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Move code to update dominator information after basic block is split

Browse Source 
from LoopSimplify.cpp to Dominator.cpp

llvm-svn: 37689
This commit is contained in:
Devang Patel 2007-06-21 17:23:45 +00:00
parent 72af1305fb
commit bfb1c7192e
4 changed files with 216 additions and 202 deletions
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10
include/llvm/Analysis/Dominators.h
View File

@ -302,6 +302,11 @@ public:
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
}
/// splitBlock
/// BB is split and now it has one successor. Update dominator tree to
/// reflect this change.
void splitBlock(BasicBlock *BB);
private:
void calculate(Function& F);
DomTreeNode *getNodeForBlock(BasicBlock *BB);
@ -587,6 +592,11 @@ public:
AU.addRequired<DominatorTree>();
}
/// splitBlock
/// BB is split and now it has one successor. Update dominace frontier to
/// reflect this change.
void splitBlock(BasicBlock *BB);
private:
const DomSetType &calculate(const DominatorTree &DT,
const DomTreeNode *Node);

15
lib/Transforms/Utils/CodeExtractor.cpp
View File

@ -140,19 +140,8 @@ void CodeExtractor::severSplitPHINodes(BasicBlock *&Header) {
// Okay, update dominator sets. The blocks that dominate the new one are the
// blocks that dominate TIBB plus the new block itself.
if (DT) {
DomTreeNode *OPNode = DT->getNode(OldPred);
DomTreeNode *IDomNode = OPNode->getIDom();
BasicBlock* idom = IDomNode->getBlock();
DT->addNewBlock(NewBB, idom);
// Additionally, NewBB replaces OldPred as the immediate dominator of blocks
Function *F = Header->getParent();
for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I)
if (DT->getIDomBlock(I) == OldPred) {
DT->changeImmediateDominator(I, NewBB);
}
}
if (DT)
DT->splitBlock(NewBB);
// Okay, now we need to adjust the PHI nodes and any branches from within the
// region to go to the new header block instead of the old header block.

209
lib/Transforms/Utils/LoopSimplify.cpp
View File

@ -61,7 +61,7 @@ namespace {
// this is null.
AliasAnalysis *AA;
LoopInfo *LI;
DominatorTree *DT;
virtual bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
@ -85,9 +85,6 @@ namespace {
void PlaceSplitBlockCarefully(BasicBlock *NewBB,
std::vector<BasicBlock*> &SplitPreds,
Loop *L);
void UpdateDomInfoForRevectoredPreds(BasicBlock *NewBB,
std::vector<BasicBlock*> &PredBlocks);
};
char LoopSimplify::ID = 0;
@ -106,6 +103,7 @@ bool LoopSimplify::runOnFunction(Function &F) {
bool Changed = false;
LI = &getAnalysis<LoopInfo>();
AA = getAnalysisToUpdate<AliasAnalysis>();
DT = &getAnalysis<DominatorTree>();
// Check to see that no blocks (other than the header) in loops have
// predecessors that are not in loops. This is not valid for natural loops,
@ -341,6 +339,7 @@ BasicBlock *LoopSimplify::SplitBlockPredecessors(BasicBlock *BB,
PN->addIncoming(Constant::getNullValue(PN->getType()), NewBB);
}
}
return NewBB;
}
@ -371,8 +370,10 @@ void LoopSimplify::InsertPreheaderForLoop(Loop *L) {
if (Loop *Parent = L->getParentLoop())
Parent->addBasicBlockToLoop(NewBB, *LI);
UpdateDomInfoForRevectoredPreds(NewBB, OutsideBlocks);
DT->splitBlock(NewBB);
if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>())
DF->splitBlock(NewBB);
// Make sure that NewBB is put someplace intelligent, which doesn't mess up
// code layout too horribly.
PlaceSplitBlockCarefully(NewBB, OutsideBlocks, L);
@ -401,8 +402,11 @@ BasicBlock *LoopSimplify::RewriteLoopExitBlock(Loop *L, BasicBlock *Exit) {
if (SuccLoop)
SuccLoop->addBasicBlockToLoop(NewBB, *LI);
// Update dominator information (set, immdom, domtree, and domfrontier)
UpdateDomInfoForRevectoredPreds(NewBB, LoopBlocks);
// Update Dominator Information
DT->splitBlock(NewBB);
if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>())
DF->splitBlock(NewBB);
return NewBB;
}
@ -507,7 +511,6 @@ void LoopSimplify::PlaceSplitBlockCarefully(BasicBlock *NewBB,
/// created.
///
Loop *LoopSimplify::SeparateNestedLoop(Loop *L) {
DominatorTree *DT = getAnalysisToUpdate<DominatorTree>();
PHINode *PN = FindPHIToPartitionLoops(L, DT, AA);
if (PN == 0) return 0; // No known way to partition.
@ -523,8 +526,10 @@ Loop *LoopSimplify::SeparateNestedLoop(Loop *L) {
BasicBlock *Header = L->getHeader();
BasicBlock *NewBB = SplitBlockPredecessors(Header, ".outer", OuterLoopPreds);
// Update dominator information (set, immdom, domtree, and domfrontier)
UpdateDomInfoForRevectoredPreds(NewBB, OuterLoopPreds);
// Update dominator information
DT->splitBlock(NewBB);
if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>())
DF->splitBlock(NewBB);
// Make sure that NewBB is put someplace intelligent, which doesn't mess up
// code layout too horribly.
@ -677,184 +682,10 @@ void LoopSimplify::InsertUniqueBackedgeBlock(Loop *L) {
// loop and all parent loops.
L->addBasicBlockToLoop(BEBlock, *LI);
// Update dominator information (set, immdom, domtree, and domfrontier)
UpdateDomInfoForRevectoredPreds(BEBlock, BackedgeBlocks);
}
// Returns true if BasicBlock A dominates at least one block in vector B
// Helper function for UpdateDomInfoForRevectoredPreds
static bool BlockDominatesAny(BasicBlock* A, const std::vector<BasicBlock*>& B,
DominatorTree &DT) {
for (std::vector<BasicBlock*>::const_iterator BI = B.begin(), BE = B.end();
BI != BE; ++BI) {
if (DT.dominates(A, *BI))
return true;
}
return false;
}
/// UpdateDomInfoForRevectoredPreds - This method is used to update
/// dominator trees and dominance frontiers after a new block has
/// been added to the CFG.
///
/// This only supports the case when an existing block (known as "NewBBSucc"),
/// had some of its predecessors factored into a new basic block. This
/// transformation inserts a new basic block ("NewBB"), with a single
/// unconditional branch to NewBBSucc, and moves some predecessors of
/// "NewBBSucc" to now branch to NewBB. These predecessors are listed in
/// PredBlocks, even though they are the same as
/// pred_begin(NewBB)/pred_end(NewBB).
///
void LoopSimplify::UpdateDomInfoForRevectoredPreds(BasicBlock *NewBB,
std::vector<BasicBlock*> &PredBlocks) {
assert(!PredBlocks.empty() && "No predblocks??");
assert(NewBB->getTerminator()->getNumSuccessors() == 1
&& "NewBB should have a single successor!");
BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
DominatorTree &DT = getAnalysis<DominatorTree>();
// The newly inserted basic block will dominate existing basic blocks iff the
// PredBlocks dominate all of the non-pred blocks. If all predblocks dominate
// the non-pred blocks, then they all must be the same block!
//
bool NewBBDominatesNewBBSucc = true;
{
BasicBlock *OnePred = PredBlocks[0];
unsigned i = 1, e = PredBlocks.size();
for (i = 1; !DT.isReachableFromEntry(OnePred); ++i) {
assert(i != e && "Didn't find reachable pred?");
OnePred = PredBlocks[i];
}
for (; i != e; ++i)
if (PredBlocks[i] != OnePred && DT.isReachableFromEntry(OnePred)){
NewBBDominatesNewBBSucc = false;
break;
}
if (NewBBDominatesNewBBSucc)
for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
PI != E; ++PI)
if (*PI != NewBB && !DT.dominates(NewBBSucc, *PI)) {
NewBBDominatesNewBBSucc = false;
break;
}
}
// The other scenario where the new block can dominate its successors are when
// all predecessors of NewBBSucc that are not NewBB are dominated by NewBBSucc
// already.
if (!NewBBDominatesNewBBSucc) {
NewBBDominatesNewBBSucc = true;
for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
PI != E; ++PI)
if (*PI != NewBB && !DT.dominates(NewBBSucc, *PI)) {
NewBBDominatesNewBBSucc = false;
break;
}
}
// Update DominatorTree information if it is active.
// Find NewBB's immediate dominator and create new dominator tree node for NewBB.
BasicBlock *NewBBIDom = 0;
unsigned i = 0;
for (i = 0; i < PredBlocks.size(); ++i)
if (DT.isReachableFromEntry(PredBlocks[i])) {
NewBBIDom = PredBlocks[i];
break;
}
assert(i != PredBlocks.size() && "No reachable preds?");
for (i = i + 1; i < PredBlocks.size(); ++i) {
if (DT.isReachableFromEntry(PredBlocks[i]))
NewBBIDom = DT.findNearestCommonDominator(NewBBIDom, PredBlocks[i]);
}
assert(NewBBIDom && "No immediate dominator found??");
// Create the new dominator tree node... and set the idom of NewBB.
DomTreeNode *NewBBNode = DT.addNewBlock(NewBB, NewBBIDom);
// If NewBB strictly dominates other blocks, then it is now the immediate
// dominator of NewBBSucc. Update the dominator tree as appropriate.
if (NewBBDominatesNewBBSucc) {
DomTreeNode *NewBBSuccNode = DT.getNode(NewBBSucc);
DT.changeImmediateDominator(NewBBSuccNode, NewBBNode);
}
// Update dominance frontier information...
if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>()) {
// 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.
if (NewBBDominatesNewBBSucc) {
DominanceFrontier::iterator DFI = DF->find(PredBlocks[0]);
if (DFI != DF->end()) {
DominanceFrontier::DomSetType Set = DFI->second;
// Filter out stuff in Set that we do not dominate a predecessor of.
for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
E = Set.end(); SetI != E;) {
bool DominatesPred = false;
for (pred_iterator PI = pred_begin(*SetI), E = pred_end(*SetI);
PI != E; ++PI)
if (DT.dominates(NewBB, *PI))
DominatesPred = true;
if (!DominatesPred)
Set.erase(SetI++);
else
++SetI;
}
DF->addBasicBlock(NewBB, Set);
}
} else {
// DF(NewBB) is {NewBBSucc} because NewBB does not strictly dominate
// NewBBSucc, but it does dominate itself (and there is an edge (NewBB ->
// NewBBSucc)). NewBBSucc is the single successor of NewBB.
DominanceFrontier::DomSetType NewDFSet;
NewDFSet.insert(NewBBSucc);
DF->addBasicBlock(NewBB, NewDFSet);
}
// Now we must loop over all of the dominance frontiers in the function,
// replacing occurrences of NewBBSucc with NewBB in some cases. All
// blocks that dominate a block in PredBlocks and contained NewBBSucc in
// their dominance frontier must be updated to contain NewBB instead.
//
for (Function::iterator FI = NewBB->getParent()->begin(),
FE = NewBB->getParent()->end(); FI != FE; ++FI) {
DominanceFrontier::iterator DFI = DF->find(FI);
if (DFI == DF->end()) continue; // unreachable block.
// Only consider dominators of NewBBSucc
if (!DFI->second.count(NewBBSucc)) continue;
if (BlockDominatesAny(FI, PredBlocks, DT)) {
// If NewBBSucc should not stay in our dominator frontier, remove it.
// We remove it unless there is a predecessor of NewBBSucc that we
// dominate, but we don't strictly dominate NewBBSucc.
bool ShouldRemove = true;
if ((BasicBlock*)FI == NewBBSucc
|| !DT.dominates(FI, NewBBSucc)) {
// Okay, we know that PredDom does not strictly dominate NewBBSucc.
// Check to see if it dominates any predecessors of NewBBSucc.
for (pred_iterator PI = pred_begin(NewBBSucc),
E = pred_end(NewBBSucc); PI != E; ++PI)
if (DT.dominates(FI, *PI)) {
ShouldRemove = false;
break;
}
if (ShouldRemove)
DF->removeFromFrontier(DFI, NewBBSucc);
DF->addToFrontier(DFI, NewBB);
break;
}
}
}
}
// Update dominator information
DT->splitBlock(BEBlock);
if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>())
DF->splitBlock(BEBlock);
}

184
lib/VMCore/Dominators.cpp
View File

@ -63,6 +63,89 @@ char DominatorTree::ID = 0;
static RegisterPass<DominatorTree>
E("domtree", "Dominator Tree Construction", true);
// NewBB is split and now it has one successor. Update dominator tree to
// reflect this change.
void DominatorTree::splitBlock(BasicBlock *NewBB) {
assert(NewBB->getTerminator()->getNumSuccessors() == 1
&& "NewBB should have a single successor!");
BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
std::vector<BasicBlock*> PredBlocks;
for (pred_iterator PI = pred_begin(NewBB), PE = pred_end(NewBB);
PI != PE; ++PI)
PredBlocks.push_back(*PI);
assert(!PredBlocks.empty() && "No predblocks??");
// The newly inserted basic block will dominate existing basic blocks iff the
// PredBlocks dominate all of the non-pred blocks. If all predblocks dominate
// the non-pred blocks, then they all must be the same block!
//
bool NewBBDominatesNewBBSucc = true;
{
BasicBlock *OnePred = PredBlocks[0];
unsigned i = 1, e = PredBlocks.size();
for (i = 1; !isReachableFromEntry(OnePred); ++i) {
assert(i != e && "Didn't find reachable pred?");
OnePred = PredBlocks[i];
}
for (; i != e; ++i)
if (PredBlocks[i] != OnePred && isReachableFromEntry(OnePred)){
NewBBDominatesNewBBSucc = false;
break;
}
if (NewBBDominatesNewBBSucc)
for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
PI != E; ++PI)
if (*PI != NewBB && !dominates(NewBBSucc, *PI)) {
NewBBDominatesNewBBSucc = false;
break;
}
}
// The other scenario where the new block can dominate its successors are when
// all predecessors of NewBBSucc that are not NewBB are dominated by NewBBSucc
// already.
if (!NewBBDominatesNewBBSucc) {
NewBBDominatesNewBBSucc = true;
for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
PI != E; ++PI)
if (*PI != NewBB && !dominates(NewBBSucc, *PI)) {
NewBBDominatesNewBBSucc = false;
break;
}
}
// Find NewBB's immediate dominator and create new dominator tree node for NewBB.
BasicBlock *NewBBIDom = 0;
unsigned i = 0;
for (i = 0; i < PredBlocks.size(); ++i)
if (isReachableFromEntry(PredBlocks[i])) {
NewBBIDom = PredBlocks[i];
break;
}
assert(i != PredBlocks.size() && "No reachable preds?");
for (i = i + 1; i < PredBlocks.size(); ++i) {
if (isReachableFromEntry(PredBlocks[i]))
NewBBIDom = findNearestCommonDominator(NewBBIDom, PredBlocks[i]);
}
assert(NewBBIDom && "No immediate dominator found??");
// Create the new dominator tree node... and set the idom of NewBB.
DomTreeNode *NewBBNode = addNewBlock(NewBB, NewBBIDom);
// If NewBB strictly dominates other blocks, then it is now the immediate
// dominator of NewBBSucc. Update the dominator tree as appropriate.
if (NewBBDominatesNewBBSucc) {
DomTreeNode *NewBBSuccNode = getNode(NewBBSucc);
changeImmediateDominator(NewBBSuccNode, NewBBNode);
}
}
unsigned DominatorTree::DFSPass(BasicBlock *V, InfoRec &VInfo,
unsigned N) {
// This is more understandable as a recursive algorithm, but we can't use the
@ -520,6 +603,107 @@ char DominanceFrontier::ID = 0;
static RegisterPass<DominanceFrontier>
G("domfrontier", "Dominance Frontier Construction", true);
// NewBB is split and now it has one successor. Update dominace frontier to
// reflect this change.
void DominanceFrontier::splitBlock(BasicBlock *NewBB) {
assert(NewBB->getTerminator()->getNumSuccessors() == 1
&& "NewBB should have a single successor!");
BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
std::vector<BasicBlock*> PredBlocks;
for (pred_iterator PI = pred_begin(NewBB), PE = pred_end(NewBB);
PI != PE; ++PI)
PredBlocks.push_back(*PI);
assert(!PredBlocks.empty() && "No predblocks??");
DominatorTree &DT = getAnalysis<DominatorTree>();
bool NewBBDominatesNewBBSucc = true;
if (!DT.dominates(NewBB, NewBBSucc))
NewBBDominatesNewBBSucc = false;
// 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.
if (NewBBDominatesNewBBSucc) {
DominanceFrontier::iterator DFI = find(PredBlocks[0]);
if (DFI != end()) {
DominanceFrontier::DomSetType Set = DFI->second;
// Filter out stuff in Set that we do not dominate a predecessor of.
for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
E = Set.end(); SetI != E;) {
bool DominatesPred = false;
for (pred_iterator PI = pred_begin(*SetI), E = pred_end(*SetI);
PI != E; ++PI)
if (DT.dominates(NewBB, *PI))
DominatesPred = true;
if (!DominatesPred)
Set.erase(SetI++);
else
++SetI;
}
addBasicBlock(NewBB, Set);
}
} else {
// DF(NewBB) is {NewBBSucc} because NewBB does not strictly dominate
// NewBBSucc, but it does dominate itself (and there is an edge (NewBB ->
// NewBBSucc)). NewBBSucc is the single successor of NewBB.
DominanceFrontier::DomSetType NewDFSet;
NewDFSet.insert(NewBBSucc);
addBasicBlock(NewBB, NewDFSet);
}
// Now we must loop over all of the dominance frontiers in the function,
// replacing occurrences of NewBBSucc with NewBB in some cases. All
// blocks that dominate a block in PredBlocks and contained NewBBSucc in
// their dominance frontier must be updated to contain NewBB instead.
//
for (Function::iterator FI = NewBB->getParent()->begin(),
FE = NewBB->getParent()->end(); FI != FE; ++FI) {
DominanceFrontier::iterator DFI = find(FI);
if (DFI == end()) continue; // unreachable block.
// Only consider dominators of NewBBSucc
if (!DFI->second.count(NewBBSucc)) continue;
bool BlockDominatesAny = false;
for (std::vector<BasicBlock*>::const_iterator BI = PredBlocks.begin(),
BE = PredBlocks.end(); BI != BE; ++BI) {
if (DT.dominates(FI, *BI)) {
BlockDominatesAny = true;
break;
}
}
if (BlockDominatesAny) {
// If NewBBSucc should not stay in our dominator frontier, remove it.
// We remove it unless there is a predecessor of NewBBSucc that we
// dominate, but we don't strictly dominate NewBBSucc.
bool ShouldRemove = true;
if ((BasicBlock*)FI == NewBBSucc
|| !DT.dominates(FI, NewBBSucc)) {
// Okay, we know that PredDom does not strictly dominate NewBBSucc.
// Check to see if it dominates any predecessors of NewBBSucc.
for (pred_iterator PI = pred_begin(NewBBSucc),
E = pred_end(NewBBSucc); PI != E; ++PI)
if (DT.dominates(FI, *PI)) {
ShouldRemove = false;
break;
}
if (ShouldRemove)
removeFromFrontier(DFI, NewBBSucc);
addToFrontier(DFI, NewBB);
break;
}
}
}
}
namespace {
class DFCalculateWorkObject {
public: