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Do not try to update dominator info while manipulating CFG. This code does not handle all cases and keeps invalid dom info around some cases, which misleads other passes down stream.

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Right now, dom info is recaluclated in the end if the loop is switched.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53106 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel 2008-07-03 17:37:52 +00:00
parent 9da02b844f
commit 77a01136ff
1 changed files with 19 additions and 281 deletions
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300
lib/Transforms/Scalar/LoopUnswitch.cpp
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@ -77,21 +77,13 @@ namespace {
BasicBlock *loopHeader;
BasicBlock *loopPreheader;
/// LoopDF - Loop's dominance frontier. This set is a collection of
/// loop exiting blocks' DF member blocks. However this does set does not
/// includes basic blocks that are inside loop.
SmallPtrSet<BasicBlock *, 8> LoopDF;
/// OrigLoopExitMap - This is used to map loop exiting block with
/// corresponding loop exit block, before updating CFG.
DenseMap<BasicBlock *, BasicBlock *> OrigLoopExitMap;
// LoopBlocks contains all of the basic blocks of the loop, including the
// preheader of the loop, the body of the loop, and the exit blocks of the
// loop, in that order.
std::vector<BasicBlock*> LoopBlocks;
// NewBlocks contained cloned copy of basic blocks from LoopBlocks.
std::vector<BasicBlock*> NewBlocks;
public:
static char ID; // Pass ID, replacement for typeid
explicit LoopUnswitch(bool Os = false) :
@ -134,14 +126,8 @@ namespace {
/// Split all of the edges from inside the loop to their exit blocks.
/// Update the appropriate Phi nodes as we do so.
void SplitExitEdges(Loop *L, const SmallVector<BasicBlock *, 8> &ExitBlocks,
SmallVector<BasicBlock *, 8> &MiddleBlocks);
void SplitExitEdges(Loop *L, const SmallVector<BasicBlock *, 8> &ExitBlocks);
/// If BB's dominance frontier has a member that is not part of loop L then
/// remove it. Add NewDFMember in BB's dominance frontier.
void ReplaceLoopExternalDFMember(Loop *L, BasicBlock *BB,
BasicBlock *NewDFMember);
bool UnswitchIfProfitable(Value *LoopCond, Constant *Val);
unsigned getLoopUnswitchCost(Value *LIC);
void UnswitchTrivialCondition(Loop *L, Value *Cond, Constant *Val,
@ -480,87 +466,6 @@ static inline void RemapInstruction(Instruction *I,
}
}
// CloneDomInfo - NewBB is cloned from Orig basic block. Now clone Dominator
// Info.
//
// If Orig block's immediate dominator is mapped in VM then use corresponding
// immediate dominator from the map. Otherwise Orig block's dominator is also
// NewBB's dominator.
//
// OrigPreheader is loop pre-header before this pass started
// updating CFG. NewPrehader is loops new pre-header. However, after CFG
// manipulation, loop L may not exist. So rely on input parameter NewPreheader.
static void CloneDomInfo(BasicBlock *NewBB, BasicBlock *Orig,
BasicBlock *NewPreheader, BasicBlock *OrigPreheader,
BasicBlock *OrigHeader,
DominatorTree *DT, DominanceFrontier *DF,
DenseMap<const Value*, Value*> &VM) {
// If NewBB alreay has found its place in domiantor tree then no need to do
// anything.
if (DT->getNode(NewBB))
return;
// If Orig does not have any immediate domiantor then its clone, NewBB, does
// not need any immediate dominator.
DomTreeNode *OrigNode = DT->getNode(Orig);
if (!OrigNode)
return;
DomTreeNode *OrigIDomNode = OrigNode->getIDom();
if (!OrigIDomNode)
return;
BasicBlock *OrigIDom = NULL;
// If Orig is original loop header then its immediate dominator is
// NewPreheader.
if (Orig == OrigHeader)
OrigIDom = NewPreheader;
// If Orig is new pre-header then its immediate dominator is
// original pre-header.
else if (Orig == NewPreheader)
OrigIDom = OrigPreheader;
// Otherwise ask DT to find Orig's immediate dominator.
else
OrigIDom = OrigIDomNode->getBlock();
// Initially use Orig's immediate dominator as NewBB's immediate dominator.
BasicBlock *NewIDom = OrigIDom;
DenseMap<const Value*, Value*>::iterator I = VM.find(OrigIDom);
if (I != VM.end()) {
NewIDom = cast<BasicBlock>(I->second);
// If NewIDom does not have corresponding dominatore tree node then
// get one.
if (!DT->getNode(NewIDom))
CloneDomInfo(NewIDom, OrigIDom, NewPreheader, OrigPreheader,
OrigHeader, DT, DF, VM);
}
DT->addNewBlock(NewBB, NewIDom);
// Copy cloned dominance frontiner set
DominanceFrontier::DomSetType NewDFSet;
if (DF) {
DominanceFrontier::iterator DFI = DF->find(Orig);
if ( DFI != DF->end()) {
DominanceFrontier::DomSetType S = DFI->second;
for (DominanceFrontier::DomSetType::iterator I = S.begin(), E = S.end();
I != E; ++I) {
BasicBlock *BB = *I;
DenseMap<const Value*, Value*>::iterator IDM = VM.find(BB);
if (IDM != VM.end())
NewDFSet.insert(cast<BasicBlock>(IDM->second));
else
NewDFSet.insert(BB);
}
}
DF->addBasicBlock(NewBB, NewDFSet);
}
}
/// CloneLoop - Recursively clone the specified loop and all of its children,
/// mapping the blocks with the specified map.
static Loop *CloneLoop(Loop *L, Loop *PL, DenseMap<const Value*, Value*> &VM,
@ -602,7 +507,6 @@ void LoopUnswitch::EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val,
BranchInst::Create(TrueDest, FalseDest, BranchVal, InsertPt);
}
/// UnswitchTrivialCondition - Given a loop that has a trivial unswitchable
/// condition in it (a cond branch from its header block to its latch block,
/// where the path through the loop that doesn't execute its body has no
@ -636,27 +540,6 @@ void LoopUnswitch::UnswitchTrivialCondition(Loop *L, Value *Cond,
// insert the new conditional branch.
EmitPreheaderBranchOnCondition(Cond, Val, NewExit, NewPH,
loopPreheader->getTerminator());
if (DT) {
DT->changeImmediateDominator(NewExit, loopPreheader);
DT->changeImmediateDominator(NewPH, loopPreheader);
}
if (DF) {
// NewExit is now part of NewPH and Loop Header's dominance
// frontier.
DominanceFrontier::iterator DFI = DF->find(NewPH);
if (DFI != DF->end())
DF->addToFrontier(DFI, NewExit);
DFI = DF->find(loopHeader);
DF->addToFrontier(DFI, NewExit);
// ExitBlock does not have successors then NewExit is part of
// its dominance frontier.
if (succ_begin(ExitBlock) == succ_end(ExitBlock)) {
DFI = DF->find(ExitBlock);
DF->addToFrontier(DFI, NewExit);
}
}
LPM->deleteSimpleAnalysisValue(loopPreheader->getTerminator(), L);
loopPreheader->getTerminator()->eraseFromParent();
@ -670,93 +553,52 @@ void LoopUnswitch::UnswitchTrivialCondition(Loop *L, Value *Cond,
++NumTrivial;
}
/// ReplaceLoopExternalDFMember -
/// If BB's dominance frontier has a member that is not part of loop L then
/// remove it. Add NewDFMember in BB's dominance frontier.
void LoopUnswitch::ReplaceLoopExternalDFMember(Loop *L, BasicBlock *BB,
BasicBlock *NewDFMember) {
DominanceFrontier::iterator DFI = DF->find(BB);
if (DFI == DF->end())
return;
DominanceFrontier::DomSetType &DFSet = DFI->second;
for (DominanceFrontier::DomSetType::iterator DI = DFSet.begin(),
DE = DFSet.end(); DI != DE;) {
BasicBlock *B = *DI++;
if (L->contains(B))
continue;
DF->removeFromFrontier(DFI, B);
LoopDF.insert(B);
}
DF->addToFrontier(DFI, NewDFMember);
}
/// SplitExitEdges - Split all of the edges from inside the loop to their exit
/// blocks. Update the appropriate Phi nodes as we do so.
void LoopUnswitch::SplitExitEdges(Loop *L,
const SmallVector<BasicBlock *, 8> &ExitBlocks,
SmallVector<BasicBlock *, 8> &MiddleBlocks) {
const SmallVector<BasicBlock *, 8> &ExitBlocks)
{
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
BasicBlock *ExitBlock = ExitBlocks[i];
std::vector<BasicBlock*> Preds(pred_begin(ExitBlock), pred_end(ExitBlock));
for (unsigned j = 0, e = Preds.size(); j != e; ++j) {
BasicBlock* MiddleBlock = SplitEdge(Preds[j], ExitBlock, this);
MiddleBlocks.push_back(MiddleBlock);
BasicBlock* NewExitBlock = SplitEdge(Preds[j], ExitBlock, this);
BasicBlock* StartBlock = Preds[j];
BasicBlock* EndBlock;
if (MiddleBlock->getSinglePredecessor() == ExitBlock) {
EndBlock = MiddleBlock;
MiddleBlock = EndBlock->getSinglePredecessor();;
if (NewExitBlock->getSinglePredecessor() == ExitBlock) {
EndBlock = NewExitBlock;
NewExitBlock = EndBlock->getSinglePredecessor();;
} else {
EndBlock = ExitBlock;
}
OrigLoopExitMap[StartBlock] = EndBlock;
std::set<PHINode*> InsertedPHIs;
PHINode* OldLCSSA = 0;
for (BasicBlock::iterator I = EndBlock->begin();
(OldLCSSA = dyn_cast<PHINode>(I)); ++I) {
Value* OldValue = OldLCSSA->getIncomingValueForBlock(MiddleBlock);
Value* OldValue = OldLCSSA->getIncomingValueForBlock(NewExitBlock);
PHINode* NewLCSSA = PHINode::Create(OldLCSSA->getType(),
OldLCSSA->getName() + ".us-lcssa",
MiddleBlock->getTerminator());
NewExitBlock->getTerminator());
NewLCSSA->addIncoming(OldValue, StartBlock);
OldLCSSA->setIncomingValue(OldLCSSA->getBasicBlockIndex(MiddleBlock),
OldLCSSA->setIncomingValue(OldLCSSA->getBasicBlockIndex(NewExitBlock),
NewLCSSA);
InsertedPHIs.insert(NewLCSSA);
}
BasicBlock::iterator InsertPt = EndBlock->getFirstNonPHI();
for (BasicBlock::iterator I = MiddleBlock->begin();
for (BasicBlock::iterator I = NewExitBlock->begin();
(OldLCSSA = dyn_cast<PHINode>(I)) && InsertedPHIs.count(OldLCSSA) == 0;
++I) {
PHINode *NewLCSSA = PHINode::Create(OldLCSSA->getType(),
OldLCSSA->getName() + ".us-lcssa",
InsertPt);
OldLCSSA->replaceAllUsesWith(NewLCSSA);
NewLCSSA->addIncoming(OldLCSSA, MiddleBlock);
NewLCSSA->addIncoming(OldLCSSA, NewExitBlock);
}
if (DF && DT) {
// StartBlock -- > MiddleBlock -- > EndBlock
// StartBlock is loop exiting block. EndBlock will become merge point
// of two loop exits after loop unswitch.
// If StartBlock's DF member includes a block that is not loop member
// then replace that DF member with EndBlock.
// If MiddleBlock's DF member includes a block that is not loop member
// tnen replace that DF member with EndBlock.
ReplaceLoopExternalDFMember(L, StartBlock, EndBlock);
ReplaceLoopExternalDFMember(L, MiddleBlock, EndBlock);
}
}
}
@ -789,8 +631,7 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
// Split all of the edges from inside the loop to their exit blocks. Update
// the appropriate Phi nodes as we do so.
SmallVector<BasicBlock *,8> MiddleBlocks;
SplitExitEdges(L, ExitBlocks, MiddleBlocks);
SplitExitEdges(L, ExitBlocks);
// The exit blocks may have been changed due to edge splitting, recompute.
ExitBlocks.clear();
@ -811,21 +652,6 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
LPM->cloneBasicBlockSimpleAnalysis(LoopBlocks[i], New, L);
}
// OutSiders are basic block that are dominated by original header and
// at the same time they are not part of loop.
SmallPtrSet<BasicBlock *, 8> OutSiders;
if (DT) {
DomTreeNode *OrigHeaderNode = DT->getNode(loopHeader);
for(std::vector<DomTreeNode*>::iterator DI = OrigHeaderNode->begin(),
DE = OrigHeaderNode->end(); DI != DE; ++DI) {
BasicBlock *B = (*DI)->getBlock();
DenseMap<const Value*, Value*>::iterator VI = ValueMap.find(B);
if (VI == ValueMap.end())
OutSiders.insert(B);
}
}
// Splice the newly inserted blocks into the function right before the
// original preheader.
F->getBasicBlockList().splice(LoopBlocks[0], F->getBasicBlockList(),
@ -849,7 +675,7 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
assert(NewExit->getTerminator()->getNumSuccessors() == 1 &&
"Exit block should have been split to have one successor!");
BasicBlock *ExitSucc = NewExit->getTerminator()->getSuccessor(0);
// If the successor of the exit block had PHI nodes, add an entry for
// NewExit.
PHINode *PN;
@ -878,94 +704,6 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
LPM->deleteSimpleAnalysisValue(OldBR, L);
OldBR->eraseFromParent();
// Update dominator info
if (DF && DT) {
SmallVector<BasicBlock *,4> ExitingBlocks;
L->getExitingBlocks(ExitingBlocks);
// Clone dominator info for all cloned basic block.
for (unsigned i = 0, e = LoopBlocks.size(); i != e; ++i) {
BasicBlock *LBB = LoopBlocks[i];
BasicBlock *NBB = NewBlocks[i];
CloneDomInfo(NBB, LBB, NewPreheader, loopPreheader,
loopHeader, DT, DF, ValueMap);
// If LBB's dominance frontier includes DFMember
// such that DFMember is also a member of LoopDF then
// - Remove DFMember from LBB's dominance frontier
// - Copy loop exiting blocks', that are dominated by BB,
// dominance frontier member in BB's dominance frontier
DominanceFrontier::iterator LBBI = DF->find(LBB);
DominanceFrontier::iterator NBBI = DF->find(NBB);
if (LBBI == DF->end())
continue;
DominanceFrontier::DomSetType &LBSet = LBBI->second;
for (DominanceFrontier::DomSetType::iterator LI = LBSet.begin(),
LE = LBSet.end(); LI != LE; /* NULL */) {
BasicBlock *B = *LI++;
if (B == LBB && B == loopHeader)
continue;
bool removeB = false;
if (!LoopDF.count(B))
continue;
// If LBB dominates loop exits then insert loop exit block's DF
// into B's DF.
for(SmallVector<BasicBlock *, 4>::iterator
LExitI = ExitingBlocks.begin(),
LExitE = ExitingBlocks.end(); LExitI != LExitE; ++LExitI) {
BasicBlock *E = *LExitI;
if (!DT->dominates(LBB,E))
continue;
DenseMap<BasicBlock *, BasicBlock *>::iterator DFBI =
OrigLoopExitMap.find(E);
if (DFBI == OrigLoopExitMap.end())
continue;
BasicBlock *DFB = DFBI->second;
DF->addToFrontier(LBBI, DFB);
DF->addToFrontier(NBBI, DFB);
removeB = true;
}
// If B's replacement is inserted in DF then now is the time to remove
// B.
if (removeB) {
DF->removeFromFrontier(LBBI, B);
if (L->contains(B))
DF->removeFromFrontier(NBBI, cast<BasicBlock>(ValueMap[B]));
else
DF->removeFromFrontier(NBBI, B);
}
}
}
// MiddleBlocks are dominated by original pre header. SplitEdge updated
// MiddleBlocks' dominance frontier appropriately.
for (unsigned i = 0, e = MiddleBlocks.size(); i != e; ++i) {
BasicBlock *MBB = MiddleBlocks[i];
if (!MBB->getSinglePredecessor())
DT->changeImmediateDominator(MBB, loopPreheader);
}
// All Outsiders are now dominated by original pre header.
for (SmallPtrSet<BasicBlock *, 8>::iterator OI = OutSiders.begin(),
OE = OutSiders.end(); OI != OE; ++OI) {
BasicBlock *OB = *OI;
DT->changeImmediateDominator(OB, loopPreheader);
}
// New loop headers are dominated by original preheader
DT->changeImmediateDominator(NewBlocks[0], loopPreheader);
DT->changeImmediateDominator(LoopBlocks[0], loopPreheader);
}
LoopProcessWorklist.push_back(NewLoop);
redoLoop = true;
@ -977,6 +715,7 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
// deleted. If so, don't simplify it.
if (!LoopProcessWorklist.empty() && LoopProcessWorklist.back() == NewLoop)
RewriteLoopBodyWithConditionConstant(NewLoop, LIC, Val, true);
}
/// RemoveFromWorklist - Remove all instances of I from the worklist vector
@ -1130,8 +869,6 @@ void LoopUnswitch::RemoveLoopFromHierarchy(Loop *L) {
RemoveLoopFromWorklist(L);
}
// RewriteLoopBodyWithConditionConstant - We know either that the value LIC has
// the value specified by Val in the specified loop, or we know it does NOT have
// that value. Rewrite any uses of LIC or of properties correlated to it.
@ -1193,18 +930,19 @@ void LoopUnswitch::RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC,
// trying to update it is complicated. So instead we preserve the
// loop structure and put the block on an dead code path.
BasicBlock *SISucc = SI->getSuccessor(i);
BasicBlock* Old = SI->getParent();
BasicBlock* Split = SplitBlock(Old, SI, this);
Instruction* OldTerm = Old->getTerminator();
BranchInst::Create(Split, SI->getSuccessor(i),
BranchInst::Create(Split, SISucc,
ConstantInt::getTrue(), OldTerm);
LPM->deleteSimpleAnalysisValue(Old->getTerminator(), L);
Old->getTerminator()->eraseFromParent();
PHINode *PN;
for (BasicBlock::iterator II = SI->getSuccessor(i)->begin();
for (BasicBlock::iterator II = SISucc->begin();
(PN = dyn_cast<PHINode>(II)); ++II) {
Value *InVal = PN->removeIncomingValue(Split, false);
PN->addIncoming(InVal, Old);