Fix for loop missing initializer, bug1605.

Changes

@@ -4,6 +4,8 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 * Verilator 4.023 devel
 
+****  Fix for loop missing initializer, bug1605. [Andrew Holme]
+
 
 * Verilator 4.022 2019-11-10
 

src/V3Unroll.cpp

@@ -277,7 +277,7 @@ private:
         if (initp) {
             initp->unlinkFrBack();  // Always a single statement; nextp() may be nodep
             // Don't add to list, we do it once, and setting loop index isn't
-            // needed as we're constant propagating it
+            // needed if we have > 1 loop, as we're constant propagating it
         }
         if (precondsp) {
             precondsp->unlinkFrBackWithNext();
@@ -296,8 +296,8 @@ private:
 
         AstNode* newbodysp = NULL;
         ++m_statLoops;
+        int times = 0;
         if (stmtsp) {
-            int times = 0;
             while (1) {
                 UINFO(8,"      Looping "<<loopValue<<endl);
                 V3Number res = V3Number(nodep);
@@ -352,6 +352,10 @@ private:
                 }
             }
         }
+        if (!newbodysp) {  // initp might have effects after the loop
+            newbodysp = initp;  // Maybe NULL
+            initp = NULL;
+        }
         // Replace the FOR()
         if (newbodysp) nodep->replaceWith(newbodysp);
         else nodep->unlinkFrBack();

test_regress/t/t_for_loop.v

@@ -94,6 +94,13 @@ module t (/*AUTOARG*/
 	 for (; ; ++i) begin ++loops; break; end
 	 if (loops !== 1) $stop;
 	 //
+	 // bug1605
+	 i = 1;
+	 for (i=20; 0; ) ;
+	 if (i != 20) $stop;
+	 for (i=30; i<10; i++) ;
+	 if (i != 30) $stop;
+	 //
 	 $write("*-* All Finished *-*\n");
 	 $finish;
       end