[libc-commits] [clang] [compiler-rt] [libc] [llvm] [PGO][AMDGPU] Add offload profiling with uniformity-aware optimization (PR #177665)

[Yaxun Liu via libc-commits]

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@@ -0,0 +1,68 @@
+/*===- InstrProfilingGPU.c - GPU profile counter 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
+|*
+\*===----------------------------------------------------------------------===*/
+
+#if defined(__AMDGPU__) || defined(__NVPTX__)
+
+#include <gpuintrin.h>
+#include <stdint.h>
+
+#define ATOMIC_ADD(ptr, val)                                                   \
+  __scoped_atomic_fetch_add(ptr, val, __ATOMIC_RELAXED, __MEMORY_SCOPE_DEVICE)
+
+/*
+ * Check if this block is sampled (PatternOverflow mode).
+ * Samples by matching lower bits of flat block ID to 0.
+ *
+ * sampling_bits: 0 = all blocks (100%)
+ *                1 = even blocks (50%)
+ *                2 = every 4th block (25%)
+ *                3 = every 8th block (12.5%)
+ */
+__attribute__((visibility("hidden"), used)) int
+__gpu_pgo_is_sampled(uint32_t sampling_bits) {
+  if (sampling_bits == 0)
+    return 1;
+
+  uint32_t gdx = __gpu_num_blocks_x();
+  uint32_t gdy = __gpu_num_blocks_y();
+  uint32_t block_id = __gpu_block_id_x() + __gpu_block_id_y() * gdx +
+                      __gpu_block_id_z() * gdx * gdy;
+
+  uint32_t mask = (1u << sampling_bits) - 1;
+  return (block_id & mask) == 0;
+}
+
+typedef uint64_t __attribute__((address_space(1))) * global_u64_ptr;
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yxsamliu wrote:

Resolved in the refactored code — no numbered address spaces remain.

https://github.com/llvm/llvm-project/pull/177665