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Precalculate constant results of memory index expressions.

This commit is contained in:
steve 2002-01-22 01:40:04 +00:00
parent 4f28f6a770
commit 349be0f169
3 changed files with 69 additions and 5 deletions
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49
eval_tree.cc
View File

@ -17,7 +17,7 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#if !defined(WINNT) && !defined(macintosh)
#ident "$Id: eval_tree.cc,v 1.31 2001/12/30 00:39:25 steve Exp $"
#ident "$Id: eval_tree.cc,v 1.32 2002/01/22 01:40:04 steve Exp $"
#endif
# include "config.h"
@ -758,6 +758,50 @@ NetEConst* NetEConcat::eval_tree()
return res;
}
/*
* There are limits to our ability to evaluate a memory reference
* expression, because the content of a memory is never
* constant. However, the index expression may be precalculated, and
* there are certain index values that do give us constant results.
*/
NetExpr* NetEMemory::eval_tree()
{
/* Attempt to evaluate the index expression to a constant, if
it is not already. */
if (idx_ && !dynamic_cast<NetEConst*>(idx_)) {
NetExpr* tmp = idx_->eval_tree();
if (tmp) {
delete idx_;
idx_ = tmp;
}
}
NetEConst*itmp = dynamic_cast<NetEConst*>(idx_);
if (itmp == 0)
return 0;
verinum ival = itmp->value();
/* If the index expression has any x or z bits, then we know
already that the expression result is a constant x. */
if (! ival.is_defined()) {
verinum xres (verinum::Vx, mem_->width(), false);
NetEConst*res = new NetEConst(xres);
return res;
}
/* If the index expression is outside the range of the memory,
then the result is a constant x. */
unsigned norm_idx = mem_->index_to_address(ival.as_long());
if (norm_idx >= mem_->count()) {
verinum xres (verinum::Vx, mem_->width(), false);
NetEConst*res = new NetEConst(xres);
return res;
}
return 0;
}
NetExpr* NetEParam::eval_tree()
{
if (des_ == 0)
@ -1019,6 +1063,9 @@ NetEConst* NetEUReduce::eval_tree()
/*
* $Log: eval_tree.cc,v $
* Revision 1.32 2002/01/22 01:40:04 steve
* Precalculate constant results of memory index expressions.
*
* Revision 1.31 2001/12/30 00:39:25 steve
* Evaluate constant unary minus.
*

15
netlist.cc
View File

@ -17,7 +17,7 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#if !defined(WINNT) && !defined(macintosh)
#ident "$Id: netlist.cc,v 1.179 2001/12/31 00:08:14 steve Exp $"
#ident "$Id: netlist.cc,v 1.180 2002/01/22 01:40:04 steve Exp $"
#endif
# include "config.h"
@ -2084,6 +2084,16 @@ NetEMemory::~NetEMemory()
{
}
const string& NetEMemory::name() const
{
return mem_->name();
}
const NetExpr* NetEMemory::index() const
{
return idx_;
}
NetMemory::NetMemory(NetScope*sc, const string&n, long w, long s, long e)
: name_(n), width_(w), idxh_(s), idxl_(e), ram_list_(0), scope_(sc)
{
@ -2405,6 +2415,9 @@ const NetProc*NetTaskDef::proc() const
/*
* $Log: netlist.cc,v $
* Revision 1.180 2002/01/22 01:40:04 steve
* Precalculate constant results of memory index expressions.
*
* Revision 1.179 2001/12/31 00:08:14 steve
* Support $signed cast of expressions.
*

10
netlist.h
View File

@ -19,7 +19,7 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#if !defined(WINNT) && !defined(macintosh)
#ident "$Id: netlist.h,v 1.229 2002/01/19 19:02:08 steve Exp $"
#ident "$Id: netlist.h,v 1.230 2002/01/22 01:40:04 steve Exp $"
#endif
/*
@ -2467,11 +2467,12 @@ class NetEMemory : public NetExpr {
NetEMemory(NetMemory*mem, NetExpr*idx =0);
virtual ~NetEMemory();
const string& name () const { return mem_->name(); }
const NetExpr* index() const { return idx_; }
const string& name () const;
const NetExpr* index() const;
virtual bool set_width(unsigned);
NetExpr* eval_tree();
virtual NetEMemory*dup_expr() const;
virtual void expr_scan(struct expr_scan_t*) const;
@ -2864,6 +2865,9 @@ extern ostream& operator << (ostream&, NetNet::Type);
/*
* $Log: netlist.h,v $
* Revision 1.230 2002/01/22 01:40:04 steve
* Precalculate constant results of memory index expressions.
*
* Revision 1.229 2002/01/19 19:02:08 steve
* Pass back target errors processing conditionals.
*