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Internals: Make AstAssignW a procedural statement (#6280) (#6556)

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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.
This commit is contained in:
Geza Lore
2025-10-14 09:05:19 +01:00
committed by GitHub
parent 958d096e7f
commit eb53bca6fd
55 changed files with 1540 additions and 1411 deletions
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src/V3Inline.cpp
+8 -4
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@@ -171,7 +171,7 @@ class InlineMarkVisitor final : public VNVisitor {
iterateChildren(nodep);
}
void visit(AstAlways* nodep) override {
m_modp->user4Inc(); // statement count
if (nodep->keyword() != VAlwaysKwd::CONT_ASSIGN) nodep->user4Inc(); // statement count
iterateChildren(nodep);
}
void visit(AstNodeAssign* nodep) override {
@@ -480,7 +480,9 @@ void connectPort(AstNodeModule* modp, AstVar* nodep, AstNodeExpr* pinExprp) {
// the port variable. The constant can still be inlined, in which case
// this is needed for tracing the inlined port variable.
if (AstConst* const pinp = VN_CAST(pinExprp, Const)) {
modp->addStmtsp(new AstAssignW{flp, portRef(VAccess::WRITE), pinp->cloneTree(false)});
AstAssignW* const ap
= new AstAssignW{flp, portRef(VAccess::WRITE), pinp->cloneTree(false)};
modp->addStmtsp(new AstAlways{ap});
return;
}
@@ -516,9 +518,11 @@ void connectPort(AstNodeModule* modp, AstVar* nodep, AstNodeExpr* pinExprp) {
// Otherwise create the continuous assignment between the port var and the pin expression
UINFO(6, "Not inlning port variable: " << nodep);
if (nodep->direction() == VDirection::INPUT) {
modp->addStmtsp(new AstAssignW{flp, portRef(VAccess::WRITE), pinRef(VAccess::READ)});
AstAssignW* const ap = new AstAssignW{flp, portRef(VAccess::WRITE), pinRef(VAccess::READ)};
modp->addStmtsp(new AstAlways{ap});
} else if (nodep->direction() == VDirection::OUTPUT) {
modp->addStmtsp(new AstAssignW{flp, pinRef(VAccess::WRITE), portRef(VAccess::READ)});
AstAssignW* const ap = new AstAssignW{flp, pinRef(VAccess::WRITE), portRef(VAccess::READ)};
modp->addStmtsp(new AstAlways{ap});
} else {
pinExprp->v3fatalSrc("V3Tristate left INOUT port");
}