From bb39d09d5e4849b046041738217ddc4a7895b752 Mon Sep 17 00:00:00 2001
From: Martin Whitaker <icarus@martin-whitaker.me.uk>
Date: Sat, 26 Oct 2013 23:05:21 +0100
Subject: [PATCH] Eliminate spurious error message for array word lval in
 always @* block.

---
 net_nex_output.cc | 65 +++++++++++++++++++++++++----------------------
 1 file changed, 35 insertions(+), 30 deletions(-)

diff --git a/net_nex_output.cc b/net_nex_output.cc
index 5b3f4b1ca..761937fb8 100644
--- a/net_nex_output.cc
+++ b/net_nex_output.cc
@@ -38,38 +38,43 @@ void NetProc::nex_output(NexusSet&)
 
 void NetAssign_::nex_output(NexusSet&out)
 {
-      if (sig_ && !word_) {
-	    Nexus*nex = sig_->pin(0).nexus();
-	    unsigned use_base = 0;
-	    unsigned use_wid = lwidth();
-	    if (base_) {
-		  long tmp = 0;
-		  bool flag = eval_as_long(tmp, base_);
-		  if (!flag) {
-			  // Unable to evaluate the bit/part select of
-			  // the l-value, so this is a mux. Pretty
-			  // sure I don't know how to handle this yet
-			  // in synthesis, so punt for now.
-			use_base = 0;
-			use_wid = nex->vector_width();
-
-		  } else {
-			use_base = tmp;
-		  }
+      assert(sig_);
+      unsigned use_word = 0;
+      unsigned use_base = 0;
+      unsigned use_wid = lwidth();
+      if (word_) {
+	    long tmp = 0;
+	    if (eval_as_long(tmp, word_)) {
+		    // A constant word select, so add the selected word.
+		  use_word = tmp;
+	    } else {
+		    // A variable word select. The obvious thing to do
+		    // is to add the whole array, but this could cause
+		    // NetBlock::nex_input() to overprune the input set.
+		    // As array access is not yet handled in synthesis,
+		    // I'll leave this as TBD - the output set is not
+		    // otherwise used when elaborating an always @*
+		    // block.
+		  return;
 	    }
-
-	    out.add(nex, use_base, use_wid);
-
-      } else {
-	      /* Quoting from netlist.h comments for class NetMemory:
-	       * "This is not a node because memory objects can only be
-	       * accessed by behavioral code."
-	       */
-	    cerr << "?:?" << ": internal error: "
-		 << "NetAssignBase::nex_output on unsupported lval ";
-	    dump_lval(cerr);
-	    cerr << endl;
       }
+      Nexus*nex = sig_->pin(use_word).nexus();
+      if (base_) {
+	    long tmp = 0;
+	    bool flag = eval_as_long(tmp, base_);
+	    if (!flag) {
+		    // Unable to evaluate the bit/part select of
+		    // the l-value, so this is a mux. Pretty
+		    // sure I don't know how to handle this yet
+		    // in synthesis, so punt for now.
+		  use_base = 0;
+		  use_wid = nex->vector_width();
+
+	    } else {
+		  use_base = tmp;
+	    }
+      }
+      out.add(nex, use_base, use_wid);
 }
 
 /*