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Comment by theteapot | Hacker News Reader

Is that true? The loop is a branch.

The "go around" branch is obviously not completely avoidable (though unrolling helps). Branches inside the loop body sometimes are.

Who actually considers a loop a branch? A loop is a chunk of code that will be run N times depending on some evaluation that’s run before or after an iteration. A branch is a single decision which of several pieces of code to run, once.

>Who actually considers a loop a branch?

The machine?

> Who actually considers a loop a branch?

A loop contains a branch - keep looping or break. At least according to structured programming -- https://en.wikipedia.org/wiki/Structured_program_theorem.

> Who actually considers a loop a branch?

interesting question...

> A loop is a chunk of code that will be run N times depending

oh! turns out you do!

branchless for loop for funsies

  for (fn, n) = {
    stop = void (i) {}
    run  = void (i) { fn(i); go(i + 1) }
    go   = void (i) { *((i < n) * &run + (i >= n) * &stop)(i) }
    go(0)
  }

Or you could write all the implementations for each possible n and dispatch through a registry.

https://godbolt.org/z/rz8MxhdGd

Just a simple example, but the conditional branch occurs on line 14 of the generated assembly. It does a comparison (line 13) and then a conditional jump (jl, line 14).

> Who actually considers a loop a branch?

Anyone who started out programming in assembly languages

> Who actually considers a loop a branch?

The CPU.

Yeah I was like what, is branching a matter of opinion??

Usually yes, but if inside loop is even more branches. Also obviously wasteful when it's checking a computed condition.

Not categorically though: an infinite loop does not contain a branch.

It's just an unconditional branch but still a branch. Probably even not an unrollable one due to non-infinite memory.

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