On a modern Pentium it is no longer possible to give branching hints to the processor it seems. Assuming that a profiling compiler such as gcc with profile-guided optimization gains information abo...

I'd like to know how to write efficient jump tables for x64 processors, either in C, C++ or assembly. The input is known in advance, but impossible to predict algorithmically. Assuming I can look a...

I recently read the question here Why is it faster to process a sorted array than an unsorted array? and found the answer to be absolutely fascinating and it has completely changed my outlook on pr...

I have a Compare() function that looks like this: inline bool Compare(bool greater, int p1, int p2) { if (greater) return p1>=p2; else return p1<=p2; } I decided to optimize to avoid bra...

While answering another question I got curious about this. I'm well aware that if( __builtin_expect( !!a, 0 ) ) { // not likely } else { // quite likely } will make the "quite likely" branch f...

So from my understanding of delay slots, they occur when a branch instruction is called and the next instruction following the branch also gets loaded from memory. What is the point of this? Wouldn...

The GCC manual only shows examples where __builtin_expect() is placed around the entire condition of an 'if' statement. I also noticed that GCC does not complain if I use it, for example, with a t...

I'm trying to get a good understanding of branch prediction by measuring the time to run loops with predictable branches vs. loops with random branches. So I wrote a program that takes large array...

I have this C function: double f(int x) { if (x <= 0) return 0.0; else return x * log(x); } which I am calling in a tight loop, and would like to get rid of the branch to see if it improv...

X is true nearly 99.9% of the time but I need to handle Y and Z as well. Although the body of the X condition is empty, I'm thinking it should be faster than potentially checking 2 other conditions...

This question and its answer, which was recently tagged as an Epic Answer, has prompted me to wonder; Can I measure the performance of a running application in Windows in terms of its CPU branch pr...

Years ago I was learning about x86 assembler, CPU pipelining, cache misses, branch prediction, and all that jazz. It was a tale of two halves. I read about all the wonderful advantages of the leng...