Support NBAs in non-inlined tasks/functions

Signed-off-by: Krzysztof Bieganski <[email protected]>

src/V3AstNodeOther.h

@@ -1191,6 +1191,8 @@ class AstNetlist final : public AstNode {
     AstCFunc* m_evalNbap = nullptr;  // The '_eval__nba' function
     AstVarScope* m_dpiExportTriggerp = nullptr;  // The DPI export trigger variable
     AstVar* m_delaySchedulerp = nullptr;  // The delay scheduler variable
+    AstVarScope* m_nbaEventp = nullptr;  // The NBA event variable
+    AstVarScope* m_nbaEventTriggerp = nullptr;  // If set to 1, the NBA event should get triggered
     AstTopScope* m_topScopep = nullptr;  // The singleton AstTopScope under the top module
     VTimescale m_timeunit;  // Global time unit
     VTimescale m_timeprecision;  // Global time precision
@@ -1220,6 +1222,10 @@ class AstNetlist final : public AstNode {
     void dpiExportTriggerp(AstVarScope* varScopep) { m_dpiExportTriggerp = varScopep; }
     AstVar* delaySchedulerp() const { return m_delaySchedulerp; }
     void delaySchedulerp(AstVar* const varScopep) { m_delaySchedulerp = varScopep; }
+    AstVarScope* nbaEventp() const { return m_nbaEventp; }
+    void nbaEventp(AstVarScope* const varScopep) { m_nbaEventp = varScopep; }
+    AstVarScope* nbaEventTriggerp() const { return m_nbaEventTriggerp; }
+    void nbaEventTriggerp(AstVarScope* const varScopep) { m_nbaEventTriggerp = varScopep; }
     void stdPackagep(AstPackage* const packagep) { m_stdPackagep = packagep; }
     AstPackage* stdPackagep() const { return m_stdPackagep; }
     AstTopScope* topScopep() const { return m_topScopep; }

src/V3Delayed.cpp

@@ -527,8 +527,12 @@ class DelayedVisitor final : public VNVisitor {
         m_nextDlyp
             = VN_CAST(nodep->nextp(), AssignDly);  // Next assignment in same block, maybe nullptr.
         if (m_cfuncp) {
-            nodep->v3warn(E_UNSUPPORTED,
-                          "Unsupported: Delayed assignment inside public function/task");
+            if (!v3Global.rootp()->nbaEventp()) {
+                nodep->v3warn(
+                    E_NOTIMING,
+                    "Delayed assignment in a non-inlined function/task requires --timing");
+            }
+            return;
         }
         UASSERT_OBJ(m_procp, nodep, "Delayed assignment not under process");
         const bool isArray = VN_IS(nodep->lhsp(), ArraySel)

src/V3Sched.cpp

@@ -899,72 +899,83 @@ void createEval(AstNetlist* netlistp,  //
     if (icoLoop) funcp->addStmtsp(icoLoop);
 
     // Create the active eval loop
-    AstNodeStmt* const activeEvalLoopp
-        = makeEvalLoop(
-              netlistp, "act", "Active", actKit.m_vscp, actKit.m_dumpp,
-              [&]() {  // Trigger
-                  AstNodeStmt* resultp = nullptr;
-
-                  // Compute the current triggers
-                  {
-                      AstCCall* const trigsp = new AstCCall{flp, actKit.m_triggerComputep};
-                      trigsp->dtypeSetVoid();
-                      resultp = AstNode::addNext(resultp, trigsp->makeStmt());
-                  }
-
-                  // Commit trigger awaits from the previous iteration
-                  if (AstCCall* const commitp = timingKit.createCommit(netlistp)) {
-                      resultp = AstNode::addNext(resultp, commitp->makeStmt());
-                  }
-
-                  return resultp;
-              },
-              [&]() {  // Body
-                  // Compute the pre triggers
-                  AstNodeStmt* resultp
-                      = createTriggerAndNotCall(flp, preTrigsp, actKit.m_vscp, nbaKit.m_vscp);
-                  // Latch the active trigger flags under the NBA trigger flags
-                  resultp = AstNode::addNext(
-                      resultp, createTriggerSetCall(flp, nbaKit.m_vscp, actKit.m_vscp));
-                  // Resume triggered timing schedulers
-                  if (AstCCall* const resumep = timingKit.createResume(netlistp)) {
-                      resultp = AstNode::addNext(resultp, resumep->makeStmt());
-                  }
-                  // Invoke body function
-                  {
-                      AstCCall* const callp = new AstCCall{flp, actKit.m_funcp};
-                      callp->dtypeSetVoid();
-                      resultp = AstNode::addNext(resultp, callp->makeStmt());
-                  }
+    const auto& activeEvalLoop = makeEvalLoop(
+        netlistp, "act", "Active", actKit.m_vscp, actKit.m_dumpp,
+        [&]() {  // Trigger
+            AstNodeStmt* resultp = nullptr;
+
+            // Compute the current triggers
+            {
+                AstCCall* const trigsp = new AstCCall{flp, actKit.m_triggerComputep};
+                trigsp->dtypeSetVoid();
+                resultp = AstNode::addNext(resultp, trigsp->makeStmt());
+            }
+
+            // Commit trigger awaits from the previous iteration
+            if (AstCCall* const commitp = timingKit.createCommit(netlistp)) {
+                resultp = AstNode::addNext(resultp, commitp->makeStmt());
+            }
 
-                  return resultp;
-              })
-              .stmtsp;
+            return resultp;
+        },
+        [&]() {  // Body
+            // Compute the pre triggers
+            AstNodeStmt* resultp
+                = createTriggerAndNotCall(flp, preTrigsp, actKit.m_vscp, nbaKit.m_vscp);
+            // Latch the active trigger flags under the NBA trigger flags
+            resultp = AstNode::addNext(resultp,
+                                       createTriggerSetCall(flp, nbaKit.m_vscp, actKit.m_vscp));
+            // Resume triggered timing schedulers
+            if (AstCCall* const resumep = timingKit.createResume(netlistp)) {
+                resultp = AstNode::addNext(resultp, resumep->makeStmt());
+            }
+            // Invoke body function
+            {
+                AstCCall* const callp = new AstCCall{flp, actKit.m_funcp};
+                callp->dtypeSetVoid();
+                resultp = AstNode::addNext(resultp, callp->makeStmt());
+            }
+
+            return resultp;
+        });
 
     // Create the NBA eval loop. This uses the Active eval loop in the trigger section.
-    AstNodeStmt* topEvalLoopp
-        = makeEvalLoop(
-              netlistp, "nba", "NBA", nbaKit.m_vscp, nbaKit.m_dumpp,
-              [&]() {  // Trigger
-                  // Reset NBA triggers
-                  AstNodeStmt* resultp = createTriggerClearCall(flp, nbaKit.m_vscp);
-                  // Run the Active eval loop
-                  resultp = AstNode::addNext(resultp, activeEvalLoopp);
-                  return resultp;
-              },
-              [&]() {  // Body
-                  AstCCall* const callp = new AstCCall{flp, nbaKit.m_funcp};
-                  callp->dtypeSetVoid();
-                  AstNodeStmt* resultp = callp->makeStmt();
-                  // Latch the NBA trigger flags under the following region's trigger flags
-                  AstVarScope* const nextVscp = obsKit.m_vscp ? obsKit.m_vscp : reactKit.m_vscp;
-                  if (nextVscp) {
-                      resultp = AstNode::addNext(
-                          resultp, createTriggerSetCall(flp, nextVscp, nbaKit.m_vscp));
-                  }
-                  return resultp;
-              })
-              .stmtsp;
+    const auto& nbaEvalLoop = makeEvalLoop(
+        netlistp, "nba", "NBA", nbaKit.m_vscp, nbaKit.m_dumpp,
+        [&]() {  // Trigger
+            // Reset NBA triggers
+            AstNodeStmt* resultp = createTriggerClearCall(flp, nbaKit.m_vscp);
+            // Run the Active eval loop
+            resultp = AstNode::addNext(resultp, activeEvalLoop.stmtsp);
+            return resultp;
+        },
+        [&]() {  // Body
+            AstCCall* const callp = new AstCCall{flp, nbaKit.m_funcp};
+            callp->dtypeSetVoid();
+            AstNodeStmt* resultp = callp->makeStmt();
+            // Latch the NBA trigger flags under the following region's trigger flags
+            AstVarScope* const nextVscp = obsKit.m_vscp ? obsKit.m_vscp : reactKit.m_vscp;
+            if (nextVscp) {
+                resultp = AstNode::addNext(resultp,
+                                           createTriggerSetCall(flp, nextVscp, nbaKit.m_vscp));
+            }
+            return resultp;
+        });
+
+    // If the NBA event exists, trigger it in 'nba'
+    if (netlistp->nbaEventp()) {
+        AstIf* const ifp
+            = new AstIf{flp, new AstVarRef{flp, netlistp->nbaEventTriggerp(), VAccess::READ}};
+        ifp->addThensp(setVar(nbaEvalLoop.continuep, 1));
+        ifp->addThensp(setVar(netlistp->nbaEventTriggerp(), 0));
+        AstCMethodHard* const firep = new AstCMethodHard{
+            flp, new AstVarRef{flp, netlistp->nbaEventp(), VAccess::WRITE}, "fire"};
+        firep->dtypeSetVoid();
+        ifp->addThensp(firep->makeStmt());
+        activeEvalLoop.stmtsp->addNext(ifp);
+    }
+
+    AstNodeStmt* topEvalLoopp = nbaEvalLoop.stmtsp;
 
     if (obsKit.m_funcp) {
         // Create the Observed eval loop. This uses the NBA eval loop in the trigger section.

src/V3Timing.cpp

@@ -366,6 +366,10 @@ class TimingSuspendableVisitor final : public VNVisitor {
         m_underFork |= F_MIGHT_NEED_PROC;
         iterateChildren(nodep);
     }
+    void visit(AstAssignDly* nodep) override {
+        if (!VN_IS(m_procp, NodeProcedure)) v3Global.setUsesTiming();
+        visit(static_cast<AstNode*>(nodep));
+    }
     void visit(AstNode* nodep) override {
         if (nodep->isTimingControl()) {
             v3Global.setUsesTiming();
@@ -452,8 +456,10 @@ class TimingControlVisitor final : public VNVisitor {
     double m_timescaleFactor = 1.0;  // Factor to scale delays by
     int m_forkCnt = 0;  // Number of forks inside a module
     bool m_underJumpBlock = false;  // True if we are inside of a jump-block
+    bool m_underProcedure = false;  // True if we are under an always or initial
 
     // Unique names
+    V3UniqueNames m_dlyforkNames{"__Vdlyfork"};  // Names for temp AssignW vars
     V3UniqueNames m_contAssignVarNames{"__VassignWtmp"};  // Names for temp AssignW vars
     V3UniqueNames m_intraValueNames{"__Vintraval"};  // Intra assign delay value var names
     V3UniqueNames m_intraIndexNames{"__Vintraidx"};  // Intra assign delay index var names
@@ -575,6 +581,31 @@ class TimingControlVisitor final : public VNVisitor {
         m_netlistp->topScopep()->addSenTreesp(m_dynamicSensesp);
         return m_dynamicSensesp;
     }
+    // Creates the event variable to trigger in NBA region
+    AstEventControl* createNbaEventControl(FileLine* flp) {
+        if (!m_netlistp->nbaEventp()) {
+            auto* const nbaEventDtp = new AstBasicDType{m_scopeTopp->fileline(),
+                                                        VBasicDTypeKwd::EVENT, VSigning::UNSIGNED};
+            m_netlistp->typeTablep()->addTypesp(nbaEventDtp);
+            m_netlistp->nbaEventp(m_scopeTopp->createTemp("__VnbaEvent", nbaEventDtp));
+            v3Global.setHasEvents();
+        }
+        return new AstEventControl{
+            flp,
+            new AstSenTree{
+                flp, new AstSenItem{flp, VEdgeType::ET_EVENT,
+                                    new AstVarRef{flp, m_netlistp->nbaEventp(), VAccess::READ}}},
+            nullptr};
+    }
+    // Creates the variable that, if set, causes the NBA event to be triggered
+    AstAssign* createNbaEventTriggerAssignment(FileLine* flp) {
+        if (!m_netlistp->nbaEventTriggerp()) {
+            m_netlistp->nbaEventTriggerp(m_scopeTopp->createTemp("__VnbaEventTrigger", 1));
+        }
+        return new AstAssign{flp,
+                             new AstVarRef{flp, m_netlistp->nbaEventTriggerp(), VAccess::WRITE},
+                             new AstConst{flp, AstConst::BitTrue{}}};
+    }
     // Returns true if we are under a class or the given tree has any references to locals. These
     // are cases where static, globally-evaluated triggers are not suitable.
     bool needDynamicTrigger(AstNode* const nodep) const {
@@ -753,6 +784,8 @@ class TimingControlVisitor final : public VNVisitor {
     void visit(AstNodeProcedure* nodep) override {
         VL_RESTORER(m_procp);
         m_procp = nodep;
+        VL_RESTORER(m_underProcedure);
+        m_underProcedure = true;
         iterateChildren(nodep);
         if (hasFlags(nodep, T_SUSPENDEE)) nodep->setSuspendable();
         if (hasFlags(nodep, T_HAS_PROC)) nodep->setNeedProcess();
@@ -773,7 +806,8 @@ class TimingControlVisitor final : public VNVisitor {
         if (nodep->user1SetOnce()) return;
         VL_RESTORER(m_procp);
         m_procp = nodep;
-
+        VL_RESTORER(m_underProcedure);
+        m_underProcedure = true;
         // Workaround for killing `always` processes (doing that is pretty much UB)
         // TODO: Disallow killing `always` at runtime (throw an error)
         if (hasFlags(nodep, T_HAS_PROC)) addFlags(nodep, T_SUSPENDEE);
@@ -979,20 +1013,37 @@ 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;
-        AstNode* const controlp = factorOutTimingControl(nodep);
-        if (!controlp) return;
-        // Handle the intra assignment timing control
         FileLine* const flp = nodep->fileline();
-        if (VN_IS(nodep, AssignDly)) {
-            // If it's an NBA with an intra assignment delay, put it in a fork
+        AstNode* controlp = factorOutTimingControl(nodep);
+        const bool inAssignDly = VN_IS(nodep, AssignDly);
+        // Handle the intra assignment timing control
+        // Transform if:
+        // * there's a timing control in the assignment
+        // * the assignment is an AssignDly and it's in a non-inlined function
+        if (!controlp && (!inAssignDly || m_underProcedure)) return;
+        // Insert new vars before the timing control if we're in a function; in a process we can't
+        // 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) {
+            // Put it in a fork so it doesn't block
             auto* const 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);
+                insertBeforep = forkp;
+                if (!controlp) controlp = nbaEventControlp;
+            }
             controlp->replaceWith(forkp);
             forkp->addStmtsp(controlp);
         }
-        // Insert new vars before the timing control if we're in a function; in a process we can't
-        // do that. These intra-assignment vars will later be passed to forked processes by value.
-        AstNode* const insertBeforep = m_classp ? controlp : nullptr;
+        UASSERT_OBJ(nodep, controlp, "Assignment should have timing control");
         addCLocalScope(flp, insertBeforep);
         // Function for replacing values with intermediate variables
         const auto replaceWithIntermediate = [&](AstNodeExpr* const valuep,

test_regress/t/t_assigndly_dynamic.pl

@@ -0,0 +1,32 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2019 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+scenarios(simulator => 1);
+
+compile(
+    verilator_flags2 => ["--exe --main --timing"],
+    make_main => 0,
+    );
+
+execute(
+    check_finished => 1,
+    );
+
+compile(
+    verilator_flags2 => ["--exe --main --timing +define+WITH_DELAY"],
+    make_main => 0,
+    );
+
+execute(
+    check_finished => 1,
+    );
+
+ok(1);
+1;

test_regress/t/t_assigndly_dynamic.v

@@ -0,0 +1,55 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed into the Public Domain, for any use,
+// without warranty, 2023 by Antmicro Ltd.
+// SPDX-License-Identifier: CC0-1.0
+
+`ifdef WITH_DELAY
+`define DELAY #1
+`define TIME_AFTER_FIRST_WAIT 2
+`define TIME_AFTER_SECOND_WAIT 3
+`else
+`define DELAY
+`define TIME_AFTER_FIRST_WAIT 1
+`define TIME_AFTER_SECOND_WAIT 1
+`endif
+
+class nba_waiter;
+    // Task taken from UVM
+    task wait_for_nba_region;
+        int nba;
+        int next_nba;
+        next_nba++;
+        nba <= `DELAY next_nba;
+        @(nba);
+    endtask
+endclass
+
+module t;
+    nba_waiter waiter = new;
+    event e;
+    int cnt = 0;
+
+    initial begin
+        #1 ->e;
+        if (cnt != 0) $stop;
+        cnt++;
+        waiter.wait_for_nba_region;
+        ->e;
+        if (cnt != 2) $stop;
+        if ($time != `TIME_AFTER_FIRST_WAIT) $stop;
+        cnt++;
+        waiter.wait_for_nba_region;
+        if (cnt != 4) $stop;
+        if ($time != `TIME_AFTER_SECOND_WAIT) $stop;
+        $write("*-* All Finished *-*\n");
+        $finish;
+    end
+
+    initial begin
+        @e if (cnt != 1) $stop;
+        cnt++;
+        @e if (cnt != 3) $stop;
+        cnt++;
+    end
+endmodule

test_regress/t/t_assigndly_dynamic_notiming.out

@@ -0,0 +1,6 @@
+%Error-NOTIMING: t/t_assigndly_dynamic_notiming.v:10:13: Delayed assignment in a non-inlined function/task requires --timing
+                                                       : ... note: In instance '$unit::foo'
+   10 |         qux <= '1;
+      |             ^~
+                 ... For error description see https://verilator.org/warn/NOTIMING?v=latest
+%Error: Exiting due to