constfold_divzero.va

`include "disciplines.vams"

// Enhancement-333: integer division / remainder by a LITERAL zero.
//
// This must be a clean compile error (exit 65), NOT an internal error and NOT a
// silently accepted model. Enhancement-286 accepted it -- the folder declined and
// left the instruction in the IR -- but LLVM treats `sdiv x, 0` as immediate
// undefined behaviour and lowers it to poison -> `unreachable` -> `brk`, so the
// compiled .osdi killed the host simulator with SIGTRAP and no diagnostic.
//
// There is no portable value to fold to either: AArch64 returns a result where
// x86 raises SIGFPE, and this project ships x86 builds. So the honest answer is
// to reject it.
module constfold_divzero(a, b);
    inout a, b;
    electrical a, b;
    integer q, r;
    analog begin
        q = 5 / 0;                  // literal division by zero  -> error
        r = 5 % 0;                  // literal remainder by zero -> error
        I(a, b) <+ V(a, b) / 1.0e3 + 0.0 * (q + r);
    end
endmodule