Support uwire resolved writes to non-overlapping parts

The individual bits of an unresolved wire may be assigned in
different continuous assignments without generating an error.

elab_net.cc

@@ -453,13 +453,6 @@ NetNet* PEIdent::elaborate_lnet_common_(Design*des, NetScope*scope,
 	    sig->type(NetNet::UNRESOLVED_WIRE);
       }
 
-      if (sig->type() == NetNet::UNRESOLVED_WIRE && sig->pin(0).is_linked()) {
-	    cerr << get_fileline() << ": error: Unresolved net/uwire "
-	         << sig->name() << " cannot have multiple drivers." << endl;
-	    des->errors += 1;
-	    return 0;
-      }
-
 	/* Don't allow registers as assign l-values. */
       if (sig->type() == NetNet::REG) {
 	    cerr << get_fileline() << ": error: reg " << sig->name()
@@ -591,6 +584,14 @@ NetNet* PEIdent::elaborate_lnet_common_(Design*des, NetScope*scope,
 
       unsigned subnet_wid = midx-lidx+1;
 
+	/* Check if the l-value bits are double-driven. */
+      if (sig->type() == NetNet::UNRESOLVED_WIRE && sig->test_part_lref(midx,lidx)) {
+	    cerr << get_fileline() << ": error: Unresolved net/uwire "
+	         << sig->name() << " cannot have multiple drivers." << endl;
+	    des->errors += 1;
+	    return 0;
+      }
+
       if (sig->pin_count() > 1) {
 	    if (widx < 0 || widx >= (long) sig->pin_count()) {
 		  cerr << get_fileline() << ": warning: ignoring out of "

elab_sig.cc

@@ -794,7 +794,7 @@ static netstruct_t* elaborate_struct_type(Design*des, NetScope*scope,
 	    struct_member_t*curp = *cur;
 	    long use_msb = 0;
 	    long use_lsb = 0;
-	    if (! curp->range->empty()) {
+	    if (curp->range.get() && ! curp->range->empty()) {
 		  ivl_assert(*curp, curp->range->size() == 2);
 		  PExpr*msb_pex = curp->range->front();
 		  PExpr*lsb_pex = curp->range->back();

netlist.cc

@@ -856,6 +856,26 @@ unsigned NetNet::peek_eref() const
       return eref_count_;
 }
 
+/*
+ * Test each of the bits in the range, and set them. If any bits are
+ * already set then return true.
+ */
+bool NetNet::test_part_lref(unsigned msb, unsigned lsb)
+{
+      if (lref_mask_.size() == 0)
+	    lref_mask_.resize(vector_width());
+
+      bool rc = false;
+      for (unsigned idx = lsb ; idx <= msb ; idx += 1) {
+	    if (lref_mask_[idx])
+		  rc = true;
+	    else
+		  lref_mask_[idx] = true;
+      }
+
+      return rc;
+}
+
 void NetNet::incr_lref()
 {
       lref_count_ += 1;

netlist.h

@@ -660,6 +660,7 @@ class NetNet  : public NetObj {
       void incr_lref();
       void decr_lref();
       unsigned peek_lref() const { return lref_count_; }
+      bool test_part_lref(unsigned msb, unsigned lsb);
 
       unsigned get_refs() const;
 
@@ -691,6 +692,10 @@ class NetNet  : public NetObj {
 
       unsigned eref_count_;
       unsigned lref_count_;
+	// When the signal is an unresolved wire, we need more detail
+	// which bits are assigned. This mask is true for each bit
+	// that is known to be driven.
+      std::vector<bool> lref_mask_;
 
       vector<class NetDelaySrc*> delay_paths_;
 };