On one heavily optimized 3D CAD software that I've worked on, I've seen a hundreds of x86/PPC assembly snippets in #ifdefs, embedded in the C code. It was basic

On one heavily optimized 3D CAD software that I've worked on, I've seen a hundreds of x86/PPC assembly snippets in #ifdefs, embedded in the C code. It was basically for the software to be very fast on Windows and on Mac OS X PowerPCs. Some of those were legacy optimizations, because modern C++ compilers (VS 2003 and up) are smart enough to match that speed gain with better binary generation. But some other assembly parts were truly meant to recreate a customized and fast GPU-like pipeline on the CPU, using registers for really fast per-pixel/voxel operations. I've heard that Photoshop is also riddled with assembly code, that's why it took so long for Adobe to port it full-performance for the new Intel-based Macs in 2006. (Lots of PPC -> x86 mini-ports)