From c4a62dee0df46b166726fff6ad9db61eefc9938a Mon Sep 17 00:00:00 2001
From: Stephen Williams <steve@icarus.com>
Date: Wed, 11 Mar 2009 13:22:11 -0700
Subject: [PATCH] Pass unsigned-ness of arithmetic operators through operands.

The arithmetic operands are signed only if both operands are signed.
If the expression is unsigned, then the expression as a whole needs
to be processed as unsigned in order to get padding right.
---
 netlist.h    |  3 +++
 set_width.cc | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/netlist.h b/netlist.h
index 23c613f4b..256c68ebe 100644
--- a/netlist.h
+++ b/netlist.h
@@ -3262,6 +3262,7 @@ class NetEBAdd : public NetEBinary {
       virtual ivl_variable_type_t expr_type() const;
 
       virtual bool set_width(unsigned w, bool last_chance);
+      virtual void cast_signed(bool sign_flag);
       virtual NetEBAdd* dup_expr() const;
       virtual NetExpr* eval_tree(int prune_to_width = -1);
       virtual NetNet* synthesize(Design*, NetScope*scope, NetExpr*root);
@@ -3284,6 +3285,7 @@ class NetEBDiv : public NetEBinary {
       virtual ivl_variable_type_t expr_type() const;
 
       virtual bool set_width(unsigned w, bool last_chance);
+      virtual void cast_signed(bool sign_flag);
       virtual NetEBDiv* dup_expr() const;
       virtual NetExpr* eval_tree(int prune_to_width = -1);
       virtual NetNet* synthesize(Design*, NetScope*scope, NetExpr*root);
@@ -3414,6 +3416,7 @@ class NetEBMult : public NetEBinary {
       virtual ivl_variable_type_t expr_type() const;
 
       virtual bool set_width(unsigned w, bool last_chance);
+      virtual void cast_signed(bool sign_flag);
       virtual NetEBMult* dup_expr() const;
       virtual NetExpr* eval_tree(int prune_to_width = -1);
       virtual NetNet* synthesize(Design*, NetScope*scope, NetExpr*root);
diff --git a/set_width.cc b/set_width.cc
index ed209c754..2e013d438 100644
--- a/set_width.cc
+++ b/set_width.cc
@@ -106,6 +106,18 @@ bool NetEBAdd::set_width(unsigned w, bool)
       return wid == w;
 }
 
+void NetEBAdd::cast_signed(bool sign_flag)
+{
+      if (has_sign() == sign_flag)
+	    return;
+
+      if (sign_flag == false) {
+	    left_->cast_signed(sign_flag);
+	    right_->cast_signed(sign_flag);
+      }
+      cast_signed_base_(sign_flag);
+}
+
 /*
  * The bitwise logical operators have operands the same size as the
  * result. Anything else is a mess. I first try to get the operands to
@@ -168,6 +180,19 @@ bool NetEBDiv::set_width(unsigned w, bool)
       return w == expr_width();
 }
 
+void NetEBDiv::cast_signed(bool sign_flag)
+{
+      if (has_sign() == sign_flag)
+	    return;
+
+      if (sign_flag == false) {
+	    left_->cast_signed(sign_flag);
+	    right_->cast_signed(sign_flag);
+      }
+
+      cast_signed_base_(sign_flag);
+}
+
 bool NetEBLogic::set_width(unsigned w, bool)
 {
       bool flag;
@@ -192,6 +217,19 @@ bool NetEBMult::set_width(unsigned w, bool)
       return true;
 }
 
+void NetEBMult::cast_signed(bool sign_flag)
+{
+      if (has_sign() == sign_flag)
+	    return;
+
+      if (sign_flag == false) {
+	    left_->cast_signed(sign_flag);
+	    right_->cast_signed(sign_flag);
+      }
+
+      cast_signed_base_(sign_flag);
+}
+
 bool NetEBPow::set_width(unsigned w, bool last_chance)
 {
       return w == expr_width();