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by tedunangst 5002 days ago
Maybe some day they will add profile guided optimization to C compilers.
2 comments

They're not the same. VMs can assume invariants (which may not always hold) and compile specialized methods which depend on those assumptions and then fall back to a non-optimized version during the execution of a method. To do something like that (OSR) in C, you'll have to have a very sophisticated runtime.
you're kidding right? and at least referring to gcc's -fprofile-generate -fprofile-use right?
Profile-guided optimization is decades old. It was, for example, one of the things people loved about the (Ultrix?) DEC Alpha compiler was profile-driven optimization.
First VMS.

That was one of the outstanding compilers ever written.

There is a major difference between performing profile-generated optimizations at compile-time based on sample data, and performing it at run-time based on real data. It is one pretty good way in which JITs could beat programs implemented directly in C.
Not really since the 'sample' data is 'real' data which has been gathered during run-time.
That is the most optimistic statement about profile-directed optimization that I have ever read.