static BasicBlock *findPredecessorBlock(const CompilationUnit *cUnit,
const BasicBlock *bb)
{
int numPred = dvmCountSetBits(bb->predecessors);
BitVectorIterator bvIterator;
dvmBitVectorIteratorInit(bb->predecessors, &bvIterator);
if (numPred == 1) {
int predIdx = dvmBitVectorIteratorNext(&bvIterator);
return (BasicBlock *) dvmGrowableListGetElement(&cUnit->blockList,
predIdx);
/* First loop block */
} else if ((numPred == 2) &&
dvmIsBitSet(bb->predecessors, cUnit->entryBlock->id)) {
while (true) {
int predIdx = dvmBitVectorIteratorNext(&bvIterator);
if (predIdx == cUnit->entryBlock->id) continue;
return (BasicBlock *) dvmGrowableListGetElement(&cUnit->blockList,
predIdx);
}
/* Doesn't support other shape of control flow yet */
} else {
return NULL;
}
}
/*
* Worker function to insert phi-operands with latest SSA names from
* predecessor blocks
*/
static bool insertPhiNodeOperands(CompilationUnit *cUnit, BasicBlock *bb) {
BitVector *ssaRegV = cUnit->tempSSARegisterV;
BitVectorIterator bvIterator;
GrowableList *blockList = &cUnit->blockList;
MIR *mir;
/* Phi nodes are at the beginning of each block */
for (mir = bb->firstMIRInsn; mir; mir = mir->next) {
if (mir->dalvikInsn.opcode != (Opcode) kMirOpPhi)
return true;
int ssaReg = mir->ssaRep->defs[0];
int encodedDalvikValue =
(int) dvmGrowableListGetElement(cUnit->ssaToDalvikMap, ssaReg);
int dalvikReg = DECODE_REG(encodedDalvikValue);
dvmClearAllBits(ssaRegV);
/* Iterate through the predecessors */
dvmBitVectorIteratorInit(bb->predecessors, &bvIterator);
while (true) {
int predIdx = dvmBitVectorIteratorNext(&bvIterator);
if (predIdx == -1) break;
BasicBlock *predBB = (BasicBlock *) dvmGrowableListGetElement(
blockList, predIdx);
int encodedSSAValue =
predBB->dataFlowInfo->dalvikToSSAMap[dalvikReg];
int ssaReg = DECODE_REG(encodedSSAValue);
dvmSetBit(ssaRegV, ssaReg);
}
/* Count the number of SSA registers for a Dalvik register */
int numUses = dvmCountSetBits(ssaRegV);
mir->ssaRep->numUses = numUses;
mir->ssaRep->uses =
(int *) dvmCompilerNew(sizeof(int) * numUses, false);
mir->ssaRep->fpUse =
(bool *) dvmCompilerNew(sizeof(bool) * numUses, true);
BitVectorIterator phiIterator;
dvmBitVectorIteratorInit(ssaRegV, &phiIterator);
int *usePtr = mir->ssaRep->uses;
/* Set the uses array for the phi node */
while (true) {
int ssaRegIdx = dvmBitVectorIteratorNext(&phiIterator);
if (ssaRegIdx == -1) break;
*usePtr++ = ssaRegIdx;
}
}
return true;
}
/* Worker function to compute each block's dominators */
static bool computeBlockDominators(CompilationUnit *cUnit, BasicBlock *bb) {
GrowableList *blockList = &cUnit->blockList;
int numTotalBlocks = blockList->numUsed;
BitVector *tempBlockV = cUnit->tempBlockV;
BitVectorIterator bvIterator;
/*
* The dominator of the entry block has been preset to itself and we need
* to skip the calculation here.
*/
if (bb == cUnit->entryBlock) return false;
dvmSetInitialBits(tempBlockV, numTotalBlocks);
/* Iterate through the predecessors */
dvmBitVectorIteratorInit(bb->predecessors, &bvIterator);
while (true) {
int predIdx = dvmBitVectorIteratorNext(&bvIterator);
if (predIdx == -1) break;
BasicBlock *predBB = (BasicBlock *) dvmGrowableListGetElement(
blockList, predIdx);
/* tempBlockV = tempBlockV ^ dominators */
dvmIntersectBitVectors(tempBlockV, tempBlockV, predBB->dominators);
}
dvmSetBit(tempBlockV, bb->id);
if (dvmCompareBitVectors(tempBlockV, bb->dominators)) {
dvmCopyBitVector(bb->dominators, tempBlockV);
return true;
}
return false;
}
/* Worker function to compute the dominance frontier */
static bool computeDominanceFrontier(CompilationUnit *cUnit, BasicBlock *bb) {
GrowableList *blockList = &cUnit->blockList;
/* Calculate DF_local */
if (bb->taken) {
checkForDominanceFrontier(bb, bb->taken);
}
if (bb->fallThrough) {
checkForDominanceFrontier(bb, bb->fallThrough);
}
if (bb->successorBlockList.blockListType != kNotUsed) {
GrowableListIterator iterator;
dvmGrowableListIteratorInit(&bb->successorBlockList.blocks,
&iterator);
while (true) {
SuccessorBlockInfo *successorBlockInfo =
(SuccessorBlockInfo *) dvmGrowableListIteratorNext(&iterator);
if (successorBlockInfo == NULL) break;
BasicBlock *succBB = successorBlockInfo->block;
checkForDominanceFrontier(bb, succBB);
}
}
/* Calculate DF_up */
BitVectorIterator bvIterator;
dvmBitVectorIteratorInit(bb->iDominated, &bvIterator);
while (true) {
int dominatedIdx = dvmBitVectorIteratorNext(&bvIterator);
if (dominatedIdx == -1) break;
BasicBlock *dominatedBB = (BasicBlock *)
dvmGrowableListGetElement(blockList, dominatedIdx);
BitVectorIterator dfIterator;
dvmBitVectorIteratorInit(dominatedBB->domFrontier, &dfIterator);
while (true) {
int dfUpIdx = dvmBitVectorIteratorNext(&dfIterator);
if (dfUpIdx == -1) break;
BasicBlock *dfUpBlock = (BasicBlock *)
dvmGrowableListGetElement(blockList, dfUpIdx);
checkForDominanceFrontier(bb, dfUpBlock);
}
}
return true;
}
/* Worker function to compute the idom */
static bool computeImmediateDominator(CompilationUnit *cUnit, BasicBlock *bb) {
GrowableList *blockList = &cUnit->blockList;
BitVector *tempBlockV = cUnit->tempBlockV;
BitVectorIterator bvIterator;
BasicBlock *iDom;
if (bb == cUnit->entryBlock) return false;
dvmCopyBitVector(tempBlockV, bb->dominators);
dvmClearBit(tempBlockV, bb->id);
dvmBitVectorIteratorInit(tempBlockV, &bvIterator);
/* Should not see any dead block */
assert(dvmCountSetBits(tempBlockV) != 0);
if (dvmCountSetBits(tempBlockV) == 1) {
iDom = (BasicBlock *) dvmGrowableListGetElement(
blockList, dvmBitVectorIteratorNext(&bvIterator));
bb->iDom = iDom;
} else {
int iDomIdx = dvmBitVectorIteratorNext(&bvIterator);
assert(iDomIdx != -1);
while (true) {
int nextDom = dvmBitVectorIteratorNext(&bvIterator);
if (nextDom == -1) break;
BasicBlock *nextDomBB = (BasicBlock *)
dvmGrowableListGetElement(blockList, nextDom);
/* iDom dominates nextDom - set new iDom */
if (dvmIsBitSet(nextDomBB->dominators, iDomIdx)) {
iDomIdx = nextDom;
}
}
iDom = (BasicBlock *) dvmGrowableListGetElement(blockList, iDomIdx);
/* Set the immediate dominator block for bb */
bb->iDom = iDom;
}
/* Add bb to the iDominated set of the immediate dominator block */
dvmCompilerSetBit(iDom->iDominated, bb->id);
return true;
}
/* Compute the post-order traversal of the CFG */
static void computeDomPostOrderTraversal(CompilationUnit *cUnit, BasicBlock *bb) {
BitVectorIterator bvIterator;
dvmBitVectorIteratorInit(bb->iDominated, &bvIterator);
GrowableList *blockList = &cUnit->blockList;
/* Iterate through the dominated blocks first */
while (true) {
int bbIdx = dvmBitVectorIteratorNext(&bvIterator);
if (bbIdx == -1) break;
BasicBlock *dominatedBB =
(BasicBlock *) dvmGrowableListGetElement(blockList, bbIdx);
computeDomPostOrderTraversal(cUnit, dominatedBB);
}
/* Enter the current block id */
dvmInsertGrowableList(&cUnit->domPostOrderTraversal, bb->id);
/* hacky loop detection */
if (bb->taken && dvmIsBitSet(bb->dominators, bb->taken->id)) {
cUnit->hasLoop = true;
}
}
/* Insert phi nodes to for each variable to the dominance frontiers */
static void insertPhiNodes(CompilationUnit *cUnit) {
int dalvikReg;
const GrowableList *blockList = &cUnit->blockList;
BitVector *phiBlocks =
dvmCompilerAllocBitVector(cUnit->numBlocks, false);
BitVector *tmpBlocks =
dvmCompilerAllocBitVector(cUnit->numBlocks, false);
BitVector *inputBlocks =
dvmCompilerAllocBitVector(cUnit->numBlocks, false);
cUnit->tempDalvikRegisterV =
dvmCompilerAllocBitVector(cUnit->numDalvikRegisters, false);
dvmCompilerDataFlowAnalysisDispatcher(cUnit, computeBlockLiveIns,
kPostOrderDFSTraversal,
true /* isIterative */);
/* Iterate through each Dalvik register */
for (dalvikReg = 0; dalvikReg < cUnit->numDalvikRegisters; dalvikReg++) {
bool change;
BitVectorIterator iterator;
dvmCopyBitVector(inputBlocks, cUnit->defBlockMatrix[dalvikReg]);
dvmClearAllBits(phiBlocks);
/* Calculate the phi blocks for each Dalvik register */
do {
change = false;
dvmClearAllBits(tmpBlocks);
dvmBitVectorIteratorInit(inputBlocks, &iterator);
while (true) {
int idx = dvmBitVectorIteratorNext(&iterator);
if (idx == -1) break;
BasicBlock *defBB =
(BasicBlock *) dvmGrowableListGetElement(blockList, idx);
/* Merge the dominance frontier to tmpBlocks */
dvmUnifyBitVectors(tmpBlocks, tmpBlocks, defBB->domFrontier);
}
if (dvmCompareBitVectors(phiBlocks, tmpBlocks)) {
change = true;
dvmCopyBitVector(phiBlocks, tmpBlocks);
/*
* Iterate through the original blocks plus the new ones in
* the dominance frontier.
*/
dvmCopyBitVector(inputBlocks, phiBlocks);
dvmUnifyBitVectors(inputBlocks, inputBlocks,
cUnit->defBlockMatrix[dalvikReg]);
}
} while (change);
/*
* Insert a phi node for dalvikReg in the phiBlocks if the Dalvik
* register is in the live-in set.
*/
dvmBitVectorIteratorInit(phiBlocks, &iterator);
while (true) {
int idx = dvmBitVectorIteratorNext(&iterator);
if (idx == -1) break;
BasicBlock *phiBB =
(BasicBlock *) dvmGrowableListGetElement(blockList, idx);
/* Variable will be clobbered before being used - no need for phi */
if (!dvmIsBitSet(phiBB->dataFlowInfo->liveInV, dalvikReg)) continue;
MIR *phi = (MIR *) dvmCompilerNew(sizeof(MIR), true);
phi->dalvikInsn.opcode = (Opcode) kMirOpPhi;
phi->dalvikInsn.vA = dalvikReg;
phi->offset = phiBB->startOffset;
dvmCompilerPrependMIR(phiBB, phi);
}
}
}
