[Compiled LLVMpipe/Softpipe for Windows]

Done. The portable version still includes the old cygwin binary and runtime for 32-bit apps, though, so please use the DLL from my previous post in place to benchmark as I decided to wait for your results. If you are wondering why I ditched the 64-bit cygwin binary, it isn't just because I was able to build libtxc_dxtn for 64-bit to begin with, but also it was causing instant exits or hangs with 100% CPU utilization on a hyperthread. And all this with an app that doesn't even actively use the extension. It just detects it to show up in a system information board.

[Compiled LLVMpipe/Softpipe for Windows]

Voilà! 1-2 FPS

 

@lowenz, you have complained about poor performance with S3TC, If this is a 32-bit game, this S3TC DLL might help as it does not require cygwin runtime which may deplete performance due its "middleman" position.

I was finally successful on building libtxc_dxtn from source for 32-bit Windows. The problem was Msys2 mingw-w64-i686-toolchain being buggy and failing to make a proper 32-bit DLL. I used mingw-w64-i686 standalone with dwarf exceptions and posix threading. The DLL is also much smaller, only 59 KB.

[Compiled LLVMpipe/Softpipe for Windows]

I posted the next release 17.0.1.391-2 with S3TC support. It should be live in a few minutes.

[Compiled LLVMpipe/Softpipe for Windows]

I was able to build 64-bit libtxc_dxtn, but 32-bit does not work even if built with same parameters.

mingw32-w64-i686-gcc was always troublesome. See this:

https://github.com/Alexpux/MINGW-packages/issues/2089

[Compiled LLVMpipe/Softpipe for Windows]

Found a S3TC standard implementation in CygWin archive.

In theory mesa opengl32.dll + dxtn.dll = complete S3TC support in OpenGL 2.1

Unfortunately Mesa codebase makes clear distinction between Cygwin and Win32. Additionally libtxc_dxtn source code does not include a sconscript so Visual Studio is not an option. The only option left is Msys2 cross-compilation and with this, things go bad,

Compilation fails.

$ make
  CC     txc_compress_dxtn.lo
txc_compress_dxtn.c: In function 'storedxtencodedblock':
txc_compress_dxtn.c:287:16: error: 'GL_COMPRESSED_RGB_S3TC_DXT1_EXT' undeclared (first use in this function)
    if (type == GL_COMPRESSED_RGB_S3TC_DXT1_EXT || type == GL_COMPRESSED_RGBA_S3TC_DXT1_EXT) {
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
txc_compress_dxtn.c:287:16: note: each undeclared identifier is reported only once for each function it appears in
txc_compress_dxtn.c:287:59: error: 'GL_COMPRESSED_RGBA_S3TC_DXT1_EXT' undeclared (first use in this function)
    if (type == GL_COMPRESSED_RGB_S3TC_DXT1_EXT || type == GL_COMPRESSED_RGBA_S3TC_DXT1_EXT) {
                                                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
txc_compress_dxtn.c: In function 'encodedxtcolorblockfaster':
txc_compress_dxtn.c:376:23: error: 'GL_COMPRESSED_RGBA_S3TC_DXT1_EXT' undeclared (first use in this function)
          if ((type != GL_COMPRESSED_RGBA_S3TC_DXT1_EXT) || (srccolors[j][i][3] > ALPHACUT)) {
                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
txc_compress_dxtn.c: In function 'tx_compress_dxtn':
txc_compress_dxtn.c:769:9: error: 'GL_COMPRESSED_RGB_S3TC_DXT1_EXT' undeclared (first use in this function)
    case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
txc_compress_dxtn.c:770:9: error: 'GL_COMPRESSED_RGBA_S3TC_DXT1_EXT' undeclared (first use in this function)
    case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
txc_compress_dxtn.c:790:9: error: 'GL_COMPRESSED_RGBA_S3TC_DXT3_EXT' undeclared (first use in this function)
    case GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
txc_compress_dxtn.c:817:9: error: 'GL_COMPRESSED_RGBA_S3TC_DXT5_EXT' undeclared (first use in this function)
    case GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
make: *** [Makefile:328: txc_compress_dxtn.lo] Error 1

prodea2@DESKTOP-H4RKMNR MINGW64 /home/s3tc
$