HADOOP-19663. Add RISC-V CRC32 build scaffolding and placeholder

Co-authored-by: gong-flying <gongxiaofei24@iscas.ac.cn>

Author: peterpetrica

hadoop-common-project/hadoop-common/src/CMakeLists.txt

@@ -157,6 +157,8 @@ if(CMAKE_SYSTEM_PROCESSOR MATCHES "^i.86$" OR CMAKE_SYSTEM_PROCESSOR STREQUAL "x
   set(BULK_CRC_ARCH_SOURCE_FIlE "${SRC}/util/bulk_crc32_x86.c")
 elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL "aarch64")
   set(BULK_CRC_ARCH_SOURCE_FIlE "${SRC}/util/bulk_crc32_aarch64.c")
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^riscv64" OR CMAKE_SYSTEM_PROCESSOR MATCHES "^riscv32")
+  set(BULK_CRC_ARCH_SOURCE_FIlE "${SRC}/util/bulk_crc32_riscv.c")
 else()
   message("No HW CRC acceleration for ${CMAKE_SYSTEM_PROCESSOR}, falling back to SW")
 endif()

hadoop-common-project/hadoop-common/src/main/native/src/org/apache/hadoop/util/bulk_crc32_riscv.c

@@ -0,0 +1,39 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * RISC-V CRC32 hardware acceleration (placeholder)
+ *
+ * Phase 1: provide a RISC-V-specific compilation unit that currently makes
+ * no runtime changes and falls back to the generic software path in
+ * bulk_crc32.c. Future work will add Zbc-based acceleration and runtime
+ * dispatch.
+ */
+
+#include <assert.h>
+#include <stddef.h> // for size_t
+
+#include "bulk_crc32.h"
+#include "gcc_optimizations.h"
+
+/* Constructor hook reserved for future HW capability detection and
+ * function-pointer dispatch. Intentionally a no-op for the initial phase. */
+void __attribute__((constructor)) init_riscv_crc_support(void)
+{
+  /* No-op: keep using the default software implementations. */
+}