Third in the "An introduction to compiling for the Cell Broadband Engine architecture" series, this tutorial discusses the compiler issues in optimizing code to run efficiently on SIMD-capable processors. In particular, it shows how to optimize code that must run both on the VMX SIMD engine of the PowerPC core of the Cell Broadband Engine (Cell BE) processor, and also on the SIMD-only Synergistic Processor Elements (SPEs).