Internals: Refactor AstNodeBlock representation (#6280)
AstNodeBlock now has 2 child lists: 'declsp' to hold declarations within
the block, and 'stmtsp' to hold the procedural statements.
AstBegin is then just a simple subtype of AstNodeBlock.
AstFork is a proper superset of AstNodeBlock (and also AstBegin), and
adds 'forksp' which hold the parallel statements. Having the sequential
'stmtsp' in AstFork is required to properly implement variable
initializers in fork blocks (IEEE 1800-2023 9.3.2), this makes that
clear, while also separating the non AstNodeStmt declarations
(for #6280). The actual fork branches in 'AstFork::forkps()' are all
AstBegin nodes. This is required as lowering stages will introduce
additional statements in each parallel branch. (We used to wrap AstFork
statements into AstBegin in 3 different places, now they always are
AstBegin and this is enforced via the type checker/V3Broken).
Also fixes incorrect disabling of forked processes from within the `fork`.
Remove the large variety of ways raw "text" is represented in the Ast.
Particularly, the only thing that represents a string to be emitted in
the output is AstText.
There are 5 AstNodes that can contain AstText, and V3Emit will throw an
error if an AstText is encountered anywhere else:
- AstCStmt: Internally generated procedural statements involving raw
text.
- AstCStmtUser: This is the old AstUCStmt, renamed so it sorts next to
AstCStmt, as it's largely equivalent. We should never create this
internally unless used to represent user input. It is used for $c,
statements in the input, and for some 'systemc_* blocks.
- AstCExpr: Internally generaged expression involving raw text.
- AstCExprUser: This is the old AstUCFunc, renamed so it sorts next to
AstCExpr. It is largely equivalent, but also has more optimizations
disabled. This should never be created internally, it is only used for
$c expressions in the input.
- AstTextBlock: Use by V3ProtectLib only, to generate the hierarchical
wrappers.
Text "tracking" for indentation is always on for AstCStmt, AstCExpr, and
AstTextBlock, as these are always generated by us, and should always be
well formed.
Tracking is always off for AstCStmtUser and AstCExprUser, as these
contain arbitrary user input that might not be safe to parse for
indentation.
Remove subsequently redundant AstNodeSimpleText and AstNodeText types.
This patch also fixes incorrect indentation in emitted waveform tracing
functions, and makes the output more readable for hier block SV stubs.
With that, all raw text nodes are handled as a proper AstNodeStmt or
AstNodeExpr as required for #6280.
Initial idea was to remodel AssignW as Assign under Alway. Trying that
uncovered some issues, the most difficult of them was that a delay
attached to a continuous assignment behaves differently from a delay
attached to a blocking assignment statement, so we need to keep the
knowledge of which flavour an assignment was until V3Timing.
So instead of removing AstAssignW, we always wrap it in an AstAlways,
with a special `keyword()` type. This makes it into a proper procedural
statement, which is almost equivalent to AstAssign, except for the case
when they contain a delay. We still gain the benefits of #6280 and can
simplify some code. Every AstNodeStmt should now be under an
AstNodeProcedure - which we should rename to AstProcess, or an
AstNodeFTask). As a result, V3Table can now handle AssignW for free.
Also uncovered and fixed a bug in handling intra-assignment delays if
a function is present on the RHS of an AssignW.
There is more work to be done towards #6280, and potentially simplifying
AssignW handing, but this is the minimal change required to tick it off
the TODO list for #6280.
Srinivasan Venkataramanan
Geza Lore
Pawel Kojma
Wilson Snyder
Jose Drowne
Ryszard Rozak
Thomas Aldrian
Dan Ruelas-Petrisko
em2machine
Artur Bieniek
Jakub Wasilewski
Dan Ruelas-Petrisko
Pawel Kojma
Bartłomiej Chmiel
Igor Zaworski