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/*
 * 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.dx.dex.code;

import com.android.dx.dex.DexOptions;
import com.android.dx.io.Opcodes;
import com.android.dx.rop.code.LocalItem;
import com.android.dx.rop.code.RegisterSpec;
import com.android.dx.rop.code.RegisterSpecList;
import com.android.dx.rop.code.RegisterSpecSet;
import com.android.dx.rop.code.SourcePosition;
import com.android.dx.rop.cst.Constant;
import com.android.dx.rop.cst.CstMemberRef;
import com.android.dx.rop.cst.CstString;
import com.android.dx.rop.cst.CstType;
import com.android.dx.rop.type.Type;
import com.android.dx.ssa.BasicRegisterMapper;

import com.android.dex.DexException;
import java.util.ArrayList;
import java.util.BitSet;
import java.util.HashSet;

/**
 * Processor for instruction lists, which takes a "first cut" of
 * instruction selection as a basis and produces a "final cut" in the
 * form of a {@link DalvInsnList} instance.
 */
public final class OutputFinisher {
    /** {@code non-null;} options for dex output */
    private final DexOptions dexOptions;

    /**
     * {@code >= 0;} register count for the method, not including any extra
     * "reserved" registers needed to translate "difficult" instructions
     */
    private final int unreservedRegCount;

    /** {@code non-null;} the list of instructions, per se */
    private ArrayList insns;

    /** whether any instruction has position info */
    private boolean hasAnyPositionInfo;

    /** whether any instruction has local variable info */
    private boolean hasAnyLocalInfo;

    /**
     * {@code >= 0;} the count of reserved registers (low-numbered
     * registers used when expanding instructions that can't be
     * represented simply); becomes valid after a call to {@link
     * #massageInstructions}
     */
    private int reservedCount;

    /**
     * {@code >= 0;} the count of reserved registers just before parameters in order to align them.
     */
    private int reservedParameterCount;

    /**
     * Size, in register units, of all the parameters to this method
     */
    private final int paramSize;

    /**
     * Constructs an instance. It initially contains no instructions.
     *
     * @param dexOptions {@code non-null;} options for dex output
     * @param initialCapacity {@code >= 0;} initial capacity of the
     * instructions list
     * @param regCount {@code >= 0;} register count for the method
     * @param paramSize size, in register units, of all the parameters for this method
     */
    public OutputFinisher(DexOptions dexOptions, int initialCapacity, int regCount, int paramSize) {
        this.dexOptions = dexOptions;
        this.unreservedRegCount = regCount;
        this.insns = new ArrayList(initialCapacity);
        this.reservedCount = -1;
        this.hasAnyPositionInfo = false;
        this.hasAnyLocalInfo = false;
        this.paramSize = paramSize;
    }

    /**
     * Returns whether any of the instructions added to this instance
     * come with position info.
     *
     * @return whether any of the instructions added to this instance
     * come with position info
     */
    public boolean hasAnyPositionInfo() {
        return hasAnyPositionInfo;
    }

    /**
     * Returns whether this instance has any local variable information.
     *
     * @return whether this instance has any local variable information
     */
    public boolean hasAnyLocalInfo() {
        return hasAnyLocalInfo;
    }

    /**
     * Helper for {@link #add} which scrutinizes a single
     * instruction for local variable information.
     *
     * @param insn {@code non-null;} instruction to scrutinize
     * @return {@code true} iff the instruction refers to any
     * named locals
     */
    private static boolean hasLocalInfo(DalvInsn insn) {
        if (insn instanceof LocalSnapshot) {
            RegisterSpecSet specs = ((LocalSnapshot) insn).getLocals();
            int size = specs.size();
            for (int i = 0; i < size; i++) {
                if (hasLocalInfo(specs.get(i))) {
                    return true;
                }
            }
        } else if (insn instanceof LocalStart) {
            RegisterSpec spec = ((LocalStart) insn).getLocal();
            if (hasLocalInfo(spec)) {
                return true;
            }
        }

        return false;
    }

    /**
     * Helper for {@link #hasAnyLocalInfo} which scrutinizes a single
     * register spec.
     *
     * @param spec {@code non-null;} spec to scrutinize
     * @return {@code true} iff the spec refers to any
     * named locals
     */
    private static boolean hasLocalInfo(RegisterSpec spec) {
        return (spec != null)
            && (spec.getLocalItem().getName() != null);
    }

    /**
     * Returns the set of all constants referred to by instructions added
     * to this instance.
     *
     * @return {@code non-null;} the set of constants
     */
    public HashSet getAllConstants() {
        HashSet result = new HashSet(20);

        for (DalvInsn insn : insns) {
            addConstants(result, insn);
        }

        return result;
    }

    /**
     * Helper for {@link #getAllConstants} which adds all the info for
     * a single instruction.
     *
     * @param result {@code non-null;} result set to add to
     * @param insn {@code non-null;} instruction to scrutinize
     */
    private static void addConstants(HashSet result,
            DalvInsn insn) {
        if (insn instanceof CstInsn) {
            Constant cst = ((CstInsn) insn).getConstant();
            result.add(cst);
        } else if (insn instanceof LocalSnapshot) {
            RegisterSpecSet specs = ((LocalSnapshot) insn).getLocals();
            int size = specs.size();
            for (int i = 0; i < size; i++) {
                addConstants(result, specs.get(i));
            }
        } else if (insn instanceof LocalStart) {
            RegisterSpec spec = ((LocalStart) insn).getLocal();
            addConstants(result, spec);
        }
    }

    /**
     * Helper for {@link #getAllConstants} which adds all the info for
     * a single {@code RegisterSpec}.
     *
     * @param result {@code non-null;} result set to add to
     * @param spec {@code null-ok;} register spec to add
     */
    private static void addConstants(HashSet result,
            RegisterSpec spec) {
        if (spec == null) {
            return;
        }

        LocalItem local = spec.getLocalItem();
        CstString name = local.getName();
        CstString signature = local.getSignature();
        Type type = spec.getType();

        if (type != Type.KNOWN_NULL) {
            result.add(CstType.intern(type));
        }

        if (name != null) {
            result.add(name);
        }

        if (signature != null) {
            result.add(signature);
        }
    }

    /**
     * Adds an instruction to the output.
     *
     * @param insn {@code non-null;} the instruction to add
     */
    public void add(DalvInsn insn) {
        insns.add(insn);
        updateInfo(insn);
    }

    /**
     * Inserts an instruction in the output at the given offset.
     *
     * @param at {@code >= 0;} what index to insert at
     * @param insn {@code non-null;} the instruction to insert
     */
    public void insert(int at, DalvInsn insn) {
        insns.add(at, insn);
        updateInfo(insn);
    }

    /**
     * Helper for {@link #add} and {@link #insert},
     * which updates the position and local info flags.
     *
     * @param insn {@code non-null;} an instruction that was just introduced
     */
    private void updateInfo(DalvInsn insn) {
        if (! hasAnyPositionInfo) {
            SourcePosition pos = insn.getPosition();
            if (pos.getLine() >= 0) {
                hasAnyPositionInfo = true;
            }
        }

        if (! hasAnyLocalInfo) {
            if (hasLocalInfo(insn)) {
                hasAnyLocalInfo = true;
            }
        }
    }

    /**
     * Reverses a branch which is buried a given number of instructions
     * backward in the output. It is illegal to call this unless the
     * indicated instruction really is a reversible branch.
     *
     * @param which how many instructions back to find the branch;
     * {@code 0} is the most recently added instruction,
     * {@code 1} is the instruction before that, etc.
     * @param newTarget {@code non-null;} the new target for the
     * reversed branch
     */
    public void reverseBranch(int which, CodeAddress newTarget) {
        int size = insns.size();
        int index = size - which - 1;
        TargetInsn targetInsn;

        try {
            targetInsn = (TargetInsn) insns.get(index);
        } catch (IndexOutOfBoundsException ex) {
            // Translate the exception.
            throw new IllegalArgumentException("too few instructions");
        } catch (ClassCastException ex) {
            // Translate the exception.
            throw new IllegalArgumentException("non-reversible instruction");
        }

        /*
         * No need to call this.set(), since the format and other info
         * are the same.
         */
        insns.set(index, targetInsn.withNewTargetAndReversed(newTarget));
    }

    /**
     * Assigns indices in all instructions that need them, using the
     * given callback to perform lookups. This should be called before
     * calling {@link #finishProcessingAndGetList}.
     *
     * @param callback {@code non-null;} callback object
     */
    public void assignIndices(DalvCode.AssignIndicesCallback callback) {
        for (DalvInsn insn : insns) {
            if (insn instanceof CstInsn) {
                assignIndices((CstInsn) insn, callback);
            }
        }
    }

    /**
     * Helper for {@link #assignIndices} which does assignment for one
     * instruction.
     *
     * @param insn {@code non-null;} the instruction
     * @param callback {@code non-null;} the callback
     */
    private static void assignIndices(CstInsn insn,
            DalvCode.AssignIndicesCallback callback) {
        Constant cst = insn.getConstant();
        int index = callback.getIndex(cst);

        if (index >= 0) {
            insn.setIndex(index);
        }

        if (cst instanceof CstMemberRef) {
            CstMemberRef member = (CstMemberRef) cst;
            CstType definer = member.getDefiningClass();
            index = callback.getIndex(definer);
            if (index >= 0) {
                insn.setClassIndex(index);
            }
        }
    }

    /**
     * Does final processing on this instance and gets the output as
     * a {@link DalvInsnList}. Final processing consists of:
     *
     * 
    *
  • optionally renumbering registers (to make room as needed for * expanded instructions)
  • *
  • picking a final opcode for each instruction
  • *
  • rewriting instructions, because of register number, * constant pool index, or branch target size issues
  • *
  • assigning final addresses
  • *
* *

Note: This method may only be called once per instance * of this class.

* * @return {@code non-null;} the output list * @throws UnsupportedOperationException if this method has * already been called */ public DalvInsnList finishProcessingAndGetList() { if (reservedCount >= 0) { throw new UnsupportedOperationException("already processed"); } Dop[] opcodes = makeOpcodesArray(); reserveRegisters(opcodes); if (dexOptions.ALIGN_64BIT_REGS_IN_OUTPUT_FINISHER) { align64bits(opcodes); } massageInstructions(opcodes); assignAddressesAndFixBranches(); return DalvInsnList.makeImmutable(insns, reservedCount + unreservedRegCount + reservedParameterCount); } /** * Helper for {@link #finishProcessingAndGetList}, which extracts * the opcode out of each instruction into a separate array, to be * further manipulated as things progress. * * @return {@code non-null;} the array of opcodes */ private Dop[] makeOpcodesArray() { int size = insns.size(); Dop[] result = new Dop[size]; for (int i = 0; i < size; i++) { result[i] = insns.get(i).getOpcode(); } return result; } /** * Helper for {@link #finishProcessingAndGetList}, which figures * out how many reserved registers are required and then reserving * them. It also updates the given {@code opcodes} array so * as to avoid extra work when constructing the massaged * instruction list. * * @param opcodes {@code non-null;} array of per-instruction * opcode selections * @return true if reservedCount is expanded, false otherwise */ private boolean reserveRegisters(Dop[] opcodes) { boolean reservedCountExpanded = false; int oldReservedCount = (reservedCount < 0) ? 0 : reservedCount; /* * Call calculateReservedCount() and then perform register * reservation, repeatedly until no new reservations happen. */ for (;;) { int newReservedCount = calculateReservedCount(opcodes); if (oldReservedCount >= newReservedCount) { break; } reservedCountExpanded = true; int reservedDifference = newReservedCount - oldReservedCount; int size = insns.size(); for (int i = 0; i < size; i++) { /* * CodeAddress instance identity is used to link * TargetInsns to their targets, so it is * inappropriate to make replacements, and they don't * have registers in any case. Hence, the instanceof * test below. */ DalvInsn insn = insns.get(i); if (!(insn instanceof CodeAddress)) { /* * No need to call this.set() since the format and * other info are the same. */ insns.set(i, insn.withRegisterOffset(reservedDifference)); } } oldReservedCount = newReservedCount; } reservedCount = oldReservedCount; return reservedCountExpanded; } /** * Helper for {@link #reserveRegisters}, which does one * pass over the instructions, calculating the number of * registers that need to be reserved. It also updates the * {@code opcodes} list to help avoid extra work in future * register reservation passes. * * @param opcodes {@code non-null;} array of per-instruction * opcode selections * @return {@code >= 0;} the count of reserved registers */ private int calculateReservedCount(Dop[] opcodes) { int size = insns.size(); /* * Potential new value of reservedCount, which gets updated in the * following loop. It starts out with the existing reservedCount * and gets increased if it turns out that additional registers * need to be reserved. */ int newReservedCount = reservedCount; for (int i = 0; i < size; i++) { DalvInsn insn = insns.get(i); Dop originalOpcode = opcodes[i]; Dop newOpcode = findOpcodeForInsn(insn, originalOpcode); if (newOpcode == null) { /* * The instruction will need to be expanded, so find the * expanded opcode and reserve registers for it. */ Dop expandedOp = findExpandedOpcodeForInsn(insn); BitSet compatRegs = expandedOp.getFormat().compatibleRegs(insn); int reserve = insn.getMinimumRegisterRequirement(compatRegs); if (reserve > newReservedCount) { newReservedCount = reserve; } } else if (originalOpcode == newOpcode) { continue; } opcodes[i] = newOpcode; } return newReservedCount; } /** * Attempts to fit the given instruction into a specific opcode, * returning the opcode whose format that the instruction fits * into or {@code null} to indicate that the instruction will need * to be expanded. This fitting process starts with the given * opcode as a first "best guess" and then pessimizes from there * if necessary. * * @param insn {@code non-null;} the instruction in question * @param guess {@code null-ok;} the current guess as to the best * opcode; {@code null} means that no simple opcode fits * @return {@code null-ok;} a possibly-different opcode; either a * {@code non-null} good fit or {@code null} to indicate that no * simple opcode fits */ private Dop findOpcodeForInsn(DalvInsn insn, Dop guess) { /* * Note: The initial guess might be null, meaning that an * earlier call to this method already determined that there * was no possible simple opcode fit. */ while (guess != null) { if (guess.getFormat().isCompatible(insn)) { /* * Don't break out for const_string to generate jumbo version * when option is enabled. */ if (!dexOptions.forceJumbo || guess.getOpcode() != Opcodes.CONST_STRING) { break; } } guess = Dops.getNextOrNull(guess, dexOptions); } return guess; } /** * Finds the proper opcode for the given instruction, ignoring * register constraints. * * @param insn {@code non-null;} the instruction in question * @return {@code non-null;} the opcode that fits */ private Dop findExpandedOpcodeForInsn(DalvInsn insn) { Dop result = findOpcodeForInsn(insn.getLowRegVersion(), insn.getOpcode()); if (result == null) { throw new DexException("No expanded opcode for " + insn); } return result; } /** * Helper for {@link #finishProcessingAndGetList}, which goes * through each instruction in the output, making sure its opcode * can accomodate its arguments. In cases where the opcode is * unable to do so, this replaces the instruction with a larger * instruction with identical semantics that will work. * *

This method may also reserve a number of low-numbered * registers, renumbering the instructions' original registers, in * order to have register space available in which to move * very-high registers when expanding instructions into * multi-instruction sequences. This expansion is done when no * simple instruction format can be found for a given instruction that * is able to accomodate that instruction's registers.

* *

This method ignores issues of branch target size, since * final addresses aren't known at the point that this method is * called.

* * @param opcodes {@code non-null;} array of per-instruction * opcode selections */ private void massageInstructions(Dop[] opcodes) { if (reservedCount == 0) { /* * The easy common case: No registers were reserved, so we * merely need to replace any instructions whose format * (and hence whose opcode) changed during the reservation * pass, but all instructions will stay at their original * indices, and the instruction list doesn't grow. */ int size = insns.size(); for (int i = 0; i < size; i++) { DalvInsn insn = insns.get(i); Dop originalOpcode = insn.getOpcode(); Dop currentOpcode = opcodes[i]; if (originalOpcode != currentOpcode) { insns.set(i, insn.withOpcode(currentOpcode)); } } } else { /* * The difficult uncommon case: Some instructions have to be * expanded to deal with high registers. */ insns = performExpansion(opcodes); } } /** * Helper for {@link #massageInstructions}, which constructs a * replacement list, where each {link DalvInsn} instance that * couldn't be represented simply (due to register representation * problems) is expanded into a series of instances that together * perform the proper function. * * @param opcodes {@code non-null;} array of per-instruction * opcode selections * @return {@code non-null;} the replacement list */ private ArrayList performExpansion(Dop[] opcodes) { int size = insns.size(); ArrayList result = new ArrayList(size * 2); ArrayList closelyBoundAddresses = new ArrayList(); for (int i = 0; i < size; i++) { DalvInsn insn = insns.get(i); Dop originalOpcode = insn.getOpcode(); Dop currentOpcode = opcodes[i]; DalvInsn prefix; DalvInsn suffix; if (currentOpcode != null) { // No expansion is necessary. prefix = null; suffix = null; } else { // Expansion is required. currentOpcode = findExpandedOpcodeForInsn(insn); BitSet compatRegs = currentOpcode.getFormat().compatibleRegs(insn); prefix = insn.expandedPrefix(compatRegs); suffix = insn.expandedSuffix(compatRegs); // Expand necessary registers to fit the new format insn = insn.expandedVersion(compatRegs); } if (insn instanceof CodeAddress) { // If we have a closely bound address, don't add it yet, // because we need to add it after the prefix for the // instruction it is bound to. if (((CodeAddress) insn).getBindsClosely()) { closelyBoundAddresses.add((CodeAddress)insn); continue; } } if (prefix != null) { result.add(prefix); } // Add any pending closely bound addresses if (!(insn instanceof ZeroSizeInsn) && closelyBoundAddresses.size() > 0) { for (CodeAddress codeAddress: closelyBoundAddresses) { result.add(codeAddress); } closelyBoundAddresses.clear(); } if (currentOpcode != originalOpcode) { insn = insn.withOpcode(currentOpcode); } result.add(insn); if (suffix != null) { result.add(suffix); } } return result; } /** * Helper for {@link #finishProcessingAndGetList}, which assigns * addresses to each instruction, possibly rewriting branches to * fix ones that wouldn't otherwise be able to reach their * targets. */ private void assignAddressesAndFixBranches() { for (;;) { assignAddresses(); if (!fixBranches()) { break; } } } /** * Helper for {@link #assignAddressesAndFixBranches}, which * assigns an address to each instruction, in order. */ private void assignAddresses() { int address = 0; int size = insns.size(); for (int i = 0; i < size; i++) { DalvInsn insn = insns.get(i); insn.setAddress(address); address += insn.codeSize(); } } /** * Helper for {@link #assignAddressesAndFixBranches}, which checks * the branch target size requirement of each branch instruction * to make sure it fits. For instructions that don't fit, this * rewrites them to use a {@code goto} of some sort. In the * case of a conditional branch that doesn't fit, the sense of the * test is reversed in order to branch around a {@code goto} * to the original target. * * @return whether any branches had to be fixed */ private boolean fixBranches() { int size = insns.size(); boolean anyFixed = false; for (int i = 0; i < size; i++) { DalvInsn insn = insns.get(i); if (!(insn instanceof TargetInsn)) { // This loop only needs to inspect TargetInsns. continue; } Dop opcode = insn.getOpcode(); TargetInsn target = (TargetInsn) insn; if (opcode.getFormat().branchFits(target)) { continue; } if (opcode.getFamily() == Opcodes.GOTO) { // It is a goto; widen it if possible. opcode = findOpcodeForInsn(insn, opcode); if (opcode == null) { /* * The branch is already maximally large. This should * only be possible if a method somehow manages to have * more than 2^31 code units. */ throw new UnsupportedOperationException("method too long"); } insns.set(i, insn.withOpcode(opcode)); } else { /* * It is a conditional: Reverse its sense, and arrange for * it to branch around an absolute goto to the original * branch target. * * Note: An invariant of the list being processed is * that every TargetInsn is followed by a CodeAddress. * Hence, it is always safe to get the next element * after a TargetInsn and cast it to CodeAddress, as * is happening a few lines down. * * Also note: Size gets incremented by one here, as we * have -- in the net -- added one additional element * to the list, so we increment i to match. The added * and changed elements will be inspected by a repeat * call to this method after this invocation returns. */ CodeAddress newTarget; try { newTarget = (CodeAddress) insns.get(i + 1); } catch (IndexOutOfBoundsException ex) { // The TargetInsn / CodeAddress invariant was violated. throw new IllegalStateException( "unpaired TargetInsn (dangling)"); } catch (ClassCastException ex) { // The TargetInsn / CodeAddress invariant was violated. throw new IllegalStateException("unpaired TargetInsn"); } TargetInsn gotoInsn = new TargetInsn(Dops.GOTO, target.getPosition(), RegisterSpecList.EMPTY, target.getTarget()); insns.set(i, gotoInsn); insns.add(i, target.withNewTargetAndReversed(newTarget)); size++; i++; } anyFixed = true; } return anyFixed; } private void align64bits(Dop[] opcodes) { while (true) { int notAligned64bitRegAccess = 0; int aligned64bitRegAccess = 0; int notAligned64bitParamAccess = 0; int aligned64bitParamAccess = 0; int lastParameter = unreservedRegCount + reservedCount + reservedParameterCount; int firstParameter = lastParameter - paramSize; // Collects the number of time that 64-bit registers are accessed aligned or not. for (DalvInsn insn : insns) { RegisterSpecList regs = insn.getRegisters(); for (int usedRegIdx = 0; usedRegIdx < regs.size(); usedRegIdx++) { RegisterSpec reg = regs.get(usedRegIdx); if (reg.isCategory2()) { boolean isParameter = reg.getReg() >= firstParameter; if (reg.isEvenRegister()) { if (isParameter) { aligned64bitParamAccess++; } else { aligned64bitRegAccess++; } } else { if (isParameter) { notAligned64bitParamAccess++; } else { notAligned64bitRegAccess++; } } } } } if (notAligned64bitParamAccess > aligned64bitParamAccess && notAligned64bitRegAccess > aligned64bitRegAccess) { addReservedRegisters(1); } else if (notAligned64bitParamAccess > aligned64bitParamAccess) { addReservedParameters(1); } else if (notAligned64bitRegAccess > aligned64bitRegAccess) { addReservedRegisters(1); // Need to shift parameters if they exist and if number of unaligned is greater than // aligned. We test the opposite because we previously shift all registers by one, // so the number of aligned become the number of unaligned. if (paramSize != 0 && aligned64bitParamAccess > notAligned64bitParamAccess) { addReservedParameters(1); } } else { break; } if (!reserveRegisters(opcodes)) { break; } } } private void addReservedParameters(int delta) { shiftParameters(delta); reservedParameterCount += delta; } private void addReservedRegisters(int delta) { shiftAllRegisters(delta); reservedCount += delta; } private void shiftAllRegisters(int delta) { int insnSize = insns.size(); for (int i = 0; i < insnSize; i++) { DalvInsn insn = insns.get(i); // Since there is no need to replace CodeAddress since it does not use registers, skips it to // avoid to update all TargetInsn that contain a reference to CodeAddress if (!(insn instanceof CodeAddress)) { insns.set(i, insn.withRegisterOffset(delta)); } } } private void shiftParameters(int delta) { int insnSize = insns.size(); int lastParameter = unreservedRegCount + reservedCount + reservedParameterCount; int firstParameter = lastParameter - paramSize; BasicRegisterMapper mapper = new BasicRegisterMapper(lastParameter); for (int i = 0; i < lastParameter; i++) { if (i >= firstParameter) { mapper.addMapping(i, i + delta, 1); } else { mapper.addMapping(i, i, 1); } } for (int i = 0; i < insnSize; i++) { DalvInsn insn = insns.get(i); // Since there is no need to replace CodeAddress since it does not use registers, skips it to // avoid to update all TargetInsn that contain a reference to CodeAddress if (!(insn instanceof CodeAddress)) { insns.set(i, insn.withMapper(mapper)); } } } }




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