Add support to &PV<> for signed base values from thread space.

When calculating a value from thread space we need to tell &PV<>
if the base value is signed or not. This patch adds support for
that functionality.

tgt-vvp/draw_vpi.c

@@ -212,19 +212,11 @@ static int get_vpi_taskfunc_signal_arg(struct args_info *result,
 		    /* Fallback case: evaluate the expression. */
 		  struct vector_info rv;
 		  rv = draw_eval_expr(bexpr, STUFF_OK_XZ);
-		    /* We need to enhance &PV<> to support a signed index. */
-		  if (ivl_expr_signed(bexpr) &&
-		      (ivl_expr_width(bexpr) < 8*sizeof(int))) {
-			fprintf(stderr, "%s:%u: tgt-vvp warning: V0.9 may give "
-			                "incorrect results for a select with a "
-			                "signed index less than %zu bits.\n",
-			                ivl_expr_file(expr),
-			                ivl_expr_lineno(expr),
-			                8*sizeof(int));
-		  }
-		  snprintf(buffer, sizeof buffer, "&PV<v%p_0, %u %u, %u>",
+		  snprintf(buffer, sizeof buffer,
+		           "&PV<v%p_0, %u %u \"%s\", %u>",
 		           ivl_expr_signal(vexpr),
 		           rv.base, rv.wid,
+		           (ivl_expr_signed(bexpr) ? "s" : "u"),
 		           ivl_expr_width(expr));
 		  result->vec = rv;
 		  result->vec_flag = 1;

vvp/README.txt

@@ -824,12 +824,15 @@ retrieves the index from thread space (<width> bits starting at <base>).
 The &PV<> argument is a reference to part of a signal. The syntax is:
 
    &PV '<' <symbol> , <base> , <width> '>'
-   &PV '<' <symbol> , <tbase> <twid> , <width> '>'
+   &PV '<' <symbol> , <base_symbol> , <width> '>'
+   &PV '<' <symbol> , <tbase> <twid> <"s" or "u"> , <width> '>'
 
 The <symbol> is the label for a signal, the <base> is the canonical
 starting bit of the part select and <width> is the number of bits in
-the select. The second form retrieves the <base> from thread space
-using <twid> bits starting at <tbase>.
+the select. The second form retrieves the <base> from the given signal
+or &A<>/&PV<> select. The third form retrieves the <base> from thread
+space using <twid> bits starting at <tbase>. The base value may be
+signed or unsigned.
 
 * The T<> argument
 

vvp/parse.y

@@ -887,8 +887,8 @@ symbol_access
       { $$ = vpip_make_PV($3, $5, $7); }
   | K_PV '<' T_SYMBOL ',' symbol_access ',' T_NUMBER '>'
       { $$ = vpip_make_PV($3, $5, $7); }
-  | K_PV '<' T_SYMBOL ',' T_NUMBER T_NUMBER ',' T_NUMBER '>'
-      { $$ = vpip_make_PV($3, $5, $6, $8); }
+  | K_PV '<' T_SYMBOL ',' T_NUMBER T_NUMBER T_STRING ',' T_NUMBER '>'
+      { $$ = vpip_make_PV($3, $5, $6, $7, $9); }
 
   /* functor operands can only be a list of symbols. */
 symbols

vvp/vpi_priv.h

@@ -264,11 +264,13 @@ struct __vpiPV {
       vpiHandle sbase;
       int tbase;
       unsigned twid, width;
+      bool is_signed;
 };
 extern vpiHandle vpip_make_PV(char*name, int base, int width);
 extern vpiHandle vpip_make_PV(char*name, char*symbol, int width);
 extern vpiHandle vpip_make_PV(char*name, vpiHandle handle, int width);
-extern vpiHandle vpip_make_PV(char*name, int tbase, int twid, int width);
+extern vpiHandle vpip_make_PV(char*name, int tbase, int twid, char*is_signed,
+                              int width);
 
 extern struct __vpiPV* vpip_PV_from_handle(vpiHandle obj);
 extern void vpip_part_select_value_change(struct __vpiCallback*cbh, vpiHandle obj);

vvp/vpi_signal.cc

@@ -1027,6 +1027,15 @@ static int PV_get_base(struct __vpiPV*rfp)
 	    }
       }
 
+	/* Check to see if we need to sign extend the result. */
+      if (rfp->is_signed && (rfp->twid < 8*sizeof(tval))) {
+	    vvp_bit4_t msb = vthread_get_bit(vpip_current_vthread,
+	                                     rfp->tbase + rfp->twid - 1);
+	    if (msb == BIT4_1) {
+		  tval |= ~((1 << rfp->twid) - 1);
+	    }
+      }
+
       return tval;
 }
 
@@ -1281,7 +1290,7 @@ vpiHandle vpip_make_PV(char*var, vpiHandle handle, int width)
       return &obj->base;
 }
 
-vpiHandle vpip_make_PV(char*var, int tbase, int twid, int width)
+vpiHandle vpip_make_PV(char*var, int tbase, int twid, char*is_signed, int width)
 {
       struct __vpiPV*obj = (struct __vpiPV*) malloc(sizeof(struct __vpiPV));
       obj->base.vpi_type = &vpip_PV_rt;
@@ -1289,10 +1298,13 @@ vpiHandle vpip_make_PV(char*var, int tbase, int twid, int width)
       obj->sbase = 0;
       obj->tbase = tbase;
       obj->twid = (unsigned) twid;
+      obj->is_signed = strcmp(is_signed, "s") == 0;
       obj->width = (unsigned) width;
       obj->net = 0;
       functor_ref_lookup(&obj->net, var);
 
+      delete [] is_signed;
+
       return &obj->base;
 }