Future Systems on Chips (SoCs) will integrate a large number of processor and storage cores onto a single chip and require Networks on Chip (NoC) to support the heavy communication demands of the system. The individual components of the SoCs will be heterogeneous in nature with widely varying functionality and communication requirements. The communication infrastructure should optimally match communication patterns among these components accounting for the individual component needs. In this paper we present ×pipesCompiler, a tool for automatically instantiating an application-specific NoC for heterogeneous Multi-Processor SoCs. The ×pipesCompiler instantiates a network of building blocks from a library of composable soft macros (switches, network interfaces and links) described in SystemC at the cycle-accurate level. The network components are optimized for that particular network and support reliable, latency-insensitive operation. Example systems with application-specific NoCs built using the ×pipesCompiler show large savings in area (factorof 6.5), power (factor of 2.4) and latency (factor of 1.42) when compared to a general-purpose mesh-based NoC architecture.