[Arc] AddTaps: guard self-referential hw.wire against RAUW-with-self - #10896
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[Arc] AddTaps: guard self-referential hw.wire against RAUW-with-self#10896AmurG wants to merge 1 commit into
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…hang A degenerate self-linked wire (`assign w = w;`, ivtest pr509.v) reaches tap(hw::WireOp) with input == result; replaceAllUsesWith then replaces the value with itself and never drains the use list, hanging the pass. Such a wire carries no driver: materialize a zero constant for its users (two-valued interpretation of an undriven net) and erase the wire; non-integer self-wires are left in place.
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assign w = w;yields a self-referentialhw.wire, and replacing its result with its input RAUWs the value with itself, so the pass spun forever. We substitute a zero constant for integer self-wires (the two-valued reading of an undriven net) and leave non-integer self-wires in place.