V0.8: fix signed parameter multiply

This patch mirrors what was done in development to fix the
multiplication of signed values.

net_design.cc

@@ -424,10 +424,6 @@ void NetScope::evaluate_parameters(Design*des)
 			assert(nexpr);
 			delete expr;
 			(*cur).second.expr = nexpr;
-
-			  // Set the signedness flag.
-			(*cur).second.expr
-			      ->cast_signed( (*cur).second.signed_flag );
 		  }
 		  break;
 
@@ -440,7 +436,9 @@ void NetScope::evaluate_parameters(Design*des)
 	    }
 
 	      /* If the parameter has range information, then make
-		 sure the value is set right. */
+		 sure the value is set right. Note that if the
+		 parameter doesn't have an explicit range, then it
+		 will get the signedness from the expression itself. */
 	    if (range_flag) {
 		  unsigned long wid = (msb >= lsb)? msb - lsb : lsb - msb;
 		  wid += 1;

verinum.cc

@@ -734,14 +734,18 @@ verinum operator * (const verinum&left, const verinum&right)
       verinum result(verinum::V0, left.len() + right.len(), has_len_flag);
       result.has_sign(left.has_sign() || right.has_sign());
 
-      for (unsigned rdx = 0 ;  rdx < right.len() ;  rdx += 1) {
+      verinum::V r_sign = sign_bit(right);
+      for (unsigned rdx = 0 ;  rdx < result.len() ;  rdx += 1) {
 
-	    if (right.get(rdx) == verinum::V0)
+	    verinum::V r_bit = rdx < right.len()? right.get(rdx) : r_sign;
+	    if (r_bit == verinum::V0)
 		  continue;
 
+	    verinum::V l_sign = sign_bit(left);
 	    verinum::V carry = verinum::V0;
-	    for (unsigned ldx = 0 ;  ldx < left.len() ;  ldx += 1) {
+	    for (unsigned ldx = 0 ;  ldx < result.len()-rdx ;  ldx += 1) {
-		  result.set(ldx+rdx, add_with_carry(left[ldx],
+		  verinum::V l_bit = ldx < left.len()? left[ldx] : l_sign;
+		  result.set(ldx+rdx, add_with_carry(l_bit,
 						     result[rdx+ldx],
 						     carry));
 	    }

verinum.h

@@ -106,6 +106,19 @@ class verinum {
       bool string_flag_;
 };
 
+/*
+ * This returns the sign bit of the verinum value. If the value is
+ * unsigned, then return an implicit sign bit of 0. Otherwise, return
+ * the high bit.
+ */
+inline verinum::V sign_bit(const verinum&val)
+{
+      if (val.has_sign())
+	    return val.get(val.len()-1);
+      else
+	    return verinum::V0;
+}
+
 /* Return a verinum that is minimal. That is, it has only the length
    needed to accurately represent the contained value, signed or not. */
 extern verinum trim_vnum(const verinum&);