Copilot commented on code in PR #3390:
URL: https://github.com/apache/brpc/pull/3390#discussion_r3592386748
##########
BUILD.bazel:
##########
@@ -128,6 +128,7 @@ BUTIL_SRCS = [
"src/butil/third_party/icu/icu_utf.cc",
"src/butil/third_party/superfasthash/superfasthash.c",
"src/butil/third_party/modp_b64/modp_b64.cc",
+ "src/butil/third_party/modp_b64/modp_b64_rvv.cc",
Review Comment:
`BUTIL_SRCS` includes `src/butil/third_party/modp_b64/modp_b64_rvv.cc`, but
that file does not exist in the repo (glob found no matches). This will break
Bazel builds with a missing input file error. Remove the entry or add the
corresponding source file in this PR.
##########
src/butil/string_compare_rvv.cc:
##########
@@ -0,0 +1,105 @@
+/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 4 -*- */
+/* vi: set expandtab shiftwidth=4 tabstop=4: */
+/**
+ * \file
+ * RISC-V Vector (RVV) accelerated memcmp/memchr for StringPiece operations.
+ *
+ * Algorithm follows glibc's RVV memcmp/memchr patterns:
+ * - Use vsetvli with e8/m8 for maximum throughput (hardware-adaptive VL)
+ * - Use vfirst.m to find first differing/matching byte (no vcpop needed)
+ * - Simple loop: load → compare → find first → branch
+ *
+ * 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.
+ */
+
+#include "butil/strings/string_piece.h"
+
+#if defined(__riscv) && defined(__riscv_vector)
+#include <riscv_vector.h>
+#include <stdint.h>
+#include <string.h>
+
+namespace butil {
+
+/**
+ * rvv_memcmp - RVV-accelerated byte comparison following glibc pattern.
+ *
+ * Compares two byte arrays and returns:
+ * < 0 if p1 < p2
+ * 0 if p1 == p2
+ * > 0 if p1 > p2
+ *
+ * Uses RVV m8 with hardware-adaptive VL for maximum throughput.
+ */
+int rvv_memcmp(const void* p1, const void* p2, size_t n) {
+ const uint8_t* src1 = static_cast<const uint8_t*>(p1);
+ const uint8_t* src2 = static_cast<const uint8_t*>(p2);
+ size_t remaining = n;
+
+ while (remaining > 0) {
+ size_t vl = __riscv_vsetvl_e8m8(remaining);
+ vuint8m8_t v1 = __riscv_vle8_v_u8m8(src1, vl);
+ vuint8m8_t v2 = __riscv_vle8_v_u8m8(src2, vl);
+ vbool1_t neq = __riscv_vmsne_vv_u8m8_b1(v1, v2, vl);
+ long first = __riscv_vfirst_m_b1(neq, vl);
+
+ if (first >= 0) {
+ uint8_t b1 = src1[first];
+ uint8_t b2 = src2[first];
+ return (b1 < b2) ? -1 : 1;
+ }
Review Comment:
`rvv_memcmp` currently returns only -1 or 1 on mismatch, which may change
observable behavior vs `traits_type::compare`/`memcmp` (many implementations
return the byte difference). It also indexes with `long` directly. Returning
the byte difference and casting the index preserves prior semantics and avoids
sign/diagnostic issues.
##########
src/butil/string_compare_rvv.cc:
##########
@@ -0,0 +1,105 @@
+/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 4 -*- */
+/* vi: set expandtab shiftwidth=4 tabstop=4: */
+/**
+ * \file
+ * RISC-V Vector (RVV) accelerated memcmp/memchr for StringPiece operations.
+ *
+ * Algorithm follows glibc's RVV memcmp/memchr patterns:
+ * - Use vsetvli with e8/m8 for maximum throughput (hardware-adaptive VL)
+ * - Use vfirst.m to find first differing/matching byte (no vcpop needed)
+ * - Simple loop: load → compare → find first → branch
+ *
+ * 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.
+ */
+
+#include "butil/strings/string_piece.h"
+
+#if defined(__riscv) && defined(__riscv_vector)
+#include <riscv_vector.h>
+#include <stdint.h>
+#include <string.h>
+
+namespace butil {
+
+/**
+ * rvv_memcmp - RVV-accelerated byte comparison following glibc pattern.
+ *
+ * Compares two byte arrays and returns:
+ * < 0 if p1 < p2
+ * 0 if p1 == p2
+ * > 0 if p1 > p2
+ *
+ * Uses RVV m8 with hardware-adaptive VL for maximum throughput.
+ */
+int rvv_memcmp(const void* p1, const void* p2, size_t n) {
+ const uint8_t* src1 = static_cast<const uint8_t*>(p1);
+ const uint8_t* src2 = static_cast<const uint8_t*>(p2);
+ size_t remaining = n;
+
+ while (remaining > 0) {
+ size_t vl = __riscv_vsetvl_e8m8(remaining);
+ vuint8m8_t v1 = __riscv_vle8_v_u8m8(src1, vl);
+ vuint8m8_t v2 = __riscv_vle8_v_u8m8(src2, vl);
+ vbool1_t neq = __riscv_vmsne_vv_u8m8_b1(v1, v2, vl);
+ long first = __riscv_vfirst_m_b1(neq, vl);
+
+ if (first >= 0) {
+ uint8_t b1 = src1[first];
+ uint8_t b2 = src2[first];
+ return (b1 < b2) ? -1 : 1;
+ }
+
+ src1 += vl;
+ src2 += vl;
+ remaining -= vl;
+ }
+ return 0;
+}
+
+/**
+ * rvv_memchr - RVV-accelerated byte search following glibc pattern.
+ *
+ * Searches for the first occurrence of byte 'c' in buffer 's' of length 'n'.
+ * Returns pointer to first match, or NULL if not found.
+ *
+ * Uses RVV m8 with hardware-adaptive VL for maximum throughput.
Review Comment:
The doc comment says this returns `NULL` when not found, but the
implementation returns `nullptr`. Aligning the comment with the actual return
value avoids confusion for readers.
##########
src/butil/string_compare_rvv.cc:
##########
@@ -0,0 +1,105 @@
+/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 4 -*- */
+/* vi: set expandtab shiftwidth=4 tabstop=4: */
+/**
+ * \file
+ * RISC-V Vector (RVV) accelerated memcmp/memchr for StringPiece operations.
+ *
+ * Algorithm follows glibc's RVV memcmp/memchr patterns:
+ * - Use vsetvli with e8/m8 for maximum throughput (hardware-adaptive VL)
+ * - Use vfirst.m to find first differing/matching byte (no vcpop needed)
+ * - Simple loop: load → compare → find first → branch
+ *
+ * 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.
+ */
+
+#include "butil/strings/string_piece.h"
+
+#if defined(__riscv) && defined(__riscv_vector)
+#include <riscv_vector.h>
+#include <stdint.h>
+#include <string.h>
+
+namespace butil {
+
+/**
+ * rvv_memcmp - RVV-accelerated byte comparison following glibc pattern.
+ *
+ * Compares two byte arrays and returns:
+ * < 0 if p1 < p2
+ * 0 if p1 == p2
+ * > 0 if p1 > p2
+ *
+ * Uses RVV m8 with hardware-adaptive VL for maximum throughput.
+ */
+int rvv_memcmp(const void* p1, const void* p2, size_t n) {
+ const uint8_t* src1 = static_cast<const uint8_t*>(p1);
+ const uint8_t* src2 = static_cast<const uint8_t*>(p2);
+ size_t remaining = n;
+
+ while (remaining > 0) {
+ size_t vl = __riscv_vsetvl_e8m8(remaining);
+ vuint8m8_t v1 = __riscv_vle8_v_u8m8(src1, vl);
+ vuint8m8_t v2 = __riscv_vle8_v_u8m8(src2, vl);
+ vbool1_t neq = __riscv_vmsne_vv_u8m8_b1(v1, v2, vl);
+ long first = __riscv_vfirst_m_b1(neq, vl);
+
+ if (first >= 0) {
+ uint8_t b1 = src1[first];
+ uint8_t b2 = src2[first];
+ return (b1 < b2) ? -1 : 1;
+ }
+
+ src1 += vl;
+ src2 += vl;
+ remaining -= vl;
+ }
+ return 0;
+}
+
+/**
+ * rvv_memchr - RVV-accelerated byte search following glibc pattern.
+ *
+ * Searches for the first occurrence of byte 'c' in buffer 's' of length 'n'.
+ * Returns pointer to first match, or NULL if not found.
+ *
+ * Uses RVV m8 with hardware-adaptive VL for maximum throughput.
+ */
+const void* rvv_memchr(const void* s, int c, size_t n) {
+ const uint8_t* src = static_cast<const uint8_t*>(s);
+ uint8_t ch = static_cast<uint8_t>(c);
+ size_t remaining = n;
+
+ while (remaining > 0) {
+ size_t vl = __riscv_vsetvl_e8m8(remaining);
+ vuint8m8_t v = __riscv_vle8_v_u8m8(src, vl);
+ vbool1_t eq = __riscv_vmseq_vx_u8m8_b1(v, ch, vl);
+ long first = __riscv_vfirst_m_b1(eq, vl);
+
+ if (first >= 0) {
+ return src + first;
+ }
Review Comment:
This PR adds an RVV `rvv_memchr`, but there are no call sites: `StringPiece`
character search currently uses `std::find`/`std::search` in `string_piece.cc`,
and a repo-wide search only finds the declaration/definition of `rvv_memchr`.
If the goal is to accelerate `StringPiece::find(char)`/related functions, the
dispatch needs to be wired into those implementations; otherwise consider
dropping `rvv_memchr` to avoid carrying unused code.
##########
src/butil/strings/string_piece.h:
##########
@@ -43,6 +43,12 @@
namespace butil {
+// RVV-accelerated byte comparison and search (implemented in
string_compare_rvv.cc)
+#if defined(__riscv) && defined(__riscv_vector)
+int rvv_memcmp(const void* p1, const void* p2, size_t n);
+const void* rvv_memchr(const void* s, int c, size_t n);
+#endif
Review Comment:
`rvv_memcmp`/`rvv_memchr` are declared in a public header and called from an
inline function, but they are not marked with `BUTIL_EXPORT`. In
`COMPONENT_BUILD` configurations this can cause unresolved symbols when linking
users of `StringPiece` against the shared butil component.
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