add sw_64 platform support (#3421)

Co-authored-by: wangzhengyang <wangzhengyang@uniontech.com>

CMakeLists.txt

@@ -205,6 +205,11 @@ elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(xtensa)")
     set(NCNN_TARGET_ARCH xtensa)
 elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(s390x)")
     set(NCNN_TARGET_ARCH s390x)
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(sw_64)")
+    set(NCNN_TARGET_ARCH sw_64)
+    #sw_64 is alpha-like platform
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mieee")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mieee")
 else()
     set(NCNN_TARGET_ARCH x86)
     option(NCNN_SSE2 "optimize x86 platform with sse2" ON)