SPIR-V/Xe machine
+//
+//===----------------------------------------------------------------------===//
+
+#include "L0Kernel.h"
+#include "L0Device.h"
+#include "L0Plugin.h"
+#include "L0Program.h"
+
+namespace llvm::omp::target::plugin {
+
+Error L0KernelTy::launchImpl(GenericDeviceTy &GenericDevice,
+                             uint32_t NumThreads[3], uint32_t NumBlocks[3],
+                             KernelArgsTy &KernelArgs,
+                             KernelLaunchParamsTy LaunchParams,
+                             AsyncInfoWrapperTy &AsyncInfoWrapper) const {
+
+  auto &l0Device = L0DeviceTy::makeL0Device(GenericDevice);
+  int32_t RC = runTargetTeamRegion(l0Device, KernelArgs,
+                                   std::move(LaunchParams), AsyncInfoWrapper);
+  if (RC == OFFLOAD_SUCCESS)
+    return Plugin::success();
+  return Plugin::error(error::ErrorCode::UNKNOWN,
+                       "Error in launch Kernel %s: %d", getName(), RC);
+}
+
+Error L0KernelTy::buildKernel(L0ProgramTy &Program) {
+  const auto *KernelName = getName();
+
+  auto Module = Program.findModuleFromKernelName(KernelName);
+  ze_kernel_desc_t KernelDesc = {ZE_STRUCTURE_TYPE_KERNEL_DESC, nullptr, 0,
+                                 KernelName};
+  CALL_ZE_RET_ERROR(zeKernelCreate, Module, &KernelDesc, &zeKernel);
+  return Plugin::success();
+}
+
+Error L0KernelTy::initImpl(GenericDeviceTy &GenericDevice,
+                           DeviceImageTy &Image) {
+  auto &Program = L0ProgramTy::makeL0Program(Image);
+
+  Error Err = buildKernel(Program);
+  if (Err)
+    return Err;
+  Program.addKernel(this);
+
+  return Plugin::success();
+}
+
+/// Read global thread limit and max teams from the host runtime. These values
+/// are subject to change at any program point, so every kernel execution
+/// needs to read the most recent values.
+static std::tuple<int32_t, int32_t> readTeamsThreadLimit() {
+  int ThrLimit;
+  ThrLimit = omp_get_teams_thread_limit();
+  DP("omp_get_teams_thread_limit() returned %" PRId32 "\n", ThrLimit);
+  // omp_get_thread_limit() would return INT_MAX by default.
+  // NOTE: Windows.h defines max() macro, so we have to guard
+  //       the call with parentheses.
+  int32_t ThreadLimit =
+      (ThrLimit > 0 && ThrLimit != (std::numeric_limits<int32_t>::max)())
+          ? ThrLimit
+          : 0;
+
+  int NTeams = omp_get_max_teams();
----------------
adurang wrote:

It's not linked against OpenMP, there's a wrapper that accesses OpenMP information if available or otherwise returns a default value.

Should this be here? the answer is eventually no. This should be provided by the higher levels (libomptarget, liboffload, ...) but the current interfaces do not provide this information so we had to get some way. 

I hope we can move this to where belongs in a subsequent PR but I would like to avoid changing the Plugin interfaces here.

https://github.com/llvm/llvm-project/pull/158900