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The Linux kernel exploits that by using two macros (likely() and unlikely()) that give hints to the compiler using GCC's __builtin_expect:

if(likely(condition)) dosomething();

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even without likely/unlikely, branch prediction still occurs in branch-prediction supporting processors. the kernel optimization just optimizes for the first case. once the branch prediction state machine as aligned itself towards the more likely branch, accurate branch prediction will occur for the resulting calls (typically iterations or something like that)

:) That's what I came to say

http://kerneltrap.org/node/4705

I also have some other links :

These people saw 10% gain in their Scheme http://people.csail.mit.edu/jaffer/CNS/interpreter-branch

And this concerns reducing power consumption using Branch Prediction Prediction ! http://www.eecg.toronto.edu/~moshovos/research/iccd02.pdf

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