[tracing] Uniformize VCS and Verilator support of waveform dumps.

Created by: zchamski

This PR supports core-v-verif PR https://github.com/openhwgroup/core-v-verif/pull/1427 which unifies the control of waveform generation between VCS and Verilator simulation targets. It supersedes PR #954 and PR #963 in order to reduce the change set and simplify history.

Outline

VCS

For VCS configurations, the control of trace generation is handled entirely at the level of VCS and vsim invocations in core-v-verif/cva6/sim/Makefile (see PR https://github.com/openhwgroup/core-v-verif/pull/1427).

Verilator

For Verilator, the control of trace generation is partially implemented in the C++ simulation wrapper (cf. file corev_apu/tb/ariane_tb.cpp) according to the settings of two C++ macros: VM_TRACE and VM_TRACE_FST. Due to current limitations of Verilator, the VCD and FST waveform formats cannot be supported by a single simulator build; in other words, a simulator built for a specific trace format needs to be rebuilt in order to produce traces in the other format.

Usage of the macros:

• If defined, VM_TRACE enables tracing. If macro VM_TRACE_FST is not defined (the default), waveform generation will use VCD format. If the command-line option -v FILE or --vcd=FILE is given to the compiled simulator, the VCD output will be written to file named FILE in the current working dir of the verilated simulator. If no -v/--vcd= option is given on cmdline, or an FST-specific trace option is used, the simulator will generate a VCD trace according to the settings in the RTL code.
• if VM_TRACE_FST is defined as well, then FST format is used instead of VCD. If the command line option -f FILE or --fst=FILE is given to the simulator, the trace will be stored in file FILE in the current working dir of the verilated simulator. If no -f/--fst= option is given, or a VCD-specific trace option is used, the simulator will generate an FST trace according to the settings in the RTL code.

Files changed

• Makefile (verilate_command): Set defines according to requested trace mode (fast/compact). Request inclusion of appropriate support files (source code, compression libraries) into the Verilator-generated Makefile.
• corev_apu/tb/ariane_tb.cpp (toplevel): Include appropriate trace header according to tracing mode (FST or VCD). (usage): Add description of flag and sample command line for FST tracing. (main): Add long and short FST format option. Add FST format handling. Issue dump requests only if there is a valid dump file that was opened from the C++ wrapper.

Signed-off-by: Zbigniew Chamski zbigniew.chamski@thalesgroup.com