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Update dominator info for the middle blocks created while spliting 

exit edge to preserve LCSSA.

Fix dominance frontier update during loop unswitch. This fixes PR 1589, again

llvm-svn: 40737
This commit is contained in:
Devang Patel 2007-08-02 15:25:57 +00:00
parent fa3eeeedc0
commit a882328e61
3 changed files with 140 additions and 21 deletions
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96
llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
View File

@ -543,17 +543,8 @@ void LoopUnswitch::EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val,
std::swap(TrueDest, FalseDest);
// Insert the new branch.
BranchInst *BRI = new BranchInst(TrueDest, FalseDest, BranchVal, InsertPt);
new BranchInst(TrueDest, FalseDest, BranchVal, InsertPt);
// Update dominator info.
// BranchVal is a new preheader so it dominates true and false destination
// loop headers.
if (DominatorTree *DT = getAnalysisToUpdate<DominatorTree>()) {
DT->changeImmediateDominator(TrueDest, BRI->getParent());
DT->changeImmediateDominator(FalseDest, BRI->getParent());
}
// No need to update DominanceFrontier. BRI->getParent() dominated TrueDest
// and FalseDest anyway. Now it immediately dominates them.
}
@ -635,12 +626,14 @@ 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;
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* StartBlock = Preds[j];
BasicBlock* EndBlock;
if (MiddleBlock->getSinglePredecessor() == ExitBlock) {
@ -685,6 +678,9 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
// Add exit blocks to the loop blocks.
LoopBlocks.insert(LoopBlocks.end(), ExitBlocks.begin(), ExitBlocks.end());
DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>();
DominatorTree *DT = getAnalysisToUpdate<DominatorTree>();
// Next step, clone all of the basic blocks that make up the loop (including
// the loop preheader and exit blocks), keeping track of the mapping between
// the instructions and blocks.
@ -698,16 +694,21 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
LPM->cloneBasicBlockSimpleAnalysis(LoopBlocks[i], New, L);
}
// Update dominator info
DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>();
if (DominatorTree *DT = getAnalysisToUpdate<DominatorTree>())
for (unsigned i = 0, e = LoopBlocks.size(); i != e; ++i) {
BasicBlock *LBB = LoopBlocks[i];
BasicBlock *NBB = NewBlocks[i];
CloneDomInfo(NBB, LBB, NewPreheader, OrigPreheader,
OrigHeader, DT, DF, ValueMap);
// 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(OrigHeader);
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(),
@ -759,7 +760,62 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
EmitPreheaderBranchOnCondition(LIC, Val, NewBlocks[0], LoopBlocks[0], OldBR);
OldBR->eraseFromParent();
LPM->deleteSimpleAnalysisValue(OldBR, L);
// Update dominator info
if (DF && DT) {
// 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, OrigPreheader,
OrigHeader, DT, DF, ValueMap);
// Remove any OutSiders from LBB and NBB's dominance frontier.
DominanceFrontier::iterator LBBI = DF->find(LBB);
if (LBBI != DF->end()) {
DominanceFrontier::DomSetType &LBSet = LBBI->second;
for (DominanceFrontier::DomSetType::iterator LI = LBSet.begin(),
LE = LBSet.end(); LI != LE; ++LI) {
BasicBlock *B = *LI;
if (OutSiders.count(B))
DF->removeFromFrontier(LBBI, B);
}
}
// Remove any OutSiders from LBB and NBB's dominance frontier.
DominanceFrontier::iterator NBBI = DF->find(NBB);
if (NBBI != DF->end()) {
DominanceFrontier::DomSetType NBSet = NBBI->second;
for (DominanceFrontier::DomSetType::iterator NI = NBSet.begin(),
NE = NBSet.end(); NI != NE; ++NI) {
BasicBlock *B = *NI;
if (OutSiders.count(B))
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, OrigPreheader);
}
// 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, OrigPreheader);
}
// New loop headers are dominated by original preheader
DT->changeImmediateDominator(NewBlocks[0], OrigPreheader);
DT->changeImmediateDominator(LoopBlocks[0], OrigPreheader);
}
LoopProcessWorklist.push_back(NewLoop);
redoLoop = true;

10
llvm/lib/VMCore/Dominators.cpp
View File

@ -627,6 +627,15 @@ void DominanceFrontier::splitBlock(BasicBlock *NewBB) {
if (!DT.dominates(NewBB, NewBBSucc))
NewBBDominatesNewBBSucc = false;
// NewBBSucc inherites original NewBB frontier.
DominanceFrontier::iterator NewBBI = find(NewBB);
if (NewBBI != end()) {
DominanceFrontier::DomSetType NewBBSet = NewBBI->second;
DominanceFrontier::DomSetType NewBBSuccSet;
NewBBSuccSet.insert(NewBBSet.begin(), NewBBSet.end());
addBasicBlock(NewBBSucc, NewBBSuccSet);
}
// If NewBB dominates NewBBSucc, then DF(NewBB) is now going to be the
// DF(PredBlocks[0]) without the stuff that the new block does not dominate
// a predecessor of.
@ -648,7 +657,6 @@ void DominanceFrontier::splitBlock(BasicBlock *NewBB) {
++SetI;
}
DominanceFrontier::iterator NewBBI = find(NewBB);
if (NewBBI != end()) {
DominanceFrontier::DomSetType NewBBSet = NewBBI->second;
NewBBSet.insert(Set.begin(), Set.end());

55
llvm/test/Transforms/LoopUnswitch/2007-08-01-LCSSA.ll Normal file
View File

@ -0,0 +1,55 @@
; RUN: llvm-as < %s | opt -loop-unswitch -instcombine -disable-output
%struct.ClassDef = type { %struct.QByteArray, %struct.QByteArray, %"struct.QList<ArgumentDef>", %"struct.QList<ArgumentDef>", i8, i8, %"struct.QList<ArgumentDef>", %"struct.QList<ArgumentDef>", %"struct.QList<ArgumentDef>", %"struct.QList<ArgumentDef>", %"struct.QList<ArgumentDef>", %"struct.QList<ArgumentDef>", %"struct.QMap<QByteArray,QByteArray>", %"struct.QList<ArgumentDef>", %"struct.QMap<QByteArray,QByteArray>", i32, i32 }
%struct.FILE = type { i32, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, %struct._IO_marker*, %struct.FILE*, i32, i32, i32, i16, i8, [1 x i8], i8*, i64, i8*, i8*, i8*, i8*, i32, i32, [40 x i8] }
%struct.Generator = type { %struct.FILE*, %struct.ClassDef*, %"struct.QList<ArgumentDef>", %struct.QByteArray, %"struct.QList<ArgumentDef>" }
%struct.QBasicAtomic = type { i32 }
%struct.QByteArray = type { %"struct.QByteArray::Data"* }
%"struct.QByteArray::Data" = type { %struct.QBasicAtomic, i32, i32, i8*, [1 x i8] }
%"struct.QList<ArgumentDef>" = type { %"struct.QList<ArgumentDef>::._19" }
%"struct.QList<ArgumentDef>::._19" = type { %struct.QListData }
%struct.QListData = type { %"struct.QListData::Data"* }
%"struct.QListData::Data" = type { %struct.QBasicAtomic, i32, i32, i32, i8, [1 x i8*] }
%"struct.QMap<QByteArray,QByteArray>" = type { %"struct.QMap<QByteArray,QByteArray>::._56" }
%"struct.QMap<QByteArray,QByteArray>::._56" = type { %struct.QMapData* }
%struct.QMapData = type { %struct.QMapData*, [12 x %struct.QMapData*], %struct.QBasicAtomic, i32, i32, i32, i8 }
%struct._IO_marker = type { %struct._IO_marker*, %struct.FILE*, i32 }
@.str9 = external constant [1 x i8] ; <[1 x i8]*> [#uses=1]
declare i32 @strcmp(i8*, i8*)
define i32 @_ZN9Generator6strregEPKc(%struct.Generator* %this, i8* %s) {
entry:
%s_addr.0 = select i1 false, i8* getelementptr ([1 x i8]* @.str9, i32 0, i32 0), i8* %s ; <i8*> [#uses=2]
%tmp122 = icmp eq i8* %s_addr.0, null ; <i1> [#uses=1]
br label %bb184
bb55: ; preds = %bb184
ret i32 0
bb88: ; preds = %bb184
br i1 %tmp122, label %bb154, label %bb128
bb128: ; preds = %bb88
%tmp138 = call i32 @strcmp( i8* null, i8* %s_addr.0 ) ; <i32> [#uses=1]
%iftmp.37.0.in4 = icmp eq i32 %tmp138, 0 ; <i1> [#uses=1]
br i1 %iftmp.37.0.in4, label %bb250, label %bb166
bb154: ; preds = %bb88
br i1 false, label %bb250, label %bb166
bb166: ; preds = %bb154, %bb128
%tmp175 = add i32 %idx.0, 1 ; <i32> [#uses=1]
%tmp177 = add i32 %tmp175, 0 ; <i32> [#uses=1]
%tmp181 = add i32 %tmp177, 0 ; <i32> [#uses=1]
%tmp183 = add i32 %i33.0, 1 ; <i32> [#uses=1]
br label %bb184
bb184: ; preds = %bb166, %entry
%i33.0 = phi i32 [ 0, %entry ], [ %tmp183, %bb166 ] ; <i32> [#uses=2]
%idx.0 = phi i32 [ 0, %entry ], [ %tmp181, %bb166 ] ; <i32> [#uses=2]
%tmp49 = icmp slt i32 %i33.0, 0 ; <i1> [#uses=1]
br i1 %tmp49, label %bb88, label %bb55
bb250: ; preds = %bb154, %bb128
ret i32 %idx.0
}