I've been looking into porting libjpeg/SIMD to 64-bit, and thus far, it's making my brain hurt. Converting the register names is easy enough and can be done through macros, but then the problem becomes how to handle the different calling conventions (x86-64 usually passes everything in registers, whereas x86 passes everything on the stack.) There is a lot of subtlety in how libjpeg/SIMD handles stack arguments, because it's trying to align things to 128-bit boundaries for SSE2, etc. I'm having difficulty sorting out exactly what's happening in the setup portion of each function.
I'm wondering whether it wouldn't be a better idea to just use Open mediaLib for the SSE2 code path in libjpeg/SIMD. It's licensed under LGPL v2.1, so there shouldn't be any legal issues with embedding it. It would certainly be easier for me, and I think it would be more maintainable than doing a lot of #ifdefs at the assembly level to support 64-bit. There are several other key advantages to using OML: -- well-proven and well-tested code base -- builds and runs cleanly as a 64-bit library -- works on a variety of platforms, including Windows, Linux, Mac, and Solaris/x86. -- written in C using SSE intrinsics, thus easier to maintain -- would not require NASM. This is key, because it turns out that x86-64 support was not added to NASM until v2.0, and thus many platforms (including RedHat 5) cannot assemble x86-64 code without downloading an upgrade to NASM, which is somewhat hard to find (the RPMs distributed by the NASM project don't work on RHEL 5.) We'd still use the MMX code for 32-bit, for the time being (although I think I'd like to try porting the MMX code to C as well in the long term -- after 1.0.0.) Essentially, I think it would take me less time to introduce the Open mediaLib routines into libjpeg/SIMD than it would to modify the assembly code to support multiple pixel formats. Corollary to the above, I am having trouble getting the 4-byte color conversion code paths in libjpeg/SIMD to compile. For some reason, it's giving me the following error: jccolss2.asm:245: error: comma or end of line expected jccolss2.asm:250: error: comma or end of line expected I'm using nasm v2.05.01. ------------------------------------------------------------------------------ _______________________________________________ Tigervnc-devel mailing list Tigervnc-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/tigervnc-devel
