dx/src/com/android/jack/dx/dex/code/form/Form12x.java

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.jack.dx.dex.code.form;

import com.android.jack.dx.dex.code.DalvInsn;
import com.android.jack.dx.dex.code.InsnFormat;
import com.android.jack.dx.dex.code.SimpleInsn;
import com.android.jack.dx.rop.code.RegisterSpec;
import com.android.jack.dx.rop.code.RegisterSpecList;
import com.android.jack.dx.util.AnnotatedOutput;

import java.util.BitSet;

/**
 * Instruction format {@code 12x}. See the instruction format spec
 * for details.
 */
public final class Form12x extends InsnFormat {
  /** {@code non-null;} unique instance of this class */
  public static final InsnFormat THE_ONE = new Form12x();

  /**
   * Constructs an instance. This class is not publicly
   * instantiable. Use {@link #THE_ONE}.
   */
  private Form12x() {
    // This space intentionally left blank.
  }

  /** {@inheritDoc} */
  @Override
  public String insnArgString(DalvInsn insn) {
    RegisterSpecList regs = insn.getRegisters();
    int sz = regs.size();

    /*
     * The (sz - 2) and (sz - 1) below makes this code work for
     * both the two- and three-register ops. (See "case 3" in
     * isCompatible(), below.)
     */

return regs.get(sz - 2).regString() + ", " + regs.get(sz - 1).regString();
  }

  /** {@inheritDoc} */
  @Override
  public String insnCommentString(DalvInsn insn, boolean noteIndices) {
    // This format has no comment.
    return "";
  }

  /** {@inheritDoc} */
  @Override
  public int codeSize() {
    return 1;
  }

  /** {@inheritDoc} */
  @Override
  public boolean isCompatible(DalvInsn insn) {
    if (!(insn instanceof SimpleInsn)) {
      return false;
    }

    RegisterSpecList regs = insn.getRegisters();
    RegisterSpec rs1;
    RegisterSpec rs2;

    switch (regs.size()) {
      case 2: {
        rs1 = regs.get(0);
        rs2 = regs.get(1);
        break;
      }
      case 3: {
        /*
         * This format is allowed for ops that are effectively
         * 3-arg but where the first two args are identical.
         */
        rs1 = regs.get(1);
        rs2 = regs.get(2);
        if (rs1.getReg() != regs.get(0).getReg()) {
          return false;
        }
        break;
      }
      default: {
        return false;
      }
    }

    return unsignedFitsInNibble(rs1.getReg()) && unsignedFitsInNibble(rs2.getReg());
  }

  /** {@inheritDoc} */
  @Override
  public BitSet compatibleRegs(DalvInsn insn) {
    RegisterSpecList regs = insn.getRegisters();
    BitSet bits = new BitSet(2);
    int r0 = regs.get(0).getReg();
    int r1 = regs.get(1).getReg();

    switch (regs.size()) {
      case 2: {
        bits.set(0, unsignedFitsInNibble(r0));
        bits.set(1, unsignedFitsInNibble(r1));
        break;
      }
      case 3: {
        if (r0 != r1) {
          bits.set(0, false);
          bits.set(1, false);
        } else {
          boolean dstRegComp = unsignedFitsInNibble(r1);
          bits.set(0, dstRegComp);
          bits.set(1, dstRegComp);
        }

        bits.set(2, unsignedFitsInNibble(regs.get(2).getReg()));
        break;
      }
      default: {
        throw new AssertionError();
      }
    }

    return bits;
  }

  /** {@inheritDoc} */
  @Override
  public void writeTo(AnnotatedOutput out, DalvInsn insn) {
    RegisterSpecList regs = insn.getRegisters();
    int sz = regs.size();

    /*
     * The (sz - 2) and (sz - 1) below makes this code work for
     * both the two- and three-register ops. (See "case 3" in
     * isCompatible(), above.)
     */

write(out, opcodeUnit(insn, makeByte(regs.get(sz - 2).getReg(), regs.get(sz - 1).getReg())));
  }
}