clang/llvm can generate graphviz dot files.
Example:
clang -S -emit-llvm -o hello.ll hello.cpp
opt hello.ll -dot-cfg -o hello.dot
This will output several .dot files, one for each function defined in hello.cpp.
You can also generate dominance graph, post dominance graph and more (see here).
After you have your .dotfiles you can use dot to convert it to a .png file.
The .dot file itself contains only the structure of the graph, so the output of dot should be highly configurable (but I am not really familiar with it).