Mercurial > hg > graal-jvmci-8
view graal/GraalCompiler/src/com/sun/c1x/graph/MemoryMap.java @ 2661:194d93d089bd
Towards clean up of canTrap().
author | Thomas Wuerthinger <thomas@wuerthinger.net> |
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date | Wed, 11 May 2011 17:18:31 +0200 |
parents | 16b9a8b5ad39 |
children |
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/* * Copyright (c) 2009, 2010, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package com.sun.c1x.graph; import static java.lang.reflect.Modifier.*; import java.util.*; import com.sun.c1x.ir.*; import com.sun.cri.ri.*; /** * The {@code MemoryMap} class is an approximation of memory that is used redundant load and * store elimination. In C1, tracking of fields of new objects' fields was precise, * while tracking of other fields is managed at the offset granularity (i.e. a write of a field with offset * {@code off} will "overwrite" all fields with the offset {@code off}. However, C1X distinguishes all * loaded fields as separate locations. Static fields have just one location, while instance fields are * tracked for at most one instance object. Loads or stores of unloaded fields kill all memory locations. * An object is no longer "new" if it is stored into a field or array. * * @author Ben L. Titzer */ public class MemoryMap { private final HashMap<RiField, Value> objectMap = new HashMap<RiField, Value>(); private final HashMap<RiField, Value> valueMap = new HashMap<RiField, Value>(); private final IdentityHashMap<Value, Value> newObjects = new IdentityHashMap<Value, Value>(); /** * Kills all memory locations. */ public void kill() { objectMap.clear(); valueMap.clear(); newObjects.clear(); } /** * The specified instruction has just escaped, it can no longer be considered a "new object". * @param x the instruction that just escaped */ public void storeValue(Value x) { newObjects.remove(x); } /** * Record a newly allocated object. * @param n the instruction generating the new object */ public void newInstance(NewInstance n) { newObjects.put(n, n); } /** * Look up a load for load elimination, and put this load into the load elimination map. * @param load the instruction representing the load * @return a reference to the previous instruction that already loaded the value, if it is available; the * {@code load} parameter otherwise */ public Value load(LoadField load) { if (!load.isLoaded()) { // the field is not loaded, kill everything, because it will need to be resolved kill(); return load; } RiField field = load.field(); if (load.isStatic()) { // the field is static, look in the static map Value r = valueMap.get(field); if (r != null) { return r; } valueMap.put(field, load); } else { // see if the value for this object for this field is in the map if (objectMap.get(field) == load.object()) { return valueMap.get(field); } objectMap.put(field, load.object()); valueMap.put(field, load); } return load; // load cannot be eliminated } /** * Insert a new result for a load into the memory map. * @param load the load instruction * @param result the result that the load instruction should produce */ public void setResult(LoadField load, Value result) { if (load.isLoaded()) { RiField field = load.field(); if (load.isStatic()) { // the field is static, put it in the static map valueMap.put(field, result); } else { // put the result for the loaded object into the map objectMap.put(field, load.object()); valueMap.put(field, result); } } } /** * Look up a store for store elimination, and put this store into the load elimination map. * @param store the store instruction to put into the map * @return {@code null} if the store operation is redundant; the {@code store} parameter * otherwise */ public StoreField store(StoreField store) { if (!store.isLoaded()) { // the field is not loaded, kill everything, because it will need to be resolved kill(); return store; } RiField field = store.field(); Value value = store.value(); if (store.isStatic()) { // the field is static, overwrite it into the static map valueMap.put(field, value); } else { if (newObjects.containsKey(store.object())) { // this is a store to a new object's field if (fieldHasNoStores(field) && value.isConstant() && value.asConstant().isDefaultValue()) { // this is a redundant initialization of a new object's field that has not been assigned to return null; } } Value obj = objectMap.get(field); if (obj == store.object()) { // is this a redundant store? if (value == valueMap.get(field) && !isVolatile(field.accessFlags())) { return null; } } objectMap.put(field, store.object()); valueMap.put(field, value); } storeValue(value); // the value stored just escaped return store; // the store cannot be eliminated } private boolean fieldHasNoStores(RiField field) { return objectMap.get(field) == null; } }