SignExtendGenerator.java

/*
Copyright 2011-2016 Google Inc. All Rights Reserved.

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.google.security.zynamics.reil.translators.ppc;

import com.google.security.zynamics.reil.OperandSize;
import com.google.security.zynamics.reil.ReilHelpers;
import com.google.security.zynamics.reil.ReilInstruction;
import com.google.security.zynamics.reil.translators.ITranslationEnvironment;
import com.google.security.zynamics.reil.translators.InternalTranslationException;
import com.google.security.zynamics.reil.translators.TranslationHelpers;
import com.google.security.zynamics.zylib.disassembly.IInstruction;
import com.google.security.zynamics.zylib.disassembly.IOperandTreeNode;

import java.util.List;


public class SignExtendGenerator {
  public static void generate(long baseOffset, final ITranslationEnvironment environment,
      final IInstruction instruction, final List<ReilInstruction> instructions,
      final String mnemonic, final OperandSize opSize, final boolean setCr)
      throws InternalTranslationException {
    TranslationHelpers.checkTranslationArguments(environment, instruction, instructions, mnemonic);

    final IOperandTreeNode registerOperand1 =
        instruction.getOperands().get(0).getRootNode().getChildren().get(0);
    final IOperandTreeNode registerOperand2 =
        instruction.getOperands().get(1).getRootNode().getChildren().get(0);

    final String targetRegister = registerOperand1.getValue();
    final String sourceRegister = registerOperand2.getValue();

    final String tmpVar1 = environment.getNextVariableString();
    final String tmpVar2 = environment.getNextVariableString();

    final OperandSize dw = OperandSize.DWORD;
    final OperandSize bt = OperandSize.BYTE;

    if (opSize == bt) {
      instructions.add(ReilHelpers.createAdd(baseOffset++, dw, sourceRegister, dw,
          String.valueOf(0x00000080), dw, tmpVar1));
      instructions.add(ReilHelpers.createAnd(baseOffset++, dw, tmpVar1, dw,
          String.valueOf(0x000000FFL), dw, tmpVar2));
      instructions.add(ReilHelpers.createSub(baseOffset++, dw, tmpVar2, dw,
          String.valueOf(0x00000080L), dw, targetRegister));
    } else {
      instructions.add(ReilHelpers.createAdd(baseOffset++, dw, sourceRegister, dw,
          String.valueOf(0x00008000), dw, tmpVar1));
      instructions.add(ReilHelpers.createAnd(baseOffset++, dw, tmpVar1, dw,
          String.valueOf(0x0000FFFFL), dw, tmpVar2));
      instructions.add(ReilHelpers.createSub(baseOffset++, dw, tmpVar2, dw,
          String.valueOf(0x00008000L), dw, targetRegister));
    }

    if (setCr) {
      final String crTemp = environment.getNextVariableString();

      // EQ CR0
      instructions.add(ReilHelpers.createBisz(baseOffset++, OperandSize.DWORD, targetRegister,
          OperandSize.BYTE, Helpers.CR0_EQUAL));

      // LT CR0
      instructions.add(ReilHelpers.createBsh(baseOffset++, OperandSize.DWORD, targetRegister,
          OperandSize.WORD, "-31", OperandSize.BYTE, Helpers.CR0_LESS_THEN));

      // GT CR0
      instructions.add(ReilHelpers.createOr(baseOffset++, OperandSize.BYTE, Helpers.CR0_EQUAL,
          OperandSize.BYTE, Helpers.CR0_LESS_THEN, OperandSize.BYTE, crTemp));
      instructions.add(ReilHelpers.createBisz(baseOffset++, OperandSize.BYTE, crTemp,
          OperandSize.BYTE, Helpers.CR0_GREATER_THEN));

      // SO CR0
      instructions.add(ReilHelpers.createStr(baseOffset, OperandSize.BYTE,
          Helpers.XER_SUMMARY_OVERFLOW, OperandSize.BYTE, Helpers.CRO_SUMMARY_OVERFLOW));
    }

  }
}