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>

modules/core/include/opencv2/core/cv_cpu_dispatch.h

@@ -172,6 +172,11 @@
 #  define CV_MSA 1
 #endif
 
+#ifdef CV_CPU_COMPILE_LASX
+#  include <lasxintrin.h>
+#  define CV_LASX 1
+#endif
+
 #ifdef __EMSCRIPTEN__
 #  define CV_WASM_SIMD 1
 #  include <wasm_simd128.h>
@@ -370,3 +375,7 @@ struct VZeroUpperGuard {
 #ifndef CV_RVV
 #  define CV_RVV 0
 #endif
+
+#ifndef CV_LASX
+#  define CV_LASX 0
+#endif

modules/core/include/opencv2/core/cv_cpu_helper.h

@@ -525,5 +525,26 @@
 #endif
 #define __CV_CPU_DISPATCH_CHAIN_RVV(fn, args, mode, ...)  CV_CPU_CALL_RVV(fn, args); __CV_EXPAND(__CV_CPU_DISPATCH_CHAIN_ ## mode(fn, args, __VA_ARGS__))
 
+#if !defined CV_DISABLE_OPTIMIZATION && defined CV_ENABLE_INTRINSICS && defined CV_CPU_COMPILE_LASX
+#  define CV_TRY_LASX 1
+#  define CV_CPU_FORCE_LASX 1
+#  define CV_CPU_HAS_SUPPORT_LASX 1
+#  define CV_CPU_CALL_LASX(fn, args) return (cpu_baseline::fn args)
+#  define CV_CPU_CALL_LASX_(fn, args) return (opt_LASX::fn args)
+#elif !defined CV_DISABLE_OPTIMIZATION && defined CV_ENABLE_INTRINSICS && defined CV_CPU_DISPATCH_COMPILE_LASX
+#  define CV_TRY_LASX 1
+#  define CV_CPU_FORCE_LASX 0
+#  define CV_CPU_HAS_SUPPORT_LASX (cv::checkHardwareSupport(CV_CPU_LASX))
+#  define CV_CPU_CALL_LASX(fn, args) if (CV_CPU_HAS_SUPPORT_LASX) return (opt_LASX::fn args)
+#  define CV_CPU_CALL_LASX_(fn, args) if (CV_CPU_HAS_SUPPORT_LASX) return (opt_LASX::fn args)
+#else
+#  define CV_TRY_LASX 0
+#  define CV_CPU_FORCE_LASX 0
+#  define CV_CPU_HAS_SUPPORT_LASX 0
+#  define CV_CPU_CALL_LASX(fn, args)
+#  define CV_CPU_CALL_LASX_(fn, args)
+#endif
+#define __CV_CPU_DISPATCH_CHAIN_LASX(fn, args, mode, ...)  CV_CPU_CALL_LASX(fn, args); __CV_EXPAND(__CV_CPU_DISPATCH_CHAIN_ ## mode(fn, args, __VA_ARGS__))
+
 #define CV_CPU_CALL_BASELINE(fn, args) return (cpu_baseline::fn args)
 #define __CV_CPU_DISPATCH_CHAIN_BASELINE(fn, args, mode, ...)  CV_CPU_CALL_BASELINE(fn, args) /* last in sequence */

modules/core/include/opencv2/core/cvdef.h

@@ -279,6 +279,8 @@ namespace cv {
 
 #define CV_CPU_RVV              210
 
+#define CV_CPU_LASX             230
+
 // CPU features groups
 #define CV_CPU_AVX512_SKX       256
 #define CV_CPU_AVX512_COMMON    257
@@ -336,6 +338,8 @@ enum CpuFeatures {
 
     CPU_RVV             = 210,
 
+    CPU_LASX             = 230,
+
     CPU_AVX512_SKX      = 256, //!< Skylake-X with AVX-512F/CD/BW/DQ/VL
     CPU_AVX512_COMMON   = 257, //!< Common instructions AVX-512F/CD for all CPUs that support AVX-512
     CPU_AVX512_KNL      = 258, //!< Knights Landing with AVX-512F/CD/ER/PF

modules/core/include/opencv2/core/hal/intrin.hpp

@@ -231,8 +231,16 @@ using namespace CV_CPU_OPTIMIZATION_HAL_NAMESPACE;
 
 #elif CV_RVV && !defined(CV_FORCE_SIMD128_CPP) && !defined(CV_RVV_SCALABLE)
 #include "opencv2/core/hal/intrin_rvv.hpp"
+
 #elif CV_RVV && !defined(CV_FORCE_SIMD128_CPP) && CV_RVV_SCALABLE
 #include "opencv2/core/hal/intrin_rvv_scalable.hpp"
+
+#elif CV_LASX
+    #if !defined(CV_FORCE_SIMD128_CPP)
+    #define CV_FORCE_SIMD128_CPP 1
+    #endif
+#include "opencv2/core/hal/intrin_cpp.hpp"
+
 #else
 
 #include "opencv2/core/hal/intrin_cpp.hpp"
@@ -267,6 +275,14 @@ using namespace CV_CPU_OPTIMIZATION_HAL_NAMESPACE;
 
 #endif
 
+#if CV_LASX
+
+#define CV__SIMD_FORWARD 256
+#include "opencv2/core/hal/intrin_forward.hpp"
+#include "opencv2/core/hal/intrin_lasx.hpp"
+
+#endif
+
 //! @cond IGNORED
 
 namespace cv {