try to re-enable SSE2 support by default on mingw 64-bit

README.md

@@ -6,7 +6,7 @@ single-file public domain libraries for C/C++
 library    | lastest version | category | LoC | description
 --------------------- | ---- | -------- | --- | --------------------------------
 **stb_vorbis.c** | 1.04 | audio | 5443 | decode ogg vorbis files from file/memory to float/16-bit signed output
-**stb_image.h** | 2.03 | graphics | 6426 | image loading/decoding from file/memory: JPG, PNG, TGA, BMP, PSD, GIF, HDR, PIC
+**stb_image.h** | 2.04 | graphics | 6433 | image loading/decoding from file/memory: JPG, PNG, TGA, BMP, PSD, GIF, HDR, PIC
 **stb_truetype.h** | 1.04 | graphics | 2631 | parse, decode, and rasterize characters from truetype fonts
 **stb_image_write.h** | 0.98 | graphics | 730 | image writing to disk: PNG, TGA, BMP
 **stb_image_resize.h** | 0.90 | graphics | 2585 | resize images larger/smaller with good quality
@@ -25,7 +25,7 @@ library    | lastest version | category | LoC | description
 **stb_leakcheck.h** | 0.2 | misc | 117 | quick-and-dirty malloc/free leak-checking
 
 Total libraries: 18  
-Total lines of C code: 45235
+Total lines of C code: 45242
 
 
 FAQ

stb_image.h

@@ -1,4 +1,4 @@
-/* stb_image - v2.03 - public domain image loader - http://nothings.org/stb_image.h
+/* stb_image - v2.04 - public domain image loader - http://nothings.org/stb_image.h
                                      no warranty implied; use at your own risk
 
    Do this:
@@ -143,6 +143,7 @@
 
 
    Latest revision history:
+      2.04  (2015-04-15) try to re-enable SIMD on MinGW 64-bit
       2.03  (2015-04-12) additional corruption checking
                          stbi_set_flip_vertically_on_load
                          fix NEON support; fix mingw support
@@ -633,11 +634,14 @@ typedef unsigned char validate_uint32[sizeof(stbi__uint32)==4 ? 1 : -1];
 #endif
 
 // x86/x64 detection
-#if defined(__x86_64__) || defined(_M_X64) || defined(__i386) || defined(_M_IX86)
+#if defined(__x86_64__) || defined(_M_X64)
+#define STBI__X64_TARGET
+#elif defined(__i386) || defined(_M_IX86)
 #define STBI__X86_TARGET
 #endif
 
-#if defined(__GNUC__) && defined(STBI__X86_TARGET) && !defined(__SSE2__) && !defined(STBI_NO_SIMD)
+#if defined(__GNUC__) && (defined(STBI__X86_TARGET) || defined(STBI__X64_TARGET)) && !defined(__SSE2__) && !defined(STBI_NO_SIMD)
+// NOTE: not clear do we actually need this for the 64-bit path?
 // gcc doesn't support sse2 intrinsics unless you compile with -msse2,
 // (but compiling with -msse2 allows the compiler to use SSE2 everywhere;
 // this is just broken and gcc are jerks for not fixing it properly
@@ -646,6 +650,8 @@ typedef unsigned char validate_uint32[sizeof(stbi__uint32)==4 ? 1 : -1];
 #endif
 
 #if defined(__MINGW32__) && defined(STBI__X86_TARGET) && !defined(STBI_MINGW_ENABLE_SSE2) && !defined(STBI_NO_SIMD)
+// Note that __MINGW32__ doesn't actually mean 32-bit, so we have to avoid STBI__X64_TARGET
+//
 // 32-bit MinGW wants ESP to be 16-byte aligned, but this is not in the
 // Windows ABI and VC++ as well as Windows DLLs don't maintain that invariant.
 // As a result, enabling SSE2 on 32-bit MinGW is dangerous when not
@@ -6287,6 +6293,7 @@ STBIDEF int stbi_info_from_callbacks(stbi_io_callbacks const *c, void *user, int
 
 /*
    revision history:
+      2.04  (2015-04-15) try to re-enable SIMD on MinGW 64-bit
       2.03  (2015-04-12) extra corruption checking (mmozeiko)
                          stbi_set_flip_vertically_on_load (nguillemot)
                          fix NEON support; fix mingw support