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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.ssa.back;
import com.android.dx.rop.code.RegOps;
import com.android.dx.rop.code.RegisterSpec;
import com.android.dx.rop.code.PlainInsn;
import com.android.dx.rop.code.Rops;
import com.android.dx.rop.code.SourcePosition;
import com.android.dx.rop.code.RegisterSpecList;
import com.android.dx.ssa.NormalSsaInsn;
import com.android.dx.ssa.RegisterMapper;
import com.android.dx.ssa.SsaInsn;
import com.android.dx.ssa.SsaMethod;
import com.android.dx.ssa.SsaBasicBlock;
import com.android.dx.util.IntSet;
import com.android.dx.util.IntIterator;
import java.util.BitSet;
import java.util.ArrayList;
/**
* Base class of all register allocators.
*/
public abstract class RegisterAllocator {
/** method being processed */
protected final SsaMethod ssaMeth;
/** interference graph, indexed by register in both dimensions */
protected final InterferenceGraph interference;
/**
* Creates an instance. Call {@code allocateRegisters} to run.
* @param ssaMeth method to process.
* @param interference Interference graph, indexed by register in both
* dimensions.
*/
public RegisterAllocator(SsaMethod ssaMeth,
InterferenceGraph interference) {
this.ssaMeth = ssaMeth;
this.interference = interference;
}
/**
* Indicates whether the method params were allocated at the bottom
* of the namespace, and thus should be moved up to the top of the
* namespace after phi removal.
*
* @return {@code true} if params should be moved from low to high
*/
public abstract boolean wantsParamsMovedHigh();
/**
* Runs the algorithm.
*
* @return a register mapper to apply to the {@code SsaMethod}
*/
public abstract RegisterMapper allocateRegisters();
/**
* Returns the category (width) of the definition site of the register.
* Returns {@code 1} for undefined registers.
*
* @param reg register
* @return {@code 1..2}
*/
protected final int getCategoryForSsaReg(int reg) {
SsaInsn definition = ssaMeth.getDefinitionForRegister(reg);
if (definition == null) {
// an undefined reg
return 1;
} else {
return definition.getResult().getCategory();
}
}
/**
* Returns the RegisterSpec of the definition of the register.
*
* @param reg {@code >= 0;} SSA register
* @return definition spec of the register or null if it is never defined
* (for the case of "version 0" SSA registers)
*/
protected final RegisterSpec getDefinitionSpecForSsaReg(int reg) {
SsaInsn definition = ssaMeth.getDefinitionForRegister(reg);
return definition == null ? null : definition.getResult();
}
/**
* Returns true if the definition site of this register is a
* move-param (ie, this is a method parameter).
*
* @param reg register in question
* @return {@code true} if this is a method parameter
*/
protected boolean isDefinitionMoveParam(int reg) {
SsaInsn defInsn = ssaMeth.getDefinitionForRegister(reg);
if (defInsn instanceof NormalSsaInsn) {
NormalSsaInsn ndefInsn = (NormalSsaInsn) defInsn;
return ndefInsn.getOpcode().getOpcode() == RegOps.MOVE_PARAM;
}
return false;
}
/**
* Inserts a move instruction for a specified SSA register before a
* specified instruction, creating a new SSA register and adjusting the
* interference graph in the process. The insn currently must be the
* last insn in a block.
*
* @param insn {@code non-null;} insn to insert move before, must
* be last insn in block
* @param reg {@code non-null;} SSA register to duplicate
* @return {@code non-null;} spec of new SSA register created by move
*/
protected final RegisterSpec insertMoveBefore(SsaInsn insn,
RegisterSpec reg) {
SsaBasicBlock block = insn.getBlock();
ArrayList<SsaInsn> insns = block.getInsns();
int insnIndex = insns.indexOf(insn);
if (insnIndex < 0) {
throw new IllegalArgumentException (
"specified insn is not in this block");
}
if (insnIndex != insns.size() - 1) {
/*
* Presently, the interference updater only works when
* adding before the last insn, and the last insn must have no
* result
*/
throw new IllegalArgumentException(
"Adding move here not supported:" + insn.toHuman());
}
/*
* Get new register and make new move instruction.
*/
// The new result must not have an associated local variable.
RegisterSpec newRegSpec = RegisterSpec.make(ssaMeth.makeNewSsaReg(),
reg.getTypeBearer());
SsaInsn toAdd = SsaInsn.makeFromRop(
new PlainInsn(Rops.opMove(newRegSpec.getType()),
SourcePosition.NO_INFO, newRegSpec,
RegisterSpecList.make(reg)), block);
insns.add(insnIndex, toAdd);
int newReg = newRegSpec.getReg();
/*
* Adjust interference graph based on what's live out of the current
* block and what's used by the final instruction.
*/
IntSet liveOut = block.getLiveOutRegs();
IntIterator liveOutIter = liveOut.iterator();
while (liveOutIter.hasNext()) {
interference.add(newReg, liveOutIter.next());
}
// Everything that's a source in the last insn interferes.
RegisterSpecList sources = insn.getSources();
int szSources = sources.size();
for (int i = 0; i < szSources; i++) {
interference.add(newReg, sources.get(i).getReg());
}
ssaMeth.onInsnsChanged();
return newRegSpec;
}
}
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