[tracking] Completion of VHPI support in Questa

Questa is working on supporting VHPI in addition to FLI (which continues to work and is fully supported).

The current 2021.4 release shows the following test failures in the cocotb test suite:

Failure in testsuite: 'all' classname: 'test_vhdl_access' testcase: 'check_objects' with parameters 'all'
Failure in testsuite: 'all' classname: 'test_array' testcase: 'test_gen_loop' with parameters 'all'
Failure in testsuite: 'all' classname: 'test_array' testcase: 'test_discover_all' with parameters 'all'
Failure in testsuite: 'all' classname: 'test_vhdl_zerovector' testcase: 'test_long_signal' with parameters 'all'
Failure in testsuite: 'all' classname: 'test_vhdl_zerovector' testcase: 'test_read_zero_signal' with parameters 'all'
Failure in testsuite: 'all' classname: 'test_vhdl_zerovector' testcase: 'test_write_zero_signal_with_0' with parameters 'all'
Failure in testsuite: 'all' classname: 'test_vhdl_zerovector' testcase: 'test_write_zero_signal_with_1' with parameters 'all'
Failure in testsuite: 'all' classname: 'test_force_release' testcase: 'test_force_release' with parameters 'all'
Failure in testsuite: 'all' classname: 'test_iteration' testcase: 'recursive_discovery' with parameters 'all'

Plus #2749, which is expected to be fixed by Questa 2022.1 (to be confirmed), but will also be fixed by #2750 on the cocotb side.

Let’s use this issue to track progress towards a full VHPI implementation (as far as cocotb needs it), and then remove the experimental label (https://github.com/cocotb/cocotb/blob/master/documentation/source/simulator_support.rst#mentorsiemens-eda-questa).

Steps to reproduce these failures:

git clone https://github.com/cocotb/cocotb.git
git checkout cb876412fdaee249407619c1d4e34d3c04241754 # at the time of writing, but also try master!
VHDL_GPI_INTERFACE=vhpi SIM=questa TOPLEVEL_LANG=vhdl tox -e py3

[imphil]

All code updates should be in cocotb now. Let’s wait for the upcoming Questa release and close this issue if we can verify the functionality with the released version.

[imphil]

The documentation is now updated as well, let’s consider this task done!