Support disable for loop escapes.

Changes

@@ -3,6 +3,10 @@ Revision history for Verilator
 The contributors that suggested a given feature are shown in [].  [by ...]
 indicates the contributor was also the author of the fix; Thanks!
 
+* Verilator 3.814****
+
+***  Support disable for loop escapes.
+
 * Verilator 3.813 2011/06/28
 
 ***  Support bit vectors > 64 bits wide in DPI import and exports.

bin/verilator

@@ -2258,6 +2258,13 @@ not arrays nor structs.
 Treated as a "longint"; does not yet warn about operations that are
 specified as illegal on chandles.
 
+=item disable
+
+Disable statements may be used only if the block being disabled is a block
+the disable statement itself is inside.  This is commonly used to provide
+loop break and continue functionality before SystemVerilog added the break
+and continue keywords.
+
 =item priority if, unique if
 
 Priority and unique if's are treated as normal ifs and not asserted to be

src/V3AstNodes.h

@@ -1973,6 +1973,18 @@ struct AstContinue : public AstNodeStmt {
     virtual bool isSplittable() const { return false; }	// SPECIAL: We don't process code after breaks
 };
 
+struct AstDisable : public AstNodeStmt {
+private:
+    string	m_name;		// Name of block
+public:
+    AstDisable(FileLine* fileline, const string& name)
+	: AstNodeStmt(fileline), m_name(name) {}
+    ASTNODE_NODE_FUNCS(Disable, DISABLE)
+    virtual string name()	const { return m_name; }		// * = Block name
+    void name(const string& flag) { m_name=flag; }
+    virtual bool isSplittable() const { return false; }	// SPECIAL: We don't process code after breaks
+};
+
 struct AstReturn : public AstNodeStmt {
     AstReturn(FileLine* fileline, AstNode* lhsp=NULL)
 	: AstNodeStmt (fileline) {

src/V3EmitV.cpp

@@ -217,6 +217,9 @@ class EmitVBaseVisitor : public EmitCBaseVisitor {
 	}
 	puts(");\n");
     }
+    virtual void visit(AstDisable* nodep, AstNUser*) {
+	putbs("disable "+nodep->name()+";\n");
+    }
     virtual void visit(AstDisplay* nodep, AstNUser*) {
 	visitNodeDisplay(nodep, nodep->filep(), nodep->fmtp()->text(), nodep->fmtp()->exprsp());
     }

src/V3LinkJump.cpp

@@ -211,6 +211,27 @@ private:
 	}
 	nodep->unlinkFrBack(); pushDeletep(nodep); nodep=NULL;
     }
+    virtual void visit(AstDisable* nodep, AstNUser*) {
+	UINFO(8,"   DISABLE "<<nodep<<endl);
+	nodep->iterateChildren(*this);
+	AstBegin* beginp = NULL;
+	for (BeginStack::reverse_iterator it = m_beginStack.rbegin(); it != m_beginStack.rend(); ++it) {
+	    UINFO(9,"    UNDERBLK  "<<*it<<endl);
+	    if ((*it)->name() == nodep->name()) {
+		beginp = *it;
+		break;
+	    }
+	}
+	//if (debug()>=9) { UINFO(0,"\n"); beginp->dumpTree(cout,"  labeli: "); }
+	if (!beginp) { nodep->v3error("disable isn't underneath a begin with name: "<<nodep->name()); }
+	else {
+	    // Jump to the end of the named begin
+	    AstJumpLabel* labelp = findAddLabel(beginp, false);
+	    nodep->addNextHere(new AstJumpGo(nodep->fileline(), labelp));
+	}
+	nodep->unlinkFrBack(); pushDeletep(nodep); nodep=NULL;
+	//if (debug()>=9) { UINFO(0,"\n"); beginp->dumpTree(cout,"  labelo: "); }
+    }
     virtual void visit(AstVarRef* nodep, AstNUser*) {
 	if (m_loopInc && nodep->varp()) nodep->varp()->usedLoopIdx(true);
     }

src/verilog.y

@@ -1886,7 +1886,7 @@ statement_item<nodep>:		// IEEE: statement_item
 	|	statementVerilatorPragmas			{ $$ = $1; }
 	//
 	//			// IEEE: disable_statement
-	//UNSUP	yDISABLE idAny/*hierarchical_identifier-task_or_block*/ ';'	{ UNSUP }
+	|	yDISABLE idAny/*hierarchical_identifier-task_or_block*/ ';'	{ $$ = new AstDisable($1,*$2); }
 	//UNSUP	yDISABLE yFORK ';'			{ UNSUP }
 	//			// IEEE: event_trigger
 	//UNSUP	yP_MINUSGT hierarchical_identifier/*event*/ ';'	{ UNSUP }

test_regress/t/t_for_break.v

@@ -92,8 +92,17 @@ module t (/*AUTOARG*/
       input  [3:0] loop_continue;
       integer 	     i;
 
-      // Placeholder
+      Test1 = 0;
-      return Test0(loop_stop,loop_break,loop_continue);
+      begin : outer_block
+         for (i=1; i<20; i=i+1) begin : inner_block
+   	 Test1 = Test1 + 1;
+	 // continue, IE jump to end-of-inner_block.  Must be inside inner_block.
+         if (i[3:0] == loop_continue) disable inner_block;
+	 // break, IE jump to end-of-outer_block.  Must be inside outer_block.
+   	 if (i[3:0] == loop_break) disable outer_block;
+   	 Test1 = Test1 + i[15:0];
+         end : inner_block
+      end : outer_block
    endfunction
 
    function [15:0] Test2;