.Net framework JIT and Bulldozer special instructions

Question

AMD Bulldozer has been successful in the server space but has performed poorly on the desktop. As I understand it, a major cause of this is that server applications have been rewritten to use Bulldozer's special instructions, which are still not being used in desktop applications. Will or do we expect the Just in time Compiler (JIT) to use these in 4.5, can/ will they be back ported to 4.0?

Clarification: My understanding was that the JIT compiles for the machine it is running on, not the machine on which it was compiled to IL instructions. It has been claimed that because of this JIT applications can actually have higher performance than normal code which is compiled and linked straight down to binary.

Answer 1

Unfortunately, the .NET JIT is not particularly sophisticated when it comes to performance:

• Even on servers it does not do heavy optimizations like a C++ compiler does, although it has the same information as a C++ compiler has. It just does not do certain things
• It uses special instructions only for some operations with floats
• The x64 even has quality problems with invalid optimizations being done
• Some obvious optimizations like escape analysis are missing

It seems like the JIT is not being developed with a particularly high budget. So I doubt we will see such specialized instructions being used.