00-00-2000 to 00-00-2000

We present a compiler algorithm called BitValue, which can discover unused and constant bits in dusty-deck C programs. BitValue uses forward and backward dataflow analyses, generalizing constant-folding and dead-code detection at the bit-level. This algorithm enables compiler optimizations targeting special processor architectures for computing on non-standard bitwidths. Using this algorithm we show that up to 36 % of the computed bytes are thrown away; also, we show that on average 26.8 % of the values computed require 16 bits or less (for programs from SpecINT95 and Mediabench). A compiler for recongurable hardware uses this algorithm to achieve substantial reductions (up to 20-fold) in the size of the synthesized circuits