stb_image: use SDL_TARGETING("sse2") macro for supporting intrinsics on 386

src/video/stb_image.h

@@ -772,7 +772,7 @@ typedef unsigned char validate_uint32[sizeof(stbi__uint32)==4 ? 1 : -1];
 // exposed in GCC/Clang is, sadly, not really suited for one-file libs.
 // New behavior: if compiled with -msse2, we use SSE2 without any
 // detection; if not, we don't use it at all.
-#define STBI_NO_SIMD
+// #define STBI_NO_SIMD /* Changed by SDL: use SDL_TARGETING("sse2") */
 #endif
 
 #if defined(__MINGW32__) && defined(STBI__X86_TARGET) && !defined(STBI_MINGW_ENABLE_SSE2) && !defined(STBI_NO_SIMD)
@@ -2690,7 +2690,7 @@ static void stbi__idct_block(stbi_uc *out, int out_stride, short data[64])
 // sse2 integer IDCT. not the fastest possible implementation but it
 // produces bit-identical results to the generic C version so it's
 // fully "transparent".
-static void stbi__idct_simd(stbi_uc *out, int out_stride, short data[64])
+static void SDL_TARGETING("sse2") stbi__idct_simd(stbi_uc *out, int out_stride, short data[64]) /* Changed by SDL: SDL_TARGETING("sse2") */
 {
    // This is constructed to match our regular (generic) integer IDCT exactly.
    __m128i row0, row1, row2, row3, row4, row5, row6, row7;
@@ -3690,7 +3690,12 @@ static stbi_uc *stbi__resample_row_hv_2(stbi_uc *out, stbi_uc *in_near, stbi_uc
 }
 
 #if defined(STBI_SSE2) || defined(STBI_NEON)
-static stbi_uc *stbi__resample_row_hv_2_simd(stbi_uc *out, stbi_uc *in_near, stbi_uc *in_far, int w, int hs)
+#ifdef STBI_SSE2 /* Added by SDL */
+#define TARGETING_SSE2 SDL_TARGETING("sse2") /* Added by SDL */
+#else
+#define TARGETING_SSE2
+#endif /* Added by SDL */
+static stbi_uc *TARGETING_SSE2 stbi__resample_row_hv_2_simd(stbi_uc *out, stbi_uc *in_near, stbi_uc *in_far, int w, int hs) /* Changed by SDL: TARGETING_SSE2 */
 {
    // need to generate 2x2 samples for every one in input
    int i=0,t0,t1;
@@ -3846,7 +3851,7 @@ static void stbi__YCbCr_to_RGB_row(stbi_uc *out, const stbi_uc *y, const stbi_uc
 }
 
 #if defined(STBI_SSE2) || defined(STBI_NEON)
-static void stbi__YCbCr_to_RGB_simd(stbi_uc *out, stbi_uc const *y, stbi_uc const *pcb, stbi_uc const *pcr, int count, int step)
+static void TARGETING_SSE2 stbi__YCbCr_to_RGB_simd(stbi_uc *out, stbi_uc const *y, stbi_uc const *pcb, stbi_uc const *pcr, int count, int step) /* Changed by SDL: TARGETING_SSE2 */
 {
    int i = 0;