1. A method of building a callgraph for multiple entry functions in a software program using dynamic instrumentation comprising: inserting function count probe code at each function entry point of each multiple entry function in the software program, wherein the multiple entry function has multiple function entry points; inserting inter-entry point arc probe code substantially before each arc source address of an arc in the software program; and collecting data resulting from execution of the software program including the function count probe code and the inter-entry point arc probe code, wherein the collected data includes a function count value and an inter-entry point arc count value for each arc source address obtained from execution of the software program.