[clang] [libc] [Clang] Implement resource directory headers for common GPU intrinsics (PR #110179)

[Joseph Huber via cfe-commits]

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@@ -0,0 +1,86 @@
+//===-- gpuintrin.h - Generic GPU intrinsic functions ---------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Provides wrappers around the clang builtins for accessing GPU hardware
+// features. The interface is intended to be portable between architectures, but
+// some targets may provide different implementations. This header can be
+// included for all the common GPU programming languages, namely OpenMP, HIP,
+// CUDA, and OpenCL.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __GPUINTRIN_H
+#define __GPUINTRIN_H
+
+#if defined(__NVPTX__)
+#include <nvptxintrin.h>
+#elif defined(__AMDGPU__)
+#include <amdgpuintrin.h>
+#else
+#error "This header is only meant to be used on GPU architectures."
+#endif
+
+// Returns the total number of blocks / workgroups.
+_DEFAULT_ATTRS static inline uint64_t __gpu_num_blocks() {
+  return __gpu_num_blocks_x() * __gpu_num_blocks_y() * __gpu_num_blocks_z();
+}
+
+// Returns the absolute id of the block / workgroup.
+_DEFAULT_ATTRS static inline uint64_t __gpu_block_id() {
+  return __gpu_block_id_x() +
+         (uint64_t)__gpu_num_blocks_x() * __gpu_block_id_y() +
+         (uint64_t)__gpu_num_blocks_x() * __gpu_num_blocks_y() *
+             __gpu_block_id_z();
+}
+
+// Returns the total number of threads in the block / workgroup.
+_DEFAULT_ATTRS static inline uint32_t __gpu_num_threads() {
+  return __gpu_num_threads_x() * __gpu_num_threads_y() * __gpu_num_threads_z();
+}
+
+// Returns the absolute id of the thread in the current block / workgroup.
+_DEFAULT_ATTRS static inline uint32_t __gpu_thread_id() {
+  return __gpu_thread_id_x() + __gpu_num_threads_x() * __gpu_thread_id_y() +
+         __gpu_num_threads_x() * __gpu_num_threads_y() * __gpu_thread_id_z();
+}
+
+// Get the first active thread inside the lane.
+_DEFAULT_ATTRS static inline uint64_t
+__gpu_first_lane_id(uint64_t __lane_mask) {
+  return __builtin_ffsll(__lane_mask) - 1;
+}
+
+// Conditional that is only true for a single thread in a lane.
+_DEFAULT_ATTRS static inline bool __gpu_is_first_lane(uint64_t __lane_mask) {
+  return __gpu_lane_id() == __gpu_first_lane_id(__lane_mask);
+}
+
+// Gets the sum of all lanes inside the warp or wavefront.
+_DEFAULT_ATTRS static inline uint32_t
+__gpu_lane_reduce_u32(uint64_t __lane_mask, uint32_t x) {
+  for (uint32_t step = __gpu_num_lanes() / 2; step > 0; step /= 2) {
+    uint32_t index = step + __gpu_lane_id();
+    x += __gpu_shuffle_idx_u32(__lane_mask, index, x);
+  }
+  return __gpu_broadcast_u32(__lane_mask, x);
+}
+
+// Gets the accumulator scan of the threads in the warp or wavefront.
+_DEFAULT_ATTRS static inline uint32_t __gpu_lane_scan_u32(uint64_t __lane_mask,
+                                                          uint32_t x) {
+  for (uint32_t step = 1; step < __gpu_num_lanes(); step *= 2) {
+    uint32_t index = __gpu_lane_id() - step;
+    uint32_t bitmask = __gpu_lane_id() >= step;
+    x += -bitmask & __gpu_shuffle_idx_u32(__lane_mask, index, x);
+  }
+  return x;
+}
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jhuber6 wrote:

I'll need to look at how to do that on AMDGPU, maybe can add it in a follow-up.

https://github.com/llvm/llvm-project/pull/110179