Code Optimization Technique for Indirect Addressing DSPs with Consideration in Local Computational Order and Memory Allocation

Nobuhiko SUGINO  Akinori NISHIHARA  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E84-A   No.8   pp.1960-1968
Publication Date: 2001/08/01
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Digital Signal Processing)
Category: Implementations of Signal Processing Systems
DSP compiler,  indirect memory addressing,  memory allocation,  code optimization,  

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Digital signal processors (DSPs) usually employ indirect addressing using address registers (ARs) to indicate their memory addresses, which often introduces overhead codes in AR updates for next memory accesses. Reduction of such overhead code is one of the important issues in automatic generation of highly-efficient DSP codes. In this paper, a new automatic address allocation method incorpolated with computational order rearrangement at local commutative parts is proposed. The method formulates a given memory access sequence by a graph representation, where several strategies to handle freedom in memory access orders at the computational commutative parts are introduced and examined. A compiler scheme is also extended such that computational order at the commutative parts is rearranged according to the derived memory allocation. The proposed methods are applied to an existing DSP compiler for µPD77230(NEC), and codes generated for several examples are compared with memory allocations by the conventional methods.