blob: a91f53ba663f39457d016e68795925bc15f62002 [file] [log] [blame]
//===- 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.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar/LoopRotation.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BasicAliasAnalysis.h"
#include "llvm/Analysis/CodeMetrics.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Scalar/LoopPassManager.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/LoopUtils.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
#include "llvm/Transforms/Utils/ValueMapper.h"
using namespace llvm;
#define DEBUG_TYPE "loop-rotate"
static cl::opt<unsigned> DefaultRotationThreshold(
"rotation-max-header-size", cl::init(16), cl::Hidden,
cl::desc("The default maximum header size for automatic loop rotation"));
STATISTIC(NumRotated, "Number of loops rotated");
namespace {
/// A simple loop rotation transformation.
class LoopRotate {
const unsigned MaxHeaderSize;
LoopInfo *LI;
const TargetTransformInfo *TTI;
AssumptionCache *AC;
DominatorTree *DT;
ScalarEvolution *SE;
const SimplifyQuery &SQ;
public:
LoopRotate(unsigned MaxHeaderSize, LoopInfo *LI,
const TargetTransformInfo *TTI, AssumptionCache *AC,
DominatorTree *DT, ScalarEvolution *SE, const SimplifyQuery &SQ)
: MaxHeaderSize(MaxHeaderSize), LI(LI), TTI(TTI), AC(AC), DT(DT), SE(SE),
SQ(SQ) {}
bool processLoop(Loop *L);
private:
bool rotateLoop(Loop *L, bool SimplifiedLatch);
bool simplifyLoopLatch(Loop *L);
};
} // end anonymous namespace
/// RewriteUsesOfClonedInstructions - We just cloned the instructions from the
/// old header into the preheader. If there were uses of the values produced by
/// these instruction that were outside of the loop, we have to insert PHI nodes
/// to merge the two values. Do this now.
static void RewriteUsesOfClonedInstructions(BasicBlock *OrigHeader,
BasicBlock *OrigPreheader,
ValueToValueMapTy &ValueMap,
SmallVectorImpl<PHINode*> *InsertedPHIs) {
// Remove PHI node entries that are no longer live.
BasicBlock::iterator I, E = OrigHeader->end();
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(InsertedPHIs);
for (I = OrigHeader->begin(); I != E; ++I) {
Value *OrigHeaderVal = &*I;
// If there are no uses of the value (e.g. because it returns void), there
// is nothing to rewrite.
if (OrigHeaderVal->use_empty())
continue;
Value *OrigPreHeaderVal = ValueMap.lookup(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->getType(), OrigHeaderVal->getName());
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;
// 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);
}
// Replace MetadataAsValue(ValueAsMetadata(OrigHeaderVal)) uses in debug
// intrinsics.
SmallVector<DbgValueInst *, 1> DbgValues;
llvm::findDbgValues(DbgValues, OrigHeaderVal);
for (auto &DbgValue : DbgValues) {
// The original users in the OrigHeader are already using the original
// definitions.
BasicBlock *UserBB = DbgValue->getParent();
if (UserBB == OrigHeader)
continue;
// Users in the OrigPreHeader need to use the value to which the
// original definitions are mapped and anything else can be handled by
// the SSAUpdater. To avoid adding PHINodes, check if the value is
// available in UserBB, if not substitute undef.
Value *NewVal;
if (UserBB == OrigPreheader)
NewVal = OrigPreHeaderVal;
else if (SSA.HasValueForBlock(UserBB))
NewVal = SSA.GetValueInMiddleOfBlock(UserBB);
else
NewVal = UndefValue::get(OrigHeaderVal->getType());
DbgValue->setOperand(0,
MetadataAsValue::get(OrigHeaderVal->getContext(),
ValueAsMetadata::get(NewVal)));
}
}
}
/// Propagate dbg.value intrinsics through the newly inserted Phis.
static void insertDebugValues(BasicBlock *OrigHeader,
SmallVectorImpl<PHINode*> &InsertedPHIs) {
ValueToValueMapTy DbgValueMap;
// Map existing PHI nodes to their dbg.values.
for (auto &I : *OrigHeader) {
if (auto DbgII = dyn_cast<DbgInfoIntrinsic>(&I)) {
if (auto *Loc = dyn_cast_or_null<PHINode>(DbgII->getVariableLocation()))
DbgValueMap.insert({Loc, DbgII});
}
}
// Then iterate through the new PHIs and look to see if they use one of the
// previously mapped PHIs. If so, insert a new dbg.value intrinsic that will
// propagate the info through the new PHI.
LLVMContext &C = OrigHeader->getContext();
for (auto PHI : InsertedPHIs) {
for (auto VI : PHI->operand_values()) {
auto V = DbgValueMap.find(VI);
if (V != DbgValueMap.end()) {
auto *DbgII = cast<DbgInfoIntrinsic>(V->second);
Instruction *NewDbgII = DbgII->clone();
auto PhiMAV = MetadataAsValue::get(C, ValueAsMetadata::get(PHI));
NewDbgII->setOperand(0, PhiMAV);
BasicBlock *Parent = PHI->getParent();
NewDbgII->insertBefore(Parent->getFirstNonPHIOrDbgOrLifetime());
}
}
}
}
/// Rotate loop LP. Return true if the loop is rotated.
///
/// \param SimplifiedLatch is true if the latch was just folded into the final
/// loop exit. In this case we may want to rotate even though the new latch is
/// now an exiting branch. This rotation would have happened had the latch not
/// been simplified. However, if SimplifiedLatch is false, then we avoid
/// rotating loops in which the latch exits to avoid excessive or endless
/// rotation. LoopRotate should be repeatable and converge to a canonical
/// form. This property is satisfied because simplifying the loop latch can only
/// happen once across multiple invocations of the LoopRotate pass.
bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
// If the loop has only one block then there is not much to rotate.
if (L->getBlocks().size() == 1)
return false;
BasicBlock *OrigHeader = L->getHeader();
BasicBlock *OrigLatch = L->getLoopLatch();
BranchInst *BI = dyn_cast<BranchInst>(OrigHeader->getTerminator());
if (!BI || BI->isUnconditional())
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;
// If the loop latch already contains a branch that leaves the loop then the
// loop is already rotated.
if (!OrigLatch)
return false;
// Rotate if either the loop latch does *not* exit the loop, or if the loop
// latch was just simplified.
if (L->isLoopExiting(OrigLatch) && !SimplifiedLatch)
return false;
// Check size of original header and reject loop if it is very big or we can't
// duplicate blocks inside it.
{
SmallPtrSet<const Value *, 32> EphValues;
CodeMetrics::collectEphemeralValues(L, AC, EphValues);
CodeMetrics Metrics;
Metrics.analyzeBasicBlock(OrigHeader, *TTI, EphValues);
if (Metrics.notDuplicatable) {
DEBUG(dbgs() << "LoopRotation: NOT rotating - contains non-duplicatable"
<< " instructions: ";
L->dump());
return false;
}
if (Metrics.convergent) {
DEBUG(dbgs() << "LoopRotation: NOT rotating - contains convergent "
"instructions: ";
L->dump());
return false;
}
if (Metrics.NumInsts > MaxHeaderSize)
return false;
}
// Now, this loop is suitable for rotation.
BasicBlock *OrigPreheader = L->getLoopPreheader();
// If the loop could not be converted to canonical form, it must have an
// indirectbr in it, just give up.
if (!OrigPreheader)
return false;
// Anything ScalarEvolution may know about this loop or the PHI nodes
// in its header will soon be invalidated.
if (SE)
SE->forgetLoop(L);
DEBUG(dbgs() << "LoopRotation: rotating "; L->dump());
// 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.
BasicBlock *Exit = BI->getSuccessor(0);
BasicBlock *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();
ValueToValueMapTy 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->getIncomingValueForBlock(OrigPreheader);
// For the rest of the instructions, either hoist to the OrigPreheader if
// possible or create a clone in the OldPreHeader if not.
TerminatorInst *LoopEntryBranch = OrigPreheader->getTerminator();
// Record all debug intrinsics preceding LoopEntryBranch to avoid duplication.
using DbgIntrinsicHash =
std::pair<std::pair<Value *, DILocalVariable *>, DIExpression *>;
auto makeHash = [](DbgInfoIntrinsic *D) -> DbgIntrinsicHash {
return {{D->getVariableLocation(), D->getVariable()}, D->getExpression()};
};
SmallDenseSet<DbgIntrinsicHash, 8> DbgIntrinsics;
for (auto I = std::next(OrigPreheader->rbegin()), E = OrigPreheader->rend();
I != E; ++I) {
if (auto *DII = dyn_cast<DbgInfoIntrinsic>(&*I))
DbgIntrinsics.insert(makeHash(DII));
else
break;
}
while (I != E) {
Instruction *Inst = &*I++;
// If the instruction's operands are invariant and it doesn't read or write
// memory, then it is safe to hoist. Doing this doesn't change the order of
// execution in the preheader, but does prevent the instruction from
// executing in each iteration of the loop. This means it is safe to hoist
// something that might trap, but isn't safe to hoist something that reads
// memory (without proving that the loop doesn't write).
if (L->hasLoopInvariantOperands(Inst) && !Inst->mayReadFromMemory() &&
!Inst->mayWriteToMemory() && !isa<TerminatorInst>(Inst) &&
!isa<DbgInfoIntrinsic>(Inst) && !isa<AllocaInst>(Inst)) {
Inst->moveBefore(LoopEntryBranch);
continue;
}
// Otherwise, create a duplicate of the instruction.
Instruction *C = Inst->clone();
// Eagerly remap the operands of the instruction.
RemapInstruction(C, ValueMap,
RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
// Avoid inserting the same intrinsic twice.
if (auto *DII = dyn_cast<DbgInfoIntrinsic>(C))
if (DbgIntrinsics.count(makeHash(DII))) {
C->deleteValue();
continue;
}
// With the operands remapped, see if the instruction constant folds or is
// otherwise simplifyable. This commonly occurs because the entry from PHI
// nodes allows icmps and other instructions to fold.
Value *V = SimplifyInstruction(C, SQ);
if (V && LI->replacementPreservesLCSSAForm(C, V)) {
// If so, then delete the temporary instruction and stick the folded value
// in the map.
ValueMap[Inst] = V;
if (!C->mayHaveSideEffects()) {
C->deleteValue();
C = nullptr;
}
} else {
ValueMap[Inst] = C;
}
if (C) {
// Otherwise, stick the new instruction into the new block!
C->setName(Inst->getName());
C->insertBefore(LoopEntryBranch);
if (auto *II = dyn_cast<IntrinsicInst>(C))
if (II->getIntrinsicID() == Intrinsic::assume)
AC->registerAssumption(II);
}
}
// 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 (BasicBlock *SuccBB : TI->successors())
for (BasicBlock::iterator BI = SuccBB->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();
SmallVector<PHINode*, 2> InsertedPHIs;
// If there were any uses of instructions in the duplicated block outside the
// loop, update them, inserting PHI nodes as required
RewriteUsesOfClonedInstructions(OrigHeader, OrigPreheader, ValueMap,
&InsertedPHIs);
// Attach dbg.value intrinsics to the new phis if that phi uses a value that
// previously had debug metadata attached. This keeps the debug info
// up-to-date in the loop body.
if (!InsertedPHIs.empty())
insertDebugValues(OrigHeader, InsertedPHIs);
// NewHeader is now the header of the loop.
L->moveToHeader(NewHeader);
assert(L->getHeader() == NewHeader && "Latch block is our new header");
// Inform DT about changes to the CFG.
if (DT) {
// The OrigPreheader branches to the NewHeader and Exit now. Then, inform
// the DT about the removed edge to the OrigHeader (that got removed).
SmallVector<DominatorTree::UpdateType, 3> Updates;
Updates.push_back({DominatorTree::Insert, OrigPreheader, Exit});
Updates.push_back({DominatorTree::Insert, OrigPreheader, NewHeader});
Updates.push_back({DominatorTree::Delete, OrigPreheader, OrigHeader});
DT->applyUpdates(Updates);
}
// At this point, we've finished our major CFG changes. As part of cloning
// the loop into the preheader we've simplified instructions and the
// duplicated conditional branch may now be branching on a constant. If it is
// branching on a constant and if that constant means that we enter the loop,
// then we fold away the cond branch to an uncond branch. This simplifies the
// loop in cases important for nested loops, and it also means we don't have
// to split as many edges.
BranchInst *PHBI = cast<BranchInst>(OrigPreheader->getTerminator());
assert(PHBI->isConditional() && "Should be clone of BI condbr!");
if (!isa<ConstantInt>(PHBI->getCondition()) ||
PHBI->getSuccessor(cast<ConstantInt>(PHBI->getCondition())->isZero()) !=
NewHeader) {
// The conditional branch can't be folded, handle the general case.
// Split edges as necessary to preserve LoopSimplify form.
// Right now OrigPreHeader has two successors, NewHeader and ExitBlock, and
// thus is not a preheader anymore.
// Split the edge to form a real preheader.
BasicBlock *NewPH = SplitCriticalEdge(
OrigPreheader, NewHeader,
CriticalEdgeSplittingOptions(DT, LI).setPreserveLCSSA());
NewPH->setName(NewHeader->getName() + ".lr.ph");
// Preserve canonical loop form, which means that 'Exit' should have only
// one predecessor. Note that Exit could be an exit block for multiple
// nested loops, causing both of the edges to now be critical and need to
// be split.
SmallVector<BasicBlock *, 4> ExitPreds(pred_begin(Exit), pred_end(Exit));
bool SplitLatchEdge = false;
for (BasicBlock *ExitPred : ExitPreds) {
// We only need to split loop exit edges.
Loop *PredLoop = LI->getLoopFor(ExitPred);
if (!PredLoop || PredLoop->contains(Exit))
continue;
if (isa<IndirectBrInst>(ExitPred->getTerminator()))
continue;
SplitLatchEdge |= L->getLoopLatch() == ExitPred;
BasicBlock *ExitSplit = SplitCriticalEdge(
ExitPred, Exit,
CriticalEdgeSplittingOptions(DT, LI).setPreserveLCSSA());
ExitSplit->moveBefore(Exit);
}
assert(SplitLatchEdge &&
"Despite splitting all preds, failed to split latch exit?");
} else {
// We can fold the conditional branch in the preheader, this makes things
// simpler. The first step is to remove the extra edge to the Exit block.
Exit->removePredecessor(OrigPreheader, true /*preserve LCSSA*/);
BranchInst *NewBI = BranchInst::Create(NewHeader, PHBI);
NewBI->setDebugLoc(PHBI->getDebugLoc());
PHBI->eraseFromParent();
// With our CFG finalized, update DomTree if it is available.
if (DT) DT->deleteEdge(OrigPreheader, Exit);
}
assert(L->getLoopPreheader() && "Invalid loop preheader after loop rotation");
assert(L->getLoopLatch() && "Invalid loop latch after loop rotation");
// Now that the CFG and DomTree are in a consistent state again, try to merge
// the OrigHeader block into OrigLatch. This will succeed if they are
// connected by an unconditional branch. This is just a cleanup so the
// emitted code isn't too gross in this common case.
MergeBlockIntoPredecessor(OrigHeader, DT, LI);
DEBUG(dbgs() << "LoopRotation: into "; L->dump());
++NumRotated;
return true;
}
/// Determine whether the instructions in this range may be safely and cheaply
/// speculated. This is not an important enough situation to develop complex
/// heuristics. We handle a single arithmetic instruction along with any type
/// conversions.
static bool shouldSpeculateInstrs(BasicBlock::iterator Begin,
BasicBlock::iterator End, Loop *L) {
bool seenIncrement = false;
bool MultiExitLoop = false;
if (!L->getExitingBlock())
MultiExitLoop = true;
for (BasicBlock::iterator I = Begin; I != End; ++I) {
if (!isSafeToSpeculativelyExecute(&*I))
return false;
if (isa<DbgInfoIntrinsic>(I))
continue;
switch (I->getOpcode()) {
default:
return false;
case Instruction::GetElementPtr:
// GEPs are cheap if all indices are constant.
if (!cast<GEPOperator>(I)->hasAllConstantIndices())
return false;
// fall-thru to increment case
LLVM_FALLTHROUGH;
case Instruction::Add:
case Instruction::Sub:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr: {
Value *IVOpnd =
!isa<Constant>(I->getOperand(0))
? I->getOperand(0)
: !isa<Constant>(I->getOperand(1)) ? I->getOperand(1) : nullptr;
if (!IVOpnd)
return false;
// If increment operand is used outside of the loop, this speculation
// could cause extra live range interference.
if (MultiExitLoop) {
for (User *UseI : IVOpnd->users()) {
auto *UserInst = cast<Instruction>(UseI);
if (!L->contains(UserInst))
return false;
}
}
if (seenIncrement)
return false;
seenIncrement = true;
break;
}
case Instruction::Trunc:
case Instruction::ZExt:
case Instruction::SExt:
// ignore type conversions
break;
}
}
return true;
}
/// Fold the loop tail into the loop exit by speculating the loop tail
/// instructions. Typically, this is a single post-increment. In the case of a
/// simple 2-block loop, hoisting the increment can be much better than
/// duplicating the entire loop header. In the case of loops with early exits,
/// rotation will not work anyway, but simplifyLoopLatch will put the loop in
/// canonical form so downstream passes can handle it.
///
/// I don't believe this invalidates SCEV.
bool LoopRotate::simplifyLoopLatch(Loop *L) {
BasicBlock *Latch = L->getLoopLatch();
if (!Latch || Latch->hasAddressTaken())
return false;
BranchInst *Jmp = dyn_cast<BranchInst>(Latch->getTerminator());
if (!Jmp || !Jmp->isUnconditional())
return false;
BasicBlock *LastExit = Latch->getSinglePredecessor();
if (!LastExit || !L->isLoopExiting(LastExit))
return false;
BranchInst *BI = dyn_cast<BranchInst>(LastExit->getTerminator());
if (!BI)
return false;
if (!shouldSpeculateInstrs(Latch->begin(), Jmp->getIterator(), L))
return false;
DEBUG(dbgs() << "Folding loop latch " << Latch->getName() << " into "
<< LastExit->getName() << "\n");
// Hoist the instructions from Latch into LastExit.
LastExit->getInstList().splice(BI->getIterator(), Latch->getInstList(),
Latch->begin(), Jmp->getIterator());
unsigned FallThruPath = BI->getSuccessor(0) == Latch ? 0 : 1;
BasicBlock *Header = Jmp->getSuccessor(0);
assert(Header == L->getHeader() && "expected a backward branch");
// Remove Latch from the CFG so that LastExit becomes the new Latch.
BI->setSuccessor(FallThruPath, Header);
Latch->replaceSuccessorsPhiUsesWith(LastExit);
Jmp->eraseFromParent();
// Nuke the Latch block.
assert(Latch->empty() && "unable to evacuate Latch");
LI->removeBlock(Latch);
if (DT)
DT->eraseNode(Latch);
Latch->eraseFromParent();
return true;
}
/// Rotate \c L, and return true if any modification was made.
bool LoopRotate::processLoop(Loop *L) {
// Save the loop metadata.
MDNode *LoopMD = L->getLoopID();
// Simplify the loop latch before attempting to rotate the header
// upward. Rotation may not be needed if the loop tail can be folded into the
// loop exit.
bool SimplifiedLatch = simplifyLoopLatch(L);
bool MadeChange = rotateLoop(L, SimplifiedLatch);
assert((!MadeChange || L->isLoopExiting(L->getLoopLatch())) &&
"Loop latch should be exiting after loop-rotate.");
// Restore the loop metadata.
// NB! We presume LoopRotation DOESN'T ADD its own metadata.
if ((MadeChange || SimplifiedLatch) && LoopMD)
L->setLoopID(LoopMD);
return MadeChange || SimplifiedLatch;
}
LoopRotatePass::LoopRotatePass(bool EnableHeaderDuplication)
: EnableHeaderDuplication(EnableHeaderDuplication) {}
PreservedAnalyses LoopRotatePass::run(Loop &L, LoopAnalysisManager &AM,
LoopStandardAnalysisResults &AR,
LPMUpdater &) {
int Threshold = EnableHeaderDuplication ? DefaultRotationThreshold : 0;
const DataLayout &DL = L.getHeader()->getModule()->getDataLayout();
const SimplifyQuery SQ = getBestSimplifyQuery(AR, DL);
LoopRotate LR(Threshold, &AR.LI, &AR.TTI, &AR.AC, &AR.DT, &AR.SE,
SQ);
bool Changed = LR.processLoop(&L);
if (!Changed)
return PreservedAnalyses::all();
return getLoopPassPreservedAnalyses();
}
namespace {
class LoopRotateLegacyPass : public LoopPass {
unsigned MaxHeaderSize;
public:
static char ID; // Pass ID, replacement for typeid
LoopRotateLegacyPass(int SpecifiedMaxHeaderSize = -1) : LoopPass(ID) {
initializeLoopRotateLegacyPassPass(*PassRegistry::getPassRegistry());
if (SpecifiedMaxHeaderSize == -1)
MaxHeaderSize = DefaultRotationThreshold;
else
MaxHeaderSize = unsigned(SpecifiedMaxHeaderSize);
}
// LCSSA form makes instruction renaming easier.
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<AssumptionCacheTracker>();
AU.addRequired<TargetTransformInfoWrapperPass>();
getLoopAnalysisUsage(AU);
}
bool runOnLoop(Loop *L, LPPassManager &LPM) override {
if (skipLoop(L))
return false;
Function &F = *L->getHeader()->getParent();
auto *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
const auto *TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
auto *AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
auto *DTWP = getAnalysisIfAvailable<DominatorTreeWrapperPass>();
auto *DT = DTWP ? &DTWP->getDomTree() : nullptr;
auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
auto *SE = SEWP ? &SEWP->getSE() : nullptr;
const SimplifyQuery SQ = getBestSimplifyQuery(*this, F);
LoopRotate LR(MaxHeaderSize, LI, TTI, AC, DT, SE, SQ);
return LR.processLoop(L);
}
};
}
char LoopRotateLegacyPass::ID = 0;
INITIALIZE_PASS_BEGIN(LoopRotateLegacyPass, "loop-rotate", "Rotate Loops",
false, false)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(LoopPass)
INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
INITIALIZE_PASS_END(LoopRotateLegacyPass, "loop-rotate", "Rotate Loops", false,
false)
Pass *llvm::createLoopRotatePass(int MaxHeaderSize) {
return new LoopRotateLegacyPass(MaxHeaderSize);
}