gecko-dev/ef/Compiler/Optimizer/PrimitiveOptimizer.cpp

62 строки
2.1 KiB
C++

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
*
* The contents of this file are subject to the Netscape Public
* License Version 1.1 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.mozilla.org/NPL/
*
* Software distributed under the License is distributed on an "AS
* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
* implied. See the License for the specific language governing
* rights and limitations under the License.
*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is Netscape
* Communications Corporation. Portions created by Netscape are
* Copyright (C) 1998 Netscape Communications Corporation. All
* Rights Reserved.
*
* Contributor(s):
*/
#include "PrimitiveOptimizer.h"
#include "ControlGraph.h"
//
// Quickly trim primitives whose results are not used from the graph.
// This is a quick-and-dirty implementation that misses some opportunities;
// for example, cycles of dead primitives are not detected.
//
void simpleTrimDeadPrimitives(ControlGraph &cg)
{
cg.dfsSearch();
ControlNode **dfsList = cg.dfsList;
ControlNode **pcn = dfsList + cg.nNodes;
while (pcn != dfsList) {
ControlNode &cn = **--pcn;
// Search the primitives backwards; remove any whose outputs are not used
// and which are not roots.
DoublyLinkedList<Primitive> &primitives = cn.getPrimitives();
DoublyLinkedList<Primitive>::iterator primIter = primitives.end();
while (!primitives.done(primIter)) {
Primitive &p = primitives.get(primIter);
primIter = primitives.retreat(primIter);
if (!p.isRoot() && !p.hasConsumers())
p.destroy();
}
// Search the phi nodes backwards; remove any whose outputs are not used.
DoublyLinkedList<PhiNode> &phiNodes = cn.getPhiNodes();
DoublyLinkedList<PhiNode>::iterator phiIter = phiNodes.end();
while (!phiNodes.done(phiIter)) {
PhiNode &n = phiNodes.get(phiIter);
phiIter = phiNodes.retreat(phiIter);
if (!n.hasConsumers())
n.remove();
}
}
}