Add SIMD headers

src/libImaging/ImPlatform.h

@@ -96,3 +96,5 @@ typedef signed __int64 int64_t;
 #ifdef __GNUC__
 #define GCC_VERSION (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__)
 #endif
+
+#include "ImagingSIMD.h"

src/libImaging/ImagingSIMD.h

@@ -0,0 +1,41 @@
+/* Microsoft compiler doesn't limit intrinsics for an architecture.
+   This macro is set only on x86 and means SSE2 and above including AVX2. */
+#if defined(_M_X64) || _M_IX86_FP == 2
+    #define __SSE2__
+#endif
+
+#ifdef __SSE4_2__
+    #define __SSE4__
+#endif
+
+#ifdef __SSE2__
+    #include <mmintrin.h>  // MMX
+    #include <xmmintrin.h>  // SSE
+    #include <emmintrin.h>  // SSE2
+#endif
+#ifdef __SSE4__
+    #include <pmmintrin.h>  // SSE3
+    #include <tmmintrin.h>  // SSSE3
+    #include <smmintrin.h>  // SSE4.1
+    #include <nmmintrin.h>  // SSE4.2
+#endif
+#ifdef __AVX2__
+    #include <immintrin.h>  // AVX, AVX2
+#endif
+#ifdef __aarch64__
+    #include <arm_neon.h>  // ARM NEON
+#endif
+
+#ifdef __SSE4__
+static __m128i inline
+mm_cvtepu8_epi32(void *ptr) {
+    return _mm_cvtepu8_epi32(_mm_cvtsi32_si128(*(INT32 *) ptr));
+}
+#endif
+
+#ifdef __AVX2__
+static __m256i inline
+mm256_cvtepu8_epi32(void *ptr) {
+    return _mm256_cvtepu8_epi32(_mm_loadl_epi64((__m128i *) ptr));
+}
+#endif