Novel VLIW Code Compaction Method for a 3D Geometry Processor

Hiroaki SUZUKI  Hiroyuki KAWAI  Hiroshi MAKINO  Yoshio MATSUDA  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E84-A   No.11   pp.2885-2893
Publication Date: 2001/11/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8508
Type of Manuscript: PAPER
Category: Digital Signal Processing
Keyword: 
VLIW,  code compaction,  ASSP,  3D geometry processor,  computer graphics,  

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Summary: 
A VLIW (Very Long Instruction Word) architecture with a new code compaction method has been proposed. For a 3D-geometry processor, we consider two types of 2-issue VLIW architectures, the floating-point execution accelerating VLIW (FP-VLIW) and the data-move enhancing VLIW (MV-VLIW) architectures, as expansions of a Single-Streaming Single Instruction, Multiple Data (SS-SIMD) architecture. To solve the code bloat problem which is common to VLIW architectures, the proposed method makes it possible to compact original codes into the VLIW codes by software tools and decompact the VLIW codes by a simple hardware decompactor composed of an instruction swap circuit on a chip. Speeds and code densities of the two VLIWs with the code compaction are compared to the SS-SIMD with the same instruction set and the same building blocks. The FP-VLIW shows the fastest speed performance in the evaluation results of the viewperf CDRS-03 benchmark programs. It is 36% faster than the SS-SIMD used as reference. The proposed compaction method keeps the 95% code density of the SS-SIMD. One test program shows that the code density of the MV-VLIW is higher than that of the SS-SIMD. This result demonstrates that the merit of compacting nops can be greater than the VLIW penalty. The FP-VLIW architecture with the code compaction achieves 1.36 times the speed performance without significant code-density deterioration.