You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
1281 lines
44 KiB
1281 lines
44 KiB
//===- LoopInterchange.cpp - Loop interchange pass------------------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This Pass handles loop interchange transform.
|
|
// This pass interchanges loops to provide a more cache-friendly memory access
|
|
// patterns.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/ADT/SmallVector.h"
|
|
#include "llvm/Analysis/AliasAnalysis.h"
|
|
#include "llvm/Analysis/AssumptionCache.h"
|
|
#include "llvm/Analysis/BlockFrequencyInfo.h"
|
|
#include "llvm/Analysis/CodeMetrics.h"
|
|
#include "llvm/Analysis/DependenceAnalysis.h"
|
|
#include "llvm/Analysis/LoopInfo.h"
|
|
#include "llvm/Analysis/LoopIterator.h"
|
|
#include "llvm/Analysis/LoopPass.h"
|
|
#include "llvm/Analysis/ScalarEvolution.h"
|
|
#include "llvm/Analysis/ScalarEvolutionExpander.h"
|
|
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
|
|
#include "llvm/Analysis/TargetTransformInfo.h"
|
|
#include "llvm/Analysis/ValueTracking.h"
|
|
#include "llvm/IR/Dominators.h"
|
|
#include "llvm/IR/Function.h"
|
|
#include "llvm/IR/IRBuilder.h"
|
|
#include "llvm/IR/InstIterator.h"
|
|
#include "llvm/IR/IntrinsicInst.h"
|
|
#include "llvm/IR/Module.h"
|
|
#include "llvm/Pass.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/Support/raw_ostream.h"
|
|
#include "llvm/Transforms/Scalar.h"
|
|
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
|
|
#include "llvm/Transforms/Utils/LoopUtils.h"
|
|
#include "llvm/Transforms/Utils/SSAUpdater.h"
|
|
using namespace llvm;
|
|
|
|
#define DEBUG_TYPE "loop-interchange"
|
|
|
|
namespace {
|
|
|
|
typedef SmallVector<Loop *, 8> LoopVector;
|
|
|
|
// TODO: Check if we can use a sparse matrix here.
|
|
typedef std::vector<std::vector<char>> CharMatrix;
|
|
|
|
// Maximum number of dependencies that can be handled in the dependency matrix.
|
|
static const unsigned MaxMemInstrCount = 100;
|
|
|
|
// Maximum loop depth supported.
|
|
static const unsigned MaxLoopNestDepth = 10;
|
|
|
|
struct LoopInterchange;
|
|
|
|
#ifdef DUMP_DEP_MATRICIES
|
|
void printDepMatrix(CharMatrix &DepMatrix) {
|
|
for (auto I = DepMatrix.begin(), E = DepMatrix.end(); I != E; ++I) {
|
|
std::vector<char> Vec = *I;
|
|
for (auto II = Vec.begin(), EE = Vec.end(); II != EE; ++II)
|
|
DEBUG(dbgs() << *II << " ");
|
|
DEBUG(dbgs() << "\n");
|
|
}
|
|
}
|
|
#endif
|
|
|
|
static bool populateDependencyMatrix(CharMatrix &DepMatrix, unsigned Level,
|
|
Loop *L, DependenceInfo *DI) {
|
|
typedef SmallVector<Value *, 16> ValueVector;
|
|
ValueVector MemInstr;
|
|
|
|
if (Level > MaxLoopNestDepth) {
|
|
DEBUG(dbgs() << "Cannot handle loops of depth greater than "
|
|
<< MaxLoopNestDepth << "\n");
|
|
return false;
|
|
}
|
|
|
|
// For each block.
|
|
for (Loop::block_iterator BB = L->block_begin(), BE = L->block_end();
|
|
BB != BE; ++BB) {
|
|
// Scan the BB and collect legal loads and stores.
|
|
for (BasicBlock::iterator I = (*BB)->begin(), E = (*BB)->end(); I != E;
|
|
++I) {
|
|
Instruction *Ins = dyn_cast<Instruction>(I);
|
|
if (!Ins)
|
|
return false;
|
|
LoadInst *Ld = dyn_cast<LoadInst>(I);
|
|
StoreInst *St = dyn_cast<StoreInst>(I);
|
|
if (!St && !Ld)
|
|
continue;
|
|
if (Ld && !Ld->isSimple())
|
|
return false;
|
|
if (St && !St->isSimple())
|
|
return false;
|
|
MemInstr.push_back(&*I);
|
|
}
|
|
}
|
|
|
|
DEBUG(dbgs() << "Found " << MemInstr.size()
|
|
<< " Loads and Stores to analyze\n");
|
|
|
|
ValueVector::iterator I, IE, J, JE;
|
|
|
|
for (I = MemInstr.begin(), IE = MemInstr.end(); I != IE; ++I) {
|
|
for (J = I, JE = MemInstr.end(); J != JE; ++J) {
|
|
std::vector<char> Dep;
|
|
Instruction *Src = dyn_cast<Instruction>(*I);
|
|
Instruction *Des = dyn_cast<Instruction>(*J);
|
|
if (Src == Des)
|
|
continue;
|
|
if (isa<LoadInst>(Src) && isa<LoadInst>(Des))
|
|
continue;
|
|
if (auto D = DI->depends(Src, Des, true)) {
|
|
DEBUG(dbgs() << "Found Dependency between Src=" << Src << " Des=" << Des
|
|
<< "\n");
|
|
if (D->isFlow()) {
|
|
// TODO: Handle Flow dependence.Check if it is sufficient to populate
|
|
// the Dependence Matrix with the direction reversed.
|
|
DEBUG(dbgs() << "Flow dependence not handled");
|
|
return false;
|
|
}
|
|
if (D->isAnti()) {
|
|
DEBUG(dbgs() << "Found Anti dependence \n");
|
|
unsigned Levels = D->getLevels();
|
|
char Direction;
|
|
for (unsigned II = 1; II <= Levels; ++II) {
|
|
const SCEV *Distance = D->getDistance(II);
|
|
const SCEVConstant *SCEVConst =
|
|
dyn_cast_or_null<SCEVConstant>(Distance);
|
|
if (SCEVConst) {
|
|
const ConstantInt *CI = SCEVConst->getValue();
|
|
if (CI->isNegative())
|
|
Direction = '<';
|
|
else if (CI->isZero())
|
|
Direction = '=';
|
|
else
|
|
Direction = '>';
|
|
Dep.push_back(Direction);
|
|
} else if (D->isScalar(II)) {
|
|
Direction = 'S';
|
|
Dep.push_back(Direction);
|
|
} else {
|
|
unsigned Dir = D->getDirection(II);
|
|
if (Dir == Dependence::DVEntry::LT ||
|
|
Dir == Dependence::DVEntry::LE)
|
|
Direction = '<';
|
|
else if (Dir == Dependence::DVEntry::GT ||
|
|
Dir == Dependence::DVEntry::GE)
|
|
Direction = '>';
|
|
else if (Dir == Dependence::DVEntry::EQ)
|
|
Direction = '=';
|
|
else
|
|
Direction = '*';
|
|
Dep.push_back(Direction);
|
|
}
|
|
}
|
|
while (Dep.size() != Level) {
|
|
Dep.push_back('I');
|
|
}
|
|
|
|
DepMatrix.push_back(Dep);
|
|
if (DepMatrix.size() > MaxMemInstrCount) {
|
|
DEBUG(dbgs() << "Cannot handle more than " << MaxMemInstrCount
|
|
<< " dependencies inside loop\n");
|
|
return false;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// We don't have a DepMatrix to check legality return false.
|
|
if (DepMatrix.size() == 0)
|
|
return false;
|
|
return true;
|
|
}
|
|
|
|
// A loop is moved from index 'from' to an index 'to'. Update the Dependence
|
|
// matrix by exchanging the two columns.
|
|
static void interChangeDepedencies(CharMatrix &DepMatrix, unsigned FromIndx,
|
|
unsigned ToIndx) {
|
|
unsigned numRows = DepMatrix.size();
|
|
for (unsigned i = 0; i < numRows; ++i) {
|
|
char TmpVal = DepMatrix[i][ToIndx];
|
|
DepMatrix[i][ToIndx] = DepMatrix[i][FromIndx];
|
|
DepMatrix[i][FromIndx] = TmpVal;
|
|
}
|
|
}
|
|
|
|
// Checks if outermost non '=','S'or'I' dependence in the dependence matrix is
|
|
// '>'
|
|
static bool isOuterMostDepPositive(CharMatrix &DepMatrix, unsigned Row,
|
|
unsigned Column) {
|
|
for (unsigned i = 0; i <= Column; ++i) {
|
|
if (DepMatrix[Row][i] == '<')
|
|
return false;
|
|
if (DepMatrix[Row][i] == '>')
|
|
return true;
|
|
}
|
|
// All dependencies were '=','S' or 'I'
|
|
return false;
|
|
}
|
|
|
|
// Checks if no dependence exist in the dependency matrix in Row before Column.
|
|
static bool containsNoDependence(CharMatrix &DepMatrix, unsigned Row,
|
|
unsigned Column) {
|
|
for (unsigned i = 0; i < Column; ++i) {
|
|
if (DepMatrix[Row][i] != '=' || DepMatrix[Row][i] != 'S' ||
|
|
DepMatrix[Row][i] != 'I')
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
static bool validDepInterchange(CharMatrix &DepMatrix, unsigned Row,
|
|
unsigned OuterLoopId, char InnerDep,
|
|
char OuterDep) {
|
|
|
|
if (isOuterMostDepPositive(DepMatrix, Row, OuterLoopId))
|
|
return false;
|
|
|
|
if (InnerDep == OuterDep)
|
|
return true;
|
|
|
|
// It is legal to interchange if and only if after interchange no row has a
|
|
// '>' direction as the leftmost non-'='.
|
|
|
|
if (InnerDep == '=' || InnerDep == 'S' || InnerDep == 'I')
|
|
return true;
|
|
|
|
if (InnerDep == '<')
|
|
return true;
|
|
|
|
if (InnerDep == '>') {
|
|
// If OuterLoopId represents outermost loop then interchanging will make the
|
|
// 1st dependency as '>'
|
|
if (OuterLoopId == 0)
|
|
return false;
|
|
|
|
// If all dependencies before OuterloopId are '=','S'or 'I'. Then
|
|
// interchanging will result in this row having an outermost non '='
|
|
// dependency of '>'
|
|
if (!containsNoDependence(DepMatrix, Row, OuterLoopId))
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
// Checks if it is legal to interchange 2 loops.
|
|
// [Theorem] A permutation of the loops in a perfect nest is legal if and only
|
|
// if
|
|
// the direction matrix, after the same permutation is applied to its columns,
|
|
// has no ">" direction as the leftmost non-"=" direction in any row.
|
|
static bool isLegalToInterChangeLoops(CharMatrix &DepMatrix,
|
|
unsigned InnerLoopId,
|
|
unsigned OuterLoopId) {
|
|
|
|
unsigned NumRows = DepMatrix.size();
|
|
// For each row check if it is valid to interchange.
|
|
for (unsigned Row = 0; Row < NumRows; ++Row) {
|
|
char InnerDep = DepMatrix[Row][InnerLoopId];
|
|
char OuterDep = DepMatrix[Row][OuterLoopId];
|
|
if (InnerDep == '*' || OuterDep == '*')
|
|
return false;
|
|
else if (!validDepInterchange(DepMatrix, Row, OuterLoopId, InnerDep,
|
|
OuterDep))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
static void populateWorklist(Loop &L, SmallVector<LoopVector, 8> &V) {
|
|
|
|
DEBUG(dbgs() << "Calling populateWorklist called\n");
|
|
LoopVector LoopList;
|
|
Loop *CurrentLoop = &L;
|
|
const std::vector<Loop *> *Vec = &CurrentLoop->getSubLoops();
|
|
while (!Vec->empty()) {
|
|
// The current loop has multiple subloops in it hence it is not tightly
|
|
// nested.
|
|
// Discard all loops above it added into Worklist.
|
|
if (Vec->size() != 1) {
|
|
LoopList.clear();
|
|
return;
|
|
}
|
|
LoopList.push_back(CurrentLoop);
|
|
CurrentLoop = Vec->front();
|
|
Vec = &CurrentLoop->getSubLoops();
|
|
}
|
|
LoopList.push_back(CurrentLoop);
|
|
V.push_back(std::move(LoopList));
|
|
}
|
|
|
|
static PHINode *getInductionVariable(Loop *L, ScalarEvolution *SE) {
|
|
PHINode *InnerIndexVar = L->getCanonicalInductionVariable();
|
|
if (InnerIndexVar)
|
|
return InnerIndexVar;
|
|
if (L->getLoopLatch() == nullptr || L->getLoopPredecessor() == nullptr)
|
|
return nullptr;
|
|
for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I) {
|
|
PHINode *PhiVar = cast<PHINode>(I);
|
|
Type *PhiTy = PhiVar->getType();
|
|
if (!PhiTy->isIntegerTy() && !PhiTy->isFloatingPointTy() &&
|
|
!PhiTy->isPointerTy())
|
|
return nullptr;
|
|
const SCEVAddRecExpr *AddRec =
|
|
dyn_cast<SCEVAddRecExpr>(SE->getSCEV(PhiVar));
|
|
if (!AddRec || !AddRec->isAffine())
|
|
continue;
|
|
const SCEV *Step = AddRec->getStepRecurrence(*SE);
|
|
const SCEVConstant *C = dyn_cast<SCEVConstant>(Step);
|
|
if (!C)
|
|
continue;
|
|
// Found the induction variable.
|
|
// FIXME: Handle loops with more than one induction variable. Note that,
|
|
// currently, legality makes sure we have only one induction variable.
|
|
return PhiVar;
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
/// LoopInterchangeLegality checks if it is legal to interchange the loop.
|
|
class LoopInterchangeLegality {
|
|
public:
|
|
LoopInterchangeLegality(Loop *Outer, Loop *Inner, ScalarEvolution *SE,
|
|
LoopInfo *LI, DominatorTree *DT, bool PreserveLCSSA)
|
|
: OuterLoop(Outer), InnerLoop(Inner), SE(SE), LI(LI), DT(DT),
|
|
PreserveLCSSA(PreserveLCSSA), InnerLoopHasReduction(false) {}
|
|
|
|
/// Check if the loops can be interchanged.
|
|
bool canInterchangeLoops(unsigned InnerLoopId, unsigned OuterLoopId,
|
|
CharMatrix &DepMatrix);
|
|
/// Check if the loop structure is understood. We do not handle triangular
|
|
/// loops for now.
|
|
bool isLoopStructureUnderstood(PHINode *InnerInductionVar);
|
|
|
|
bool currentLimitations();
|
|
|
|
bool hasInnerLoopReduction() { return InnerLoopHasReduction; }
|
|
|
|
private:
|
|
bool tightlyNested(Loop *Outer, Loop *Inner);
|
|
bool containsUnsafeInstructionsInHeader(BasicBlock *BB);
|
|
bool areAllUsesReductions(Instruction *Ins, Loop *L);
|
|
bool containsUnsafeInstructionsInLatch(BasicBlock *BB);
|
|
bool findInductionAndReductions(Loop *L,
|
|
SmallVector<PHINode *, 8> &Inductions,
|
|
SmallVector<PHINode *, 8> &Reductions);
|
|
Loop *OuterLoop;
|
|
Loop *InnerLoop;
|
|
|
|
ScalarEvolution *SE;
|
|
LoopInfo *LI;
|
|
DominatorTree *DT;
|
|
bool PreserveLCSSA;
|
|
|
|
bool InnerLoopHasReduction;
|
|
};
|
|
|
|
/// LoopInterchangeProfitability checks if it is profitable to interchange the
|
|
/// loop.
|
|
class LoopInterchangeProfitability {
|
|
public:
|
|
LoopInterchangeProfitability(Loop *Outer, Loop *Inner, ScalarEvolution *SE)
|
|
: OuterLoop(Outer), InnerLoop(Inner), SE(SE) {}
|
|
|
|
/// Check if the loop interchange is profitable.
|
|
bool isProfitable(unsigned InnerLoopId, unsigned OuterLoopId,
|
|
CharMatrix &DepMatrix);
|
|
|
|
private:
|
|
int getInstrOrderCost();
|
|
|
|
Loop *OuterLoop;
|
|
Loop *InnerLoop;
|
|
|
|
/// Scev analysis.
|
|
ScalarEvolution *SE;
|
|
};
|
|
|
|
/// LoopInterchangeTransform interchanges the loop.
|
|
class LoopInterchangeTransform {
|
|
public:
|
|
LoopInterchangeTransform(Loop *Outer, Loop *Inner, ScalarEvolution *SE,
|
|
LoopInfo *LI, DominatorTree *DT,
|
|
BasicBlock *LoopNestExit,
|
|
bool InnerLoopContainsReductions)
|
|
: OuterLoop(Outer), InnerLoop(Inner), SE(SE), LI(LI), DT(DT),
|
|
LoopExit(LoopNestExit),
|
|
InnerLoopHasReduction(InnerLoopContainsReductions) {}
|
|
|
|
/// Interchange OuterLoop and InnerLoop.
|
|
bool transform();
|
|
void restructureLoops(Loop *InnerLoop, Loop *OuterLoop);
|
|
void removeChildLoop(Loop *OuterLoop, Loop *InnerLoop);
|
|
|
|
private:
|
|
void splitInnerLoopLatch(Instruction *);
|
|
void splitInnerLoopHeader();
|
|
bool adjustLoopLinks();
|
|
void adjustLoopPreheaders();
|
|
bool adjustLoopBranches();
|
|
void updateIncomingBlock(BasicBlock *CurrBlock, BasicBlock *OldPred,
|
|
BasicBlock *NewPred);
|
|
|
|
Loop *OuterLoop;
|
|
Loop *InnerLoop;
|
|
|
|
/// Scev analysis.
|
|
ScalarEvolution *SE;
|
|
LoopInfo *LI;
|
|
DominatorTree *DT;
|
|
BasicBlock *LoopExit;
|
|
bool InnerLoopHasReduction;
|
|
};
|
|
|
|
// Main LoopInterchange Pass.
|
|
struct LoopInterchange : public FunctionPass {
|
|
static char ID;
|
|
ScalarEvolution *SE;
|
|
LoopInfo *LI;
|
|
DependenceInfo *DI;
|
|
DominatorTree *DT;
|
|
bool PreserveLCSSA;
|
|
LoopInterchange()
|
|
: FunctionPass(ID), SE(nullptr), LI(nullptr), DI(nullptr), DT(nullptr) {
|
|
initializeLoopInterchangePass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
void getAnalysisUsage(AnalysisUsage &AU) const override {
|
|
AU.addRequired<ScalarEvolutionWrapperPass>();
|
|
AU.addRequired<AAResultsWrapperPass>();
|
|
AU.addRequired<DominatorTreeWrapperPass>();
|
|
AU.addRequired<LoopInfoWrapperPass>();
|
|
AU.addRequired<DependenceAnalysisWrapperPass>();
|
|
AU.addRequiredID(LoopSimplifyID);
|
|
AU.addRequiredID(LCSSAID);
|
|
}
|
|
|
|
bool runOnFunction(Function &F) override {
|
|
if (skipFunction(F))
|
|
return false;
|
|
|
|
SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
|
|
LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
|
|
DI = &getAnalysis<DependenceAnalysisWrapperPass>().getDI();
|
|
auto *DTWP = getAnalysisIfAvailable<DominatorTreeWrapperPass>();
|
|
DT = DTWP ? &DTWP->getDomTree() : nullptr;
|
|
PreserveLCSSA = mustPreserveAnalysisID(LCSSAID);
|
|
|
|
// Build up a worklist of loop pairs to analyze.
|
|
SmallVector<LoopVector, 8> Worklist;
|
|
|
|
for (Loop *L : *LI)
|
|
populateWorklist(*L, Worklist);
|
|
|
|
DEBUG(dbgs() << "Worklist size = " << Worklist.size() << "\n");
|
|
bool Changed = true;
|
|
while (!Worklist.empty()) {
|
|
LoopVector LoopList = Worklist.pop_back_val();
|
|
Changed = processLoopList(LoopList, F);
|
|
}
|
|
return Changed;
|
|
}
|
|
|
|
bool isComputableLoopNest(LoopVector LoopList) {
|
|
for (Loop *L : LoopList) {
|
|
const SCEV *ExitCountOuter = SE->getBackedgeTakenCount(L);
|
|
if (ExitCountOuter == SE->getCouldNotCompute()) {
|
|
DEBUG(dbgs() << "Couldn't compute Backedge count\n");
|
|
return false;
|
|
}
|
|
if (L->getNumBackEdges() != 1) {
|
|
DEBUG(dbgs() << "NumBackEdges is not equal to 1\n");
|
|
return false;
|
|
}
|
|
if (!L->getExitingBlock()) {
|
|
DEBUG(dbgs() << "Loop Doesn't have unique exit block\n");
|
|
return false;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
unsigned selectLoopForInterchange(const LoopVector &LoopList) {
|
|
// TODO: Add a better heuristic to select the loop to be interchanged based
|
|
// on the dependence matrix. Currently we select the innermost loop.
|
|
return LoopList.size() - 1;
|
|
}
|
|
|
|
bool processLoopList(LoopVector LoopList, Function &F) {
|
|
|
|
bool Changed = false;
|
|
CharMatrix DependencyMatrix;
|
|
if (LoopList.size() < 2) {
|
|
DEBUG(dbgs() << "Loop doesn't contain minimum nesting level.\n");
|
|
return false;
|
|
}
|
|
if (!isComputableLoopNest(LoopList)) {
|
|
DEBUG(dbgs() << "Not vaild loop candidate for interchange\n");
|
|
return false;
|
|
}
|
|
Loop *OuterMostLoop = *(LoopList.begin());
|
|
|
|
DEBUG(dbgs() << "Processing LoopList of size = " << LoopList.size()
|
|
<< "\n");
|
|
|
|
if (!populateDependencyMatrix(DependencyMatrix, LoopList.size(),
|
|
OuterMostLoop, DI)) {
|
|
DEBUG(dbgs() << "Populating Dependency matrix failed\n");
|
|
return false;
|
|
}
|
|
#ifdef DUMP_DEP_MATRICIES
|
|
DEBUG(dbgs() << "Dependence before inter change \n");
|
|
printDepMatrix(DependencyMatrix);
|
|
#endif
|
|
|
|
BasicBlock *OuterMostLoopLatch = OuterMostLoop->getLoopLatch();
|
|
BranchInst *OuterMostLoopLatchBI =
|
|
dyn_cast<BranchInst>(OuterMostLoopLatch->getTerminator());
|
|
if (!OuterMostLoopLatchBI)
|
|
return false;
|
|
|
|
// Since we currently do not handle LCSSA PHI's any failure in loop
|
|
// condition will now branch to LoopNestExit.
|
|
// TODO: This should be removed once we handle LCSSA PHI nodes.
|
|
|
|
// Get the Outermost loop exit.
|
|
BasicBlock *LoopNestExit;
|
|
if (OuterMostLoopLatchBI->getSuccessor(0) == OuterMostLoop->getHeader())
|
|
LoopNestExit = OuterMostLoopLatchBI->getSuccessor(1);
|
|
else
|
|
LoopNestExit = OuterMostLoopLatchBI->getSuccessor(0);
|
|
|
|
if (isa<PHINode>(LoopNestExit->begin())) {
|
|
DEBUG(dbgs() << "PHI Nodes in loop nest exit is not handled for now "
|
|
"since on failure all loops branch to loop nest exit.\n");
|
|
return false;
|
|
}
|
|
|
|
unsigned SelecLoopId = selectLoopForInterchange(LoopList);
|
|
// Move the selected loop outwards to the best possible position.
|
|
for (unsigned i = SelecLoopId; i > 0; i--) {
|
|
bool Interchanged =
|
|
processLoop(LoopList, i, i - 1, LoopNestExit, DependencyMatrix);
|
|
if (!Interchanged)
|
|
return Changed;
|
|
// Loops interchanged reflect the same in LoopList
|
|
std::swap(LoopList[i - 1], LoopList[i]);
|
|
|
|
// Update the DependencyMatrix
|
|
interChangeDepedencies(DependencyMatrix, i, i - 1);
|
|
DT->recalculate(F);
|
|
#ifdef DUMP_DEP_MATRICIES
|
|
DEBUG(dbgs() << "Dependence after inter change \n");
|
|
printDepMatrix(DependencyMatrix);
|
|
#endif
|
|
Changed |= Interchanged;
|
|
}
|
|
return Changed;
|
|
}
|
|
|
|
bool processLoop(LoopVector LoopList, unsigned InnerLoopId,
|
|
unsigned OuterLoopId, BasicBlock *LoopNestExit,
|
|
std::vector<std::vector<char>> &DependencyMatrix) {
|
|
|
|
DEBUG(dbgs() << "Processing Innder Loop Id = " << InnerLoopId
|
|
<< " and OuterLoopId = " << OuterLoopId << "\n");
|
|
Loop *InnerLoop = LoopList[InnerLoopId];
|
|
Loop *OuterLoop = LoopList[OuterLoopId];
|
|
|
|
LoopInterchangeLegality LIL(OuterLoop, InnerLoop, SE, LI, DT,
|
|
PreserveLCSSA);
|
|
if (!LIL.canInterchangeLoops(InnerLoopId, OuterLoopId, DependencyMatrix)) {
|
|
DEBUG(dbgs() << "Not interchanging Loops. Cannot prove legality\n");
|
|
return false;
|
|
}
|
|
DEBUG(dbgs() << "Loops are legal to interchange\n");
|
|
LoopInterchangeProfitability LIP(OuterLoop, InnerLoop, SE);
|
|
if (!LIP.isProfitable(InnerLoopId, OuterLoopId, DependencyMatrix)) {
|
|
DEBUG(dbgs() << "Interchanging Loops not profitable\n");
|
|
return false;
|
|
}
|
|
|
|
LoopInterchangeTransform LIT(OuterLoop, InnerLoop, SE, LI, DT,
|
|
LoopNestExit, LIL.hasInnerLoopReduction());
|
|
LIT.transform();
|
|
DEBUG(dbgs() << "Loops interchanged\n");
|
|
return true;
|
|
}
|
|
};
|
|
|
|
} // end of namespace
|
|
bool LoopInterchangeLegality::areAllUsesReductions(Instruction *Ins, Loop *L) {
|
|
return !std::any_of(Ins->user_begin(), Ins->user_end(), [=](User *U) -> bool {
|
|
PHINode *UserIns = dyn_cast<PHINode>(U);
|
|
RecurrenceDescriptor RD;
|
|
return !UserIns || !RecurrenceDescriptor::isReductionPHI(UserIns, L, RD);
|
|
});
|
|
}
|
|
|
|
bool LoopInterchangeLegality::containsUnsafeInstructionsInHeader(
|
|
BasicBlock *BB) {
|
|
for (auto I = BB->begin(), E = BB->end(); I != E; ++I) {
|
|
// Load corresponding to reduction PHI's are safe while concluding if
|
|
// tightly nested.
|
|
if (LoadInst *L = dyn_cast<LoadInst>(I)) {
|
|
if (!areAllUsesReductions(L, InnerLoop))
|
|
return true;
|
|
} else if (I->mayHaveSideEffects() || I->mayReadFromMemory())
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
bool LoopInterchangeLegality::containsUnsafeInstructionsInLatch(
|
|
BasicBlock *BB) {
|
|
for (auto I = BB->begin(), E = BB->end(); I != E; ++I) {
|
|
// Stores corresponding to reductions are safe while concluding if tightly
|
|
// nested.
|
|
if (StoreInst *L = dyn_cast<StoreInst>(I)) {
|
|
PHINode *PHI = dyn_cast<PHINode>(L->getOperand(0));
|
|
if (!PHI)
|
|
return true;
|
|
} else if (I->mayHaveSideEffects() || I->mayReadFromMemory())
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
bool LoopInterchangeLegality::tightlyNested(Loop *OuterLoop, Loop *InnerLoop) {
|
|
BasicBlock *OuterLoopHeader = OuterLoop->getHeader();
|
|
BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
|
|
BasicBlock *OuterLoopLatch = OuterLoop->getLoopLatch();
|
|
|
|
DEBUG(dbgs() << "Checking if Loops are Tightly Nested\n");
|
|
|
|
// A perfectly nested loop will not have any branch in between the outer and
|
|
// inner block i.e. outer header will branch to either inner preheader and
|
|
// outerloop latch.
|
|
BranchInst *outerLoopHeaderBI =
|
|
dyn_cast<BranchInst>(OuterLoopHeader->getTerminator());
|
|
if (!outerLoopHeaderBI)
|
|
return false;
|
|
unsigned num = outerLoopHeaderBI->getNumSuccessors();
|
|
for (unsigned i = 0; i < num; i++) {
|
|
if (outerLoopHeaderBI->getSuccessor(i) != InnerLoopPreHeader &&
|
|
outerLoopHeaderBI->getSuccessor(i) != OuterLoopLatch)
|
|
return false;
|
|
}
|
|
|
|
DEBUG(dbgs() << "Checking instructions in Loop header and Loop latch \n");
|
|
// We do not have any basic block in between now make sure the outer header
|
|
// and outer loop latch doesn't contain any unsafe instructions.
|
|
if (containsUnsafeInstructionsInHeader(OuterLoopHeader) ||
|
|
containsUnsafeInstructionsInLatch(OuterLoopLatch))
|
|
return false;
|
|
|
|
DEBUG(dbgs() << "Loops are perfectly nested \n");
|
|
// We have a perfect loop nest.
|
|
return true;
|
|
}
|
|
|
|
|
|
bool LoopInterchangeLegality::isLoopStructureUnderstood(
|
|
PHINode *InnerInduction) {
|
|
|
|
unsigned Num = InnerInduction->getNumOperands();
|
|
BasicBlock *InnerLoopPreheader = InnerLoop->getLoopPreheader();
|
|
for (unsigned i = 0; i < Num; ++i) {
|
|
Value *Val = InnerInduction->getOperand(i);
|
|
if (isa<Constant>(Val))
|
|
continue;
|
|
Instruction *I = dyn_cast<Instruction>(Val);
|
|
if (!I)
|
|
return false;
|
|
// TODO: Handle triangular loops.
|
|
// e.g. for(int i=0;i<N;i++)
|
|
// for(int j=i;j<N;j++)
|
|
unsigned IncomBlockIndx = PHINode::getIncomingValueNumForOperand(i);
|
|
if (InnerInduction->getIncomingBlock(IncomBlockIndx) ==
|
|
InnerLoopPreheader &&
|
|
!OuterLoop->isLoopInvariant(I)) {
|
|
return false;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
bool LoopInterchangeLegality::findInductionAndReductions(
|
|
Loop *L, SmallVector<PHINode *, 8> &Inductions,
|
|
SmallVector<PHINode *, 8> &Reductions) {
|
|
if (!L->getLoopLatch() || !L->getLoopPredecessor())
|
|
return false;
|
|
for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I) {
|
|
RecurrenceDescriptor RD;
|
|
InductionDescriptor ID;
|
|
PHINode *PHI = cast<PHINode>(I);
|
|
if (InductionDescriptor::isInductionPHI(PHI, SE, ID))
|
|
Inductions.push_back(PHI);
|
|
else if (RecurrenceDescriptor::isReductionPHI(PHI, L, RD))
|
|
Reductions.push_back(PHI);
|
|
else {
|
|
DEBUG(
|
|
dbgs() << "Failed to recognize PHI as an induction or reduction.\n");
|
|
return false;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
static bool containsSafePHI(BasicBlock *Block, bool isOuterLoopExitBlock) {
|
|
for (auto I = Block->begin(); isa<PHINode>(I); ++I) {
|
|
PHINode *PHI = cast<PHINode>(I);
|
|
// Reduction lcssa phi will have only 1 incoming block that from loop latch.
|
|
if (PHI->getNumIncomingValues() > 1)
|
|
return false;
|
|
Instruction *Ins = dyn_cast<Instruction>(PHI->getIncomingValue(0));
|
|
if (!Ins)
|
|
return false;
|
|
// Incoming value for lcssa phi's in outer loop exit can only be inner loop
|
|
// exits lcssa phi else it would not be tightly nested.
|
|
if (!isa<PHINode>(Ins) && isOuterLoopExitBlock)
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
static BasicBlock *getLoopLatchExitBlock(BasicBlock *LatchBlock,
|
|
BasicBlock *LoopHeader) {
|
|
if (BranchInst *BI = dyn_cast<BranchInst>(LatchBlock->getTerminator())) {
|
|
unsigned Num = BI->getNumSuccessors();
|
|
assert(Num == 2);
|
|
for (unsigned i = 0; i < Num; ++i) {
|
|
if (BI->getSuccessor(i) == LoopHeader)
|
|
continue;
|
|
return BI->getSuccessor(i);
|
|
}
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
// This function indicates the current limitations in the transform as a result
|
|
// of which we do not proceed.
|
|
bool LoopInterchangeLegality::currentLimitations() {
|
|
|
|
BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
|
|
BasicBlock *InnerLoopHeader = InnerLoop->getHeader();
|
|
BasicBlock *InnerLoopLatch = InnerLoop->getLoopLatch();
|
|
BasicBlock *OuterLoopLatch = OuterLoop->getLoopLatch();
|
|
BasicBlock *OuterLoopHeader = OuterLoop->getHeader();
|
|
|
|
PHINode *InnerInductionVar;
|
|
SmallVector<PHINode *, 8> Inductions;
|
|
SmallVector<PHINode *, 8> Reductions;
|
|
if (!findInductionAndReductions(InnerLoop, Inductions, Reductions))
|
|
return true;
|
|
|
|
// TODO: Currently we handle only loops with 1 induction variable.
|
|
if (Inductions.size() != 1) {
|
|
DEBUG(dbgs() << "We currently only support loops with 1 induction variable."
|
|
<< "Failed to interchange due to current limitation\n");
|
|
return true;
|
|
}
|
|
if (Reductions.size() > 0)
|
|
InnerLoopHasReduction = true;
|
|
|
|
InnerInductionVar = Inductions.pop_back_val();
|
|
Reductions.clear();
|
|
if (!findInductionAndReductions(OuterLoop, Inductions, Reductions))
|
|
return true;
|
|
|
|
// Outer loop cannot have reduction because then loops will not be tightly
|
|
// nested.
|
|
if (!Reductions.empty())
|
|
return true;
|
|
// TODO: Currently we handle only loops with 1 induction variable.
|
|
if (Inductions.size() != 1)
|
|
return true;
|
|
|
|
// TODO: Triangular loops are not handled for now.
|
|
if (!isLoopStructureUnderstood(InnerInductionVar)) {
|
|
DEBUG(dbgs() << "Loop structure not understood by pass\n");
|
|
return true;
|
|
}
|
|
|
|
// TODO: We only handle LCSSA PHI's corresponding to reduction for now.
|
|
BasicBlock *LoopExitBlock =
|
|
getLoopLatchExitBlock(OuterLoopLatch, OuterLoopHeader);
|
|
if (!LoopExitBlock || !containsSafePHI(LoopExitBlock, true))
|
|
return true;
|
|
|
|
LoopExitBlock = getLoopLatchExitBlock(InnerLoopLatch, InnerLoopHeader);
|
|
if (!LoopExitBlock || !containsSafePHI(LoopExitBlock, false))
|
|
return true;
|
|
|
|
// TODO: Current limitation: Since we split the inner loop latch at the point
|
|
// were induction variable is incremented (induction.next); We cannot have
|
|
// more than 1 user of induction.next since it would result in broken code
|
|
// after split.
|
|
// e.g.
|
|
// for(i=0;i<N;i++) {
|
|
// for(j = 0;j<M;j++) {
|
|
// A[j+1][i+2] = A[j][i]+k;
|
|
// }
|
|
// }
|
|
Instruction *InnerIndexVarInc = nullptr;
|
|
if (InnerInductionVar->getIncomingBlock(0) == InnerLoopPreHeader)
|
|
InnerIndexVarInc =
|
|
dyn_cast<Instruction>(InnerInductionVar->getIncomingValue(1));
|
|
else
|
|
InnerIndexVarInc =
|
|
dyn_cast<Instruction>(InnerInductionVar->getIncomingValue(0));
|
|
|
|
if (!InnerIndexVarInc)
|
|
return true;
|
|
|
|
// Since we split the inner loop latch on this induction variable. Make sure
|
|
// we do not have any instruction between the induction variable and branch
|
|
// instruction.
|
|
|
|
bool FoundInduction = false;
|
|
for (const Instruction &I : reverse(*InnerLoopLatch)) {
|
|
if (isa<BranchInst>(I) || isa<CmpInst>(I) || isa<TruncInst>(I))
|
|
continue;
|
|
// We found an instruction. If this is not induction variable then it is not
|
|
// safe to split this loop latch.
|
|
if (!I.isIdenticalTo(InnerIndexVarInc))
|
|
return true;
|
|
|
|
FoundInduction = true;
|
|
break;
|
|
}
|
|
// The loop latch ended and we didn't find the induction variable return as
|
|
// current limitation.
|
|
if (!FoundInduction)
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
bool LoopInterchangeLegality::canInterchangeLoops(unsigned InnerLoopId,
|
|
unsigned OuterLoopId,
|
|
CharMatrix &DepMatrix) {
|
|
|
|
if (!isLegalToInterChangeLoops(DepMatrix, InnerLoopId, OuterLoopId)) {
|
|
DEBUG(dbgs() << "Failed interchange InnerLoopId = " << InnerLoopId
|
|
<< "and OuterLoopId = " << OuterLoopId
|
|
<< "due to dependence\n");
|
|
return false;
|
|
}
|
|
|
|
// Create unique Preheaders if we already do not have one.
|
|
BasicBlock *OuterLoopPreHeader = OuterLoop->getLoopPreheader();
|
|
BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
|
|
|
|
// Create a unique outer preheader -
|
|
// 1) If OuterLoop preheader is not present.
|
|
// 2) If OuterLoop Preheader is same as OuterLoop Header
|
|
// 3) If OuterLoop Preheader is same as Header of the previous loop.
|
|
// 4) If OuterLoop Preheader is Entry node.
|
|
if (!OuterLoopPreHeader || OuterLoopPreHeader == OuterLoop->getHeader() ||
|
|
isa<PHINode>(OuterLoopPreHeader->begin()) ||
|
|
!OuterLoopPreHeader->getUniquePredecessor()) {
|
|
OuterLoopPreHeader =
|
|
InsertPreheaderForLoop(OuterLoop, DT, LI, PreserveLCSSA);
|
|
}
|
|
|
|
if (!InnerLoopPreHeader || InnerLoopPreHeader == InnerLoop->getHeader() ||
|
|
InnerLoopPreHeader == OuterLoop->getHeader()) {
|
|
InnerLoopPreHeader =
|
|
InsertPreheaderForLoop(InnerLoop, DT, LI, PreserveLCSSA);
|
|
}
|
|
|
|
// TODO: The loops could not be interchanged due to current limitations in the
|
|
// transform module.
|
|
if (currentLimitations()) {
|
|
DEBUG(dbgs() << "Not legal because of current transform limitation\n");
|
|
return false;
|
|
}
|
|
|
|
// Check if the loops are tightly nested.
|
|
if (!tightlyNested(OuterLoop, InnerLoop)) {
|
|
DEBUG(dbgs() << "Loops not tightly nested\n");
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
int LoopInterchangeProfitability::getInstrOrderCost() {
|
|
unsigned GoodOrder, BadOrder;
|
|
BadOrder = GoodOrder = 0;
|
|
for (auto BI = InnerLoop->block_begin(), BE = InnerLoop->block_end();
|
|
BI != BE; ++BI) {
|
|
for (Instruction &Ins : **BI) {
|
|
if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&Ins)) {
|
|
unsigned NumOp = GEP->getNumOperands();
|
|
bool FoundInnerInduction = false;
|
|
bool FoundOuterInduction = false;
|
|
for (unsigned i = 0; i < NumOp; ++i) {
|
|
const SCEV *OperandVal = SE->getSCEV(GEP->getOperand(i));
|
|
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(OperandVal);
|
|
if (!AR)
|
|
continue;
|
|
|
|
// If we find the inner induction after an outer induction e.g.
|
|
// for(int i=0;i<N;i++)
|
|
// for(int j=0;j<N;j++)
|
|
// A[i][j] = A[i-1][j-1]+k;
|
|
// then it is a good order.
|
|
if (AR->getLoop() == InnerLoop) {
|
|
// We found an InnerLoop induction after OuterLoop induction. It is
|
|
// a good order.
|
|
FoundInnerInduction = true;
|
|
if (FoundOuterInduction) {
|
|
GoodOrder++;
|
|
break;
|
|
}
|
|
}
|
|
// If we find the outer induction after an inner induction e.g.
|
|
// for(int i=0;i<N;i++)
|
|
// for(int j=0;j<N;j++)
|
|
// A[j][i] = A[j-1][i-1]+k;
|
|
// then it is a bad order.
|
|
if (AR->getLoop() == OuterLoop) {
|
|
// We found an OuterLoop induction after InnerLoop induction. It is
|
|
// a bad order.
|
|
FoundOuterInduction = true;
|
|
if (FoundInnerInduction) {
|
|
BadOrder++;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return GoodOrder - BadOrder;
|
|
}
|
|
|
|
static bool isProfitabileForVectorization(unsigned InnerLoopId,
|
|
unsigned OuterLoopId,
|
|
CharMatrix &DepMatrix) {
|
|
// TODO: Improve this heuristic to catch more cases.
|
|
// If the inner loop is loop independent or doesn't carry any dependency it is
|
|
// profitable to move this to outer position.
|
|
unsigned Row = DepMatrix.size();
|
|
for (unsigned i = 0; i < Row; ++i) {
|
|
if (DepMatrix[i][InnerLoopId] != 'S' && DepMatrix[i][InnerLoopId] != 'I')
|
|
return false;
|
|
// TODO: We need to improve this heuristic.
|
|
if (DepMatrix[i][OuterLoopId] != '=')
|
|
return false;
|
|
}
|
|
// If outer loop has dependence and inner loop is loop independent then it is
|
|
// profitable to interchange to enable parallelism.
|
|
return true;
|
|
}
|
|
|
|
bool LoopInterchangeProfitability::isProfitable(unsigned InnerLoopId,
|
|
unsigned OuterLoopId,
|
|
CharMatrix &DepMatrix) {
|
|
|
|
// TODO: Add better profitability checks.
|
|
// e.g
|
|
// 1) Construct dependency matrix and move the one with no loop carried dep
|
|
// inside to enable vectorization.
|
|
|
|
// This is rough cost estimation algorithm. It counts the good and bad order
|
|
// of induction variables in the instruction and allows reordering if number
|
|
// of bad orders is more than good.
|
|
int Cost = 0;
|
|
Cost += getInstrOrderCost();
|
|
DEBUG(dbgs() << "Cost = " << Cost << "\n");
|
|
if (Cost < 0)
|
|
return true;
|
|
|
|
// It is not profitable as per current cache profitability model. But check if
|
|
// we can move this loop outside to improve parallelism.
|
|
bool ImprovesPar =
|
|
isProfitabileForVectorization(InnerLoopId, OuterLoopId, DepMatrix);
|
|
return ImprovesPar;
|
|
}
|
|
|
|
void LoopInterchangeTransform::removeChildLoop(Loop *OuterLoop,
|
|
Loop *InnerLoop) {
|
|
for (Loop::iterator I = OuterLoop->begin(), E = OuterLoop->end(); I != E;
|
|
++I) {
|
|
if (*I == InnerLoop) {
|
|
OuterLoop->removeChildLoop(I);
|
|
return;
|
|
}
|
|
}
|
|
llvm_unreachable("Couldn't find loop");
|
|
}
|
|
|
|
void LoopInterchangeTransform::restructureLoops(Loop *InnerLoop,
|
|
Loop *OuterLoop) {
|
|
Loop *OuterLoopParent = OuterLoop->getParentLoop();
|
|
if (OuterLoopParent) {
|
|
// Remove the loop from its parent loop.
|
|
removeChildLoop(OuterLoopParent, OuterLoop);
|
|
removeChildLoop(OuterLoop, InnerLoop);
|
|
OuterLoopParent->addChildLoop(InnerLoop);
|
|
} else {
|
|
removeChildLoop(OuterLoop, InnerLoop);
|
|
LI->changeTopLevelLoop(OuterLoop, InnerLoop);
|
|
}
|
|
|
|
while (!InnerLoop->empty())
|
|
OuterLoop->addChildLoop(InnerLoop->removeChildLoop(InnerLoop->begin()));
|
|
|
|
InnerLoop->addChildLoop(OuterLoop);
|
|
}
|
|
|
|
bool LoopInterchangeTransform::transform() {
|
|
|
|
DEBUG(dbgs() << "transform\n");
|
|
bool Transformed = false;
|
|
Instruction *InnerIndexVar;
|
|
|
|
if (InnerLoop->getSubLoops().size() == 0) {
|
|
BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
|
|
DEBUG(dbgs() << "Calling Split Inner Loop\n");
|
|
PHINode *InductionPHI = getInductionVariable(InnerLoop, SE);
|
|
if (!InductionPHI) {
|
|
DEBUG(dbgs() << "Failed to find the point to split loop latch \n");
|
|
return false;
|
|
}
|
|
|
|
if (InductionPHI->getIncomingBlock(0) == InnerLoopPreHeader)
|
|
InnerIndexVar = dyn_cast<Instruction>(InductionPHI->getIncomingValue(1));
|
|
else
|
|
InnerIndexVar = dyn_cast<Instruction>(InductionPHI->getIncomingValue(0));
|
|
|
|
//
|
|
// Split at the place were the induction variable is
|
|
// incremented/decremented.
|
|
// TODO: This splitting logic may not work always. Fix this.
|
|
splitInnerLoopLatch(InnerIndexVar);
|
|
DEBUG(dbgs() << "splitInnerLoopLatch Done\n");
|
|
|
|
// Splits the inner loops phi nodes out into a separate basic block.
|
|
splitInnerLoopHeader();
|
|
DEBUG(dbgs() << "splitInnerLoopHeader Done\n");
|
|
}
|
|
|
|
Transformed |= adjustLoopLinks();
|
|
if (!Transformed) {
|
|
DEBUG(dbgs() << "adjustLoopLinks Failed\n");
|
|
return false;
|
|
}
|
|
|
|
restructureLoops(InnerLoop, OuterLoop);
|
|
return true;
|
|
}
|
|
|
|
void LoopInterchangeTransform::splitInnerLoopLatch(Instruction *Inc) {
|
|
BasicBlock *InnerLoopLatch = InnerLoop->getLoopLatch();
|
|
BasicBlock *InnerLoopLatchPred = InnerLoopLatch;
|
|
InnerLoopLatch = SplitBlock(InnerLoopLatchPred, Inc, DT, LI);
|
|
}
|
|
|
|
void LoopInterchangeTransform::splitInnerLoopHeader() {
|
|
|
|
// Split the inner loop header out. Here make sure that the reduction PHI's
|
|
// stay in the innerloop body.
|
|
BasicBlock *InnerLoopHeader = InnerLoop->getHeader();
|
|
BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
|
|
if (InnerLoopHasReduction) {
|
|
// FIXME: Check if the induction PHI will always be the first PHI.
|
|
BasicBlock *New = InnerLoopHeader->splitBasicBlock(
|
|
++(InnerLoopHeader->begin()), InnerLoopHeader->getName() + ".split");
|
|
if (LI)
|
|
if (Loop *L = LI->getLoopFor(InnerLoopHeader))
|
|
L->addBasicBlockToLoop(New, *LI);
|
|
|
|
// Adjust Reduction PHI's in the block.
|
|
SmallVector<PHINode *, 8> PHIVec;
|
|
for (auto I = New->begin(); isa<PHINode>(I); ++I) {
|
|
PHINode *PHI = dyn_cast<PHINode>(I);
|
|
Value *V = PHI->getIncomingValueForBlock(InnerLoopPreHeader);
|
|
PHI->replaceAllUsesWith(V);
|
|
PHIVec.push_back((PHI));
|
|
}
|
|
for (PHINode *P : PHIVec) {
|
|
P->eraseFromParent();
|
|
}
|
|
} else {
|
|
SplitBlock(InnerLoopHeader, InnerLoopHeader->getFirstNonPHI(), DT, LI);
|
|
}
|
|
|
|
DEBUG(dbgs() << "Output of splitInnerLoopHeader InnerLoopHeaderSucc & "
|
|
"InnerLoopHeader \n");
|
|
}
|
|
|
|
/// \brief Move all instructions except the terminator from FromBB right before
|
|
/// InsertBefore
|
|
static void moveBBContents(BasicBlock *FromBB, Instruction *InsertBefore) {
|
|
auto &ToList = InsertBefore->getParent()->getInstList();
|
|
auto &FromList = FromBB->getInstList();
|
|
|
|
ToList.splice(InsertBefore->getIterator(), FromList, FromList.begin(),
|
|
FromBB->getTerminator()->getIterator());
|
|
}
|
|
|
|
void LoopInterchangeTransform::updateIncomingBlock(BasicBlock *CurrBlock,
|
|
BasicBlock *OldPred,
|
|
BasicBlock *NewPred) {
|
|
for (auto I = CurrBlock->begin(); isa<PHINode>(I); ++I) {
|
|
PHINode *PHI = cast<PHINode>(I);
|
|
unsigned Num = PHI->getNumIncomingValues();
|
|
for (unsigned i = 0; i < Num; ++i) {
|
|
if (PHI->getIncomingBlock(i) == OldPred)
|
|
PHI->setIncomingBlock(i, NewPred);
|
|
}
|
|
}
|
|
}
|
|
|
|
bool LoopInterchangeTransform::adjustLoopBranches() {
|
|
|
|
DEBUG(dbgs() << "adjustLoopBranches called\n");
|
|
// Adjust the loop preheader
|
|
BasicBlock *InnerLoopHeader = InnerLoop->getHeader();
|
|
BasicBlock *OuterLoopHeader = OuterLoop->getHeader();
|
|
BasicBlock *InnerLoopLatch = InnerLoop->getLoopLatch();
|
|
BasicBlock *OuterLoopLatch = OuterLoop->getLoopLatch();
|
|
BasicBlock *OuterLoopPreHeader = OuterLoop->getLoopPreheader();
|
|
BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
|
|
BasicBlock *OuterLoopPredecessor = OuterLoopPreHeader->getUniquePredecessor();
|
|
BasicBlock *InnerLoopLatchPredecessor =
|
|
InnerLoopLatch->getUniquePredecessor();
|
|
BasicBlock *InnerLoopLatchSuccessor;
|
|
BasicBlock *OuterLoopLatchSuccessor;
|
|
|
|
BranchInst *OuterLoopLatchBI =
|
|
dyn_cast<BranchInst>(OuterLoopLatch->getTerminator());
|
|
BranchInst *InnerLoopLatchBI =
|
|
dyn_cast<BranchInst>(InnerLoopLatch->getTerminator());
|
|
BranchInst *OuterLoopHeaderBI =
|
|
dyn_cast<BranchInst>(OuterLoopHeader->getTerminator());
|
|
BranchInst *InnerLoopHeaderBI =
|
|
dyn_cast<BranchInst>(InnerLoopHeader->getTerminator());
|
|
|
|
if (!OuterLoopPredecessor || !InnerLoopLatchPredecessor ||
|
|
!OuterLoopLatchBI || !InnerLoopLatchBI || !OuterLoopHeaderBI ||
|
|
!InnerLoopHeaderBI)
|
|
return false;
|
|
|
|
BranchInst *InnerLoopLatchPredecessorBI =
|
|
dyn_cast<BranchInst>(InnerLoopLatchPredecessor->getTerminator());
|
|
BranchInst *OuterLoopPredecessorBI =
|
|
dyn_cast<BranchInst>(OuterLoopPredecessor->getTerminator());
|
|
|
|
if (!OuterLoopPredecessorBI || !InnerLoopLatchPredecessorBI)
|
|
return false;
|
|
BasicBlock *InnerLoopHeaderSuccessor = InnerLoopHeader->getUniqueSuccessor();
|
|
if (!InnerLoopHeaderSuccessor)
|
|
return false;
|
|
|
|
// Adjust Loop Preheader and headers
|
|
|
|
unsigned NumSucc = OuterLoopPredecessorBI->getNumSuccessors();
|
|
for (unsigned i = 0; i < NumSucc; ++i) {
|
|
if (OuterLoopPredecessorBI->getSuccessor(i) == OuterLoopPreHeader)
|
|
OuterLoopPredecessorBI->setSuccessor(i, InnerLoopPreHeader);
|
|
}
|
|
|
|
NumSucc = OuterLoopHeaderBI->getNumSuccessors();
|
|
for (unsigned i = 0; i < NumSucc; ++i) {
|
|
if (OuterLoopHeaderBI->getSuccessor(i) == OuterLoopLatch)
|
|
OuterLoopHeaderBI->setSuccessor(i, LoopExit);
|
|
else if (OuterLoopHeaderBI->getSuccessor(i) == InnerLoopPreHeader)
|
|
OuterLoopHeaderBI->setSuccessor(i, InnerLoopHeaderSuccessor);
|
|
}
|
|
|
|
// Adjust reduction PHI's now that the incoming block has changed.
|
|
updateIncomingBlock(InnerLoopHeaderSuccessor, InnerLoopHeader,
|
|
OuterLoopHeader);
|
|
|
|
BranchInst::Create(OuterLoopPreHeader, InnerLoopHeaderBI);
|
|
InnerLoopHeaderBI->eraseFromParent();
|
|
|
|
// -------------Adjust loop latches-----------
|
|
if (InnerLoopLatchBI->getSuccessor(0) == InnerLoopHeader)
|
|
InnerLoopLatchSuccessor = InnerLoopLatchBI->getSuccessor(1);
|
|
else
|
|
InnerLoopLatchSuccessor = InnerLoopLatchBI->getSuccessor(0);
|
|
|
|
NumSucc = InnerLoopLatchPredecessorBI->getNumSuccessors();
|
|
for (unsigned i = 0; i < NumSucc; ++i) {
|
|
if (InnerLoopLatchPredecessorBI->getSuccessor(i) == InnerLoopLatch)
|
|
InnerLoopLatchPredecessorBI->setSuccessor(i, InnerLoopLatchSuccessor);
|
|
}
|
|
|
|
// Adjust PHI nodes in InnerLoopLatchSuccessor. Update all uses of PHI with
|
|
// the value and remove this PHI node from inner loop.
|
|
SmallVector<PHINode *, 8> LcssaVec;
|
|
for (auto I = InnerLoopLatchSuccessor->begin(); isa<PHINode>(I); ++I) {
|
|
PHINode *LcssaPhi = cast<PHINode>(I);
|
|
LcssaVec.push_back(LcssaPhi);
|
|
}
|
|
for (PHINode *P : LcssaVec) {
|
|
Value *Incoming = P->getIncomingValueForBlock(InnerLoopLatch);
|
|
P->replaceAllUsesWith(Incoming);
|
|
P->eraseFromParent();
|
|
}
|
|
|
|
if (OuterLoopLatchBI->getSuccessor(0) == OuterLoopHeader)
|
|
OuterLoopLatchSuccessor = OuterLoopLatchBI->getSuccessor(1);
|
|
else
|
|
OuterLoopLatchSuccessor = OuterLoopLatchBI->getSuccessor(0);
|
|
|
|
if (InnerLoopLatchBI->getSuccessor(1) == InnerLoopLatchSuccessor)
|
|
InnerLoopLatchBI->setSuccessor(1, OuterLoopLatchSuccessor);
|
|
else
|
|
InnerLoopLatchBI->setSuccessor(0, OuterLoopLatchSuccessor);
|
|
|
|
updateIncomingBlock(OuterLoopLatchSuccessor, OuterLoopLatch, InnerLoopLatch);
|
|
|
|
if (OuterLoopLatchBI->getSuccessor(0) == OuterLoopLatchSuccessor) {
|
|
OuterLoopLatchBI->setSuccessor(0, InnerLoopLatch);
|
|
} else {
|
|
OuterLoopLatchBI->setSuccessor(1, InnerLoopLatch);
|
|
}
|
|
|
|
return true;
|
|
}
|
|
void LoopInterchangeTransform::adjustLoopPreheaders() {
|
|
|
|
// We have interchanged the preheaders so we need to interchange the data in
|
|
// the preheader as well.
|
|
// This is because the content of inner preheader was previously executed
|
|
// inside the outer loop.
|
|
BasicBlock *OuterLoopPreHeader = OuterLoop->getLoopPreheader();
|
|
BasicBlock *InnerLoopPreHeader = InnerLoop->getLoopPreheader();
|
|
BasicBlock *OuterLoopHeader = OuterLoop->getHeader();
|
|
BranchInst *InnerTermBI =
|
|
cast<BranchInst>(InnerLoopPreHeader->getTerminator());
|
|
|
|
// These instructions should now be executed inside the loop.
|
|
// Move instruction into a new block after outer header.
|
|
moveBBContents(InnerLoopPreHeader, OuterLoopHeader->getTerminator());
|
|
// These instructions were not executed previously in the loop so move them to
|
|
// the older inner loop preheader.
|
|
moveBBContents(OuterLoopPreHeader, InnerTermBI);
|
|
}
|
|
|
|
bool LoopInterchangeTransform::adjustLoopLinks() {
|
|
|
|
// Adjust all branches in the inner and outer loop.
|
|
bool Changed = adjustLoopBranches();
|
|
if (Changed)
|
|
adjustLoopPreheaders();
|
|
return Changed;
|
|
}
|
|
|
|
char LoopInterchange::ID = 0;
|
|
INITIALIZE_PASS_BEGIN(LoopInterchange, "loop-interchange",
|
|
"Interchanges loops for cache reuse", false, false)
|
|
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
|
|
INITIALIZE_PASS_DEPENDENCY(DependenceAnalysisWrapperPass)
|
|
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
|
|
INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)
|
|
INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
|
|
INITIALIZE_PASS_DEPENDENCY(LCSSAWrapperPass)
|
|
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
|
|
|
|
INITIALIZE_PASS_END(LoopInterchange, "loop-interchange",
|
|
"Interchanges loops for cache reuse", false, false)
|
|
|
|
Pass *llvm::createLoopInterchangePass() { return new LoopInterchange(); }
|