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/*
* Copyright (C) 2009 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.
*/
#include "Dalvik.h"
#include "vm/compiler/CompilerInternals.h"
#include "ArmLIR.h"
/*
* Perform a pass of top-down walk to
* 1) Eliminate redundant loads and stores
* 2) Sink stores to latest possible slot
*/
static void applyLoadStoreElimination(CompilationUnit *cUnit,
ArmLIR *headLIR,
ArmLIR *tailLIR)
{
ArmLIR *thisLIR;
cUnit->optRound++;
for (thisLIR = headLIR;
thisLIR != tailLIR;
thisLIR = NEXT_LIR(thisLIR)) {
/* Skip newly added instructions */
if (thisLIR->age >= cUnit->optRound) {
continue;
}
if (thisLIR->opCode == THUMB_STR_RRI5 &&
thisLIR->operands[1] == rFP) {
int dRegId = thisLIR->operands[2];
int nativeRegId = thisLIR->operands[0];
ArmLIR *checkLIR;
int sinkDistance = 0;
for (checkLIR = NEXT_LIR(thisLIR);
checkLIR != tailLIR;
checkLIR = NEXT_LIR(checkLIR)) {
/* Check if a Dalvik register load is redundant */
if (checkLIR->opCode == THUMB_LDR_RRI5 &&
checkLIR->operands[1] == rFP &&
checkLIR->operands[2] == dRegId) {
/* Insert a move to replace the load */
if (checkLIR->operands[0] != nativeRegId) {
ArmLIR *moveLIR =
dvmCompilerNew(sizeof(ArmLIR), true);
moveLIR->opCode = THUMB_MOV_RR;
moveLIR->operands[0] = checkLIR->operands[0];
moveLIR->operands[1] = nativeRegId;
/*
* Insertion is guaranteed to succeed since checkLIR
* is never the first LIR on the list
*/
dvmCompilerInsertLIRBefore((LIR *) checkLIR,
(LIR *) moveLIR);
}
checkLIR->isNop = true;
continue;
/* Found a true output dependency - nuke the previous store */
} else if (checkLIR->opCode == THUMB_STR_RRI5 &&
checkLIR->operands[1] == rFP &&
checkLIR->operands[2] == dRegId) {
thisLIR->isNop = true;
break;
/* Find out the latest slot that the store can be sunk into */
} else {
bool stopHere = false;
/* Last instruction reached */
stopHere |= checkLIR->generic.next == NULL;
/* Store data is clobbered */
stopHere |= (EncodingMap[checkLIR->opCode].flags &
CLOBBER_DEST) != 0 &&
checkLIR->operands[0] == nativeRegId;
/*
* Conservatively assume there is a memory dependency
* for st/ld multiples and reg+reg address mode
*/
stopHere |= checkLIR->opCode == THUMB_STMIA ||
checkLIR->opCode == THUMB_LDMIA ||
checkLIR->opCode == THUMB_STR_RRR ||
checkLIR->opCode == THUMB_LDR_RRR;
stopHere |= (EncodingMap[checkLIR->opCode].flags &
IS_BRANCH) != 0;
/* Found a new place to put the store - move it here */
if (stopHere == true) {
/* The store can be sunk for at least one cycle */
if (sinkDistance != 0) {
ArmLIR *newStoreLIR =
dvmCompilerNew(sizeof(ArmLIR), true);
*newStoreLIR = *thisLIR;
newStoreLIR->age = cUnit->optRound;
/*
* Insertion is guaranteed to succeed since checkLIR
* is never the first LIR on the list
*/
dvmCompilerInsertLIRBefore((LIR *) checkLIR,
(LIR *) newStoreLIR);
thisLIR->isNop = true;
}
break;
}
/*
* Saw a real instruction that the store can be sunk after
*/
if (!isPseudoOpCode(checkLIR->opCode)) {
sinkDistance++;
}
}
}
}
}
}
void dvmCompilerApplyLocalOptimizations(CompilationUnit *cUnit, LIR *headLIR,
LIR *tailLIR)
{
applyLoadStoreElimination(cUnit,
(ArmLIR *) headLIR,
(ArmLIR *) tailLIR);
}
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