From bd4d73d9ae02b89b31ffa3b648fbac2dad1eb39f Mon Sep 17 00:00:00 2001
From: Martin Whitaker <icarus@martin-whitaker.me.uk>
Date: Sat, 15 Dec 2018 11:11:35 +0000
Subject: [PATCH] Fix GitHub issue #219 and #220 - incorrect results from SV
 size cast.

(cherry picked from commit 230f0bc13c1adc695a68c0345340ac32ae3c495d)
---
 elab_expr.cc | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/elab_expr.cc b/elab_expr.cc
index 699c4f5d5..3901b5723 100644
--- a/elab_expr.cc
+++ b/elab_expr.cc
@@ -2535,7 +2535,13 @@ NetExpr* PECastSize::elaborate_expr(Design*des, NetScope*scope,
       ivl_assert(*this, size_);
       ivl_assert(*this, base_);
 
-      NetExpr*sub = base_->elaborate_expr(des, scope, base_->expr_width(), flags);
+        // When changing size, a cast behaves exactly like an assignment,
+        // so the result size affects the final expression width.
+      unsigned cast_width = base_->expr_width();
+      if (cast_width < expr_width_)
+            cast_width = expr_width_;
+
+      NetExpr*sub = base_->elaborate_expr(des, scope, cast_width, flags);
 
 	// Perform the cast. The extension method (zero/sign), if needed,
 	// depends on the type of the base expression.