From 49366d1334b5c80cbf949b8c2bb82786d831a7c4 Mon Sep 17 00:00:00 2001
From: steve <steve>
Date: Thu, 26 Aug 2004 03:51:51 +0000
Subject: [PATCH]  Add the $is_signed function.

---
 README.txt   |  5 +++++
 elab_expr.cc | 29 ++++++++++++++++++++++++++++-
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/README.txt b/README.txt
index 2db9eb32d..646877abc 100644
--- a/README.txt
+++ b/README.txt
@@ -364,6 +364,11 @@ IEEE1364 standard, but have well defined meaning, and also sometimes
 gives nonstandard (but extended) meanings to some features of the
 language that are defined.
 
+    $is_signed(<expr>)
+	This system function returns 1 if the expression contained is
+	signed, or 0 otherwise. This is mostly of use for compiler
+	regression tests.
+
     $sizeof(<expr>)
     $bits(<expr>)
 	The $bits system function returns the size in bits of the
diff --git a/elab_expr.cc b/elab_expr.cc
index dd780a66e..9820d1a7b 100644
--- a/elab_expr.cc
+++ b/elab_expr.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: elab_expr.cc,v 1.88 2004/06/17 16:06:18 steve Exp $"
+#ident "$Id: elab_expr.cc,v 1.89 2004/08/26 03:52:07 steve Exp $"
 #endif
 
 # include "config.h"
@@ -221,6 +221,30 @@ NetExpr* PECallFunction::elaborate_sfunc_(Design*des, NetScope*scope) const
 	    return sub;
       }
 
+	/* Interpret the internal $is_signed system function to return
+	   a single bit flag -- 1 if the expression is signed, 0
+	   otherwise. The subexpression is elaborated but not
+	   evaluated. */
+      if (strcmp(path_.peek_name(0), "$is_signed") == 0) {
+	    if ((parms_.count() != 1) || (parms_[0] == 0)) {
+		  cerr << get_line() << ": error: The $is_signed() function "
+		       << "takes exactly one(1) argument." << endl;
+		  des->errors += 1;
+		  return 0;
+	    }
+
+	    PExpr*expr = parms_[0];
+	    NetExpr*sub = expr->elaborate_expr(des, scope, true);
+
+	    verinum val (sub->has_sign()? verinum::V1 : verinum::V0, 1);
+	    delete sub;
+
+	    sub = new NetEConst(val);
+	    sub->set_line(*this);
+
+	    return sub;
+      }
+
 	/* Get the return type of the system function by looking it up
 	   in the sfunc_table. */
       const struct sfunc_return_type*sfunc_info
@@ -967,6 +991,9 @@ NetExpr* PEUnary::elaborate_expr(Design*des, NetScope*scope, bool) const
 
 /*
  * $Log: elab_expr.cc,v $
+ * Revision 1.89  2004/08/26 03:52:07  steve
+ *  Add the $is_signed function.
+ *
  * Revision 1.88  2004/06/17 16:06:18  steve
  *  Help system function signedness survive elaboration.
  *