#1243 Support for $countdrivers

[Martin Whitaker]

This is split into two patches. The first patch reworks the vvp implementation of resolver networks to be akin to wide functors (as per my proposal on iverilog-devel), which allows all the driver values for a multiply-driven wire to be extracted by a VPI function. The second patch implements the $countdrivers function.

I have done some performance measurements on my new implementation of resolver networks, using a test case that instantiates wires with between 2 and 10 drivers. In all case, both run time and memory usage were slightly lower with the new implementation, so I'm reasonably confident that nobody is going to see a performance hit with this change.

The $countdrivers implementation does not yet support wires connected to island ports (it does output a suitable "sorry" message when it detects this case). This is going to take a bit more work.

Also attached is a patch for the test suite that adds a couple of tests for the $countdrivers functionality, and removes the check for the old warning message that $countdrivers was not supported.

[Martin Whitaker]

First patch

[Martin Whitaker]

Second patch

[Martin Whitaker]

Test suite patch

[Martin Whitaker]

Third compiler patch

[Martin Whitaker]

Second test suite patch

[Martin Whitaker]

I've attached a third patch which adds $countdrivers support for wires connected to islands. I believe the implementation of $countdrivers is now complete.

Also attached is a second patch for the test suite, which adds some tests for the new functionality.

[Stephen Williams]

Applied to git master.

[Stephen Williams]

Also applied to ivtest patches to git master.