simpleBinOp

fn simpleBinOp(
    gz: *GenZir,
    scope: *Scope,
    ri: ResultInfo,
    node: Ast.Node.Index,
    op_inst_tag: Zir.Inst.Tag,
) InnerError!Zir.Inst.Ref {
    const astgen = gz.astgen;
    const tree = astgen.tree;

    const lhs_node, const rhs_node = tree.nodeData(node).node_and_node;

    if (op_inst_tag == .cmp_neq or op_inst_tag == .cmp_eq) {
        const str = if (op_inst_tag == .cmp_eq) "==" else "!=";
        if (tree.nodeTag(lhs_node) == .string_literal or
            tree.nodeTag(rhs_node) == .string_literal)
            return astgen.failNode(node, "cannot compare strings with {s}", .{str});
    }

    const lhs = try reachableExpr(gz, scope, .{ .rl = .none }, lhs_node, node);
    const cursor = switch (op_inst_tag) {
        .add, .sub, .mul, .div, .mod_rem => maybeAdvanceSourceCursorToMainToken(gz, node),
        else => undefined,
    };
    const rhs = try reachableExpr(gz, scope, .{ .rl = .none }, rhs_node, node);

    switch (op_inst_tag) {
        .add, .sub, .mul, .div, .mod_rem => {
            try emitDbgStmt(gz, cursor);
        },
        else => {},
    }
    const result = try gz.addPlNode(op_inst_tag, node, Zir.Inst.Bin{ .lhs = lhs, .rhs = rhs });
    return rvalue(gz, ri, result, node);
}