Fix DLYSYNC with for loop variables

src/V3Active.cpp

@@ -160,7 +160,9 @@ public:
 
 class ActiveDlyVisitor : public ActiveBaseVisitor {
 private:
-    bool m_combo;	// Combo logic
+    bool 	m_combo;	// Combo logic
+    AstNode*	m_alwaysp;	// Always we're under
+    AstNode*	m_assignp;	// In assign
     // VISITORS
     virtual void visit(AstAssignDly* nodep, AstNUser*) {
 	if (m_combo) {
@@ -176,12 +178,30 @@ private:
     }
     virtual void visit(AstAssign* nodep, AstNUser*) {
 	if (!m_combo) {
-	    // Convert to a non-delayed assignment
-	    nodep->v3warn(BLKSEQ,"Blocking assignments (=) in sequential (flop or latch) block; suggest delayed assignments (<=).");
+	    AstNode* las = m_assignp;
+	    m_assignp = nodep;
+	    nodep->lhsp()->iterateAndNext(*this);
+	    m_assignp = las;
+	}
+    }
+    virtual void visit(AstVarRef* nodep, AstNUser*) {
+	AstVar* varp=nodep->varp();
+	if (!m_combo
+	    && m_assignp
+	    && !varp->isUsedLoopIdx() // Ignore loop indicies
+	    && !varp->isTemp()
+	    ) {
+	    // Allow turning off warnings on the always, or the variable also
+	    if (!m_alwaysp->fileline()->warnIsOff(V3ErrorCode::BLKSEQ)
+		&& !m_assignp->fileline()->warnIsOff(V3ErrorCode::BLKSEQ)
+		&& !varp->fileline()->warnIsOff(V3ErrorCode::BLKSEQ)
+		) {
+		m_alwaysp->fileline()->modifyWarnOff(V3ErrorCode::BLKSEQ, true);  // Complain just once for the entire always
+		varp->fileline()->modifyWarnOff(V3ErrorCode::BLKSEQ, true);
+		nodep->v3warn(BLKSEQ,"Blocking assignments (=) in sequential (flop or latch) block; suggest delayed assignments (<=).");
+	    }
 	}
     }
-    // Empty visitors, speed things up
-    virtual void visit(AstNodeMath* nodep, AstNUser*) {}
     //--------------------
     virtual void visit(AstNode* nodep, AstNUser*) {
 	nodep->iterateChildren(*this);
@@ -189,7 +209,9 @@ private:
 public:
     // CONSTUCTORS
     ActiveDlyVisitor(AstNode* nodep, bool combo) {
+	m_alwaysp = nodep;
 	m_combo = combo;
+	m_assignp = NULL;
 	nodep->accept(*this);
     }
     virtual ~ActiveDlyVisitor() {}

src/V3AstNodes.h

@@ -553,6 +553,7 @@ private:
     bool	m_sigUserRWPublic:1; // User C code accesses this signal, read-write
     bool	m_usedClock:1;	// Signal used as a clock
     bool	m_usedParam:1;	// Parameter is referenced (on link; later signals not setup)
+    bool	m_usedLoopIdx:1; // Variable subject of for unrolling
     bool	m_funcLocal:1;	// Local variable for a function
     bool	m_funcReturn:1;	// Return variable for a function
     bool	m_attrClockEn:1;// User clock enable attribute
@@ -567,7 +568,7 @@ private:
 	m_input=false; m_output=false; m_tristate=false;
 	m_primaryIO=false;
 	m_sc=false; m_scClocked=false; m_scSensitive=false;
-	m_usedClock=false; m_usedParam=false;
+	m_usedClock=false; m_usedParam=false; m_usedLoopIdx=false;
 	m_sigPublic=false; m_sigModPublic=false; m_sigUserRdPublic=false; m_sigUserRWPublic=false;
 	m_funcLocal=false; m_funcReturn=false;
 	m_attrClockEn=false; m_attrIsolateAssign=false; m_attrSFormat=false;
@@ -635,6 +636,7 @@ public:
     void	attrSFormat(bool flag) { m_attrSFormat = flag; }
     void	usedClock(bool flag) { m_usedClock = flag; }
     void	usedParam(bool flag) { m_usedParam = flag; }
+    void	usedLoopIdx(bool flag) { m_usedLoopIdx = flag; }
     void	sigPublic(bool flag) { m_sigPublic = flag; }
     void	sigModPublic(bool flag) { m_sigModPublic = flag; }
     void	sigUserRdPublic(bool flag) { m_sigUserRdPublic = flag; if (flag) sigPublic(true); }
@@ -675,6 +677,7 @@ public:
     bool	isBitLogic() const { AstBasicDType* bdtypep = basicp(); return bdtypep && bdtypep->isBitLogic(); }
     bool	isUsedClock() const { return m_usedClock; }
     bool	isUsedParam() const { return m_usedParam; }
+    bool	isUsedLoopIdx() const { return m_usedLoopIdx; }
     bool	isSc() const { return m_sc; }
     bool	isScQuad() const;
     bool	isScBv() const;

src/V3Unroll.cpp

@@ -250,6 +250,9 @@ private:
 	    incp->unlinkFrBackWithNext();
 	    stmtsp = stmtsp->addNextNull(incp);  // Maybe null if no body
 	}
+	// Mark variable to disable some later warnings
+	m_forVarp->usedLoopIdx(true);
+
 	// If it's a While, then incp is already part of bodysp.
 	V3Number loopValue(nodep->fileline(), m_forVarp->width());  // May differ in size from numInitp
 	loopValue.opAssign(numInit);

test_regress/t/t_lint_blksync_bad.v

@@ -9,13 +9,19 @@ module t (/*AUTOARG*/
    );
    input clk;
 
+   integer i;
+
    reg 	 sync_blk;
+   reg 	 sync_blk2;
    reg 	 sync_nblk;
+   reg   sync2_ok;
+   reg   sync3_ok;
    reg 	 combo_blk;
    reg 	 combo_nblk;
 
    always @(posedge clk) begin
       sync_blk = 1'b1; 
+      sync_blk2 = 1'b1;   // Only warn once per block
       sync_nblk <= 1'b1; 
    end
 
@@ -24,5 +30,18 @@ module t (/*AUTOARG*/
       combo_nblk <= 1'b1; 
    end
 
-endmodule
+   always @(posedge clk) begin
+      for (int i=0; i<20; i++) begin
+	 sync2_ok <= 1'b1;
+      end
+   end
 
+   always @(posedge clk) begin
+      sync3_ok <= f(sync3_ok);
+   end
+
+   function f (input v);
+      f = ~v;
+   endfunction
+
+endmodule