Add support for RISC-V Vector Extension

- Add compile options and detection logic for RISC-V Vector Extension (RVV)
- Implement RVV-optimized memory copy in the IncrementalCopy function
- Add RISC-V toolchain configuration file

Signed-off-by: w1m024 <iwangyiming@qq.com>
Co-authored-by: chenmiaoi <chenmiao.ku@gmail.com>
Co-authored-by: gong-flying <gongxiaofei24@iscas.ac.cn>

Author: 3 people

CMakeLists.txt

@@ -49,6 +49,8 @@ option(SNAPPY_REQUIRE_AVX "Target processors with AVX support." OFF)
 
 option(SNAPPY_REQUIRE_AVX2 "Target processors with AVX2 support." OFF)
 
+option(SNAPPY_REQUIRE_RVV "Target processors with RVV support." OFF)
+
 option(SNAPPY_INSTALL "Install Snappy's header and library" ON)
 
 include(TestBigEndian)
@@ -63,6 +65,8 @@ check_include_file("sys/time.h" HAVE_SYS_TIME_H)
 check_include_file("sys/uio.h" HAVE_SYS_UIO_H)
 check_include_file("unistd.h" HAVE_UNISTD_H)
 check_include_file("windows.h" HAVE_WINDOWS_H)
+check_include_file("sse2rvv.h" HAVE_SSE2RISCV_INSTRINSIC_H)
+check_include_file("riscv_vector.h" HAVE_RISCV_INSTRINSIC_H)
 
 include(CheckLibraryExists)
 check_library_exists(z zlibVersion "" HAVE_LIBZ)
@@ -73,6 +77,7 @@ CHECK_CXX_COMPILER_FLAG("/arch:AVX" HAVE_VISUAL_STUDIO_ARCH_AVX)
 CHECK_CXX_COMPILER_FLAG("/arch:AVX2" HAVE_VISUAL_STUDIO_ARCH_AVX2)
 CHECK_CXX_COMPILER_FLAG("-mavx" HAVE_CLANG_MAVX)
 CHECK_CXX_COMPILER_FLAG("-mbmi2" HAVE_CLANG_MBMI2)
+CHECK_CXX_COMPILER_FLAG("-march=rv64gcv" HAVE_CLANG_RVV)
 if(SNAPPY_REQUIRE_AVX2)
   if(HAVE_VISUAL_STUDIO_ARCH_AVX2)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /arch:AVX2")
@@ -90,6 +95,10 @@ elseif (SNAPPY_REQUIRE_AVX)
   if(HAVE_CLANG_MAVX)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mavx")
   endif(HAVE_CLANG_MAVX)
+elseif (SNAPPY_REQUIRE_RVV)
+  if(HAVE_CLANG_RVV)
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -march=rv64gcv")
+  endif(HAVE_CLANG_RVV)
 endif(SNAPPY_REQUIRE_AVX2)
 
 include(CheckCXXSourceCompiles)
@@ -115,6 +124,42 @@ int main() {
   return 0;
 }" SNAPPY_HAVE_SSSE3)
 
+check_cxx_source_compiles("
+#include <riscv_vector.h>
+
+#define vreinterpretq_f64_m128i(x) \
+  __riscv_vreinterpret_v_i64m1_i32m1(__riscv_vreinterpret_v_f64m1_i64m1(x))
+#define vreinterpretq_m128i_i64(x) __riscv_vreinterpret_v_i32m1_i64m1(x)
+#define vreinterpretq_i64_m128i(x) __riscv_vreinterpret_v_i64m1_i32m1(x)
+#define vreinterpretq_m128i_i8(x) __riscv_vreinterpret_v_i32m1_i8m1(x)
+#define vreinterpretq_i8_m128i(x) __riscv_vreinterpret_v_i8m1_i32m1(x)
+
+int main() {
+  const vint32m1_t *src = 0;
+  vint32m1_t dest;
+  const vint32m1_t shuffle_mask = vreinterpretq_f64_m128i(
+      __riscv_vle64_v_f64m1((double const *)src, 2));
+
+  vint64m1_t addr = vreinterpretq_m128i_i64(*src);
+  vint64m1_t zeros = __riscv_vmv_v_x_i64m1(0, 2);
+
+  vint32m1_t a = vreinterpretq_i64_m128i(
+      __riscv_vslideup_vx_i64m1_tu(addr, zeros, 1, 2));
+
+  vint8m1_t _a = vreinterpretq_m128i_i8(a);
+  vint8m1_t _b = vreinterpretq_m128i_i8(shuffle_mask);
+  vbool8_t mask_lt_zero = __riscv_vmslt_vx_i8m1_b8(_b, 0, 16);
+  vuint8m1_t idxs =
+      __riscv_vreinterpret_v_i8m1_u8m1(__riscv_vand_vx_i8m1(_b, 0xf, 16));
+  vint8m1_t shuffle = __riscv_vrgather_vv_i8m1(_a, idxs, 16);
+      
+  const vint32m1_t pattern = vreinterpretq_i8_m128i(
+      __riscv_vmerge_vxm_i8m1(shuffle, 0, mask_lt_zero, 16));
+      
+  dest = pattern;
+  return 0;
+}" SNAPPY_HAVE_RVV)
+
 check_cxx_source_compiles("
 #include <immintrin.h>
 int main() {

cmake/config.h.in

@@ -52,6 +52,9 @@
 /* Define to 1 if you target processors with SSSE3+ and have <tmmintrin.h>. */
 #cmakedefine01 SNAPPY_HAVE_SSSE3
 
+/* Define to 1 if you target processors with RVV and have <riscv_vector.h>. */
+#cmakedefine01 SNAPPY_HAVE_RVV
+
 /* Define to 1 if you target processors with BMI2+ and have <bmi2intrin.h>. */
 #cmakedefine01 SNAPPY_HAVE_BMI2
 

cmake/toolchain-riscv.cmake

@@ -0,0 +1,13 @@
+# Usage: cmake -DCMAKE_TOOLCHAIN_FILE=path/to/toolchain-riscv.cmake ..
+
+set(CMAKE_SYSTEM_NAME Linux)
+set(CMAKE_SYSTEM_PROCESSOR riscv64)
+
+# Specify the cross compiler
+set(CMAKE_C_COMPILER "riscv64-unknown-linux-gnu-gcc")
+set(CMAKE_CXX_COMPILER "riscv64-unknown-linux-gnu-g++")
+
+set(CMAKE_C_FLAGS "-march=rv64gcv -mabi=lp64d" CACHE INTERNAL "C compiler flags")
+set(CMAKE_CXX_FLAGS "-march=rv64gcv -mabi=lp64d -static-libstdc++" CACHE INTERNAL "C++ compiler flags")
+
+include_directories(/usr/lib/gcc-cross/riscv64-linux-gnu/14/include)

snappy.cc

@@ -62,6 +62,10 @@
 #include <tmmintrin.h>
 #endif
 
+#if SNAPPY_HAVE_RVV
+#include <riscv_vector.h>
+#endif
+
 #if SNAPPY_HAVE_BMI2
 // Please do not replace with <x86intrin.h>. or with headers that assume more
 // advanced SSE versions without checking with all the OWNERS.
@@ -252,6 +256,30 @@ inline char* IncrementalCopy(const char* src, char* op, char* const op_limit,
       if (SNAPPY_PREDICT_TRUE(op >= op_limit)) return op_limit;
     }
     return IncrementalCopySlow(src, op, op_limit);
+#elif defined (SNAPPY_HAVE_RVV)
+    size_t bytes_to_copy = op_limit - op;
+    while (bytes_to_copy > 0) {
+
+    size_t vl = __riscv_vsetvl_e8m1(bytes_to_copy);
+
+    vuint8m1_t pattern_source = __riscv_vle8_v_u8m1(
+        reinterpret_cast<const uint8_t*>(src), pattern_size);
+    vuint8m1_t indices_sequential = __riscv_vid_v_u8m1(vl);
+    vuint8m1_t indices_repeating = __riscv_vremu_vx_u8m1(
+        indices_sequential, pattern_size, vl);
+
+    vuint8m1_t pattern_to_write = __riscv_vrgather_vv_u8m1(
+        pattern_source, indices_repeating, vl);
+
+    __riscv_vse8_v_u8m1(reinterpret_cast<uint8_t*>(op), pattern_to_write, vl);
+
+    op += vl;
+    bytes_to_copy -= vl;
+  }
+
+  return op_limit;
+
+
 #else  // !SNAPPY_HAVE_SSSE3
     // If plenty of buffer space remains, expand the pattern to at least 8
     // bytes. The way the following loop is written, we need 8 bytes of buffer