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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.jack.dx.ssa.back;
import com.android.jack.dx.rop.code.CstInsn;
import com.android.jack.dx.rop.cst.CstInteger;
import com.android.jack.dx.ssa.BasicRegisterMapper;
import com.android.jack.dx.ssa.NormalSsaInsn;
import com.android.jack.dx.ssa.RegisterMapper;
import com.android.jack.dx.ssa.SsaMethod;
import com.android.jack.dx.util.BitIntSet;
import com.android.jack.dx.util.IntSet;
import java.util.BitSet;
/**
* Allocates registers via a naive n^2 register allocator.
* This allocator does not try to co-locate local variables or deal
* intelligently with different size register uses.
*/
public class FirstFitAllocator extends RegisterAllocator {
/**
* If true, allocator places parameters at the top of the frame
* in calling-convention order.
*/
private static final boolean PRESLOT_PARAMS = true;
/** indexed by old reg; the set of old regs we've mapped */
private final BitSet mapped;
/** {@inheritDoc} */
public FirstFitAllocator(final SsaMethod ssaMeth, final InterferenceGraph interference) {
super(ssaMeth, interference);
mapped = new BitSet(ssaMeth.getRegCount());
}
/** {@inheritDoc} */
@Override
public boolean wantsParamsMovedHigh() {
return PRESLOT_PARAMS;
}
/** {@inheritDoc} */
@Override
public RegisterMapper allocateRegisters() {
int oldRegCount = ssaMeth.getRegCount();
BasicRegisterMapper mapper = new BasicRegisterMapper(oldRegCount);
int nextNewRegister = 0;
if (PRESLOT_PARAMS) {
/*
* Reserve space for the params at the bottom of the register
* space. Later, we'll flip the params to the end of the register
* space.
*/
nextNewRegister = ssaMeth.getParamWidth();
}
for (int i = 0; i < oldRegCount; i++) {
if (mapped.get(i)) {
// we already got this one
continue;
}
int maxCategory = getCategoryForSsaReg(i);
IntSet current = new BitIntSet(oldRegCount);
interference.mergeInterferenceSet(i, current);
boolean isPreslotted = false;
int newReg = 0;
if (PRESLOT_PARAMS && isDefinitionMoveParam(i)) {
// Any move-param definition must be a NormalSsaInsn
NormalSsaInsn defInsn = (NormalSsaInsn) ssaMeth.getDefinitionForRegister(i);
newReg = paramNumberFromMoveParam(defInsn);
mapper.addMapping(i, newReg, maxCategory);
isPreslotted = true;
} else {
mapper.addMapping(i, nextNewRegister, maxCategory);
newReg = nextNewRegister;
}
for (int j = i + 1; j < oldRegCount; j++) {
if (mapped.get(j) || isDefinitionMoveParam(j)) {
continue;
}
/*
* If reg j doesn't interfere with the current mapping.
* Also, if this is a pre-slotted method parameter, we
* can't use more than the original param width.
*/
if (!current.has(j) && !(isPreslotted && (maxCategory < getCategoryForSsaReg(j)))) {
interference.mergeInterferenceSet(j, current);
maxCategory = Math.max(maxCategory, getCategoryForSsaReg(j));
mapper.addMapping(j, newReg, maxCategory);
mapped.set(j);
}
}
mapped.set(i);
if (!isPreslotted) {
nextNewRegister += maxCategory;
}
}
return mapper;
}
/**
* Returns the parameter number that this move-param insn refers to
* @param ndefInsn a move-param insn (otherwise, exceptions will be thrown)
* @return parameter number (offset in the total parameter width)
*/
private int paramNumberFromMoveParam(NormalSsaInsn ndefInsn) {
CstInsn origInsn = (CstInsn) ndefInsn.getOriginalRopInsn();
return ((CstInteger) origInsn.getConstant()).getValue();
}
}
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