//
// The LLVM Compiler Infrastructure
//
-// This file was developed by Devang Patel and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "loop-rotation"
-
+#define DEBUG_TYPE "loop-rotate"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/SmallVector.h"
-#include <map>
-
using namespace llvm;
#define MAX_HEADER_SIZE 16
STATISTIC(NumRotated, "Number of loops rotated");
namespace {
- cl::opt<unsigned>
- RotateThreshold("rotate-threshold", cl::init(200), cl::Hidden,
- cl::desc("The cut-off point for loop rotating"));
-
- class VISIBILITY_HIDDEN InsnReplacementData {
+ class VISIBILITY_HIDDEN RenameData {
public:
- InsnReplacementData(Instruction *O, Instruction *P, Instruction *H)
- : Original(O), PreHeader(P), Header(H) {}
+ RenameData(Instruction *O, Value *P, Instruction *H)
+ : Original(O), PreHeader(P), Header(H) { }
public:
Instruction *Original; // Original instruction
- Instruction *PreHeader; // New pre-header replacement
+ Value *PreHeader; // Original pre-header replacement
Instruction *Header; // New header replacement
};
-
+
class VISIBILITY_HIDDEN LoopRotate : public LoopPass {
public:
+ static char ID; // Pass ID, replacement for typeid
+ LoopRotate() : LoopPass(&ID) {}
+
+ // Rotate Loop L as many times as possible. Return true if
+ // loop is rotated at least once.
bool runOnLoop(Loop *L, LPPassManager &LPM);
+
+ // LCSSA form makes instruction renaming easier.
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequiredID(LoopSimplifyID);
+ AU.addPreservedID(LoopSimplifyID);
AU.addRequiredID(LCSSAID);
AU.addPreservedID(LCSSAID);
- //AU.addRequired<LoopInfo>();
- //AU.addPreserved<LoopInfo>();
+ AU.addPreserved<ScalarEvolution>();
+ AU.addPreserved<LoopInfo>();
+ AU.addPreserved<DominatorTree>();
+ AU.addPreserved<DominanceFrontier>();
}
// Helper functions
/// Make sure all Exit block PHINodes have required incoming values.
/// If incoming value is constant or defined outside the loop then
- /// PHINode may not have an entry for new pre-header.
+ /// PHINode may not have an entry for original pre-header.
void updateExitBlock();
/// Return true if this instruction is used outside original header.
/// Find Replacement information for instruction. Return NULL if it is
/// not available.
- InsnReplacementData *findReplacementData(Instruction *I);
+ const RenameData *findReplacementData(Instruction *I);
+
+ /// After loop rotation, loop pre-header has multiple sucessors.
+ /// Insert one forwarding basic block to ensure that loop pre-header
+ /// has only one successor.
+ void preserveCanonicalLoopForm(LPPassManager &LPM);
private:
BasicBlock *OrigPreHeader;
BasicBlock *OrigLatch;
BasicBlock *NewHeader;
- BasicBlock *NewPreHeader;
BasicBlock *Exit;
-
- SmallVector<InsnReplacementData, MAX_HEADER_SIZE> RD;
+ LPPassManager *LPM_Ptr;
+ SmallVector<RenameData, MAX_HEADER_SIZE> LoopHeaderInfo;
};
-
- RegisterPass<LoopRotate> X ("loop-rotate", "Rotate Loops");
}
+
+char LoopRotate::ID = 0;
+static RegisterPass<LoopRotate> X("loop-rotate", "Rotate Loops");
-LoopPass *llvm::createLoopRotatePass() { return new LoopRotate(); }
+Pass *llvm::createLoopRotatePass() { return new LoopRotate(); }
+/// Rotate Loop L as many times as possible. Return true if
+/// loop is rotated at least once.
bool LoopRotate::runOnLoop(Loop *Lp, LPPassManager &LPM) {
-
+
bool RotatedOneLoop = false;
initialize();
+ LPM_Ptr = &LPM;
// One loop can be rotated multiple times.
while (rotateLoop(Lp,LPM)) {
return RotatedOneLoop;
}
+/// Rotate loop LP. Return true if the loop is rotated.
bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
-
L = Lp;
- if ( NumRotated >= RotateThreshold)
- return false;
OrigHeader = L->getHeader();
OrigPreHeader = L->getLoopPreheader();
OrigLatch = L->getLoopLatch();
// If loop has only one block then there is not much to rotate.
- if (L->getBlocks().size() <= 1)
+ if (L->getBlocks().size() == 1)
return false;
- if (!OrigHeader || !OrigLatch || !OrigPreHeader)
- return false;
+ assert(OrigHeader && OrigLatch && OrigPreHeader &&
+ "Loop is not in canonical form");
// If loop header is not one of the loop exit block then
// either this loop is already rotated or it is not
BranchInst *BI = dyn_cast<BranchInst>(OrigHeader->getTerminator());
if (!BI)
return false;
+ assert(BI->isConditional() && "Branch Instruction is not conditional");
- std::vector<BasicBlock *> ExitBlocks;
+ // Updating PHInodes in loops with multiple exits adds complexity.
+ // Keep it simple, and restrict loop rotation to loops with one exit only.
+ // In future, lift this restriction and support for multiple exits if
+ // required.
+ SmallVector<BasicBlock*, 8> ExitBlocks;
L->getExitBlocks(ExitBlocks);
if (ExitBlocks.size() > 1)
return false;
- // Find new Loop header. NewHeader is a Header's one and only successor
- // that is inside loop. Header's all other successors are out side the
- // loop. Otherwise loop is not suitable for rotation.
- for (unsigned index = 0; index < BI->getNumSuccessors(); ++index) {
- BasicBlock *S = BI->getSuccessor(index);
- if (L->contains(S)) {
- if (!NewHeader)
- NewHeader = S;
- else
- // Loop Header has two successors inside loop. This loop is
- // not suitable for rotation.
- return false;
- } else {
- if (!Exit)
- Exit = S;
- else
- // Loop has multiple exits.
- return false;
- }
- }
- assert (NewHeader && "Unable to determine new loop header");
-
// Check size of original header and reject
// loop if it is very big.
- if (OrigHeader->getInstList().size() > MAX_HEADER_SIZE)
+ if (OrigHeader->size() > MAX_HEADER_SIZE)
return false;
// Now, this loop is suitable for rotation.
- // Copy Prepare PHI nodes and other instructions from original header
- // into new pre-header. Unlike original header, new pre-header is
- // not a member of loop. New pre-header has only one predecessor,
- // that is original loop pre-header.
+ // Find new Loop header. NewHeader is a Header's one and only successor
+ // that is inside loop. Header's other successor is outside the
+ // loop. Otherwise loop is not suitable for rotation.
+ Exit = BI->getSuccessor(0);
+ NewHeader = BI->getSuccessor(1);
+ if (L->contains(Exit))
+ std::swap(Exit, NewHeader);
+ assert(NewHeader && "Unable to determine new loop header");
+ assert(L->contains(NewHeader) && !L->contains(Exit) &&
+ "Unable to determine loop header and exit blocks");
+
+ // This code assumes that new header has exactly one predecessor. Remove any
+ // single entry PHI nodes in it.
+ assert(NewHeader->getSinglePredecessor() &&
+ "New header doesn't have one pred!");
+ FoldSingleEntryPHINodes(NewHeader);
+
+ // Copy PHI nodes and other instructions from original header
+ // into original pre-header. Unlike original header, original pre-header is
+ // not a member of loop.
//
// New loop header is one and only successor of original header that
// is inside the loop. All other original header successors are outside
// the loop. Copy PHI Nodes from original header into new loop header.
- // Add second incoming value, from new loop pre-header into these phi
+ // Add second incoming value, from original loop pre-header into these phi
// nodes. If a value defined in original header is used outside original
// header then new loop header will need new phi nodes with two incoming
// values, one definition from original header and second definition is
- // from new loop pre-header (which is a clone of original header definition).
-
- NewPreHeader = new BasicBlock("bb.nph", OrigHeader->getParent(), OrigHeader);
- for (BasicBlock::iterator I = OrigHeader->begin(), E = OrigHeader->end();
- I != E; ++I) {
- Instruction *In = I;
-
- if (PHINode *PN = dyn_cast<PHINode>(I)) {
-
- // Create new PHI node with one value incoming from OrigPreHeader.
- // NewPreHeader has only one predecessor, OrigPreHeader.
- PHINode *NPH = new PHINode(In->getType(), In->getName());
- NPH->addIncoming(PN->getIncomingValueForBlock(OrigPreHeader),
- OrigPreHeader);
- NewPreHeader->getInstList().push_back(NPH);
-
- // Create new PHI node with two incoming values for NewHeader.
- // One incoming value is from OrigLatch (through OrigHeader) and
- // second incoming value is from NewPreHeader.
- PHINode *NH = new PHINode(In->getType(), In->getName());
- NH->addIncoming(PN->getIncomingValueForBlock(OrigLatch), OrigHeader);
- NH->addIncoming(NPH, NewPreHeader);
- NewHeader->getInstList().push_front(NH);
-
- RD.push_back(InsnReplacementData(In, NPH, NH));
- } else {
- // This is not a PHI instruction. Insert its clone into NewPreHeader.
- // If this instruction is using a value from same basic block then
- // update it to use value from cloned instruction.
- Instruction *C = In->clone();
- C->setName(In->getName());
- NewPreHeader->getInstList().push_back(C);
-
- // If this instruction is used outside this basic block then
- // create new PHINode for this instruction.
- Instruction *NewHeaderReplacement = NULL;
- if (usedOutsideOriginalHeader(In)) {
- PHINode *PN = new PHINode(In->getType(), In->getName());
- PN->addIncoming(In, OrigHeader);
- PN->addIncoming(C, NewPreHeader);
- NewHeader->getInstList().push_front(PN);
- NewHeaderReplacement = PN;
- }
- RD.push_back(InsnReplacementData(In, C, NewHeaderReplacement));
- }
+ // from original loop pre-header.
+
+ // Remove terminator from Original pre-header. Original pre-header will
+ // receive a clone of original header terminator as a new terminator.
+ OrigPreHeader->getInstList().pop_back();
+ BasicBlock::iterator I = OrigHeader->begin(), E = OrigHeader->end();
+ PHINode *PN = 0;
+ for (; (PN = dyn_cast<PHINode>(I)); ++I) {
+ // PHI nodes are not copied into original pre-header. Instead their values
+ // are directly propagated.
+ Value *NPV = PN->getIncomingValueForBlock(OrigPreHeader);
+
+ // Create new PHI node with two incoming values for NewHeader.
+ // One incoming value is from OrigLatch (through OrigHeader) and
+ // second incoming value is from original pre-header.
+ PHINode *NH = PHINode::Create(PN->getType(), PN->getName(),
+ NewHeader->begin());
+ NH->addIncoming(PN->getIncomingValueForBlock(OrigLatch), OrigHeader);
+ NH->addIncoming(NPV, OrigPreHeader);
+
+ // "In" can be replaced by NH at various places.
+ LoopHeaderInfo.push_back(RenameData(PN, NPV, NH));
}
- // Update new pre-header.
- // Rename values that are defined in original header to reflects values
- // defined in new pre-header.
- for (SmallVector<InsnReplacementData, MAX_HEADER_SIZE>::iterator
- I = RD.begin(), E = RD.end(); I != E; ++I) {
-
- InsnReplacementData IRD = (*I);
- Instruction *In = IRD.Original;
- Instruction *C = IRD.PreHeader;
+ // Now, handle non-phi instructions.
+ for (; I != E; ++I) {
+ Instruction *In = I;
+ assert(!isa<PHINode>(In) && "PHINode is not expected here");
- if (C->getParent() != NewPreHeader)
- continue;
-
- // PHINodes uses value from pre-header predecessors.
- if (isa<PHINode>(In))
- continue;
+ // This is not a PHI instruction. Insert its clone into original pre-header.
+ // If this instruction is using a value from same basic block then
+ // update it to use value from cloned instruction.
+ Instruction *C = In->clone();
+ C->setName(In->getName());
+ OrigPreHeader->getInstList().push_back(C);
+
+ for (unsigned opi = 0, e = In->getNumOperands(); opi != e; ++opi) {
+ Instruction *OpInsn = dyn_cast<Instruction>(In->getOperand(opi));
+ if (!OpInsn) continue; // Ignore non-instruction values.
+ if (const RenameData *D = findReplacementData(OpInsn))
+ C->setOperand(opi, D->PreHeader);
+ }
- for (unsigned opi = 0; opi < In->getNumOperands(); ++opi) {
- if (Instruction *OpPhi = dyn_cast<PHINode>(In->getOperand(opi))) {
- if (InsnReplacementData *D = findReplacementData(OpPhi))
- C->setOperand(opi, D->PreHeader);
- }
- else if (Instruction *OpInsn =
- dyn_cast<Instruction>(In->getOperand(opi))) {
- if (InsnReplacementData *D = findReplacementData(OpInsn))
- C->setOperand(opi, D->PreHeader);
- }
+ // If this instruction is used outside this basic block then
+ // create new PHINode for this instruction.
+ Instruction *NewHeaderReplacement = NULL;
+ if (usedOutsideOriginalHeader(In)) {
+ PHINode *PN = PHINode::Create(In->getType(), In->getName(),
+ NewHeader->begin());
+ PN->addIncoming(In, OrigHeader);
+ PN->addIncoming(C, OrigPreHeader);
+ NewHeaderReplacement = PN;
}
+ LoopHeaderInfo.push_back(RenameData(In, C, NewHeaderReplacement));
}
// Rename uses of original header instructions to reflect their new
- // definitions (either from new pre-header node or from newly created
+ // definitions (either from original pre-header node or from newly created
// new header PHINodes.
//
// Original header instructions are used in
//
// If instruction is used in non-phi instructions then it is using
// defintion from original heder iteself. Do not replace this use
- // with definition from new header or new pre-header.
+ // with definition from new header or original pre-header.
//
// If instruction is used in phi node then it is an incoming
// value. Rename its use to reflect new definition from new-preheader
// 2) Inside loop but not in original header
//
// Replace this use to reflect definition from new header.
- for (SmallVector<InsnReplacementData, MAX_HEADER_SIZE>::iterator
- I = RD.begin(), E = RD.end(); I != E; ++I) {
+ for (unsigned LHI = 0, LHI_E = LoopHeaderInfo.size(); LHI != LHI_E; ++LHI) {
+ const RenameData &ILoopHeaderInfo = LoopHeaderInfo[LHI];
- InsnReplacementData IRD = (*I);
- if (!IRD.Header)
+ if (!ILoopHeaderInfo.Header)
continue;
- Instruction *OldPhi = IRD.Original;
- Instruction *NewPhi = IRD.Header;
+ Instruction *OldPhi = ILoopHeaderInfo.Original;
+ Instruction *NewPhi = ILoopHeaderInfo.Header;
// Before replacing uses, collect them first, so that iterator is
// not invalidated.
SmallVector<Instruction *, 16> AllUses;
for (Value::use_iterator UI = OldPhi->use_begin(), UE = OldPhi->use_end();
- UI != UE; ++UI ) {
- Instruction *U = cast<Instruction>(UI);
- AllUses.push_back(U);
- }
+ UI != UE; ++UI)
+ AllUses.push_back(cast<Instruction>(UI));
for (SmallVector<Instruction *, 16>::iterator UI = AllUses.begin(),
UE = AllUses.end(); UI != UE; ++UI) {
// Used inside original header
if (Parent == OrigHeader) {
// Do not rename uses inside original header non-phi instructions.
- if (!isa<PHINode>(U))
- continue;
PHINode *PU = dyn_cast<PHINode>(U);
+ if (!PU)
+ continue;
+
// Do not rename uses inside original header phi nodes, if the
// incoming value is for new header.
if (PU->getBasicBlockIndex(NewHeader) != -1
&& PU->getIncomingValueForBlock(NewHeader) == U)
continue;
-
+
U->replaceUsesOfWith(OldPhi, NewPhi);
continue;
}
// Used inside loop, but not in original header.
if (L->contains(U->getParent())) {
- if (U != NewPhi )
+ if (U != NewPhi)
U->replaceUsesOfWith(OldPhi, NewPhi);
continue;
}
-
- // Used inside Exit Block. Since we are in LCSSA form, U must be PHINode.
- assert ( U->getParent() == Exit && "Need to propagate new PHI into Exit blocks");
- assert (isa<PHINode>(U) && "Use in Exit Block that is not PHINode");
-
- PHINode *UPhi = cast<PHINode>(U);
-
- // UPhi already has one incoming argument from original header.
- // Add second incoming argument from new Pre header.
- UPhi->addIncoming(IRD.PreHeader, NewPreHeader);
+ // Used inside Exit Block. Since we are in LCSSA form, U must be PHINode.
+ if (U->getParent() == Exit) {
+ assert(isa<PHINode>(U) && "Use in Exit Block that is not PHINode");
+
+ PHINode *UPhi = cast<PHINode>(U);
+ // UPhi already has one incoming argument from original header.
+ // Add second incoming argument from new Pre header.
+ UPhi->addIncoming(ILoopHeaderInfo.PreHeader, OrigPreHeader);
+ } else {
+ // Used outside Exit block. Create a new PHI node from exit block
+ // to receive value from ne new header ane pre header.
+ PHINode *PN = PHINode::Create(U->getType(), U->getName(),
+ Exit->begin());
+ PN->addIncoming(ILoopHeaderInfo.PreHeader, OrigPreHeader);
+ PN->addIncoming(OldPhi, OrigHeader);
+ U->replaceUsesOfWith(OldPhi, PN);
+ }
}
}
// Removing incoming branch from loop preheader to original header.
// Now original header is inside the loop.
- OrigHeader->removePredecessor(OrigPreHeader);
-
- // Establish NewPreHeader as loop preheader. Add unconditional branch
- // from original loop pre-header to new loop pre-header. Add NewPreHEader
- // in loop nest.
- BranchInst *PH_BI = cast<BranchInst>(OrigPreHeader->getTerminator());
- PH_BI->setSuccessor(0, NewPreHeader);
- LoopInfo &LI = LPM.getAnalysis<LoopInfo>();
- if (Loop *PL = LI.getLoopFor(OrigPreHeader))
- PL->addBasicBlockToLoop(NewPreHeader, LI);
+ for (BasicBlock::iterator I = OrigHeader->begin(), E = OrigHeader->end();
+ I != E; ++I)
+ if (PHINode *PN = dyn_cast<PHINode>(I))
+ PN->removeIncomingValue(OrigPreHeader);
// Make NewHeader as the new header for the loop.
L->moveToHeader(NewHeader);
+ preserveCanonicalLoopForm(LPM);
+
NumRotated++;
return true;
}
-
/// Make sure all Exit block PHINodes have required incoming values.
/// If incoming value is constant or defined outside the loop then
-/// PHINode may not have an entry for new pre-header.
+/// PHINode may not have an entry for original pre-header.
void LoopRotate::updateExitBlock() {
for (BasicBlock::iterator I = Exit->begin(), E = Exit->end();
I != E; ++I) {
- if (!isa<PHINode>(I))
+ PHINode *PN = dyn_cast<PHINode>(I);
+ if (!PN)
break;
- PHINode *PN = dyn_cast<PHINode>(I);
+ // There is already one incoming value from original pre-header block.
+ if (PN->getBasicBlockIndex(OrigPreHeader) != -1)
+ continue;
- if (PN->getBasicBlockIndex(NewPreHeader) == -1) {
- Value *V = PN->getIncomingValueForBlock(OrigHeader);
- if (isa<Constant>(V))
- PN->addIncoming(V, NewPreHeader);
- else {
- InsnReplacementData *IRD = findReplacementData(cast<Instruction>(V));
- assert (IRD && IRD->PreHeader && "Missing New Preheader Instruction");
- PN->addIncoming(IRD->PreHeader, NewPreHeader);
- }
+ const RenameData *ILoopHeaderInfo;
+ Value *V = PN->getIncomingValueForBlock(OrigHeader);
+ if (isa<Instruction>(V) &&
+ (ILoopHeaderInfo = findReplacementData(cast<Instruction>(V)))) {
+ assert(ILoopHeaderInfo->PreHeader && "Missing New Preheader Instruction");
+ PN->addIncoming(ILoopHeaderInfo->PreHeader, OrigPreHeader);
+ } else {
+ PN->addIncoming(V, OrigPreHeader);
}
}
}
-
/// Initialize local data
void LoopRotate::initialize() {
L = NULL;
OrigHeader = NULL;
OrigPreHeader = NULL;
NewHeader = NULL;
- NewPreHeader = NULL;
Exit = NULL;
- RD.clear();
+ LoopHeaderInfo.clear();
}
-/// Return true if this instruction is used outside original header.
+/// Return true if this instruction is used by any instructions in the loop that
+/// aren't in original header.
bool LoopRotate::usedOutsideOriginalHeader(Instruction *In) {
-
for (Value::use_iterator UI = In->use_begin(), UE = In->use_end();
UI != UE; ++UI) {
- Instruction *U = cast<Instruction>(UI);
- if (U->getParent() != OrigHeader) {
- if (L->contains(U->getParent()))
- return true;
- }
+ BasicBlock *UserBB = cast<Instruction>(UI)->getParent();
+ if (UserBB != OrigHeader && L->contains(UserBB))
+ return true;
}
return false;
/// Find Replacement information for instruction. Return NULL if it is
/// not available.
-InsnReplacementData *LoopRotate::findReplacementData(Instruction *In) {
-
- // Since RD is small, linear walk is OK.
- for (SmallVector<InsnReplacementData, MAX_HEADER_SIZE>::iterator
- I = RD.begin(), E = RD.end(); I != E; ++I)
- if ((*I).Original == In)
- return &(*I);
+const RenameData *LoopRotate::findReplacementData(Instruction *In) {
+ // Since LoopHeaderInfo is small, linear walk is OK.
+ for (unsigned LHI = 0, LHI_E = LoopHeaderInfo.size(); LHI != LHI_E; ++LHI) {
+ const RenameData &ILoopHeaderInfo = LoopHeaderInfo[LHI];
+ if (ILoopHeaderInfo.Original == In)
+ return &ILoopHeaderInfo;
+ }
return NULL;
}
+
+/// After loop rotation, loop pre-header has multiple sucessors.
+/// Insert one forwarding basic block to ensure that loop pre-header
+/// has only one successor.
+void LoopRotate::preserveCanonicalLoopForm(LPPassManager &LPM) {
+
+ // Right now original pre-header has two successors, new header and
+ // exit block. Insert new block between original pre-header and
+ // new header such that loop's new pre-header has only one successor.
+ BasicBlock *NewPreHeader = BasicBlock::Create("bb.nph",
+ OrigHeader->getParent(),
+ NewHeader);
+ LoopInfo &LI = LPM.getAnalysis<LoopInfo>();
+ if (Loop *PL = LI.getLoopFor(OrigPreHeader))
+ PL->addBasicBlockToLoop(NewPreHeader, LI.getBase());
+ BranchInst::Create(NewHeader, NewPreHeader);
+
+ BranchInst *OrigPH_BI = cast<BranchInst>(OrigPreHeader->getTerminator());
+ if (OrigPH_BI->getSuccessor(0) == NewHeader)
+ OrigPH_BI->setSuccessor(0, NewPreHeader);
+ else {
+ assert(OrigPH_BI->getSuccessor(1) == NewHeader &&
+ "Unexpected original pre-header terminator");
+ OrigPH_BI->setSuccessor(1, NewPreHeader);
+ }
+
+ for (BasicBlock::iterator I = NewHeader->begin(), E = NewHeader->end();
+ I != E; ++I) {
+ PHINode *PN = dyn_cast<PHINode>(I);
+ if (!PN)
+ break;
+
+ int index = PN->getBasicBlockIndex(OrigPreHeader);
+ assert(index != -1 && "Expected incoming value from Original PreHeader");
+ PN->setIncomingBlock(index, NewPreHeader);
+ assert(PN->getBasicBlockIndex(OrigPreHeader) == -1 &&
+ "Expected only one incoming value from Original PreHeader");
+ }
+
+ if (DominatorTree *DT = getAnalysisToUpdate<DominatorTree>()) {
+ DT->addNewBlock(NewPreHeader, OrigPreHeader);
+ DT->changeImmediateDominator(L->getHeader(), NewPreHeader);
+ DT->changeImmediateDominator(Exit, OrigPreHeader);
+ for (Loop::block_iterator BI = L->block_begin(), BE = L->block_end();
+ BI != BE; ++BI) {
+ BasicBlock *B = *BI;
+ if (L->getHeader() != B) {
+ DomTreeNode *Node = DT->getNode(B);
+ if (Node && Node->getBlock() == OrigHeader)
+ DT->changeImmediateDominator(*BI, L->getHeader());
+ }
+ }
+ DT->changeImmediateDominator(OrigHeader, OrigLatch);
+ }
+
+ if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>()) {
+ // New Preheader's dominance frontier is Exit block.
+ DominanceFrontier::DomSetType NewPHSet;
+ NewPHSet.insert(Exit);
+ DF->addBasicBlock(NewPreHeader, NewPHSet);
+
+ // New Header's dominance frontier now includes itself and Exit block
+ DominanceFrontier::iterator HeadI = DF->find(L->getHeader());
+ if (HeadI != DF->end()) {
+ DominanceFrontier::DomSetType & HeaderSet = HeadI->second;
+ HeaderSet.clear();
+ HeaderSet.insert(L->getHeader());
+ HeaderSet.insert(Exit);
+ } else {
+ DominanceFrontier::DomSetType HeaderSet;
+ HeaderSet.insert(L->getHeader());
+ HeaderSet.insert(Exit);
+ DF->addBasicBlock(L->getHeader(), HeaderSet);
+ }
+
+ // Original header (new Loop Latch)'s dominance frontier is Exit.
+ DominanceFrontier::iterator LatchI = DF->find(L->getLoopLatch());
+ if (LatchI != DF->end()) {
+ DominanceFrontier::DomSetType &LatchSet = LatchI->second;
+ LatchSet = LatchI->second;
+ LatchSet.clear();
+ LatchSet.insert(Exit);
+ } else {
+ DominanceFrontier::DomSetType LatchSet;
+ LatchSet.insert(Exit);
+ DF->addBasicBlock(L->getHeader(), LatchSet);
+ }
+
+ // If a loop block dominates new loop latch then its frontier is
+ // new header and Exit.
+ BasicBlock *NewLatch = L->getLoopLatch();
+ DominatorTree *DT = getAnalysisToUpdate<DominatorTree>();
+ for (Loop::block_iterator BI = L->block_begin(), BE = L->block_end();
+ BI != BE; ++BI) {
+ BasicBlock *B = *BI;
+ if (DT->dominates(B, NewLatch)) {
+ DominanceFrontier::iterator BDFI = DF->find(B);
+ if (BDFI != DF->end()) {
+ DominanceFrontier::DomSetType &BSet = BDFI->second;
+ BSet = BDFI->second;
+ BSet.clear();
+ BSet.insert(L->getHeader());
+ BSet.insert(Exit);
+ } else {
+ DominanceFrontier::DomSetType BSet;
+ BSet.insert(L->getHeader());
+ BSet.insert(Exit);
+ DF->addBasicBlock(B, BSet);
+ }
+ }
+ }
+ }
+
+ // Preserve canonical loop form, which means Exit block should
+ // have only one predecessor.
+ BasicBlock *NExit = SplitEdge(L->getLoopLatch(), Exit, this);
+
+ // Preserve LCSSA.
+ BasicBlock::iterator I = Exit->begin(), E = Exit->end();
+ PHINode *PN = NULL;
+ for (; (PN = dyn_cast<PHINode>(I)); ++I) {
+ unsigned N = PN->getNumIncomingValues();
+ for (unsigned index = 0; index < N; ++index)
+ if (PN->getIncomingBlock(index) == NExit) {
+ PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName(),
+ NExit->begin());
+ NewPN->addIncoming(PN->getIncomingValue(index), L->getLoopLatch());
+ PN->setIncomingValue(index, NewPN);
+ PN->setIncomingBlock(index, NExit);
+ break;
+ }
+ }
+
+ assert(NewHeader && L->getHeader() == NewHeader &&
+ "Invalid loop header after loop rotation");
+ assert(NewPreHeader && L->getLoopPreheader() == NewPreHeader &&
+ "Invalid loop preheader after loop rotation");
+ assert(L->getLoopLatch() &&
+ "Invalid loop latch after loop rotation");
+}
projects / oota-llvm.git / blobdiff