From 3a99a5e800047ef3464daa5e304f9c76b67aca63 Mon Sep 17 00:00:00 2001
From: Stephen Williams <steve@icarus.com>
Date: Sat, 11 Oct 2008 08:39:06 -0700
Subject: [PATCH] Suppress operand has_sign if expression is unsigned.

Fix processing of arguments of +- and * when only one of the operands
is signed.
---
 PExpr.cc     |  1 -
 PExpr.h      |  2 --
 elab_expr.cc | 13 +++++++++++--
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/PExpr.cc b/PExpr.cc
index 87fa6ad39..8e1c9889b 100644
--- a/PExpr.cc
+++ b/PExpr.cc
@@ -29,7 +29,6 @@
 PExpr::PExpr()
 {
       expr_type_ = IVL_VT_NO_TYPE;
-      has_sign_ = false;
 }
 
 PExpr::~PExpr()
diff --git a/PExpr.h b/PExpr.h
index 7237cbc2f..e0e0f745a 100644
--- a/PExpr.h
+++ b/PExpr.h
@@ -79,7 +79,6 @@ class PExpr : public LineInfo {
 	// return valid results.
       ivl_variable_type_t expr_type() const { return expr_type_; }
       unsigned expr_width() const           { return expr_width_; }
-      bool has_sign() const                 { return has_sign_; }
 
 	// During the elaborate_sig phase, we may need to scan
 	// expressions to find implicit net declarations.
@@ -144,7 +143,6 @@ class PExpr : public LineInfo {
 	// The derived class test_width methods should fill these in.
       ivl_variable_type_t expr_type_;
       unsigned expr_width_;
-      bool has_sign_;
 
     private: // not implemented
       PExpr(const PExpr&);
diff --git a/elab_expr.cc b/elab_expr.cc
index d73863d76..ab3785657 100644
--- a/elab_expr.cc
+++ b/elab_expr.cc
@@ -662,6 +662,12 @@ NetExpr* PEBinary::elaborate_expr_base_mult_(Design*des,
 	    }
       }
 
+	// If this expression is unsigned, then make sure the
+	// arguments are unsigned so that the padding below doesn't
+	// cause any sign extension to happen.
+      suppress_operand_sign_if_needed_(lp, rp);
+
+
 	// Multiply will guess a width that is the sum of the
 	// widths of the operand. If that sum is too small, then
 	// pad one of the arguments enough that the sum is the
@@ -693,6 +699,11 @@ NetExpr* PEBinary::elaborate_expr_base_add_(Design*des,
       if (! type_is_vectorable(rp->expr_type()))
 	    use_lossless_flag = false;
 
+	// If the expression is unsigned, then force the operands to
+	// unsigned so taht the set_width below doesn't cause them to
+	// be sign-extended.
+      suppress_operand_sign_if_needed_(lp, rp);
+
       tmp = new NetEBAdd(op_, lp, rp, use_lossless_flag);
       if (expr_wid > 0 && type_is_vectorable(tmp->expr_type()))
 	    tmp->set_width(expr_wid);
@@ -839,7 +850,6 @@ unsigned PECallFunction::test_width_sfunc_(Design*des, NetScope*scope,
 
 	    expr_type_ = IVL_VT_BOOL;
 	    expr_width_= integer_width;
-	    has_sign_  = false;
 
 	    expr_type = expr_type_;
 	    return expr_width_;
@@ -1345,7 +1355,6 @@ unsigned PEFNumber::test_width(Design*des, NetScope*scope,
 {
       expr_type_  = IVL_VT_REAL;
       expr_width_ = 1;
-      has_sign_   = true;
       unsized_flag = true;
 
       expr_type = expr_type_;