Add wasi support

cmake -B build -DCMAKE_BUILD_TYPE=Release \
	--toolchain ${wasi_sdk}/share/cmake/wasi-sdk.cmake \
	-DNCNN_RUNTIME_CPU=OFF \
	-DNCNN_DISABLE_EXCEPTION=ON \
	-DNCNN_THREADS=OFF

cmake --build build

After build, you can run benchncnn on cmdline with wasmtime:
wasmtime --dir . benchncnn

CMakeLists.txt

@@ -559,7 +559,7 @@ else()
         unset(CMAKE_REQUIRED_FLAGS)
     endif()
 
-    if(NOT CMAKE_SYSTEM_NAME STREQUAL "Emscripten" AND NCNN_COMPILER_SUPPORT_X86_AVX)
+    if(NOT CMAKE_SYSTEM_NAME MATCHES "Emscripten|WASI" AND NCNN_COMPILER_SUPPORT_X86_AVX)
         option(NCNN_AVX "optimize x86 platform with avx extension" ON)
         if(NCNN_COMPILER_SUPPORT_X86_FMA)
             if(NCNN_AVX)

src/CMakeLists.txt

@@ -395,9 +395,10 @@ if(NCNN_TARGET_ARCH STREQUAL "x86")
             endif()
             target_compile_options(ncnn PRIVATE /D__SSE2__)
         else()
-            target_compile_options(ncnn PRIVATE -msse2 -msse)
-            if(CMAKE_SYSTEM_NAME STREQUAL "Emscripten")
+            if(CMAKE_SYSTEM_NAME MATCHES "Emscripten|WASI")
                 target_compile_options(ncnn PRIVATE -msimd128)
+            else()
+                target_compile_options(ncnn PRIVATE -msse2 -msse)
             endif()
         endif()
     endif()

src/cpu.cpp

@@ -17,8 +17,10 @@
 #include "platform.h"
 
 #include <limits.h>
+#ifndef __wasi__
 #include <setjmp.h>
 #include <signal.h>
+#endif // __wasi__
 #include <stdio.h>
 #include <string.h>