From 77f168cf2850a9f8919322fff3d86d65d61501ba Mon Sep 17 00:00:00 2001
From: Stephen Williams <steve@icarus.com>
Date: Sun, 12 Feb 2012 14:52:47 -0800
Subject: [PATCH] Support non-constant indexed part select of packed arrays.

---
 elab_expr.cc | 11 +++++------
 elab_lval.cc | 16 +++++-----------
 netmisc.cc   | 16 ++++++++++++++++
 netmisc.h    | 32 ++++++++++++++++++++++++++++++++
 4 files changed, 58 insertions(+), 17 deletions(-)

diff --git a/elab_expr.cc b/elab_expr.cc
index 79783a58f..63105d7f8 100644
--- a/elab_expr.cc
+++ b/elab_expr.cc
@@ -3299,13 +3299,12 @@ NetExpr* PEIdent::elaborate_expr_net_idx_up_(Design*des, NetScope*scope,
 	    return ss;
       }
 
-      if (net->sig()->packed_dims().size() > 1) {
-	    cerr << get_fileline() << ": sorry: Indexed part select of packed arrays not supported here." << endl;
-	    des->errors += 1;
-	    return net;
-      }
 
-      base = normalize_variable_base(base, net->msi(), net->lsi(), wid, true);
+      ivl_assert(*this, prefix_indices.size()+1 == net->sig()->packed_dims().size());
+
+	// Convert the non-constant part select index expression into
+	// an expression that returns a canonical base.
+      base = normalize_variable_part_base(prefix_indices, base, net->sig(), wid, true);
 
       NetESelect*ss = new NetESelect(net, base, wid, IVL_SEL_IDX_UP);
       ss->set_line(*this);
diff --git a/elab_lval.cc b/elab_lval.cc
index 8171d5b0c..6376c05e1 100644
--- a/elab_lval.cc
+++ b/elab_lval.cc
@@ -598,22 +598,16 @@ bool PEIdent::elaborate_lval_net_idx_(Design*des,
 		  }
 	    }
       } else {
-	    if (reg->packed_dims().size() > 1) {
-		  cerr << get_fileline() << ": sorry: "
-		       << "Indexed part select of packed arrays not supported nere." << endl;
-		  des->errors += 1;
-		  return false;
-	    }
-
+	    ivl_assert(*this, prefix_indices.size()+1 == reg->packed_dims().size());
 	      /* Correct the mux for the range of the vector. */
 	    if (use_sel == index_component_t::SEL_IDX_UP) {
-		  base = normalize_variable_base(base, reg->packed_dims(),
-		                                 wid, true);
+		  base = normalize_variable_part_base(prefix_indices, base,
+						      reg, wid, true);
 		  sel_type = IVL_SEL_IDX_UP;
 	    } else {
 		    // This is assumed to be a SEL_IDX_DO.
-		  base = normalize_variable_base(base, reg->packed_dims(),
-		                                 wid, false);
+		  base = normalize_variable_part_base(prefix_indices, base,
+						      reg, wid, false);
 		  sel_type = IVL_SEL_IDX_DOWN;
 	    }
       }
diff --git a/netmisc.cc b/netmisc.cc
index 8a08a48ff..504b58dcb 100644
--- a/netmisc.cc
+++ b/netmisc.cc
@@ -343,6 +343,22 @@ NetExpr *normalize_variable_bit_base(const list<long>&indices, NetExpr*base,
       return normalize_variable_base(base, rng.msb, rng.lsb, 1, true, slice_off);
 }
 
+NetExpr *normalize_variable_part_base(const list<long>&indices, NetExpr*base,
+				      const NetNet*reg,
+				      unsigned long wid, bool is_up)
+{
+      const list<NetNet::range_t>&packed_dims = reg->packed_dims();
+      ivl_assert(*base, indices.size()+1 == packed_dims.size());
+
+	// Get the canonical offset of the slice within which we are
+	// addressing. We need that address as a slice offset to
+	// calculate the proper complete address
+      const NetNet::range_t&rng = packed_dims.back();
+      long slice_off = reg->sb_to_idx(indices, rng.lsb);
+
+      return normalize_variable_base(base, rng.msb, rng.lsb, wid, is_up, slice_off);
+}
+
 NetExpr *normalize_variable_slice_base(const list<long>&indices, NetExpr*base,
 				       const NetNet*reg, unsigned long&lwid)
 {
diff --git a/netmisc.h b/netmisc.h
index 45b9238c2..5e96d3c8d 100644
--- a/netmisc.h
+++ b/netmisc.h
@@ -105,11 +105,43 @@ extern NetExpr*normalize_variable_base(NetExpr *base,
 				       const list<NetNet::range_t>&dims,
 				       unsigned long wid, bool is_up);
 
+/*
+ * Calculate a canonicalizing expression for a bit select, when the
+ * base expression is the last index of an otherwise complete bit
+ * select. For example:
+ *   reg [3:0][7:0] foo;
+ *   ... foo[1][x] ...
+ * base is (x) and the generated expression will be (x+8).
+ */
 extern NetExpr*normalize_variable_bit_base(const list<long>&indices, NetExpr *base,
 					   const NetNet*reg);
 
+/*
+ * This is similar to normalize_variable_bit_base, but the tail index
+ * it a base and width, instead of a bit. This is used for handling
+ * indexed part selects:
+ *   reg [3:0][7:0] foo;
+ *   ... foo[1][x +: 2]
+ * base is (x), wid input is (2), and is_up is (true). The output
+ * expression is (x+8).
+ */
+extern NetExpr *normalize_variable_part_base(const list<long>&indices, NetExpr*base,
+					     const NetNet*reg,
+					     unsigned long wid, bool is_up);
+/*
+ * Calculate a canonicalizing expression for a slice select. The
+ * indices array is less then needed to fully address a bit, so the
+ * result is a slice of the packed array. The return value is an
+ * expression that gets to the base of the slice, and (lwid) becomes
+ * the width of the slice, in bits. For example:
+ *   reg [4:1][7:0] foo
+ *   ...foo[x]...
+ * base is (x) and the generated expression will be (x*8 - 8), with
+ * lwid set to (8).
+ */
 extern NetExpr*normalize_variable_slice_base(const list<long>&indices, NetExpr *base,
 					     const NetNet*reg, unsigned long&lwid);
+
 extern NetExpr*normalize_variable_array_base(NetExpr *base, long offset,
                                              unsigned count);