ssprune.va

`include "disciplines.vams"

// Enhancement-292: the small-signal pruning pass moves a linear contribution into
// its own dimension "where possible". Whether it IS possible is decided twice, by
// two different pieces of code: `collect_linear_contributes` classifies the
// contribution as linear, and the replay inside `create_dimension` is what actually
// builds the per-dimension value. The replay deliberately declines some shapes -- a
// product both of whose operands depend on the dimension, or an opcode that falls
// through to its catch-all -- so the two can disagree. When they did, the pass
// indexed a map with a key that was never inserted and panicked ("no entry found
// for key"), taking the whole compile down.
//
// The reproducer below is a reduced fuzzer find: noise waves routed through `idt`
// into nested `laplace_nd` coefficient arrays, which is what drives the two
// analyses apart. It is deliberately dense rather than pretty -- simplifying it any
// further stops reproducing.
module ssprune(a, b);
    inout a, b;
    electrical a, b;
    parameter real q = 1e-30;
    analog begin
            begin
            end
        case ((q % 'h7fffffff))
        endcase
        V(a, b) <+ laplace_nd(laplace_nd(flicker_noise(idt(-1e308), idt(-1e308)), {flicker_noise(idt(-1e308), idt(-1e308)),flicker_noise(idt(-1e308), idt(-1e308))}, {flicker_noise(idt(-1e308), idt(-1e308)),flicker_noise(idt(-1e308), idt(-1e308))}), {laplace_nd(flicker_noise(idt(-1e308), idt(-1e308)), {flicker_noise(idt(-1e308), idt(-1e308)),flicker_noise(idt(-1e308), idt(-1e308))}, {flicker_noise(idt(-1e308), idt(-1e308)),flicker_noise(idt(-1e308), idt(-1e308))}),laplace_nd(flicker_noise(idt(-1e308), idt(-1e308)), {flicker_noise(idt(-1e308), idt(-1e308)),flicker_noise(idt(-1e308), idt(-1e308))}, {flicker_noise(idt(-1e308), idt(-1e308)),flicker_noise(idt(-1e308), idt(-1e308))})}, {laplace_nd(flicker_noise(idt(-1e308), idt(-1e308)), {flicker_noise(idt(-1e308), idt(-1e308)),flicker_noise(idt(-1e308), idt(-1e308))}, {flicker_noise(idt(-1e308), idt(-1e308)),flicker_noise(idt(-1e308), idt(-1e308))}),laplace_nd(flicker_noise(idt(-1e308), idt(-1e308)), {flicker_noise(idt(-1e308), idt(-1e308)),flicker_noise(idt(-1e308), idt(-1e308))}, {flicker_noise(idt(-1e308), idt(-1e308)),flicker_noise(idt(-1e308), idt(-1e308))})});
    end
endmodule