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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
Download Patch File Download Diff File Expand all files Collapse all files
src/V3SplitVar.cpp
+30 -30
View File
@@ -128,15 +128,6 @@ struct SplitVarImpl VL_NOT_FINAL {
// AstNodeModule::user1() -> Block number counter for generating unique names
const VNUser1InUse m_user1InUse; // Only used in SplitUnpackedVarVisitor
static AstNodeAssign* newAssign(FileLine* fileline, AstNodeExpr* lhsp, AstNodeExpr* rhsp,
const AstVar* varp) {
if (varp->isFuncLocal() || varp->isFuncReturn()) {
return new AstAssign{fileline, lhsp, rhsp};
} else {
return new AstAssignW{fileline, lhsp, rhsp};
}
}
// These check functions return valid pointer to the reason text if a variable cannot be split.
// Check if a var type can be split
@@ -622,25 +613,25 @@ class SplitUnpackedVarVisitor final : public VNVisitor, public SplitVarImpl {
AstNode* const refp = lhsp;
UINFO(9, "Creating assign idx:" << i << " + " << start_idx);
if (!lvalue) std::swap(lhsp, rhsp);
AstNode* newassignp;
if (use_simple_assign) {
AstNode* const insertp = context;
newassignp = new AstAssign{fl, lhsp, rhsp};
AstAssign* const ap = new AstAssign{fl, lhsp, rhsp};
if (lvalue) {
// If varp is LHS, this assignment must appear after the original
// assignment(context).
insertp->addNextHere(newassignp);
context->addNextHere(ap);
} else {
// If varp is RHS, this assignment comes just before the original assignment
insertp->addHereThisAsNext(newassignp);
context->addHereThisAsNext(ap);
}
UASSERT_OBJ(!m_contextp, m_contextp, "must be null");
setContextAndIterate(ap, refp);
} else {
newassignp = new AstAssignW{fl, lhsp, rhsp};
AstAssignW* const ap = new AstAssignW{fl, lhsp, rhsp};
// Continuous assignment must be in module context.
varp->addNextHere(newassignp);
varp->addNextHere(new AstAlways{ap});
UASSERT_OBJ(!m_contextp, m_contextp, "must be null");
setContextAndIterate(ap, refp);
}
UASSERT_OBJ(!m_contextp, m_contextp, "must be null");
setContextAndIterate(newassignp, refp);
}
return newVarRef(fl, varp, lvalue ? VAccess::WRITE : VAccess::READ);
}
@@ -655,18 +646,19 @@ class SplitUnpackedVarVisitor final : public VNVisitor, public SplitVarImpl {
newVarRef(fl, vars.at(i), !lvalue ? VAccess::WRITE : VAccess::READ)};
AstNodeExpr* const lhsp = nodes[lvalue ? 0 : 1];
AstNodeExpr* const rhsp = nodes[lvalue ? 1 : 0];
AstNodeAssign* const assignp = newAssign(fl, lhsp, rhsp, varp);
if (insertp) {
AstAssign* const ap = new AstAssign{fl, lhsp, rhsp};
if (lvalue) { // Just after writing to the temporary variable
insertp->addNextHere(assignp);
insertp->addNextHere(ap);
} else { // Just before reading the temporary variable
insertp->addHereThisAsNext(assignp);
insertp->addHereThisAsNext(ap);
}
setContextAndIterate(ap, nodes[1]);
} else {
UASSERT_OBJ(VN_IS(assignp, AssignW), varp, "must be AssginW");
vars.at(i)->addNextHere(assignp);
AstAssignW* const ap = new AstAssignW{fl, lhsp, rhsp};
vars.at(i)->addNextHere(new AstAlways{ap});
setContextAndIterate(ap, nodes[1]);
}
setContextAndIterate(assignp, nodes[1]);
}
}
// cppcheck-has-bug-suppress constParameter
@@ -1051,15 +1043,16 @@ class SplitPackedVarVisitor final : public VNVisitor, public SplitVarImpl {
var.lsb() - portLsb, var.bitwidth()};
AstNodeExpr* lhsp = new AstVarRef{fl, var.varp(), in ? VAccess::WRITE : VAccess::READ};
if (!in) std::swap(lhsp, rhsp);
AstNodeAssign* const assignp = newAssign(fl, lhsp, rhsp, portp);
if (insertp) {
AstAssign* const ap = new AstAssign{fl, lhsp, rhsp};
if (in) {
insertp->addHereThisAsNext(assignp);
insertp->addHereThisAsNext(ap);
} else {
insertp->addNextHere(assignp);
insertp->addNextHere(ap);
}
} else {
var.varp()->addNextHere(assignp);
AstAssignW* const ap = new AstAssignW{fl, lhsp, rhsp};
var.varp()->addNextHere(new AstAlways{ap});
}
}
}
@@ -1184,8 +1177,15 @@ class SplitPackedVarVisitor final : public VNVisitor, public SplitVarImpl {
rhsp = new AstConcat{fl, new AstVarRef{fl, vars[i].varp(), VAccess::READ},
rhsp};
}
varp->addNextHere(
newAssign(fl, new AstVarRef{fl, varp, VAccess::WRITE}, rhsp, varp));
if (varp->isFuncLocal() || varp->isFuncReturn()) {
AstAssign* const ap
= new AstAssign{fl, new AstVarRef{fl, varp, VAccess::WRITE}, rhsp};
varp->addNextHere(ap);
} else {
AstAssignW* const ap
= new AstAssignW{fl, new AstVarRef{fl, varp, VAccess::WRITE}, rhsp};
varp->addNextHere(new AstAlways{ap});
}
} else { // the original variable is not used anymore.
VL_DO_DANGLING(varp->unlinkFrBack()->deleteTree(), varp);
}