From b9fd4a13893e9d95fdd23cd94589f9c85dcd5918 Mon Sep 17 00:00:00 2001
From: Krzysztof Bieganski <kbieganski@antmicro.com>
Date: Tue, 14 Nov 2023 13:45:03 +0100
Subject: [PATCH] Fix dynamic assigns to automatic vars

Signed-off-by: Krzysztof Bieganski <kbieganski@antmicro.com>
---
 src/V3Fork.cpp                       | 19 ++++++++++++++-----
 src/V3SchedTiming.cpp                |  3 ++-
 src/V3Timing.cpp                     |  8 ++++++--
 test_regress/t/t_assigndly_dynamic.v | 18 ++++++++++++++++++
 4 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/src/V3Fork.cpp b/src/V3Fork.cpp
index 133e4352ff4..6d08aa153e1 100644
--- a/src/V3Fork.cpp
+++ b/src/V3Fork.cpp
@@ -313,11 +313,8 @@ class DynScopeVisitor final : public VNVisitor {
     }
 
     static bool hasAsyncFork(AstNode* nodep) {
-        bool afork = false;
-        nodep->foreach([&](AstFork* forkp) {
-            if (!forkp->joinType().join()) afork = true;
-        });
-        return afork;
+        return nodep->exists([](AstFork* forkp) { return !forkp->joinType().join(); })
+               || nodep->exists([](AstAssignDly*) { return true; });
     }
 
     void bindNodeToDynScope(AstNode* nodep, ForkDynScopeFrame* frame) {
@@ -415,6 +412,18 @@ class DynScopeVisitor final : public VNVisitor {
         }
         visit(static_cast<AstNodeStmt*>(nodep));
     }
+    void visit(AstAssignDly* nodep) override {
+        if (m_procp && !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);
+            forkp->addStmtsp(nodep);
+        } else {
+            iterateChildren(nodep);
+        }
+    }
     void visit(AstNode* nodep) override {
         if (nodep->isTimingControl()) m_afterTimingControl = true;
         iterateChildren(nodep);
diff --git a/src/V3SchedTiming.cpp b/src/V3SchedTiming.cpp
index 368201f0552..75b5a67d778 100644
--- a/src/V3SchedTiming.cpp
+++ b/src/V3SchedTiming.cpp
@@ -288,7 +288,8 @@ void transformForks(AstNetlist* const netlistp) {
             funcp->foreach([&](AstNodeVarRef* refp) {
                 AstVar* const varp = refp->varp();
                 AstBasicDType* const dtypep = varp->dtypep()->basicp();
-                bool passByValue = false;
+                // If not a fork..join, copy. All write refs should've been handled by V3Fork
+                bool passByValue = !m_forkp->joinType().join();
                 if (!varp->isFuncLocal()) {
                     if (VString::startsWith(varp->name(), "__Vintra")) {
                         // Pass it by value to the new function, as otherwise there are issues with
diff --git a/src/V3Timing.cpp b/src/V3Timing.cpp
index 6484a724752..f9b59ca813c 100644
--- a/src/V3Timing.cpp
+++ b/src/V3Timing.cpp
@@ -1029,8 +1029,12 @@ class TimingControlVisitor final : public VNVisitor {
         // Special case for NBA
         if (inAssignDly) {
             // Put it in a fork so it doesn't block
-            auto* const forkp = new AstFork{flp, "", nullptr};
-            forkp->joinType(VJoinType::JOIN_NONE);
+            // Could already be the only thing directly under a fork, reuse that if possible
+            AstFork* forkp = !nodep->nextp() ? VN_CAST(nodep->backp(), Fork) : nullptr;
+            if (!forkp) {
+                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
diff --git a/test_regress/t/t_assigndly_dynamic.v b/test_regress/t/t_assigndly_dynamic.v
index 9183eb767ff..f1fcc046d52 100644
--- a/test_regress/t/t_assigndly_dynamic.v
+++ b/test_regress/t/t_assigndly_dynamic.v
@@ -25,8 +25,23 @@ class nba_waiter;
     endtask
 endclass
 
+class Foo;
+    task bar(logic b);
+        int x;
+        if (b) x <= 'hDEAD;
+        #2
+        if (x != 'hDEAD) $stop;
+    endtask
+
+   task qux();
+        int x[] = new[1];
+        x[0] <= `DELAY 'hBEEF;  // Segfault check
+    endtask
+endclass
+
 module t;
     nba_waiter waiter = new;
+    Foo foo = new;
     event e;
     int cnt = 0;
 
@@ -42,6 +57,9 @@ module t;
         waiter.wait_for_nba_region;
         if (cnt != 4) $stop;
         if ($time != `TIME_AFTER_SECOND_WAIT) $stop;
+        foo.bar(1);
+        foo.qux();
+        #2
         $write("*-* All Finished *-*\n");
         $finish;
     end