Add Loongson Advanced SIMD Extension support: -DCPU_BASELINE=LASX

* Add Loongson Advanced SIMD Extension support: -DCPU_BASELINE=LASX
* Add resize.lasx.cpp for Loongson SIMD acceleration
* Add imgwarp.lasx.cpp for Loongson SIMD acceleration
* Add LASX acceleration support for dnn/conv
* Add CV_PAUSE(v) for Loongarch
* Set LASX by default on Loongarch64
* LoongArch: tune test threshold for Core/HAL.mat_decomp/15

Co-authored-by: shengwenxue <shengwenxue@loongson.cn>

cmake/OpenCVCompilerOptimizations.cmake

@@ -50,6 +50,7 @@ list(APPEND CPU_ALL_OPTIMIZATIONS NEON VFPV3 FP16 NEON_DOTPROD)
 list(APPEND CPU_ALL_OPTIMIZATIONS MSA)
 list(APPEND CPU_ALL_OPTIMIZATIONS VSX VSX3)
 list(APPEND CPU_ALL_OPTIMIZATIONS RVV)
+list(APPEND CPU_ALL_OPTIMIZATIONS LASX)
 list(REMOVE_DUPLICATES CPU_ALL_OPTIMIZATIONS)
 
 ocv_update(CPU_VFPV3_FEATURE_ALIAS "")
@@ -380,6 +381,12 @@ elseif(RISCV)
   set(CPU_DISPATCH "RVV" CACHE STRING "${HELP_CPU_DISPATCH}")
   set(CPU_BASELINE "RVV" CACHE STRING "${HELP_CPU_BASELINE}")
 
+elseif(LOONGARCH64)
+  ocv_update(CPU_LASX_TEST_FILE "${OpenCV_SOURCE_DIR}/cmake/checks/cpu_lasx.cpp")
+  ocv_update(CPU_KNOWN_OPTIMIZATIONS "LASX")
+  ocv_update(CPU_LASX_FLAGS_ON "-mlasx")
+  set(CPU_BASELINE "LASX" CACHE STRING "${HELP_CPU_BASELINE}")
+
 endif()
 
 # Helper values for cmake-gui

cmake/OpenCVDetectCXXCompiler.cmake

@@ -100,6 +100,8 @@ elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(mips.*|MIPS.*)")
   set(MIPS 1)
 elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(riscv.*|RISCV.*)")
   set(RISCV 1)
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(loongarch64.*|LOONGARCH64.*)")
+  set(LOONGARCH64 1)
 else()
   if(NOT OPENCV_SUPPRESS_MESSAGE_UNRECOGNIZED_SYSTEM_PROCESSOR)
     message(WARNING "OpenCV: unrecognized target processor configuration")

cmake/checks/cpu_lasx.cpp

@@ -0,0 +1,23 @@
+#include <stdio.h>
+
+#if defined(__loongarch_asx)
+#  include <lasxintrin.h>
+#  define CV_LASX 1
+#endif
+
+#if defined CV_LASX
+int test()
+{
+    const float src[] = { 0.0f, 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f };
+    v8f32 val = (v8f32)__lasx_xvld((const float*)(src), 0);
+    return __lasx_xvpickve2gr_w(__lasx_xvftint_w_s (val), 7);
+}
+#else
+#error "LASX is not supported"
+#endif
+
+int main()
+{
+  printf("%d\n", test());
+  return 0;
+}