#include "llvm/Transforms/Scalar.h"
#include "llvm/Function.h"
#include "llvm/IntrinsicInst.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/Transforms/Utils/SSAUpdater.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
STATISTIC(NumRotated, "Number of loops rotated");
namespace {
- class VISIBILITY_HIDDEN RenameData {
- public:
- RenameData(Instruction *O, Value *P, Instruction *H)
- : Original(O), PreHeader(P), Header(H) { }
- public:
- Instruction *Original; // Original instruction
- Value *PreHeader; // Original pre-header replacement
- Instruction *Header; // New header replacement
- };
-
- class VISIBILITY_HIDDEN LoopRotate : public LoopPass {
-
+ class LoopRotate : public LoopPass {
public:
static char ID; // Pass ID, replacement for typeid
LoopRotate() : LoopPass(&ID) {}
// LCSSA form makes instruction renaming easier.
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addPreserved<DominatorTree>();
+ AU.addPreserved<DominanceFrontier>();
+ AU.addRequired<LoopInfo>();
+ AU.addPreserved<LoopInfo>();
AU.addRequiredID(LoopSimplifyID);
AU.addPreservedID(LoopSimplifyID);
AU.addRequiredID(LCSSAID);
AU.addPreservedID(LCSSAID);
AU.addPreserved<ScalarEvolution>();
- AU.addPreserved<LoopInfo>();
- AU.addPreserved<DominatorTree>();
- AU.addPreserved<DominanceFrontier>();
}
// Helper functions
/// Initialize local data
void initialize();
- /// 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 original pre-header.
- void updateExitBlock();
-
- /// Return true if this instruction is used outside original header.
- bool usedOutsideOriginalHeader(Instruction *In);
-
- /// Find Replacement information for instruction. Return NULL if it is
- /// not available.
- 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:
-
Loop *L;
BasicBlock *OrigHeader;
BasicBlock *OrigPreHeader;
BasicBlock *NewHeader;
BasicBlock *Exit;
LPPassManager *LPM_Ptr;
- SmallVector<RenameData, MAX_HEADER_SIZE> LoopHeaderInfo;
};
}
char LoopRotate::ID = 0;
-static RegisterPass<LoopRotate> X("loop-rotate", "Rotate Loops");
+INITIALIZE_PASS(LoopRotate, "loop-rotate", "Rotate Loops", false, false);
Pass *llvm::createLoopRotatePass() { return new LoopRotate(); }
bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
L = Lp;
- OrigHeader = L->getHeader();
OrigPreHeader = L->getLoopPreheader();
+ if (!OrigPreHeader) return false;
+
OrigLatch = L->getLoopLatch();
+ if (!OrigLatch) return false;
+
+ OrigHeader = L->getHeader();
// If the loop has only one block then there is not much to rotate.
if (L->getBlocks().size() == 1)
return false;
- assert(OrigHeader && OrigLatch && OrigPreHeader &&
- "Loop is not in canonical form");
-
// If the loop header is not one of the loop exiting blocks then
// either this loop is already rotated or it is not
// suitable for loop rotation transformations.
- if (!L->isLoopExit(OrigHeader))
+ if (!L->isLoopExiting(OrigHeader))
return false;
BranchInst *BI = dyn_cast<BranchInst>(OrigHeader->getTerminator());
continue; // PHI nodes don't count.
if (isa<DbgInfoIntrinsic>(OI))
continue; // Debug intrinsics don't count as size.
- Size++;
+ ++Size;
}
if (Size > MAX_HEADER_SIZE)
// Now, this loop is suitable for rotation.
+ // Anything ScalarEvolution may know about this loop or the PHI nodes
+ // in its header will soon be invalidated.
+ if (ScalarEvolution *SE = getAnalysisIfAvailable<ScalarEvolution>())
+ SE->forgetLoop(L);
+
// 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.
"New header doesn't have one pred!");
FoldSingleEntryPHINodes(NewHeader);
- // Copy PHI nodes and other instructions from the original header
- // into the original pre-header. Unlike the original header, the original
- // pre-header is not a member of the loop.
- //
- // The new loop header is the 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 the original header into the new loop header.
- // 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 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();
+ // Begin by walking OrigHeader and populating ValueMap with an entry for
+ // each Instruction.
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 a new PHI node with two incoming values for NewHeader.
- // One incoming value is from OrigLatch (through OrigHeader) and the
- // 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));
- }
+ DenseMap<const Value *, Value *> ValueMap;
- // Now, handle non-phi instructions.
- for (; I != E; ++I) {
- Instruction *In = I;
- assert(!isa<PHINode>(In) && "PHINode is not expected here");
-
- // 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 PHI nodes, the value available in OldPreHeader is just the
+ // incoming value from OldPreHeader.
+ for (; PHINode *PN = dyn_cast<PHINode>(I); ++I)
+ ValueMap[PN] = PN->getIncomingValue(PN->getBasicBlockIndex(OrigPreHeader));
- // 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));
+ // For the rest of the instructions, create a clone in the OldPreHeader.
+ TerminatorInst *LoopEntryBranch = OrigPreHeader->getTerminator();
+ for (; I != E; ++I) {
+ Instruction *C = I->clone();
+ C->setName(I->getName());
+ C->insertBefore(LoopEntryBranch);
+ ValueMap[I] = C;
}
- // Rename uses of original header instructions to reflect their new
- // definitions (either from original pre-header node or from newly created
- // new header PHINodes.
- //
- // Original header instructions are used in
- // 1) Original header:
- //
- // 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 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
- // or new header.
- //
- // 2) Inside loop but not in original header
- //
- // Replace this use to reflect definition from new header.
- for (unsigned LHI = 0, LHI_E = LoopHeaderInfo.size(); LHI != LHI_E; ++LHI) {
- const RenameData &ILoopHeaderInfo = LoopHeaderInfo[LHI];
-
- if (!ILoopHeaderInfo.Header)
- continue;
-
- 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)
- AllUses.push_back(cast<Instruction>(UI));
-
- for (SmallVector<Instruction *, 16>::iterator UI = AllUses.begin(),
- UE = AllUses.end(); UI != UE; ++UI) {
- Instruction *U = *UI;
- BasicBlock *Parent = U->getParent();
-
- // Used inside original header
- if (Parent == OrigHeader) {
- // Do not rename uses inside original header non-phi instructions.
- PHINode *PU = dyn_cast<PHINode>(U);
- if (!PU)
+ // Along with all the other instructions, we just cloned OrigHeader's
+ // terminator into OrigPreHeader. Fix up the PHI nodes in each of OrigHeader's
+ // successors by duplicating their incoming values for OrigHeader.
+ TerminatorInst *TI = OrigHeader->getTerminator();
+ for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
+ for (BasicBlock::iterator BI = TI->getSuccessor(i)->begin();
+ PHINode *PN = dyn_cast<PHINode>(BI); ++BI)
+ PN->addIncoming(PN->getIncomingValueForBlock(OrigHeader), OrigPreHeader);
+
+ // Now that OrigPreHeader has a clone of OrigHeader's terminator, remove
+ // OrigPreHeader's old terminator (the original branch into the loop), and
+ // remove the corresponding incoming values from the PHI nodes in OrigHeader.
+ LoopEntryBranch->eraseFromParent();
+ for (I = OrigHeader->begin(); PHINode *PN = dyn_cast<PHINode>(I); ++I)
+ PN->removeIncomingValue(PN->getBasicBlockIndex(OrigPreHeader));
+
+ // Now fix up users of the instructions in OrigHeader, inserting PHI nodes
+ // as necessary.
+ SSAUpdater SSA;
+ for (I = OrigHeader->begin(); I != E; ++I) {
+ Value *OrigHeaderVal = I;
+ Value *OrigPreHeaderVal = ValueMap[OrigHeaderVal];
+
+ // The value now exits in two versions: the initial value in the preheader
+ // and the loop "next" value in the original header.
+ SSA.Initialize(OrigHeaderVal);
+ SSA.AddAvailableValue(OrigHeader, OrigHeaderVal);
+ SSA.AddAvailableValue(OrigPreHeader, OrigPreHeaderVal);
+
+ // Visit each use of the OrigHeader instruction.
+ for (Value::use_iterator UI = OrigHeaderVal->use_begin(),
+ UE = OrigHeaderVal->use_end(); UI != UE; ) {
+ // Grab the use before incrementing the iterator.
+ Use &U = UI.getUse();
+
+ // Increment the iterator before removing the use from the list.
+ ++UI;
+
+ // SSAUpdater can't handle a non-PHI use in the same block as an
+ // earlier def. We can easily handle those cases manually.
+ Instruction *UserInst = cast<Instruction>(U.getUser());
+ if (!isa<PHINode>(UserInst)) {
+ BasicBlock *UserBB = UserInst->getParent();
+
+ // The original users in the OrigHeader are already using the
+ // original definitions.
+ if (UserBB == OrigHeader)
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)
+ // Users in the OrigPreHeader need to use the value to which the
+ // original definitions are mapped.
+ if (UserBB == OrigPreHeader) {
+ U = OrigPreHeaderVal;
continue;
-
- U->replaceUsesOfWith(OldPhi, NewPhi);
- continue;
+ }
}
- // Used inside loop, but not in original header.
- if (L->contains(U->getParent())) {
- if (U != NewPhi)
- U->replaceUsesOfWith(OldPhi, NewPhi);
- continue;
- }
-
- // 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 in the exit block
- // to receive the value from the new header and 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);
- }
+ // Anything else can be handled by SSAUpdater.
+ SSA.RewriteUse(U);
}
}
-
- /// Make sure all Exit block PHINodes have required incoming values.
- updateExitBlock();
-
- // Update CFG
- // Removing incoming branch from loop preheader to original header.
- // Now original header is inside the loop.
- 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.
+ // NewHeader is now the header of the loop.
L->moveToHeader(NewHeader);
preserveCanonicalLoopForm(LPM);
- NumRotated++;
+ ++NumRotated;
return true;
}
-/// Make sure all Exit block PHINodes have required incoming values.
-/// If an incoming value is constant or defined outside the loop then
-/// PHINode may not have an entry for the original pre-header.
-void LoopRotate::updateExitBlock() {
-
- for (BasicBlock::iterator I = Exit->begin();
- PHINode *PN = dyn_cast<PHINode>(I); ++I) {
-
- // There is already one incoming value from original pre-header block.
- if (PN->getBasicBlockIndex(OrigPreHeader) != -1)
- continue;
-
- 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;
OrigPreHeader = NULL;
NewHeader = NULL;
Exit = NULL;
-
- LoopHeaderInfo.clear();
-}
-
-/// 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) {
- 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.
-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.
// 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",
+ BasicBlock *NewPreHeader = BasicBlock::Create(OrigHeader->getContext(),
+ "bb.nph",
OrigHeader->getParent(),
NewHeader);
- LoopInfo &LI = LPM.getAnalysis<LoopInfo>();
+ LoopInfo &LI = getAnalysis<LoopInfo>();
if (Loop *PL = LI.getLoopFor(OrigPreHeader))
PL->addBasicBlockToLoop(NewPreHeader, LI.getBase());
BranchInst::Create(NewHeader, NewPreHeader);
"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;
+ PHINode *PN;
+ for (BasicBlock::iterator I = NewHeader->begin();
+ (PN = dyn_cast<PHINode>(I)); ++I) {
int index = PN->getBasicBlockIndex(OrigPreHeader);
assert(index != -1 && "Expected incoming value from Original PreHeader");
PN->setIncomingBlock(index, NewPreHeader);
DF->addBasicBlock(L->getHeader(), LatchSet);
}
- // If a loop block dominates new loop latch then its frontier is
- // new header and Exit.
+ // If a loop block dominates new loop latch then add to its frontiers
+ // new header and Exit and remove new latch (which is equal to original
+ // header).
BasicBlock *NewLatch = L->getLoopLatch();
- DominatorTree *DT = getAnalysisIfAvailable<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);
+
+ assert(NewLatch == OrigHeader && "NewLatch is inequal to OrigHeader");
+
+ if (DominatorTree *DT = getAnalysisIfAvailable<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.erase(NewLatch);
+ 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;
- }
- }
+ SplitEdge(L->getLoopLatch(), Exit, this);
assert(NewHeader && L->getHeader() == NewHeader &&
"Invalid loop header after loop rotation");
projects / oota-llvm.git / blobdiff