Limit forked NBAs

Signed-off-by: Krzysztof Bieganski <[email protected]>
antmicro · Nov 14, 2023 · 3f14daa · 3f14daa
1 parent 72f94c4
commit 3f14daa
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Showing 3 changed files with 28 additions and 20 deletions.
diff --git a/src/V3SchedTiming.cpp b/src/V3SchedTiming.cpp
@@ -287,23 +287,17 @@ void transformForks(AstNetlist* const netlistp) {
             const VNUser2InUse user2InUse;  // AstVarScope -> AstVarScope: var to remap to
             funcp->foreach([&](AstNodeVarRef* refp) {
                 AstVar* const varp = refp->varp();
-                AstBasicDType* const dtypep = varp->dtypep()->basicp();
-                bool passByValue = false;
                 if (!varp->isFuncLocal()) {
                     if (VString::startsWith(varp->name(), "__Vintra")) {
                         // Pass it by value to the new function, as otherwise there are issues with
                         // -flocalize (see t_timing_intra_assign)
-                        passByValue = true;
                     } else {
                         // Not func local. Its lifetime is longer than the forked process. Skip
                         return;
                     }
                 } else if (!varp->user1()) {
                     // Not declared before the fork. It cannot outlive the forked process
                     return;
-                } else if (dtypep && dtypep->isForkSync()) {
-                    // We can just pass it by value to the new function
-                    passByValue = true;
                 }
                 // Remap the reference
                 AstVarScope* const vscp = refp->varScopep();
@@ -312,14 +306,13 @@ void transformForks(AstNetlist* const netlistp) {
                     AstVar* const newvarp
                         = new AstVar{varp->fileline(), VVarType::BLOCKTEMP, varp->name(), varp};
                     newvarp->funcLocal(true);
-                    newvarp->direction(passByValue ? VDirection::INPUT : VDirection::REF);
+                    newvarp->direction(VDirection::INPUT);
                     funcp->addArgsp(newvarp);
                     AstVarScope* const newvscp
                         = new AstVarScope{newvarp->fileline(), funcp->scopep(), newvarp};
                     funcp->scopep()->addVarsp(newvscp);
                     vscp->user2p(newvscp);
-                    callp->addArgsp(new AstVarRef{
-                        refp->fileline(), vscp, passByValue ? VAccess::READ : VAccess::READWRITE});
+                    callp->addArgsp(new AstVarRef{refp->fileline(), vscp, VAccess::READ});
                 }
                 AstVarScope* const newvscp = VN_AS(vscp->user2p(), VarScope);
                 refp->varScopep(newvscp);

diff --git a/src/V3Timing.cpp b/src/V3Timing.cpp
@@ -1015,6 +1015,7 @@ class TimingControlVisitor final : public VNVisitor {
     void visit(AstNodeAssign* nodep) override {
         // Only process once to avoid infinite loops (due to the net delay)
         if (nodep->user1SetOnce()) return;
+        bool directlyUnderFork = VN_IS(nodep->backp(), Fork) && !nodep->nextp();
         FileLine* const flp = nodep->fileline();
         AstNode* controlp = factorOutTimingControl(nodep);
         const bool inAssignDly = VN_IS(nodep, AssignDly);
@@ -1027,16 +1028,28 @@ class TimingControlVisitor final : public VNVisitor {
         // do that. These intra-assignment vars will later be passed to forked processes by value.
         AstNode* insertBeforep = m_underProcedure ? nullptr : controlp;
         // Special case for NBA
-        if (inAssignDly && !m_underProcedure) {
-            // If it's in a function, it won't be handled by V3Delayed
-            // Put it behind an additional named event that gets triggered in the NBA region
-            AstEventControl* const nbaEventControlp = createNbaEventControl(flp);
-            AstAssign* const trigAssignp = createNbaEventTriggerAssignment(flp);
-            nodep->replaceWith(trigAssignp);
-            trigAssignp->addNextHere(nbaEventControlp);
-            nbaEventControlp->addStmtsp(nodep);
-            insertBeforep = controlp;
-            if (!controlp) controlp = nbaEventControlp;
+        if (inAssignDly) {
+            // Put it in a fork so it doesn't block
+            AstFork* forkp = nullptr;
+            if (!directlyUnderFork) {
+                forkp = new AstFork{flp, "", nullptr};
+                forkp->joinType(VJoinType::JOIN_NONE);
+            }
+            if (!m_underProcedure) {
+                // If it's in a function, it won't be handled by V3Delayed
+                // Put it behind an additional named event that gets triggered in the NBA region
+                AstEventControl* const nbaEventControlp = createNbaEventControl(flp);
+                AstAssign* const trigAssignp = createNbaEventTriggerAssignment(flp);
+                nodep->replaceWith(trigAssignp);
+                trigAssignp->addNextHere(nbaEventControlp);
+                nbaEventControlp->addStmtsp(nodep);
+                if (forkp) insertBeforep = forkp;
+                if (!controlp) controlp = nbaEventControlp;
+            }
+            if (forkp) {
+                controlp->replaceWith(forkp);
+                forkp->addStmtsp(controlp);
+            }
         }
         UASSERT_OBJ(nodep, controlp, "Assignment should have timing control");
         addCLocalScope(flp, insertBeforep);

diff --git a/src/V3Width.cpp b/src/V3Width.cpp
@@ -4776,7 +4776,9 @@ class WidthVisitor final : public VNVisitor {
         }
         if (nodep->fileline()->timingOn() && v3Global.opt.timing().isSetTrue()
             && (m_ftaskp || nodep->timingControlp()) && VN_IS(nodep, AssignDly)
-            && !VN_IS(nodep->backp(), Fork)) {
+            && !VN_IS(nodep->backp(), Fork) && nodep->lhsp()->exists([](AstVarRef* refp) {
+                   return refp->varp()->isFuncLocal();
+               })) {
             auto* forkp = new AstFork{nodep->fileline(), "", nullptr};
             forkp->joinType(VJoinType::JOIN_NONE);
             nodep->replaceWith(forkp);