The chosen value shouldn't have any effect. I considered something
clearly wrong like -1, but there's no checking inside the generated
lexer, and I suspect this will cause even weirder bugs if triggered
than just setting it to INITIAL.
This code originally comes from commit 458a940. When an interface is
used via a modport, code in genrtlil.cc sets '\\interface_type' and
'\\interface_modport' properties on the wire.
In hierarchy.cc, we pick up the modport name and add it to a dict
called modports_used_in_submodule (that maps connection source to
modport name).
Before this patch, the modport name is retrieved as a strpool and then
iterated over in an arbitrary order, discarding all entries but the
last. In practice, the pool will always have 0 or 1 entries because
the string used to construct it is a valid identifier, so doesn't
contain any pipe symbols.
This patch changes the code to retrieve the modport name as just a
string. This will have the same effect in practice, but may be a bit
less confusing!
The code also gets moved down closer to where the result is used,
which might be a bit more efficient since we won't always get as far
as the check.
The patch also removes some commented-out code, which I think was
intended to add some typechecking at some point, but was never
implemented. Since this dates back to October 2018, I think it makes
more sense to just take it out.
The existing code does a search to figure out whether id is in the
dict (with the call to count()), and then looks it up again to get the
result (with the call to at()). This version calls find() instead,
avoiding the double lookup.
Code size increases slightly (6kb). I think this is because the
contents of find() are getting inlined, and then inlined into lots of
the callsites for cell() and wire().
Looking at the compiled code before this patch, you just get
a (non-inlined) call to count() followed by a call to at(). After the
patch, the contents of find() have been inlined (so you see do_hash,
then do_lookup). The result for each function is about 30 bytes / 40%
bigger, which presumably also enlarges call-sites that inline it.
There was a handwritten copy constructor, which I'm not sure was
actually legal C++ (it unconditionally read from the 'data' member of
a union, which wouldn't have been written if wire was true). It was
also a bit less efficient than the constructor you get from the
compiler by default (which is allowed to just copy the memory).
This gives a marginal (~0.25%) decrease in code size when compiled
with GCC 9.3.
These operators work by fetching the string from the global string
table and then comparing with the std::string that was passed in as
rhs.
Using str() means that we create a std::string (strlen; malloc;
memcpy), compare for equality (another memcmp if they have the same
length) and then finally free the string.
Using c_str() means that we pass the const char* straight to
std::string's equality operator. This ends up as a call to
std::string::compare (the const char* flavour), which is essentially
strcmp.
Ensures that "BV" is the logic whenever solving an exists-forall problem with Yices, moves the "(set-logic ...)" directive above any non-info line, sets the `ef-max-iters` parameter to a very high number when using Yices in exists-forall mode so as not to prematurely abandon difficult problems, and does not provide the incompatible "--incremental" Yices argument when in exists-forall mode.
This isn't actually necessary anymore after scheduling was improved,
and `clean -purge` disrupts the mapping between wires in the input
RTLIL netlist and the output CXXRTL code.
whitequark
Rupert Swarbrick
Eddie Hung
Alberto Gonzalez
clairexen
Miodrag Milanović
N. Engelhardt