Instead of __ALLfast.cpp and __ALLslow.cpp, we now create only a single
__ALL.cpp and compile it with OPT_FAST, this speeds up small builds
where the C compiler does not dominate. A separate patch will follow
turning VM_PARALLEL_BUILDS on by default at a certain size.
Given this change to the build there is now no point in emitting both
fast and slow routines into the same .cpp file when --output-split is
not set as they will be just included in the same __ALL.cpp file. To
keep things simpler and the output easier to comprehend, V3EmitC has
also been changed to always emit the fast and slow files separately.
Also change verilated.mk to apply OPT_SLOW to all slow files, not just
ones called *__Slow.cpp. This change in particular ensures __Syms.cpp
is build as slow.
Part of #2360.
- Improve flag pruning heuristic
- Set all trace activity flags in slow code. This in turns enables us
to remove checking the slow flag on the fast path.
Firstly, we always use a byte array for fine grained activity flags
instead of a bit vector (we used to use a byte array only if we had
parallel mtasks). The byte vector can be set more cheaply in eval,
closing about 1/3 of the gap in performance between compiling with
or without --trace on SweRV EH1. The speed of tracing itself is not
measurably different.
Secondly, we prune the activity tracking such that if a set of activity
flag combinations only guard a small number of signals, we will turn
those signals into awayls traced signals. This avoids code which
sometimes tests dozens of activity flags just to subsequently check one
signal and dump it if it's value changed. We can just check the signal
state straight instead, and not bother with the flags. This removes
about 30% of activity flags in SweRV EH1, and makes both single threaded
VCD and FST tracing 8-9% faster.
- Allow arbitrary number of open array dimensions, not just 3. Note
right now this only works with the array querying functions specified
in IEEE 1800-2017 H.12.2
- Issue error when passing dynamic array or queue as DPI open array
(currently unsupported)
- Also tweaked AstVar::vlArgTypeRecurse, which should now error or fail
for unsupported types.
