1 /*
   2  * Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 
  25 
  26 package org.graalvm.compiler.core.amd64;
  27 
  28 import org.graalvm.compiler.asm.amd64.AMD64Address.Scale;
  29 import org.graalvm.compiler.core.common.NumUtil;
  30 import org.graalvm.compiler.core.common.type.AbstractPointerStamp;
  31 import org.graalvm.compiler.core.common.type.IntegerStamp;
  32 import org.graalvm.compiler.debug.DebugContext;
  33 import org.graalvm.compiler.nodes.NodeView;
  34 import org.graalvm.compiler.nodes.StructuredGraph;
  35 import org.graalvm.compiler.nodes.ValueNode;
  36 import org.graalvm.compiler.nodes.calc.AddNode;
  37 import org.graalvm.compiler.nodes.calc.LeftShiftNode;
  38 import org.graalvm.compiler.nodes.calc.NegateNode;
  39 import org.graalvm.compiler.nodes.memory.address.AddressNode;
  40 import org.graalvm.compiler.phases.common.AddressLoweringPhase.AddressLowering;
  41 
  42 import jdk.vm.ci.meta.JavaConstant;
  43 
  44 public class AMD64AddressLowering extends AddressLowering {
  45     private static final int ADDRESS_BITS = 64;
  46 
  47     @Override
  48     public AddressNode lower(ValueNode base, ValueNode offset) {
  49         AMD64AddressNode ret = new AMD64AddressNode(base, offset);
  50         StructuredGraph graph = base.graph();
  51 
  52         boolean changed;
  53         do {
  54             changed = improve(graph, base.getDebug(), ret, false, false);
  55         } while (changed);
  56 
  57         assert checkAddressBitWidth(ret.getBase());
  58         assert checkAddressBitWidth(ret.getIndex());
  59         return graph.unique(ret);
  60     }
  61 
  62     private static boolean checkAddressBitWidth(ValueNode value) {
  63         return value == null || value.stamp(NodeView.DEFAULT) instanceof AbstractPointerStamp || IntegerStamp.getBits(value.stamp(NodeView.DEFAULT)) == ADDRESS_BITS;
  64     }
  65 
  66     /**
  67      * Tries to optimize addresses so that they match the AMD64-specific addressing mode better
  68      * (base + index * scale + displacement).
  69      *
  70      * @param graph the current graph
  71      * @param debug the current debug context
  72      * @param ret the address that should be optimized
  73      * @param isBaseNegated determines if the address base is negated. if so, all values that are
  74      *            extracted from the base will be negated as well
  75      * @param isIndexNegated determines if the index is negated. if so, all values that are
  76      *            extracted from the index will be negated as well
  77      * @return true if the address was modified
  78      */
  79     protected boolean improve(StructuredGraph graph, DebugContext debug, AMD64AddressNode ret, boolean isBaseNegated, boolean isIndexNegated) {
  80         ValueNode newBase = improveInput(ret, ret.getBase(), 0, isBaseNegated);
  81         if (newBase != ret.getBase()) {
  82             ret.setBase(newBase);
  83             return true;
  84         }
  85 
  86         ValueNode newIdx = improveInput(ret, ret.getIndex(), ret.getScale().log2, isIndexNegated);
  87         if (newIdx != ret.getIndex()) {
  88             ret.setIndex(newIdx);
  89             return true;
  90         }
  91 
  92         if (ret.getIndex() instanceof LeftShiftNode) {
  93             LeftShiftNode shift = (LeftShiftNode) ret.getIndex();
  94             if (shift.getY().isConstant()) {
  95                 int amount = ret.getScale().log2 + shift.getY().asJavaConstant().asInt();
  96                 Scale scale = Scale.fromShift(amount);
  97                 if (scale != null) {
  98                     ret.setIndex(shift.getX());
  99                     ret.setScale(scale);
 100                     return true;
 101                 }
 102             }
 103         }
 104 
 105         if (ret.getScale() == Scale.Times1) {
 106             if (ret.getIndex() == null && ret.getBase() instanceof AddNode) {
 107                 AddNode add = (AddNode) ret.getBase();
 108                 ret.setBase(add.getX());
 109                 ret.setIndex(considerNegation(graph, add.getY(), isBaseNegated));
 110                 return true;
 111             }
 112 
 113             if (ret.getBase() == null && ret.getIndex() instanceof AddNode) {
 114                 AddNode add = (AddNode) ret.getIndex();
 115                 ret.setBase(considerNegation(graph, add.getX(), isIndexNegated));
 116                 ret.setIndex(add.getY());
 117                 return true;
 118             }
 119 
 120             if (ret.getBase() instanceof LeftShiftNode && !(ret.getIndex() instanceof LeftShiftNode)) {
 121                 ValueNode tmp = ret.getBase();
 122                 ret.setBase(considerNegation(graph, ret.getIndex(), isIndexNegated != isBaseNegated));
 123                 ret.setIndex(considerNegation(graph, tmp, isIndexNegated != isBaseNegated));
 124                 return true;
 125             }
 126         }
 127 
 128         return improveNegation(graph, debug, ret, isBaseNegated, isIndexNegated);
 129     }
 130 
 131     private boolean improveNegation(StructuredGraph graph, DebugContext debug, AMD64AddressNode ret, boolean originalBaseNegated, boolean originalIndexNegated) {
 132         boolean baseNegated = originalBaseNegated;
 133         boolean indexNegated = originalIndexNegated;
 134 
 135         ValueNode originalBase = ret.getBase();
 136         ValueNode originalIndex = ret.getIndex();
 137 
 138         if (ret.getBase() instanceof NegateNode) {
 139             NegateNode negate = (NegateNode) ret.getBase();
 140             ret.setBase(negate.getValue());
 141             baseNegated = !baseNegated;
 142         }
 143 
 144         if (ret.getIndex() instanceof NegateNode) {
 145             NegateNode negate = (NegateNode) ret.getIndex();
 146             ret.setIndex(negate.getValue());
 147             indexNegated = !indexNegated;
 148         }
 149 
 150         if (baseNegated != originalBaseNegated || indexNegated != originalIndexNegated) {
 151             ValueNode base = ret.getBase();
 152             ValueNode index = ret.getIndex();
 153 
 154             boolean improved = improve(graph, debug, ret, baseNegated, indexNegated);
 155             if (baseNegated != originalBaseNegated) {
 156                 if (base == ret.getBase()) {
 157                     ret.setBase(originalBase);
 158                 } else if (ret.getBase() != null) {
 159                     ret.setBase(graph.maybeAddOrUnique(NegateNode.create(ret.getBase(), NodeView.DEFAULT)));
 160                 }
 161             }
 162 
 163             if (indexNegated != originalIndexNegated) {
 164                 if (index == ret.getIndex()) {
 165                     ret.setIndex(originalIndex);
 166                 } else if (ret.getIndex() != null) {
 167                     ret.setIndex(graph.maybeAddOrUnique(NegateNode.create(ret.getIndex(), NodeView.DEFAULT)));
 168                 }
 169             }
 170             return improved;
 171         } else {
 172             assert ret.getBase() == originalBase && ret.getIndex() == originalIndex;
 173         }
 174         return false;
 175     }
 176 
 177     private static ValueNode considerNegation(StructuredGraph graph, ValueNode value, boolean negate) {
 178         if (negate && value != null) {
 179             return graph.maybeAddOrUnique(NegateNode.create(value, NodeView.DEFAULT));
 180         }
 181         return value;
 182     }
 183 
 184     private static ValueNode improveInput(AMD64AddressNode address, ValueNode node, int shift, boolean negateExtractedDisplacement) {
 185         if (node == null) {
 186             return null;
 187         }
 188 
 189         JavaConstant c = node.asJavaConstant();
 190         if (c != null) {
 191             return improveConstDisp(address, node, c, null, shift, negateExtractedDisplacement);
 192         } else {
 193             if (node.stamp(NodeView.DEFAULT) instanceof IntegerStamp) {
 194                 assert IntegerStamp.getBits(node.stamp(NodeView.DEFAULT)) == ADDRESS_BITS;
 195 
 196                 /*
 197                  * we can't swallow zero-extends because of multiple reasons:
 198                  *
 199                  * a) we might encounter something like the following: ZeroExtend(Add(negativeValue,
 200                  * positiveValue)). if we swallow the zero-extend in this case and subsequently
 201                  * optimize the add, we might end up with a negative value that has less than 64
 202                  * bits in base or index. such a value would require sign extension instead of
 203                  * zero-extension but the backend can only do (implicit) zero-extension by using a
 204                  * larger register (e.g., rax instead of eax).
 205                  *
 206                  * b) our backend does not guarantee that the upper half of a 64-bit register equals
 207                  * 0 if a 32-bit value is stored in there.
 208                  *
 209                  * c) we also can't swallow zero-extends with less than 32 bits as most of these
 210                  * values are immediately sign-extended to 32 bit by the backend (therefore, the
 211                  * subsequent implicit zero-extension to 64 bit won't do what we expect).
 212                  */
 213 
 214                 if (node instanceof AddNode) {
 215                     AddNode add = (AddNode) node;
 216                     if (add.getX().isConstant()) {
 217                         return improveConstDisp(address, node, add.getX().asJavaConstant(), add.getY(), shift, negateExtractedDisplacement);
 218                     } else if (add.getY().isConstant()) {
 219                         return improveConstDisp(address, node, add.getY().asJavaConstant(), add.getX(), shift, negateExtractedDisplacement);
 220                     }
 221                 }
 222             }
 223         }
 224 
 225         return node;
 226     }
 227 
 228     private static ValueNode improveConstDisp(AMD64AddressNode address, ValueNode original, JavaConstant c, ValueNode other, int shift, boolean negateExtractedDisplacement) {
 229         if (c.getJavaKind().isNumericInteger()) {
 230             long delta = c.asLong() << shift;
 231             if (updateDisplacement(address, delta, negateExtractedDisplacement)) {
 232                 return other;
 233             }
 234         }
 235         return original;
 236     }
 237 
 238     protected static boolean updateDisplacement(AMD64AddressNode address, long displacementDelta, boolean negateDelta) {
 239         long sign = negateDelta ? -1 : 1;
 240         long disp = address.getDisplacement() + displacementDelta * sign;
 241         if (NumUtil.isInt(disp)) {
 242             address.setDisplacement((int) disp);
 243             return true;
 244         }
 245         return false;
 246     }
 247 }