Is unconditional code considered a branch?

Question

Having simple code like this:

int A=5;
object X=Console.ReadLine()
if(Condition)
   DoSomething();
else
   DoStuff();
DoSomethingElse();

Some sources say there are actually 4 branches: First unconditional, two for the IF and another unconditional after the IF statement. Some say there are only two branches. What would be correct? E.g. here: http://www.ruleworks.co.uk/testguide/BS7925-2-Annex-B7.asp

Answer 1

The origins of the word 'branch' in code comes from assembly. An example of this can be seen in MIPS assembly. A branch is a conditional statement.

Before anyone jumps on me for point out that MIPS has a b instruction which has the description of "branch unconditionally" the key to the difference between b (branch unconditionally) and j (jump) is that the branch statements work off of relative addresses and the jump statements work off of absolute addresses.

There is also some terminology of unconditional branch in the realm of branch prediction. A CPU with a pipeline will try to guess which way a branch statement goes and where it will end up after the branch. It is possible to analize the assembly to see that a given branch will always execute given a certain set of conditions at the start of the pipline. For example, the branch is based on if register 1 is greater than 0 or not. If register 1 is 0, and no instructions in the pipeline change that, it is in essence an unconditional branch which can be executed safely (and not having to worry about flush the pipeline after speculative execution or stall until the branch can be decided).

All of the above was for very low level code. In higher level code (as demonstrated in the question) the terminology of a branch is where code may follow two (or more in the case of a switch (pun not intended)) different paths. From wikipedia

A branch is sequence of code in a computer program which is conditionally executed depending on how the flow of control is altered at the branching point.

Unconditional code is not conditionally executed and thus is not a branch.

Answer 2

I think branch here is meant to represent a block of code with a single linear path (no jumps starts or ends in the block) better known as a basic block.

This concept is handy for compilers and other analysis tools to decide how a piece of code might behave (in the absence of exceptions) as each basic block is then an atomic operation in terms of the code around it.

For example, optimising compilers can look at each such block and decide how the dependencies for each individual instruction lies and possibly reorder them to make more efficient use of registers and the stack. Or, when only one exit path exists to a another block with only one entry, you can concatenate the blocks and eliminate the jump.

Answer 3

It depends on your context. For some analysis, such as what compilers do - you have 4 branches, since the post-if block can vary its behavior depending on which path the if goes (and if either conditional branch returns early). For some analysis like you might see in code coverage will vary to perhaps consider that somewhere between 2 and 4 branches depending on what is being done and if priority is given to the choice or to the path.

Neither view is particularly "correct" or not. They're human inventions to try and gain information and insight. Whichever metric does that better for the problem at hand is the "correct" one.