Fix some more errors when reading from VHDL outputs

I forgot to modify the LPM generating code with the
last patch. This *should* now always ensure a signal
is readable before code is generated to read from it.

tgt-vhdl/logic.cc

@@ -26,18 +26,6 @@
 #include <sstream>
 #include <iostream>
 
-// Return a variable reference for a nexus that is guaranteed to
-// be readable.
-static vhdl_var_ref *readable_ref(vhdl_scope* scope, ivl_nexus_t nex)
-{
-   vhdl_var_ref* ref = nexus_to_var_ref(scope, nex);
-   
-   vhdl_decl* decl = scope->get_decl(ref->get_name());
-   decl->ensure_readable();
-
-   return ref;
-}
-
 /*
  * Convert the inputs of a logic gate to a binary expression.
  */

tgt-vhdl/lpm.cc

@@ -32,7 +32,7 @@ static vhdl_expr *part_select_base(vhdl_scope *scope, ivl_lpm_t lpm)
    vhdl_expr *off;
    ivl_nexus_t base = ivl_lpm_data(lpm, 1);
    if (base != NULL)
-      off = nexus_to_var_ref(scope, base);
+      off = readable_ref(scope, base);
    else
       off = new vhdl_const_int(ivl_lpm_base(lpm));
 
@@ -49,7 +49,7 @@ static vhdl_expr *concat_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm)
       new vhdl_binop_expr(VHDL_BINOP_CONCAT, result_type);
  
    for (int i = ivl_lpm_selects(lpm) - 1; i >= 0; i--) {
-      vhdl_expr *e = nexus_to_var_ref(scope, ivl_lpm_data(lpm, i));
+      vhdl_expr *e = readable_ref(scope, ivl_lpm_data(lpm, i));
       if (NULL == e)
          return NULL;
 
@@ -67,7 +67,7 @@ static vhdl_expr *binop_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm, vhdl_binop
    vhdl_binop_expr *expr = new vhdl_binop_expr(op, result_type);
  
    for (int i = 0; i < 2; i++) {
-      vhdl_expr *e = nexus_to_var_ref(scope, ivl_lpm_data(lpm, i));
+      vhdl_expr *e = readable_ref(scope, ivl_lpm_data(lpm, i));
       if (NULL == e)
          return NULL;
 
@@ -94,7 +94,7 @@ static vhdl_expr *rel_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm, vhdl_binop_t
    vhdl_binop_expr *expr = new vhdl_binop_expr(op, vhdl_type::boolean());
   
    for (int i = 0; i < 2; i++) {
-      vhdl_expr *e = nexus_to_var_ref(scope, ivl_lpm_data(lpm, i));
+      vhdl_expr *e = readable_ref(scope, ivl_lpm_data(lpm, i));
       if (NULL == e)
          return NULL;
 
@@ -108,7 +108,7 @@ static vhdl_expr *rel_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm, vhdl_binop_t
 
 static vhdl_expr *part_select_vp_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm)
 {
-   vhdl_var_ref *selfrom = nexus_to_var_ref(scope, ivl_lpm_data(lpm, 0));
+   vhdl_var_ref *selfrom = readable_ref(scope, ivl_lpm_data(lpm, 0));
    if (NULL == selfrom)
       return NULL;
    
@@ -125,7 +125,7 @@ static vhdl_expr *part_select_vp_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm)
 
 static vhdl_expr *part_select_pv_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm)
 {   
-   return nexus_to_var_ref(scope, ivl_lpm_data(lpm, 0));
+   return readable_ref(scope, ivl_lpm_data(lpm, 0));
 }
 
 static vhdl_expr *ufunc_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm)
@@ -134,7 +134,7 @@ static vhdl_expr *ufunc_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm)
    vhdl_fcall *fcall = new vhdl_fcall(ivl_scope_basename(f_scope), NULL);
 
    for (unsigned i = 0; i < ivl_lpm_size(lpm); i++) {
-      vhdl_var_ref *ref = nexus_to_var_ref(scope, ivl_lpm_data(lpm, i));
+      vhdl_var_ref *ref = readable_ref(scope, ivl_lpm_data(lpm, i));
       if (NULL == ref)
          return NULL;
 
@@ -147,7 +147,7 @@ static vhdl_expr *ufunc_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm)
 static vhdl_expr *reduction_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm,
                                         support_function_t f, bool invert)
 {
-   vhdl_var_ref *ref = nexus_to_var_ref(scope, ivl_lpm_data(lpm, 0));
+   vhdl_var_ref *ref = readable_ref(scope, ivl_lpm_data(lpm, 0));
    if (NULL == ref)
       return NULL;
 
@@ -174,7 +174,7 @@ static vhdl_expr *reduction_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm,
 
 static vhdl_expr *sign_extend_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm)
 {
-   vhdl_expr *ref = nexus_to_var_ref(scope, ivl_lpm_data(lpm, 0));
+   vhdl_expr *ref = readable_ref(scope, ivl_lpm_data(lpm, 0));
    if (ref)
       return ref->resize(ivl_lpm_width(lpm));
    else
@@ -194,7 +194,7 @@ static vhdl_expr *array_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm)
    
    vhdl_type *atype = new vhdl_type(*adecl->get_type());
 
-   vhdl_expr *select = nexus_to_var_ref(scope, ivl_lpm_select(lpm));
+   vhdl_expr *select = readable_ref(scope, ivl_lpm_select(lpm));
    if (NULL == select)
       return NULL;
    
@@ -208,8 +208,8 @@ static vhdl_expr *array_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm)
 static vhdl_expr *shift_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm,
                                     vhdl_binop_t shift_op)
 {
-   vhdl_expr *lhs = nexus_to_var_ref(scope, ivl_lpm_data(lpm, 0));
-   vhdl_expr *rhs = nexus_to_var_ref(scope, ivl_lpm_data(lpm, 1));
+   vhdl_expr *lhs = readable_ref(scope, ivl_lpm_data(lpm, 0));
+   vhdl_expr *rhs = readable_ref(scope, ivl_lpm_data(lpm, 1));
    if (!lhs || !rhs)
       return NULL;   
    
@@ -223,7 +223,7 @@ static vhdl_expr *shift_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm,
 
 static vhdl_expr *repeat_lpm_to_expr(vhdl_scope *scope, ivl_lpm_t lpm)
 {
-   vhdl_expr *in = nexus_to_var_ref(scope, ivl_lpm_data(lpm, 0));
+   vhdl_expr *in = readable_ref(scope, ivl_lpm_data(lpm, 0));
    return new vhdl_bit_spec_expr(NULL, in);
 }
 
@@ -297,10 +297,10 @@ static int draw_mux_lpm(vhdl_arch *arch, ivl_lpm_t lpm)
 
    vhdl_scope *scope = arch->get_scope();
    
-   vhdl_expr *s0 = nexus_to_var_ref(scope, ivl_lpm_data(lpm, 0));
-   vhdl_expr *s1 = nexus_to_var_ref(scope, ivl_lpm_data(lpm, 1));
+   vhdl_expr *s0 = readable_ref(scope, ivl_lpm_data(lpm, 0));
+   vhdl_expr *s1 = readable_ref(scope, ivl_lpm_data(lpm, 1));
 
-   vhdl_expr *sel = nexus_to_var_ref(scope, ivl_lpm_select(lpm));
+   vhdl_expr *sel = readable_ref(scope, ivl_lpm_select(lpm));
    vhdl_expr *b1 = new vhdl_const_bit('1');
    vhdl_expr *t1 =
       new vhdl_binop_expr(sel, VHDL_BINOP_EQ, b1, vhdl_type::boolean());

tgt-vhdl/scope.cc

@@ -352,6 +352,18 @@ vhdl_var_ref *nexus_to_var_ref(vhdl_scope *scope, ivl_nexus_t nexus)
    return ref;
 }
 
+// Return a variable reference for a nexus that is guaranteed to
+// be readable.
+vhdl_var_ref* readable_ref(vhdl_scope* scope, ivl_nexus_t nex)
+{
+   vhdl_var_ref* ref = nexus_to_var_ref(scope, nex);
+   
+   vhdl_decl* decl = scope->get_decl(ref->get_name());
+   decl->ensure_readable();
+
+   return ref;
+}
+
 /*
  * Translate all the primitive logic gates into concurrent
  * signal assignments.
@@ -553,7 +565,8 @@ static void map_signal(ivl_signal_t to, vhdl_entity *parent,
    // The solution used here is to create an intermediate signal
    // and connect it to both ports.
    vhdl_decl* from_decl =
-      parent->get_arch()->get_scope()->get_decl(ref->get_name());   
+      parent->get_arch()->get_scope()->get_decl(ref->get_name());
+   from_decl->print();
    if (!from_decl->is_readable()
        && !arch_scope->have_declared(name + "_Readable")) {
       vhdl_decl* tmp_decl =

tgt-vhdl/vhdl_syntax.cc

@@ -406,9 +406,12 @@ void vhdl_port_decl::ensure_readable()
 }
 
 // A port is readable if it is not `out'.
+// We also make `buffer' ports not readable for these purposes since
+// buffers cannot be directly mapped to outputs without an intermediate
+// signal.
 bool vhdl_port_decl::is_readable() const
 {
-   return mode_ != VHDL_PORT_OUT;
+   return mode_ != VHDL_PORT_OUT && mode_ != VHDL_PORT_BUFFER;
 }
 
 void vhdl_var_decl::emit(std::ostream &of, int level) const

tgt-vhdl/vhdl_target.h

@@ -28,6 +28,7 @@ vhdl_expr *translate_time_expr(ivl_expr_t e);
 
 ivl_design_t get_vhdl_design();
 vhdl_var_ref *nexus_to_var_ref(vhdl_scope *arch_scope, ivl_nexus_t nexus);
+vhdl_var_ref* readable_ref(vhdl_scope* scope, ivl_nexus_t nex);
 
 int draw_stask_display(vhdl_procedural *proc, stmt_container *container,
                        ivl_statement_t stmt, bool newline = true);