wreduce: Optimize signedness when possible #4819
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widlarizer
requested changes
Dec 18, 2024
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Thanks Claire! |
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What are the reasons/motivation for this change?
See the attached test case. It can happen the RTL designer has written an explicit sign extension combined with an unsigned operation. Previously this would make
wreduceunable to reduce the size of operands.Explain how this is achieved.
We detect conditions under which the signedness of the operands is arbitrary (because the input operands are fully sized wrt to the output and the operation is one of addition, subtraction, multiplication). Under these conditions estimate the size of the reduced operator if we make the operands signed or unsigned, and then flip the signedness accordingly before the usual operand reduction of
wreducetakes place.