vlog95: convert real Verilog-A abs/min/max to $abs/$min/$max

Converting these Verilog-A functions to use the $ version allows nan
to be handled correct. This still needs to be done for the LPM code.

tgt-vlog95/expr.c

@@ -176,10 +176,19 @@ static void emit_expr_binary(ivl_scope_t scope, ivl_expr_t expr, unsigned wid)
 		  vlog_errors += 1;
 	    }
 	    break;
-	  /* Convert Verilog-A min() or max() functions. This only works
+	  /* Convert the Verilog-A min() or max() functions. */
-	   *  when the arguments have no side effect. */
 	case 'm':
 	case 'M':
+	    if (ivl_expr_value(expr) == IVL_VT_REAL) {
+		    /* For a real expression use the $min()/$max() function. */
+		  if (ivl_expr_opcode(expr) == 'm') fprintf(vlog_out, "$min(");
+		  else fprintf(vlog_out, "$max(");
+		  emit_expr(scope, ivl_expr_oper1(expr), wid);
+		  fprintf(vlog_out, ",");
+		  emit_expr(scope, ivl_expr_oper2(expr), wid);
+		  fprintf(vlog_out, ")");
+	    } else {
+		    /* This only works when the argument has no side effect. */
 		  fprintf(vlog_out, "((");
 		  emit_expr(scope, ivl_expr_oper1(expr), wid);
 		  fprintf(vlog_out, ") %s (", oper);
@@ -189,6 +198,7 @@ static void emit_expr_binary(ivl_scope_t scope, ivl_expr_t expr, unsigned wid)
 		  fprintf(vlog_out, ") : (");
 		  emit_expr(scope, ivl_expr_oper2(expr), wid);
 		  fprintf(vlog_out, "))");
+	    }
 	    break;
 	default:
 	    emit_expr(scope, ivl_expr_oper1(expr), wid);
@@ -587,19 +597,23 @@ static void emit_expr_unary(ivl_scope_t scope, ivl_expr_t expr, unsigned wid)
 	                    ivl_expr_lineno(expr));
 	    vlog_errors += 1;
 	    break;
-	  /* Convert Verilog-A abs() function. This only works when the
+	  /* Convert the Verilog-A abs() function. */
-	   * argument has no side effect. */
 	case 'm':
+	    if (ivl_expr_value(expr) == IVL_VT_REAL) {
+		    /* For a real expression use the $abs() function. */
+		  fprintf(vlog_out, "$abs(");
+		  emit_expr(scope, ivl_expr_oper1(expr), wid);
+		  fprintf(vlog_out, ")");
+	    } else {
+		    /* This only works when the argument has no side effect. */
 		  fprintf(vlog_out, "((");
 		  emit_expr(scope, ivl_expr_oper1(expr), wid);
-	    fprintf(vlog_out, ") > ");
+		  fprintf(vlog_out, ") > 0 ? (");
-	    if (ivl_expr_value(expr) == IVL_VT_REAL) fprintf(vlog_out, "0.0");
-	    else fprintf(vlog_out, "0");
-	    fprintf(vlog_out, " ? (");
 		  emit_expr(scope, ivl_expr_oper1(expr), wid);
 		  fprintf(vlog_out, ") : -(");
 		  emit_expr(scope, ivl_expr_oper1(expr), wid);
 		  fprintf(vlog_out, "))");
+	    }
 	    break;
 	default:
 	    fprintf(vlog_out, "<unknown>");

tgt-vlog95/logic_lpm.c

@@ -818,13 +818,14 @@ static void emit_lpm_func(ivl_scope_t scope, ivl_lpm_t lpm)
 static void emit_lpm_as_ca(ivl_scope_t scope, ivl_lpm_t lpm)
 {
       switch (ivl_lpm_type(lpm)) {
-	  /* Convert Verilog-A abs() function. This only works when the
+	  /* Convert the Verilog-A abs() function. This only works when the
 	   * argument has no side effect. */
 	case IVL_LPM_ABS:
+// HERE: If this is a real net then use the $abs() function to get nan to
+//       work correctly. See the expr code.
 	    fprintf(vlog_out, "((");
 	    emit_nexus_as_ca(scope, ivl_lpm_data(lpm, 0), 0);
 	    fprintf(vlog_out, ") > ");
-// HERE: If this is a real net then use 0.0. See the expr code.
 	    fprintf(vlog_out, "0 ? (");
 	    emit_nexus_as_ca(scope, ivl_lpm_data(lpm, 0), 0);
 	    fprintf(vlog_out, ") : -(");