Visualizing LLVM IR CFG using GraphViz

The LLVM IR control flow graph can be visualized using the GraphViz tool. It gives a visual depiction of the nodes formed and how the code flow follows in the IR generated. Since the important data structures in LLVM are graphs, this can be a very useful way to understand the IR flow when writing a custom pass or studying the behavior of the IR pattern.

Getting ready

1. To install graphviz on Ubuntu, first add its ppa repository:

   $ sudo apt-add-repository ppa:dperry/ppa-graphviz-test
   

2. Update the package repository:

   $ sudo apt-get update
   

3. Install graphviz:

   $ sudo apt-get install graphviz
   

   Note

   If you get the graphviz : Depends: libgraphviz4 (>= 2.18) but it is not going to be installed error, run the following commands:

   $ sudo apt-get remove libcdt4
   $ sudo apt-get remove libpathplan4
   

   Then install graphviz again with the following command:

   $ sudo apt-get install graphviz
   

How to do it…

1. Once the IR has been converted to DAG, it can be viewed in different phases...