The problem is that tailor-made FPGA designs won't run nearly as fast as a modern ASIC CPU. That's why for instance FPGA emulators are not more common, for olde

The problem is that tailor-made FPGA designs won't run nearly as fast as a modern ASIC CPU. That's why for instance FPGA emulators are not more common, for older hardware software implementations are accurate enough and manage to run in realtime so the additional cost and complexity of FPGAs is not warranted. For more modern hardware software implementations can't reach absolute accuracy in real time but FPGAs big and fast enough to handle these designs are prohibitively expensive (if they even exist in the first place). That's why FPGA GameBoy emulators are not popular and you probably won't see a FPGA PS3 emulator any time soon (unless the pricing changes dramatically in the near future). FPGAs shine when you need to process very high throughput data with low (or at least constant) latency or for special-purpose algorithm with no hardware acceleration available on CPU or GPU (video codecs, crypto, computer vision etc...). But in general when an algorithm becomes popular enough (AES, SHA-256, H264...) hardware support is backed into the ASIC eventually with much better performance and power consumption than a FPGA. I see a potential for FPGAs in CPUs for professional applications if you want to process big datastream without having to rely on external hardware. For instance I work in broadcast video transmission where we routinely handle uncompressed HD or even 4K streams, being able to prototype directly on my workstation's CPU would be pretty cool. As for general purpose programing language optimization I have a hard time imagining what it would look like. The problem is that you don't code for a FPGA the way you code for a CPU. To put it very simply on the CPU serial is cheap while forking and synchronizing threads is expensive. On an FPGA it's basically the other way around. Automatically transforming one form into the other automatically in a compiler or JIT sounds very much non-trivial. Maybe I just don't have enough imagination.