Merge pull request #26884 from lve-gh:split8u_rvv_hal

[HAL] split8u RVV 1.0 #26884

### Pull Request Readiness Checklist
* Banana Pi BF3 (SpacemiT K1)
* Compiler: Syntacore Clang 18.1.4 (build 2024.12)
```
Geometric mean (ms)

                  Name of Test                   baseline  hal      hal
                                                    ui               vs
                                                                  baseline 
                                                                     ui
                                                                 (x-factor)
split::Size_Depth_Channels::(127x61, 8UC1, 2)     0.012   0.004     3.12   
split::Size_Depth_Channels::(127x61, 8UC1, 3)     0.019   0.006     2.91   
split::Size_Depth_Channels::(127x61, 8UC1, 4)     0.028   0.011     2.64   
split::Size_Depth_Channels::(127x61, 8UC1, 5)     0.067   0.033     2.02   
split::Size_Depth_Channels::(127x61, 8UC1, 6)     0.084   0.040     2.11   
split::Size_Depth_Channels::(127x61, 8UC1, 7)     0.103   0.055     1.88   
split::Size_Depth_Channels::(127x61, 8UC1, 8)     0.113   0.032     3.50   
split::Size_Depth_Channels::(640x480, 8UC1, 2)    0.454   0.179     2.54   
split::Size_Depth_Channels::(640x480, 8UC1, 3)    0.677   0.298     2.27   
split::Size_Depth_Channels::(640x480, 8UC1, 4)    0.901   0.410     2.20   
split::Size_Depth_Channels::(640x480, 8UC1, 5)    3.781   3.010     1.26   
split::Size_Depth_Channels::(640x480, 8UC1, 6)    4.886   4.009     1.22   
split::Size_Depth_Channels::(640x480, 8UC1, 7)    5.777   4.770     1.21   
split::Size_Depth_Channels::(640x480, 8UC1, 8)    4.596   1.330     3.46   
split::Size_Depth_Channels::(1280x720, 8UC1, 2)   1.377   0.709     1.94   
split::Size_Depth_Channels::(1280x720, 8UC1, 3)   2.091   1.034     2.02   
split::Size_Depth_Channels::(1280x720, 8UC1, 4)   2.744   1.573     1.74   
split::Size_Depth_Channels::(1280x720, 8UC1, 5)   9.542   6.284     1.52   
split::Size_Depth_Channels::(1280x720, 8UC1, 6)   11.114  7.850     1.42   
split::Size_Depth_Channels::(1280x720, 8UC1, 7)   14.083  11.879    1.19   
split::Size_Depth_Channels::(1280x720, 8UC1, 8)   13.524  3.865     3.50   
split::Size_Depth_Channels::(1920x1080, 8UC1, 2)  3.108   1.395     2.23   
split::Size_Depth_Channels::(1920x1080, 8UC1, 3)  4.659   2.128     2.19   
split::Size_Depth_Channels::(1920x1080, 8UC1, 4)  6.127   2.818     2.17   
split::Size_Depth_Channels::(1920x1080, 8UC1, 5)  26.733  16.625    1.61   
split::Size_Depth_Channels::(1920x1080, 8UC1, 6)  31.242  22.414    1.39   
split::Size_Depth_Channels::(1920x1080, 8UC1, 7)  35.968  27.658    1.30   
split::Size_Depth_Channels::(1920x1080, 8UC1, 8)  29.997  8.655     3.47
```
See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

3rdparty/hal_rvv/hal_rvv.hpp

@@ -27,6 +27,7 @@
 #include "hal_rvv_1p0/convert_scale.hpp" // core
 #include "hal_rvv_1p0/minmax.hpp" // core
 #include "hal_rvv_1p0/atan.hpp" // core
+#include "hal_rvv_1p0/split.hpp" // core
 #endif
 
 #endif

3rdparty/hal_rvv/hal_rvv_1p0/split.hpp

@@ -0,0 +1,93 @@
+// This file is part of OpenCV project.
+// It is subject to the license terms in the LICENSE file found in the top-level directory
+// of this distribution and at http://opencv.org/license.html.
+#ifndef OPENCV_HAL_RVV_SPLIT_HPP_INCLUDED
+#define OPENCV_HAL_RVV_SPLIT_HPP_INCLUDED
+
+#include <riscv_vector.h>
+
+namespace cv { namespace cv_hal_rvv {
+
+#undef cv_hal_split8u
+#define cv_hal_split8u cv::cv_hal_rvv::split8u
+
+inline int split8u(const uchar* src, uchar** dst, int len, int cn)
+{
+    int vl = 0;
+    if (cn == 1)
+    {
+        uchar* dst0 = dst[0];
+        for (int i = 0; i < len; i += vl)
+        {
+            vl = __riscv_vsetvl_e8m8(len - i);
+            __riscv_vse8_v_u8m8(dst0 + i, __riscv_vle8_v_u8m8(src + i, vl), vl);
+        }
+    }
+    else if (cn == 2)
+    {
+        uchar *dst0 = dst[0], *dst1 = dst[1];
+        for (int i = 0; i < len; i += vl)
+        {
+            vl = __riscv_vsetvl_e8m4(len - i);
+            vuint8m4x2_t seg = __riscv_vlseg2e8_v_u8m4x2(src + i * cn, vl);
+            __riscv_vse8_v_u8m4(dst0 + i, __riscv_vget_v_u8m4x2_u8m4(seg, 0), vl);
+            __riscv_vse8_v_u8m4(dst1 + i, __riscv_vget_v_u8m4x2_u8m4(seg, 1), vl);
+        }
+    }
+    else if (cn == 3)
+    {
+        uchar *dst0 = dst[0], *dst1 = dst[1], *dst2 = dst[2];
+        for (int i = 0; i < len; i += vl)
+        {
+            vl = __riscv_vsetvl_e8m2(len - i);
+            vuint8m2x3_t seg = __riscv_vlseg3e8_v_u8m2x3(src + i * cn, vl);
+            __riscv_vse8_v_u8m2(dst0 + i, __riscv_vget_v_u8m2x3_u8m2(seg, 0), vl);
+            __riscv_vse8_v_u8m2(dst1 + i, __riscv_vget_v_u8m2x3_u8m2(seg, 1), vl);
+            __riscv_vse8_v_u8m2(dst2 + i, __riscv_vget_v_u8m2x3_u8m2(seg, 2), vl);
+        }
+    }
+    else if (cn == 4)
+    {
+        uchar *dst0 = dst[0], *dst1 = dst[1], *dst2 = dst[2], *dst3 = dst[3];
+        for (int i = 0; i < len; i += vl)
+        {
+            vl = __riscv_vsetvl_e8m2(len - i);
+            vuint8m2x4_t seg = __riscv_vlseg4e8_v_u8m2x4(src + i * cn, vl);
+            __riscv_vse8_v_u8m2(dst0 + i, __riscv_vget_v_u8m2x4_u8m2(seg, 0), vl);
+            __riscv_vse8_v_u8m2(dst1 + i, __riscv_vget_v_u8m2x4_u8m2(seg, 1), vl);
+            __riscv_vse8_v_u8m2(dst2 + i, __riscv_vget_v_u8m2x4_u8m2(seg, 2), vl);
+            __riscv_vse8_v_u8m2(dst3 + i, __riscv_vget_v_u8m2x4_u8m2(seg, 3), vl);
+        }
+    }
+    else
+    {
+        int k = 0;
+        for (; k <= cn - 4; k += 4)
+        {
+            uchar *dst0 = dst[k], *dst1 = dst[k + 1], *dst2 = dst[k + 2], *dst3 = dst[k + 3];
+            for (int i = 0; i < len; i += vl)
+            {
+                vl = __riscv_vsetvl_e8m2(len - i);
+                vuint8m2x4_t seg = __riscv_vlsseg4e8_v_u8m2x4(src + k + i * cn, cn, vl);
+                __riscv_vse8_v_u8m2(dst0 + i, __riscv_vget_v_u8m2x4_u8m2(seg, 0), vl);
+                __riscv_vse8_v_u8m2(dst1 + i, __riscv_vget_v_u8m2x4_u8m2(seg, 1), vl);
+                __riscv_vse8_v_u8m2(dst2 + i, __riscv_vget_v_u8m2x4_u8m2(seg, 2), vl);
+                __riscv_vse8_v_u8m2(dst3 + i, __riscv_vget_v_u8m2x4_u8m2(seg, 3), vl);
+            }
+        }
+        for (; k < cn; ++k)
+        {
+            uchar* dstK = dst[k];
+            for (int i = 0; i < len; i += vl)
+            {
+                vl = __riscv_vsetvl_e8m2(len - i);
+                vuint8m2_t seg = __riscv_vlse8_v_u8m2(src + k + i * cn, cn, vl);
+                __riscv_vse8_v_u8m2(dstK + i, seg, vl);
+            }
+        }
+    }
+    return CV_HAL_ERROR_OK;
+}
+
+}}
+#endif