Abstract: Variable Instruction Scheduling for MIMD Interpretation on Pipelined SIMD Machines and for Compositional Instruction Sets.
Functional parallelism may be supported on SIMD machines by
interpretation. The programs and data of each
function are loaded on the processing elements (PEs) and the
Control Unit of the machine executes a central control
algorithm that causes the concurrent interpretation of these
functions. The performance of this
paradigm has been shown to benefit considerably from a variable
instruction issue schedule that delays execution of
expensive and rarely occuring operations.
Two new features of the interpretation paradigm, namely pipelinined
SIMD machines and compositional instruction sets, change the nature of
the mathematical model used for variable instruction scheduling
significantly. In this paper, a previously developed mathematical
model of the interpretation process is extended to allow for
compositional instructions and pipelining. We develop and present
algorithms that produce variable instruction schedules for the
extended model and investigate whether variable instruction issue is
useful for these cases. We show that variable instruction issue
improves the performance of pipelined machines but is not very
effective for compositional instruction sets, especially when the
composition matrix is not sparse.
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