vvp: Initialize automatic 2-state vectors to 0

Automatic 2-state vectors currently get initialized to 'hx, while their
default value should be 0.

Make sure the vector is initialized to 0 at the beginning of the automatic
context.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

vvp/vvp_net.cc

@@ -1794,16 +1794,28 @@ void vvp_vector4_t::change_z2x()
       }
 }
 
-void vvp_vector4_t::set_to_x()
+void vvp_vector4_t::fill_bits(vvp_bit4_t bit)
 {
+	/* note: this relies on the bit encoding for the vvp_bit4_t. */
+      static const unsigned long init_atable[4] = {
+	    WORD_0_ABITS,
+	    WORD_1_ABITS,
+	    WORD_Z_ABITS,
+	    WORD_X_ABITS };
+      static const unsigned long init_btable[4] = {
+	    WORD_0_BBITS,
+	    WORD_1_BBITS,
+	    WORD_Z_BBITS,
+	    WORD_X_BBITS };
+
       if (size_ <= BITS_PER_WORD) {
-	    abits_val_ = vvp_vector4_t::WORD_X_ABITS;
+	    abits_val_ = init_atable[bit];
-            bbits_val_ = vvp_vector4_t::WORD_X_BBITS;
+	    bbits_val_ = init_btable[bit];
       } else {
 	    unsigned words = (size_ + BITS_PER_WORD - 1) / BITS_PER_WORD;
 	    for (unsigned idx = 0; idx < words; idx += 1) {
-		  abits_ptr_[idx] = vvp_vector4_t::WORD_X_ABITS;
+		  abits_ptr_[idx] = init_atable[bit];
-                  bbits_ptr_[idx] = vvp_vector4_t::WORD_X_BBITS;
+		  bbits_ptr_[idx] = init_btable[bit];
 	    }
       }
 }

vvp/vvp_net.h

@@ -312,8 +312,11 @@ class vvp_vector4_t {
 	// Change all Z bits to X bits.
       void change_z2x();
 
+	// Set all bits to the specified value.
+      void fill_bits(vvp_bit4_t bit);
+
 	// Change all bits to X bits.
-      void set_to_x();
+      void set_to_x() { fill_bits(BIT4_X); }
 
 	// Display the value into the buf as a string.
       char*as_string(char*buf, size_t buf_len) const;

vvp/vvp_net_sig.cc

@@ -333,12 +333,9 @@ const vvp_vector4_t& vvp_fun_signal4_sa::vec4_unfiltered_value() const
 
 vvp_fun_signal4_aa::vvp_fun_signal4_aa(unsigned wid, vvp_bit4_t init)
 {
-	/* To make init work we would need to save it and then use the
-	 * saved value when we ran reset_instance(). For now just make
-	 * sure it matches the value we use in reset_instance(). */
-      assert(init == BIT4_X);
       context_idx_ = vpip_add_item_to_context(this, vpip_peek_context_scope());
       size_ = wid;
+      init_ = init;
 }
 
 vvp_fun_signal4_aa::~vvp_fun_signal4_aa()
@@ -348,7 +345,7 @@ vvp_fun_signal4_aa::~vvp_fun_signal4_aa()
 
 void vvp_fun_signal4_aa::alloc_instance(vvp_context_t context)
 {
-      vvp_set_context_item(context, context_idx_, new vvp_vector4_t(size_));
+      vvp_set_context_item(context, context_idx_, new vvp_vector4_t(size_, init_));
 }
 
 void vvp_fun_signal4_aa::reset_instance(vvp_context_t context)
@@ -356,7 +353,7 @@ void vvp_fun_signal4_aa::reset_instance(vvp_context_t context)
       vvp_vector4_t*bits = static_cast<vvp_vector4_t*>
             (vvp_get_context_item(context, context_idx_));
 
-      bits->set_to_x();
+      bits->fill_bits(init_);
 }
 
 #ifdef CHECK_WITH_VALGRIND

vvp/vvp_net_sig.h

@@ -190,6 +190,7 @@ class vvp_fun_signal4_aa : public vvp_fun_signal_vec, public automatic_signal_ba
     private:
       unsigned context_idx_;
       unsigned size_;
+      vvp_bit4_t init_;
 };
 
 class vvp_fun_signal_real : public vvp_fun_signal_base {

vvp/words.cc

@@ -176,15 +176,18 @@ void compile_variable(char*label, char*name,
 
       vvp_net_t*net = new vvp_net_t;
 
+      vvp_bit4_t init;
+      if (vpi_type_code == vpiIntVar)
+	    init = BIT4_0;
+      else
+	    init = BIT4_X;
+
       if (vpip_peek_current_scope()->is_automatic()) {
-	    vvp_fun_signal4_aa*tmp = new vvp_fun_signal4_aa(wid);
+	    vvp_fun_signal4_aa*tmp = new vvp_fun_signal4_aa(wid, init);
 	    net->fil = tmp;
             net->fun = tmp;
-      } else if (vpi_type_code == vpiIntVar) {
-	    net->fil = new vvp_wire_vec4(wid, BIT4_0);
-            net->fun = new vvp_fun_signal4_sa(wid);
       } else {
-	    net->fil = new vvp_wire_vec4(wid, BIT4_X);
+	    net->fil = new vvp_wire_vec4(wid, init);
             net->fun = new vvp_fun_signal4_sa(wid);
       }
       vvp_signal_value*vfil = dynamic_cast<vvp_signal_value*>(net->fil);