Fix for GitHub issue steveicarus#94 - enhance support for SystemVerilog size casting.

Allow the size expression to be any constant expression. Also ensure that
the expression width and type are correctly calculated and applied.

Author: martinwhitaker

PExpr.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998-2012 Stephen Williams <[email protected]>
+ * Copyright (c) 1998-2016 Stephen Williams <[email protected]>
  * Copyright CERN 2013 / Stephen Williams ([email protected])
  *
  *    This source code is free software; you can redistribute it
@@ -137,7 +137,7 @@ bool PEBinary::has_aa_term(Design*des, NetScope*scope) const
       return left_->has_aa_term(des, scope) || right_->has_aa_term(des, scope);
 }
 
-PECastSize::PECastSize(unsigned si, PExpr*b)
+PECastSize::PECastSize(PExpr*si, PExpr*b)
 : size_(si), base_(b)
 {
 }

PExpr.h

@@ -1,7 +1,7 @@
 #ifndef IVL_PExpr_H
 #define IVL_PExpr_H
 /*
- * Copyright (c) 1998-2014 Stephen Williams <[email protected]>
+ * Copyright (c) 1998-2016 Stephen Williams <[email protected]>
  * Copyright CERN 2013 / Stephen Williams ([email protected])
  *
  *    This source code is free software; you can redistribute it
@@ -971,7 +971,7 @@ class PECallFunction : public PExpr {
 class PECastSize  : public PExpr {
 
     public:
-      explicit PECastSize(unsigned expr_wid, PExpr*base);
+      explicit PECastSize(PExpr*size, PExpr*base);
       ~PECastSize();
 
       void dump(ostream &out) const;
@@ -984,7 +984,7 @@ class PECastSize  : public PExpr {
 				  width_mode_t&mode);
 
     private:
-      unsigned size_;
+      PExpr* size_;
       PExpr* base_;
 };
 

elab_expr.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999-2015 Stephen Williams ([email protected])
+ * Copyright (c) 1999-2016 Stephen Williams ([email protected])
  * Copyright CERN 2013 / Stephen Williams ([email protected])
  *
  *    This source code is free software; you can redistribute it
@@ -2517,22 +2517,54 @@ NetExpr* PECallFunction::elaborate_expr_method_(Design*des, NetScope*scope,
 
 unsigned PECastSize::test_width(Design*des, NetScope*scope, width_mode_t&)
 {
-      expr_width_ = size_;
+      ivl_assert(*this, size_);
+      ivl_assert(*this, base_);
+
+      NetExpr*size_ex = elab_and_eval(des, scope, size_, -1, true);
+      NetEConst*size_ce = dynamic_cast<NetEConst*>(size_ex);
+      expr_width_ = size_ce ? size_ce->value().as_ulong() : 0;
+      delete size_ex;
+      if (expr_width_ == 0) {
+	    cerr << get_fileline() << ": error: Cast size expression "
+		    "must be constant and greater than zero." << endl;
+	    des->errors += 1;
+	    return 0;
+      }
 
       width_mode_t tmp_mode = PExpr::SIZED;
       base_->test_width(des, scope, tmp_mode);
 
-      return size_;
+      if (!type_is_vectorable(base_->expr_type())) {
+	    cerr << get_fileline() << ": error: Cast base expression "
+		    "must be a vector type." << endl;
+	    des->errors += 1;
+	    return 0;
+      }
+
+      expr_type_   = base_->expr_type();
+      min_width_   = expr_width_;
+      signed_flag_ = base_->has_sign();
+
+      return expr_width_;
 }
 
 NetExpr* PECastSize::elaborate_expr(Design*des, NetScope*scope,
-				    unsigned, unsigned) const
+				    unsigned expr_wid, unsigned flags) const
 {
-      NetExpr*sub = base_->elaborate_expr(des, scope, base_->expr_width(), NO_FLAGS);
-      NetESelect*sel = new NetESelect(sub, 0, size_);
-      sel->set_line(*this);
+      flags &= ~SYS_TASK_ARG; // don't propagate the SYS_TASK_ARG flag
 
-      return sel;
+      ivl_assert(*this, size_);
+      ivl_assert(*this, base_);
+
+      NetExpr*sub = base_->elaborate_expr(des, scope, base_->expr_width(), flags);
+
+	// Perform the cast. The extension method (zero/sign), if needed,
+	// depends on the type of the base expression.
+      NetExpr*tmp = cast_to_width(sub, expr_width_, base_->has_sign(), *this);
+
+	// Pad up to the expression width. The extension method (zero/sign)
+	// depends on the type of enclosing expression.
+      return pad_to_width(tmp, expr_wid, signed_flag_, *this);
 }
 
 unsigned PECastType::test_width(Design*des, NetScope*scope, width_mode_t&wid)

netmisc.h

@@ -1,7 +1,7 @@
 #ifndef IVL_netmisc_H
 #define IVL_netmisc_H
 /*
- * Copyright (c) 1999-2014 Stephen Williams ([email protected])
+ * Copyright (c) 1999-2016 Stephen Williams ([email protected])
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -66,6 +66,27 @@ inline NetScope* symbol_search(const LineInfo*li,
  * enough.
  */
 extern NetExpr*pad_to_width(NetExpr*expr, unsigned wid, const LineInfo&info);
+
+/*
+ * This function transforms an expression by either zero or sign extending
+ * the high bits until the expression has the desired width. This may mean
+ * not transforming the expression at all, if it is already wide enough.
+ * The extension method and the returned expression type is determined by
+ * signed_flag.
+ */
+extern NetExpr*pad_to_width(NetExpr*expr, unsigned wid, bool signed_flag,
+			    const LineInfo&info);
+
+/*
+ * This function transforms an expression by either zero or sign extending
+ * or discarding the high bits until the expression has the desired width.
+ * This may mean not transforming the expression at all, if it is already
+ * the correct width. The extension method (if needed) and the returned
+ * expression type is determined by signed_flag.
+ */
+extern NetExpr*cast_to_width(NetExpr*expr, unsigned wid, bool signed_flag,
+			     const LineInfo&info);
+
 extern NetNet*pad_to_width(Design*des, NetNet*n, unsigned w,
                            const LineInfo&info);
 

pad_to_width.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999-2011 Stephen Williams ([email protected])
+ * Copyright (c) 1999-2016 Stephen Williams ([email protected])
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -51,6 +51,54 @@ NetExpr*pad_to_width(NetExpr*expr, unsigned wid, const LineInfo&info)
       return tmp;
 }
 
+NetExpr*pad_to_width(NetExpr*expr, unsigned wid, bool signed_flag,
+		     const LineInfo&info)
+{
+      if (wid <= expr->expr_width()) {
+	    expr->cast_signed(signed_flag);
+	    return expr;
+      }
+
+	/* If the expression is a const, then replace it with a wider
+	   const. This is a more efficient result. */
+      if (NetEConst*tmp = dynamic_cast<NetEConst*>(expr)) {
+	    verinum oval = tmp->value();
+	    oval.has_sign(signed_flag);
+	    oval = pad_to_width(oval, wid);
+	    tmp = new NetEConst(oval);
+	    tmp->set_line(info);
+	    delete expr;
+	    return tmp;
+      }
+
+      NetESelect*tmp = new NetESelect(expr, 0, wid);
+      tmp->cast_signed(signed_flag);
+      tmp->set_line(info);
+      return tmp;
+}
+
+NetExpr*cast_to_width(NetExpr*expr, unsigned wid, bool signed_flag,
+		      const LineInfo&info)
+{
+        /* If the expression is a const, then replace it with a new
+           const. This is a more efficient result. */
+      if (NetEConst*tmp = dynamic_cast<NetEConst*>(expr)) {
+            tmp->cast_signed(signed_flag);
+            if (wid != tmp->expr_width()) {
+                  tmp = new NetEConst(verinum(tmp->value(), wid));
+                  tmp->set_line(info);
+                  delete expr;
+            }
+            return tmp;
+      }
+
+      NetESelect*tmp = new NetESelect(expr, 0, wid);
+      tmp->cast_signed(signed_flag);
+      tmp->set_line(info);
+
+      return tmp;
+}
+
 /*
  * Pad a NetNet to the desired vector width by concatenating a
  * NetConst of constant zeros. Use a NetConcat node to do the

parse.y

@@ -613,7 +613,8 @@ static void current_function_set_statement(const YYLTYPE&loc, vector<Statement*>
 %type <gates> gate_instance_list
 
 %type <pform_name> hierarchy_identifier implicit_class_handle
-%type <expr>  assignment_pattern expression expr_primary expr_mintypmax
+%type <expr>  assignment_pattern expression expr_mintypmax
+%type <expr>  expr_primary_or_typename expr_primary
 %type <expr>  class_new dynamic_array_new
 %type <expr>  inc_or_dec_expression inside_expression lpvalue
 %type <expr>  branch_probe_expression streaming_concatenation
@@ -3083,7 +3084,7 @@ branch_probe_expression
   ;
 
 expression
-  : expr_primary
+  : expr_primary_or_typename
       { $$ = $1; }
   | inc_or_dec_expression
       { $$ = $1; }
@@ -3378,6 +3379,20 @@ expression_list_proper
       }
   ;
 
+expr_primary_or_typename
+  : expr_primary
+
+  /* There are a few special cases (notably $bits argument) where the
+     expression may be a type name. Let the elaborator sort this out. */
+  | TYPE_IDENTIFIER
+      { PETypename*tmp = new PETypename($1.type);
+	FILE_NAME(tmp,@1);
+	$$ = tmp;
+	delete[]$1.text;
+      }
+
+  ;
+
 expr_primary
   : number
       { assert($1);
@@ -3419,15 +3434,6 @@ expr_primary
 	delete[]$1;
       }
 
-  /* There are a few special cases (notably $bits argument) where the
-     expression may be a type name. Let the elaborator sort this out. */
-  | TYPE_IDENTIFIER
-      { PETypename*tmp = new PETypename($1.type);
-	FILE_NAME(tmp,@1);
-	$$ = tmp;
-	delete[]$1.text;
-      }
-
   /* The hierarchy_identifier rule matches simple identifiers as well as
      indexed arrays and part selects */
 
@@ -3731,12 +3737,11 @@ expr_primary
 
   /* Cast expressions are primaries */
 
-  | DEC_NUMBER '\'' '(' expression ')'
+  | expr_primary '\'' '(' expression ')'
       { PExpr*base = $4;
 	if (gn_system_verilog()) {
-	      PECastSize*tmp = new PECastSize($1->as_ulong(), base);
+	      PECastSize*tmp = new PECastSize($1, base);
 	      FILE_NAME(tmp, @1);
-	      delete $1;
 	      $$ = tmp;
 	} else {
 	      yyerror(@1, "error: Size cast requires SystemVerilog.");

pform_dump.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998-2014 Stephen Williams ([email protected])
+ * Copyright (c) 1998-2016 Stephen Williams ([email protected])
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -318,7 +318,7 @@ void PECallFunction::dump(ostream &out) const
 
 void PECastSize::dump(ostream &out) const
 {
-      out << size_ << "'(";
+      out << *size_ << "'(";
       base_->dump(out);
       out << ")";
 }