//
// 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-rotate"
-
#include "llvm/Transforms/Scalar.h"
#include "llvm/Function.h"
-#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/SmallVector.h"
-
using namespace llvm;
#define MAX_HEADER_SIZE 16
STATISTIC(NumRotated, "Number of loops rotated");
namespace {
- class VISIBILITY_HIDDEN RenameData {
+ class RenameData {
public:
RenameData(Instruction *O, Value *P, Instruction *H)
: Original(O), PreHeader(P), Header(H) { }
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((intptr_t)&ID) {}
+ LoopRotate() : LoopPass(&ID) {}
// Rotate Loop L as many times as possible. Return true if
// loop is rotated at least once.
// 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.addPreserved<ScalarEvolution>();
AU.addPreserved<LoopInfo>();
- AU.addRequiredID(LoopSimplifyID);
- AU.addPreservedID(LoopSimplifyID);
AU.addPreserved<DominatorTree>();
- // Request DominanceFrontier now, even though Loop Rotate does
- // not use it. This allows Pass Manager to schedule Dominance
- // Frontier early enough such that one LPPassManager can handle
- // loop rotate as well as licm pass.
- AU.addRequired<DominanceFrontier>();
AU.addPreserved<DominanceFrontier>();
}
LPPassManager *LPM_Ptr;
SmallVector<RenameData, MAX_HEADER_SIZE> LoopHeaderInfo;
};
-
- char LoopRotate::ID = 0;
- 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.
+/// the loop is rotated at least once.
bool LoopRotate::runOnLoop(Loop *Lp, LPPassManager &LPM) {
-
+
bool RotatedOneLoop = false;
initialize();
LPM_Ptr = &LPM;
/// Rotate loop LP. Return true if the loop is rotated.
bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
-
L = Lp;
OrigHeader = L->getHeader();
OrigPreHeader = L->getLoopPreheader();
OrigLatch = L->getLoopLatch();
- // If loop has only one block then there is not much to rotate.
+ // 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");
+ 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
+ // 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))
return false;
BranchInst *BI = dyn_cast<BranchInst>(OrigHeader->getTerminator());
if (!BI)
return false;
- assert (BI->isConditional() && "Branch Instruction is not condiitional");
+ assert(BI->isConditional() && "Branch Instruction is not conditional");
// 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.
- std::vector<BasicBlock *> ExitBlocks;
+ SmallVector<BasicBlock*, 8> ExitBlocks;
L->getExitBlocks(ExitBlocks);
if (ExitBlocks.size() > 1)
return false;
// Check size of original header and reject
// loop if it is very big.
- if (OrigHeader->getInstList().size() > MAX_HEADER_SIZE)
+ unsigned Size = 0;
+
+ // FIXME: Use common api to estimate size.
+ for (BasicBlock::const_iterator OI = OrigHeader->begin(),
+ OE = OrigHeader->end(); OI != OE; ++OI) {
+ if (isa<PHINode>(OI))
+ continue; // PHI nodes don't count.
+ if (isa<DbgInfoIntrinsic>(OI))
+ continue; // Debug intrinsics don't count as size.
+ Size++;
+ }
+
+ if (Size > MAX_HEADER_SIZE)
return false;
// 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->forgetLoopBackedgeTakenCount(L);
+
// Find new Loop header. NewHeader is a Header's one and only successor
- // that is inside loop. Header's other successor is out side the
- // loop. Otherwise loop is not suitable for rotation.
+ // 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(NewHeader && "Unable to determine new loop header");
assert(L->contains(NewHeader) && !L->contains(Exit) &&
"Unable to determine loop header and exit blocks");
-
- // 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.
+
+ // This code assumes that the 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 the original header
+ // into the original pre-header. Unlike the original header, the original
+ // pre-header is not a member of the loop.
//
- // New loop header is one and only successor of original header that
+ // 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 original header into new loop header.
+ // 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
// 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 = NULL;
+ PHINode *PN = 0;
for (; (PN = dyn_cast<PHINode>(I)); ++I) {
- Instruction *In = I;
-
// PHI nodes are not copied into original pre-header. Instead their values
// are directly propagated.
- Value * NPV = PN->getIncomingValueForBlock(OrigPreHeader);
+ Value *NPV = PN->getIncomingValueForBlock(OrigPreHeader);
- // Create new PHI node with two incoming values for NewHeader.
- // One incoming value is from OrigLatch (through OrigHeader) and
+ // 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 = new PHINode(In->getType(), In->getName());
+ PHINode *NH = PHINode::Create(PN->getType(), PN->getName(),
+ NewHeader->begin());
NH->addIncoming(PN->getIncomingValueForBlock(OrigLatch), OrigHeader);
NH->addIncoming(NPV, OrigPreHeader);
- NewHeader->getInstList().push_front(NH);
// "In" can be replaced by NH at various places.
- LoopHeaderInfo.push_back(RenameData(In, NPV, NH));
+ LoopHeaderInfo.push_back(RenameData(PN, NPV, NH));
}
// Now, handle non-phi instructions.
for (; I != E; ++I) {
Instruction *In = I;
-
- assert (!isa<PHINode>(In) && "PHINode is not expected here");
+ 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.
OrigPreHeader->getInstList().push_back(C);
for (unsigned opi = 0, e = In->getNumOperands(); opi != e; ++opi) {
- if (Instruction *OpPhi = dyn_cast<PHINode>(In->getOperand(opi))) {
- if (const RenameData *D = findReplacementData(OpPhi)) {
- // This is using values from original header PHI node.
- // Here, directly used incoming value from original pre-header.
- C->setOperand(opi, D->PreHeader);
- }
- }
- else if (Instruction *OpInsn =
- dyn_cast<Instruction>(In->getOperand(opi))) {
- if (const RenameData *D = findReplacementData(OpInsn))
- C->setOperand(opi, D->PreHeader);
- }
+ 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);
}
-
// 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());
+ PHINode *PN = PHINode::Create(In->getType(), In->getName(),
+ NewHeader->begin());
PN->addIncoming(In, OrigHeader);
PN->addIncoming(C, OrigPreHeader);
- NewHeader->getInstList().push_front(PN);
NewHeaderReplacement = PN;
- }
-
- // "In" can be replaced by NPH or NH at various places.
+ }
LoopHeaderInfo.push_back(RenameData(In, C, NewHeaderReplacement));
}
// 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) {
+ for (unsigned LHI = 0, LHI_E = LoopHeaderInfo.size(); LHI != LHI_E; ++LHI) {
const RenameData &ILoopHeaderInfo = LoopHeaderInfo[LHI];
if (!ILoopHeaderInfo.Header)
// 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 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");
+ 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 = new PHINode(U->getType(), U->getName());
+ // 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);
- Exit->getInstList().push_front(PN);
U->replaceUsesOfWith(OldPhi, PN);
}
}
// 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) {
- Instruction *In = I;
- PHINode *PN = dyn_cast<PHINode>(In);
- if (!PN)
- break;
-
+ for (BasicBlock::iterator I = OrigHeader->begin();
+ (PN = dyn_cast<PHINode>(I)); ++I)
PN->removeIncomingValue(OrigPreHeader);
- }
// Make NewHeader as the new header for the loop.
L->moveToHeader(NewHeader);
}
/// 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.
+/// 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(), E = Exit->end();
- I != E; ++I) {
-
- PHINode *PN = dyn_cast<PHINode>(I);
- if (!PN)
- break;
+ PHINode *PN;
+ for (BasicBlock::iterator I = Exit->begin();
+ (PN = dyn_cast<PHINode>(I)); ++I) {
// There is already one incoming value from original pre-header block.
if (PN->getBasicBlockIndex(OrigPreHeader) != -1)
const RenameData *ILoopHeaderInfo;
Value *V = PN->getIncomingValueForBlock(OrigHeader);
- if (isa<Instruction>(V) &&
+ if (isa<Instruction>(V) &&
(ILoopHeaderInfo = findReplacementData(cast<Instruction>(V)))) {
assert(ILoopHeaderInfo->PreHeader && "Missing New Preheader Instruction");
PN->addIncoming(ILoopHeaderInfo->PreHeader, OrigPreHeader);
/// 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;
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) {
+ for (unsigned LHI = 0, LHI_E = LoopHeaderInfo.size(); LHI != LHI_E; ++LHI) {
const RenameData &ILoopHeaderInfo = LoopHeaderInfo[LHI];
if (ILoopHeaderInfo.Original == In)
return &ILoopHeaderInfo;
// 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 = new BasicBlock("bb.nph", OrigHeader->getParent(),
- NewHeader);
+ BasicBlock *NewPreHeader = BasicBlock::Create(OrigHeader->getContext(),
+ "bb.nph",
+ OrigHeader->getParent(),
+ NewHeader);
LoopInfo &LI = LPM.getAnalysis<LoopInfo>();
if (Loop *PL = LI.getLoopFor(OrigPreHeader))
- PL->addBasicBlockToLoop(NewPreHeader, LI);
- new BranchInst(NewHeader, NewPreHeader);
+ 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");
+ 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) {
- Instruction *In = I;
- PHINode *PN = dyn_cast<PHINode>(In);
- 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");
+ 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");
+ assert(PN->getBasicBlockIndex(OrigPreHeader) == -1 &&
+ "Expected only one incoming value from Original PreHeader");
}
- SplitEdge(L->getLoopLatch(), Exit, this);
-
- if (DominatorTree *DT = getAnalysisToUpdate<DominatorTree>()) {
+ if (DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>()) {
DT->addNewBlock(NewPreHeader, OrigPreHeader);
DT->changeImmediateDominator(L->getHeader(), NewPreHeader);
DT->changeImmediateDominator(Exit, OrigPreHeader);
DT->changeImmediateDominator(OrigHeader, OrigLatch);
}
- if(DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>()) {
+ if (DominanceFrontier *DF = getAnalysisIfAvailable<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);
+ }
- // New Preheader's dominance frontier is same as original preheader.
- DominanceFrontier::iterator DFI = DF->find(OrigPreHeader);
- if (DFI != DF->end()) {
- DominanceFrontier::DomSetType NPHSet(DFI->second), NHSet(DFI->second);
- // NPHSet.insert(DFI->second.begin(), DFI->second.end(), NPHSet.begin());
- DF->addBasicBlock(NewPreHeader, NPHSet);
-
- DominanceFrontier::iterator DHI = DF->find(L->getHeader());
- if (DHI != DF->end()) {
- DominanceFrontier::DomSetType DHSet = DHI->second;
- DHSet.clear();
- DHSet.insert(DFI->second.begin(), DFI->second.end());
- } else {
- DominanceFrontier::DomSetType NHSet(DFI->second);
- // NHSet.insert(DFI->second.begin(), DFI->second.end(), NHSet.begin());
- DF->addBasicBlock(L->getHeader(), NHSet);
- }
+ // 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);
}
- // Original header no longer dominates Exit
- DFI = DF->find(OrigHeader);
- if (DFI != DF->end()) {
- for (succ_iterator SI = succ_begin(Exit), SE = succ_end(Exit);
- SI != SE; ++SI) {
- BasicBlock *Succ = *SI;
- DominanceFrontier::DomSetType::iterator DSI = DFI->second.find(Succ);
- if (DSI != DFI->second.end())
- DFI->second.erase(DSI);
+ // 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();
+
+ 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);
+ }
+ }
}
}
}
- 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");
+ // Preserve canonical loop form, which means Exit block should
+ // have only one predecessor.
+ SplitEdge(L->getLoopLatch(), Exit, this);
+ 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");
}
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