Incorrect results with XNOR/shift expression

This should always return y=4'b1111, but Verilator f705f9b only does this for a=0:

module issue_053(a, y);
  input [3:0] a;
  output [3:0] y;
  assign y = (a >> a) ^~ (a >> a);
endmodule

Self-contained test case: test019.v, test019.cc, test019.sh

History:
2014-05-25 Reported as Issue #776
2014-09-25 Fixed in GIT commit e8edbad