[llvm-commits] [llvm] r53106 - /llvm/trunk/lib/Transforms/Scalar/LoopUnswitch.cpp
Devang Patel
dpatel at apple.com
Thu Jul 3 10:37:52 PDT 2008
Author: dpatel
Date: Thu Jul 3 12:37:52 2008
New Revision: 53106
URL: http://llvm.org/viewvc/llvm-project?rev=53106&view=rev
Log:
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.
Right now, dom info is recaluclated in the end if the loop is switched.
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopUnswitch.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/LoopUnswitch.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopUnswitch.cpp?rev=53106&r1=53105&r2=53106&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopUnswitch.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopUnswitch.cpp Thu Jul 3 12:37:52 2008
@@ -77,21 +77,13 @@
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 @@
/// 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 @@
}
}
-// 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 @@
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 @@
// 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 @@
++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 @@
// 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 @@
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 @@
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 @@
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 @@
// 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 @@
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 @@
// 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);
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