Verific incorrectly const folds a == 1'bx

CLOSED: fixed in Verific 482_32_150519

Consider the following module:

module issue_033(a, y);
    input [1:0] a;
    output y;
    assign y = a == 1'bx;

For a[1] == 1 this module should output zero. (The 1'bx is zero extended to 2'b0x. Unlike the relational operators, the == and != operators do not automatically output 1'bx if any bit in the arguments is 1'bx. Instead it must only output 1'bx if the result is ambiguous. See also 5.1.8 in IEE Std 1364-2005.)

However, Verific 463_32_140306 optimizes all logic out of this module and sets the output to constant 1'bx.

2014-03-22 Reported bug to Verific support
2014-03-26 Bug added to issue tracker: VIPER Issue #8535
2014-07-23 Still broken in Verific 463_32_140722
2015-05-20 Fixed in Verific 482_32_150519

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