Category "cfg"

How to determine if a BasicBlock is controled by a `if`

I want to use LLVM to analyze if a basic block is affected by a control flow of an if(i.e., br instruction). "A basic block BB is NOT affected by br" means that

What does the ⇒ mean in Context Free Grammar? Also, how do I derive/get the L(CFG) from a CFG?

I'm a bit confused. Does the ⇒ simply denote you going through the CFG step by step ? To use a pretty basic-ish example: sentence ⇒ subject | predicat

CFG of w != w^R

Given L={w in {a,b}* | w != w^R} I want to find its CFG. Please do not tell me the answer for that. What is the intuition of solving these kind of questions? I