Felix-Gong commented on code in PR #3360:
URL: https://github.com/apache/brpc/pull/3360#discussion_r3490609015
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src/butil/third_party/snappy/snappy.cc:
##########
@@ -97,9 +97,33 @@ static const uint32_t kMaximumTagLength = 5; //
COPY_4_BYTE_OFFSET plus the act
// or memmove().
static inline void IncrementalCopy(const char* src, char* op, ssize_t len) {
assert(len > 0);
+#if defined(__riscv) && __riscv_xlen == 64
+ // RISC-V optimized: use 8-byte copies when possible
+ if (len >= 8 && (op - src >= 8 || src - op >= 8)) {
+ // Non-overlapping or safe overlap: copy 8 bytes at a time
+ do {
+ uint64_t tmp;
+ __asm__ volatile(
+ "ld %0, %1\n\t"
+ "sd %0, %2\n\t"
+ : "=&r"(tmp)
+ : "m"(*(const uint64_t*)src), "m"(*(uint64_t*)op)
+ : "memory");
+ src += 8;
+ op += 8;
+ len -= 8;
+ } while (len >= 8);
+ }
Review Comment:
Fixed. Added runtime alignment check with `((uintptr_t)src | (uintptr_t)op)
& 7) == 0`. Only uses `ld`/`sd` when both pointers are 8-byte aligned,
otherwise falls back to byte-by-byte copy.
##########
src/butil/third_party/snappy/snappy-stubs-internal.h:
##########
@@ -164,6 +164,16 @@ inline void UNALIGNED_STORE64(void *p, uint64_t v) {
// This can be more efficient than UNALIGNED_LOAD64 + UNALIGNED_STORE64
// on some platforms, in particular ARM.
inline void UnalignedCopy64(const void *src, void *dst) {
+#if defined(__riscv) && __riscv_xlen == 64
+ // RISC-V optimized: single ld/sd pair for 8-byte copy
+ uint64_t tmp;
+ __asm__ volatile(
+ "ld %0, %1\n\t"
+ "sd %0, %2\n\t"
+ : "=&r"(tmp)
+ : "m"(*(const uint64_t*)src), "m"(*(uint64_t*)dst)
+ : "memory");
+#else
Review Comment:
Fixed. Added alignment check `(((uintptr_t)src | (uintptr_t)dst) & 7) == 0`
before using `ld`/`sd`. Falls back to `memcpy` for unaligned addresses.
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