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      1 /*
      2  * Copyright (C) 2007 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.dx.rop.code;
     18 
     19 import com.android.dx.rop.cst.Constant;
     20 import com.android.dx.rop.cst.CstInteger;
     21 import com.android.dx.rop.type.StdTypeList;
     22 import com.android.dx.rop.type.Type;
     23 import com.android.dx.rop.type.TypeBearer;
     24 import com.android.dx.rop.type.TypeList;
     25 
     26 /**
     27  * Plain instruction, which has no embedded data and which cannot possibly
     28  * throw an exception.
     29  */
     30 public final class PlainInsn
     31         extends Insn {
     32     /**
     33      * Constructs an instance.
     34      *
     35      * @param opcode {@code non-null;} the opcode
     36      * @param position {@code non-null;} source position
     37      * @param result {@code null-ok;} spec for the result, if any
     38      * @param sources {@code non-null;} specs for all the sources
     39      */
     40     public PlainInsn(Rop opcode, SourcePosition position,
     41                      RegisterSpec result, RegisterSpecList sources) {
     42         super(opcode, position, result, sources);
     43 
     44         switch (opcode.getBranchingness()) {
     45             case Rop.BRANCH_SWITCH:
     46             case Rop.BRANCH_THROW: {
     47                 throw new IllegalArgumentException("opcode with invalid branchingness: " + opcode.getBranchingness());
     48             }
     49         }
     50 
     51         if (result != null && opcode.getBranchingness() != Rop.BRANCH_NONE) {
     52             // move-result-pseudo is required here
     53             throw new IllegalArgumentException
     54                     ("can't mix branchingness with result");
     55         }
     56     }
     57 
     58     /**
     59      * Constructs a single-source instance.
     60      *
     61      * @param opcode {@code non-null;} the opcode
     62      * @param position {@code non-null;} source position
     63      * @param result {@code null-ok;} spec for the result, if any
     64      * @param source {@code non-null;} spec for the source
     65      */
     66     public PlainInsn(Rop opcode, SourcePosition position, RegisterSpec result,
     67                      RegisterSpec source) {
     68         this(opcode, position, result, RegisterSpecList.make(source));
     69     }
     70 
     71     /** {@inheritDoc} */
     72     @Override
     73     public TypeList getCatches() {
     74         return StdTypeList.EMPTY;
     75     }
     76 
     77     /** {@inheritDoc} */
     78     @Override
     79     public void accept(Visitor visitor) {
     80         visitor.visitPlainInsn(this);
     81     }
     82 
     83     /** {@inheritDoc} */
     84     @Override
     85     public Insn withAddedCatch(Type type) {
     86         throw new UnsupportedOperationException("unsupported");
     87     }
     88 
     89     /** {@inheritDoc} */
     90     @Override
     91     public Insn withRegisterOffset(int delta) {
     92         return new PlainInsn(getOpcode(), getPosition(),
     93                              getResult().withOffset(delta),
     94                              getSources().withOffset(delta));
     95     }
     96 
     97     /** {@inheritDoc} */
     98     @Override
     99     public Insn withSourceLiteral() {
    100         RegisterSpecList sources = getSources();
    101         int szSources = sources.size();
    102 
    103         if (szSources == 0) {
    104             return this;
    105         }
    106 
    107         TypeBearer lastType = sources.get(szSources - 1).getTypeBearer();
    108 
    109         if (!lastType.isConstant()) {
    110             // Check for reverse subtraction, where first source is constant
    111             TypeBearer firstType = sources.get(0).getTypeBearer();
    112             if (szSources == 2 && firstType.isConstant()) {
    113                 Constant cst = (Constant) firstType;
    114                 RegisterSpecList newSources = sources.withoutFirst();
    115                 Rop newRop = Rops.ropFor(getOpcode().getOpcode(), getResult(),
    116                                              newSources, cst);
    117                 return new PlainCstInsn(newRop, getPosition(), getResult(),
    118                                             newSources, cst);
    119             }
    120             return this;
    121         } else {
    122 
    123             Constant cst = (Constant) lastType;
    124 
    125             RegisterSpecList newSources = sources.withoutLast();
    126 
    127             Rop newRop;
    128             try {
    129                 // Check for constant subtraction and flip it to be addition
    130                 int opcode = getOpcode().getOpcode();
    131                 if (opcode == RegOps.SUB && cst instanceof CstInteger) {
    132                     opcode = RegOps.ADD;
    133                     cst = CstInteger.make(-((CstInteger)cst).getValue());
    134                 }
    135                 newRop = Rops.ropFor(opcode, getResult(), newSources, cst);
    136             } catch (IllegalArgumentException ex) {
    137                 // There's no rop for this case
    138                 return this;
    139             }
    140 
    141             return new PlainCstInsn(newRop, getPosition(),
    142                     getResult(), newSources, cst);
    143         }
    144     }
    145 
    146 
    147     /** {@inheritDoc} */
    148     @Override
    149     public Insn withNewRegisters(RegisterSpec result,
    150             RegisterSpecList sources) {
    151 
    152         return new PlainInsn(getOpcode(), getPosition(),
    153                              result,
    154                              sources);
    155 
    156     }
    157 }
    158