The following module should set y to 1'bx. But Icarus Verilog (git b1ef099) sets the output to 1'b1.
module issue_024(y); output y; assign y = 1'b1 >= |1'bx; endmodule
History:
2014-02-17 Reported bug on GitHub
2014-02-16 Fixed in GIT commit 5a06602