add test

Author: jhuber6

libc/test/integration/src/__support/GPU/CMakeLists.txt

@@ -9,3 +9,12 @@ add_integration_test(
   LOADER_ARGS
     --threads 64
 )
+
+add_integration_test(
+  shuffle_test
+  SUITE libc-support-gpu-tests
+  SRCS
+    shuffle.cpp
+  LOADER_ARGS
+    --threads 64
+)

libc/test/integration/src/__support/GPU/shuffle.cpp

@@ -0,0 +1,33 @@
+//===-- Test for the shuffle operations on the GPU ------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/GPU/utils.h"
+#include "test/IntegrationTest/test.h"
+
+using namespace LIBC_NAMESPACE;
+
+// Test to make sure the shuffle instruction works by doing a simple broadcast.
+// Each iteration reduces the width, so it will broadcast to a subset we check.
+static void test_shuffle() {
+  uint64_t mask = gpu::get_lane_mask();
+  EXPECT_EQ(cpp::popcount(mask), gpu::get_lane_size());
+
+  uint32_t x = gpu::get_lane_id();
+  for (uint32_t width = gpu::get_lane_size(); width > 0; width /= 2)
+    EXPECT_EQ(gpu::shuffle(mask, 0, x, width), (x / width) * width);
+}
+
+TEST_MAIN(int argc, char **argv, char **envp) {
+  if (gpu::get_thread_id() >= gpu::get_lane_size())
+    return 0;
+
+  test_shuffle();
+
+  return 0;
+}