Enhancing loop buffering of media and telecommunications applications using low-overhead predication

John W. Sias, Hillery C. Hunter, Wen-Mei W Hwu

Research output: Contribution to journalArticlepeer-review


Media- and telecommunications-focused processors, increasingly designed as deeply pipelined, statically-scheduled VLIWs, rely on loop buffers for low-overhead execution of simple loops. Key loops containing control flow pose a substantial problem-full predication has a high encoding overhead, and partial predication techniques do not support if-conversion, the transformation of general acyclic control flow into predicated blocks. Using a set of significant media processing benchmarks, drawn from Media-Bench and contemporary telecommunications standards, we explore a compromise approach. We demonstrate a compiler using if-conversion and specialized loop transformations to arrange for 70-99% of fetched operations to come from a simple, statically managed 256-instruction loop buffer, saving instruction fetch power and eliminating branch penalties. To complement this we introduce a “niche" form of predication specialized to permit general if-conversion with only a single bit in the encoding of each operation and to eliminate much of the hardware overhead of a predicate register-based approach.

Original languageEnglish (US)
Pages (from-to)262-273
Number of pages12
JournalProceedings of the Annual International Symposium on Microarchitecture
StatePublished - 2001

ASJC Scopus subject areas

  • Hardware and Architecture
  • Software


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