LinkDotFindVisitor queued an AstIface into m_ifaceModSyms once for every
symbol table entry it was reached through. When creating scopes,
LinkDotIfaceVisitor resolves the modport items against the AstVarScopes,
which LinkDotScopeVisitor only inserts under the entry of an AstScope. A
hierarchical block wrapper builds a second copy of the instance tree in
the symbol table, and an interface reached through that copy has no
AstVarScopes to resolve against.
Resolving is destructive (the AstModportVarRef is deleted once resolved),
so this only worked when a resolvable entry happened to be processed
first, and failed with "Modport item not found" otherwise. When creating
scopes, register from the AstScopes instead, as those are exactly the
entries that hold the AstVarScopes.
Reproduces on t_hier_block with -fno-inline, added as a test.
AstNodeCoverDecl::hier() is relative to the scope the declaration is
emitted from, as V3EmitCImp builds the reported path as 'vlNamep + hierp',
and that is how V3Coverage uses it. V3FsmDetect instead set it to the
absolute scope name, so the instance path was counted twice.
This was masked whenever the owning module was inlined, as the declaration
then ended up in the top scope. With inlining disabled, an FSM in an
instance reported 'top.t.forced_wide_u.t.forced_wide_u'. In the inlined
case it reported 'top.TOP', leaking the internal top wrapper name into
user visible coverage output, rather than plain 'top'.
Various cleanups, simplifications and improvements:
- Build the output bottom up, eliminating AstSplitPlaceholder
- Replace the 'ignore step' pruning with removing the vertices and edges
- Treat an NBA written variable as a block input, enabling more splits
- Move instead of clone leaf statements
Overall V3Split is faster, uses less memory, can do more splits, is
simpler algorithmically, and has half the lines of code in V3Split
Most notably this can now be split, which could not be before:
```systemverilog
always @(posedge clk) begin
a <= !a;
if (a) b <= c;
end
```
t_x_rand_mt_stability* pin $random values, but there is one random seed
per C thread, so they depend on which thread runs the block. More
splitting moved that block onto a different thread, so force a single
MTask in those tests to keep them stable.
Some property/assert test changed hit counts due to races, but are now
closer to what might be expected.
Artur Bieniek
Wilson Snyder
Ryszard Rozak
Jonathan Drolet
Kristof Marien
Kornel Uriasz
Kamil Danecki
Geza Lore
Marco Bartoli
Nick Brereton
Jesús Alberto López Soto
Andrii Andrieiev
Igor Zaworski
Edmund Lam
Bartosz Skorowski
Drew Risinger