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diff --git a/contrib/llvm/lib/Transforms/Scalar/LoopRotation.cpp b/contrib/llvm/lib/Transforms/Scalar/LoopRotation.cpp
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+//===- LoopRotation.cpp - Loop Rotation Pass ------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements Loop Rotation Pass.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "loop-rotate"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Function.h"
+#include "llvm/IntrinsicInst.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"
+#include "llvm/ADT/SmallVector.h"
+using namespace llvm;
+
+#define MAX_HEADER_SIZE 16
+
+STATISTIC(NumRotated, "Number of loops rotated");
+namespace {
+
+ class 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.addPreserved<ScalarEvolution>();
+ AU.addRequired<LoopInfo>();
+ AU.addPreserved<LoopInfo>();
+ AU.addPreserved<DominatorTree>();
+ AU.addPreserved<DominanceFrontier>();
+ }
+
+ // Helper functions
+
+ /// Do actual work
+ bool rotateLoop(Loop *L, LPPassManager &LPM);
+
+ /// Initialize local data
+ void initialize();
+
+ /// 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 *OrigLatch;
+ BasicBlock *NewHeader;
+ BasicBlock *Exit;
+ LPPassManager *LPM_Ptr;
+ };
+}
+
+char LoopRotate::ID = 0;
+static RegisterPass<LoopRotate> X("loop-rotate", "Rotate Loops");
+
+Pass *llvm::createLoopRotatePass() { return new LoopRotate(); }
+
+/// Rotate Loop L as many times as possible. Return true if
+/// the 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)) {
+ RotatedOneLoop = true;
+ initialize();
+ }
+
+ return RotatedOneLoop;
+}
+
+/// Rotate loop LP. Return true if the loop is rotated.
+bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
+ L = Lp;
+
+ 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;
+
+ // 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->isLoopExiting(OrigHeader))
+ return false;
+
+ BranchInst *BI = dyn_cast<BranchInst>(OrigHeader->getTerminator());
+ if (!BI)
+ return false;
+ 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.
+ 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.
+ 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->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.
+ 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 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);
+
+ // Begin by walking OrigHeader and populating ValueMap with an entry for
+ // each Instruction.
+ BasicBlock::iterator I = OrigHeader->begin(), E = OrigHeader->end();
+ DenseMap<const Value *, Value *> ValueMap;
+
+ // 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));
+
+ // 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;
+ }
+
+ // 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;
+
+ // Users in the OrigPreHeader need to use the value to which the
+ // original definitions are mapped.
+ if (UserBB == OrigPreHeader) {
+ U = OrigPreHeaderVal;
+ continue;
+ }
+ }
+
+ // Anything else can be handled by SSAUpdater.
+ SSA.RewriteUse(U);
+ }
+ }
+
+ // NewHeader is now the header of the loop.
+ L->moveToHeader(NewHeader);
+
+ preserveCanonicalLoopForm(LPM);
+
+ NumRotated++;
+ return true;
+}
+
+/// Initialize local data
+void LoopRotate::initialize() {
+ L = NULL;
+ OrigHeader = NULL;
+ OrigPreHeader = NULL;
+ NewHeader = NULL;
+ Exit = 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(OrigHeader->getContext(),
+ "bb.nph",
+ OrigHeader->getParent(),
+ NewHeader);
+ LoopInfo &LI = 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);
+ }
+
+ 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);
+ assert(PN->getBasicBlockIndex(OrigPreHeader) == -1 &&
+ "Expected only one incoming value from Original PreHeader");
+ }
+
+ if (DominatorTree *DT = getAnalysisIfAvailable<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 = 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);
+ }
+
+ // 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 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);
+ }
+ }
+ }
+ }
+ }
+
+ // 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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