This is a partial cleanup of V3Order with the aim of increasing clarity:
- Split the initial OrderGraph building and the actual ordering process
into separate classes (OrderVisitor -> OrderBuildVisitor + OrderProcess)
- Remove all the historical cruft from the graph building phase (now in
OrderBuildVisitor), and add more assertions for assumptions.
- Change the dot styling of OrderGraph to use shapes and more easily
distinguishable colors.
- Expand vague comments, remove incorrect comments, and add more.
- Replace some old code with cleaner C++11 constructs.
- Move code about a bit so logically connected sections are closer to
each other, scope some definitions where they are used rather than file
scope.
- The actual ordering process (now in OrderProcess) is still largely
unchanged.
The generated code is identical to before (within the limits of the
exiting non-determinism).
The _CONST suffix on these macros is only lexical notation, pointer
constness can be preserved by overloading the underlying
implementations appropriately. Given that the compiler will catch
invalid const usage (trying to assign a non-const pointer to a const
pointer variable, etc.), and that the declarations of symbols should
make their constness obvious, I see no reason to keep the _CONST
flavours.
The bool AstNode flags fit in a padding gap after m_type. This reduces
memory consumption by about 2% on OpenTitan. Initializing the unused
bits in the flags then avoids a read-modify-write in the constructor
(replacing it with a store constant). Overall verilation speed is about
1% faster.
Rework Ast hashing to be stable
Eliminated reliance on pointer values in AstNode hashes in order to make
them stable. This requires moving the sameHash functions into a visitor,
as nodes pointed to via members (and not child nodes) need to be hashed
themselves.
The hashes are now stable (as far as I could test them), and the impact
on verilation time is small enough not to be reliably measurable.
