64-bit JIT compiler for .NET

RyuJIT: The next-generation JIT compiler for .NET - .NET Blog - Site Home - MSDN Blogs:
"The world is moving to 64-bit computing even though it isn’t always faster or more efficient than 32-bit. A lot of programs run faster on 32-bit than on 64-bit, for a variety of reasons. One example of this is the 64-bit JIT compiler in .NET. It does a great job of making your program run fast, but it’s not a fast program itself. All that’s about to change: a new, next-generation x64 JIT compiler that compiles code twice as fast is ready to change your impressions of 64-bit .NET code.
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The .NET 64-bit JIT was originally designed to produce very efficient code throughout the long run of a server process.
This differs from the .NET x86 JIT, which was optimized to produce code quickly so that the program starts up fast."