Compilation techniques for multimedia processors

The huge processing power needed by multimedia applications has led to mul-timedia extensions in the instruction set of microprocessors which exploit sub-word parallelism. Examples of these extended instruction sets are the Visual Instruction Set of the UltraSPARC processor, the AltiVec instruction set of the PowerPC processor, the MMX and ISS extensions of the Pentium processors, and the MAX-2 instruction set of the HP PA-RISC processor. Currently, these extensions can only be used by programs written in assembly language, through system libraries or by calling specialized macros in a high-level language. There-fore, these instructions are not used by most applications. We propose two code generation techniques to produce native code using these multimedia extensions for programs written in a high level language: clas-sical vectorization and vectorization by unrolling. Vectorization by unrolling is simpler than classical vectorization since data dependence analysis is reduced to acyclic control ow graph analysis. Furthermore, we address the problem of unaligned memory accesses. This can be handled by both static analysis and dynamic run time checking. Preliminary experimental results for a code gen-erator for the UltraSPARC VIS instruction set show that speedups of up to a factor of 4.8 are possible, and that vectorization by unrolling is much simpler but as eective as classical vectorization