Re: virtual functions and optimization at compile time

Given the complete class hierarchy of a program, a compiler can use a
technique called "class hierarchy analysis" to resolve a virtual function
call to a set of target functions. There may not be a single
target/destination of a virtual function call, of course. But if the set of
targets is small enough, the compiler can replace the virtual call with a
small set of if/then type tests and direct method calls.


A research paper on this topic is:


@article{ dean95optimization,
        author = "Jeffrey Dean and David Grove and Craig Chambers",
        title = "Optimization of Object-Oriented Programs Using Static Class
Hierarchy Analysis",
        journal = "Lecture Notes in Computer Science",
        volume = "952",
        pages = "77--101",
        year = "1995",
        url = "citeseer.nj.nec.com/article/dean95optimization.html" }


and available on the web at
http://www.ifs.uni-linz.ac.at/~ecoop/cd/papers/0952/09520077.pdf.


Google "class hierarchy analysis" and "whole program optimization" for
additional resources.


        Stephen




"preetham" <pdn@sasken.com> wrote in message
> Virtual Functions Are Supposed To Be Optimized Bcoz They R Supposedly
> Resolved At Run-Time. How Can Virtual Functions Be Resolved At
> Compile-Time???
>
> Rgrds,
> Preetham
> [By flow analysis that determines that it'll always call the same
> function, I suppose. -John]

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