Loop splitting

Loop splitting (or loop peeling) is a compiler optimization technique. It attempts to simplify a loop or eliminate dependencies by breaking it into multiple loops which have the same bodies but iterate over different contiguous portions of the index range.

A useful special case is loop peeling, which can simplify a loop with a problematic first (or first few) iteration by performing that iteration separately before entering the loop.

Here is an example of loop peeling. Suppose the original code looks like this:

p = 10; for (i=0; i<10; ++i) { y [i] = x [i] + x [p] ; p = i; }

In the above code, only in the 1st iteration is p=10. For all other iterations p=i-1. We get the following after loop peeling:

y [0] = x [0] + x [10] ; for (i=1; i<10; ++i) { y [i] = x [i] + x [i-1] ; }

Loop peeling was introduced in gcc in version 3.4.

Further reading

ee also

* Loop unwinding