A compiler that forms an intermediate representation of a program using a flow graph with less than all possible edges used to model asynchronous transfers within the program. The flow graph is formed in multiple phases. In one phase, the flow graph is formed without modeling asynchronous transfers. In later phases, representations of the effects of the asynchronous transfers are selectively added. As part of the later phases, edges modeling a possible asynchronous transfer are added to the flow graph following definitions in protected regions of variables that are live outside the protected region. A modified definition of live-ness of a variable is used to incorporate use of the variable in any region, including the protected region, following an asynchronous transfer. Edges from the protected region are also added to the model if the only use of the defined variable is in a handler.