LoopUnrollPass.cpp [plain text]
#include "llvm/Transforms/Scalar.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/CodeMetrics.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Metadata.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/UnrollLoop.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include <climits>
using namespace llvm;
#define DEBUG_TYPE "loop-unroll"
static cl::opt<unsigned>
UnrollThreshold("unroll-threshold", cl::init(150), cl::Hidden,
cl::desc("The cut-off point for automatic loop unrolling"));
static cl::opt<unsigned> UnrollMaxIterationsCountToAnalyze(
"unroll-max-iteration-count-to-analyze", cl::init(0), cl::Hidden,
cl::desc("Don't allow loop unrolling to simulate more than this number of"
"iterations when checking full unroll profitability"));
static cl::opt<unsigned> UnrollMinPercentOfOptimized(
"unroll-percent-of-optimized-for-complete-unroll", cl::init(20), cl::Hidden,
cl::desc("If complete unrolling could trigger further optimizations, and, "
"by that, remove the given percent of instructions, perform the "
"complete unroll even if it's beyond the threshold"));
static cl::opt<unsigned> UnrollAbsoluteThreshold(
"unroll-absolute-threshold", cl::init(2000), cl::Hidden,
cl::desc("Don't unroll if the unrolled size is bigger than this threshold,"
" even if we can remove big portion of instructions later."));
static cl::opt<unsigned>
UnrollCount("unroll-count", cl::init(0), cl::Hidden,
cl::desc("Use this unroll count for all loops including those with "
"unroll_count pragma values, for testing purposes"));
static cl::opt<bool>
UnrollAllowPartial("unroll-allow-partial", cl::init(false), cl::Hidden,
cl::desc("Allows loops to be partially unrolled until "
"-unroll-threshold loop size is reached."));
static cl::opt<bool>
UnrollRuntime("unroll-runtime", cl::ZeroOrMore, cl::init(false), cl::Hidden,
cl::desc("Unroll loops with run-time trip counts"));
static cl::opt<unsigned>
PragmaUnrollThreshold("pragma-unroll-threshold", cl::init(16 * 1024), cl::Hidden,
cl::desc("Unrolled size limit for loops with an unroll(full) or "
"unroll_count pragma."));
namespace {
class LoopUnroll : public LoopPass {
public:
static char ID; LoopUnroll(int T = -1, int C = -1, int P = -1, int R = -1) : LoopPass(ID) {
CurrentThreshold = (T == -1) ? UnrollThreshold : unsigned(T);
CurrentAbsoluteThreshold = UnrollAbsoluteThreshold;
CurrentMinPercentOfOptimized = UnrollMinPercentOfOptimized;
CurrentCount = (C == -1) ? UnrollCount : unsigned(C);
CurrentAllowPartial = (P == -1) ? UnrollAllowPartial : (bool)P;
CurrentRuntime = (R == -1) ? UnrollRuntime : (bool)R;
UserThreshold = (T != -1) || (UnrollThreshold.getNumOccurrences() > 0);
UserAbsoluteThreshold = (UnrollAbsoluteThreshold.getNumOccurrences() > 0);
UserPercentOfOptimized =
(UnrollMinPercentOfOptimized.getNumOccurrences() > 0);
UserAllowPartial = (P != -1) ||
(UnrollAllowPartial.getNumOccurrences() > 0);
UserRuntime = (R != -1) || (UnrollRuntime.getNumOccurrences() > 0);
UserCount = (C != -1) || (UnrollCount.getNumOccurrences() > 0);
initializeLoopUnrollPass(*PassRegistry::getPassRegistry());
}
static const unsigned NoThreshold = UINT_MAX;
static const unsigned OptSizeUnrollThreshold = 50;
static const unsigned UnrollRuntimeCount = 8;
unsigned CurrentCount;
unsigned CurrentThreshold;
unsigned CurrentAbsoluteThreshold;
unsigned CurrentMinPercentOfOptimized;
bool CurrentAllowPartial;
bool CurrentRuntime;
bool UserCount; bool UserThreshold; bool UserAbsoluteThreshold; bool UserPercentOfOptimized; bool UserAllowPartial; bool UserRuntime;
bool runOnLoop(Loop *L, LPPassManager &LPM) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<AssumptionCacheTracker>();
AU.addRequired<LoopInfoWrapperPass>();
AU.addPreserved<LoopInfoWrapperPass>();
AU.addRequiredID(LoopSimplifyID);
AU.addPreservedID(LoopSimplifyID);
AU.addRequiredID(LCSSAID);
AU.addPreservedID(LCSSAID);
AU.addRequired<ScalarEvolution>();
AU.addPreserved<ScalarEvolution>();
AU.addRequired<TargetTransformInfoWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
}
void getUnrollingPreferences(Loop *L, const TargetTransformInfo &TTI,
TargetTransformInfo::UnrollingPreferences &UP) {
UP.Threshold = CurrentThreshold;
UP.AbsoluteThreshold = CurrentAbsoluteThreshold;
UP.MinPercentOfOptimized = CurrentMinPercentOfOptimized;
UP.OptSizeThreshold = OptSizeUnrollThreshold;
UP.PartialThreshold = CurrentThreshold;
UP.PartialOptSizeThreshold = OptSizeUnrollThreshold;
UP.Count = CurrentCount;
UP.MaxCount = UINT_MAX;
UP.Partial = CurrentAllowPartial;
UP.Runtime = CurrentRuntime;
TTI.getUnrollingPreferences(L, UP);
}
unsigned
selectUnrollCount(const Loop *L, unsigned TripCount, bool PragmaFullUnroll,
unsigned PragmaCount,
const TargetTransformInfo::UnrollingPreferences &UP,
bool &SetExplicitly);
void selectThresholds(const Loop *L, bool HasPragma,
const TargetTransformInfo::UnrollingPreferences &UP,
unsigned &Threshold, unsigned &PartialThreshold,
unsigned &AbsoluteThreshold,
unsigned &PercentOfOptimizedForCompleteUnroll) {
Threshold = UserThreshold ? CurrentThreshold : UP.Threshold;
PartialThreshold = UserThreshold ? CurrentThreshold : UP.PartialThreshold;
AbsoluteThreshold = UserAbsoluteThreshold ? CurrentAbsoluteThreshold
: UP.AbsoluteThreshold;
PercentOfOptimizedForCompleteUnroll = UserPercentOfOptimized
? CurrentMinPercentOfOptimized
: UP.MinPercentOfOptimized;
if (!UserThreshold &&
L->getHeader()->getParent()->hasFnAttribute(
Attribute::OptimizeForSize)) {
Threshold = UP.OptSizeThreshold;
PartialThreshold = UP.PartialOptSizeThreshold;
}
if (HasPragma) {
if (Threshold != NoThreshold)
Threshold = std::max<unsigned>(Threshold, PragmaUnrollThreshold);
if (PartialThreshold != NoThreshold)
PartialThreshold =
std::max<unsigned>(PartialThreshold, PragmaUnrollThreshold);
}
}
bool canUnrollCompletely(Loop *L, unsigned Threshold,
unsigned AbsoluteThreshold, uint64_t UnrolledSize,
unsigned NumberOfOptimizedInstructions,
unsigned PercentOfOptimizedForCompleteUnroll);
};
}
char LoopUnroll::ID = 0;
INITIALIZE_PASS_BEGIN(LoopUnroll, "loop-unroll", "Unroll loops", false, false)
INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
INITIALIZE_PASS_DEPENDENCY(LCSSA)
INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
INITIALIZE_PASS_END(LoopUnroll, "loop-unroll", "Unroll loops", false, false)
Pass *llvm::createLoopUnrollPass(int Threshold, int Count, int AllowPartial,
int Runtime) {
return new LoopUnroll(Threshold, Count, AllowPartial, Runtime);
}
Pass *llvm::createSimpleLoopUnrollPass() {
return llvm::createLoopUnrollPass(-1, -1, 0, 0);
}
namespace {
struct FindConstantPointers {
bool IndexIsConstant;
bool HaveSeenAR;
Value *BaseAddress;
const Loop *L;
ScalarEvolution &SE;
FindConstantPointers(const Loop *L, ScalarEvolution &SE)
: IndexIsConstant(true), HaveSeenAR(false), BaseAddress(nullptr),
L(L), SE(SE) {}
bool follow(const SCEV *S) {
if (const SCEVUnknown *SC = dyn_cast<SCEVUnknown>(S)) {
if (BaseAddress) {
IndexIsConstant = false;
return false;
}
BaseAddress = SC->getValue();
return false;
}
if (isa<SCEVConstant>(S))
return false;
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
if (AR->getLoop() != L) {
IndexIsConstant = false;
return false;
}
if (HaveSeenAR) {
IndexIsConstant = false;
return false;
}
HaveSeenAR = true;
}
return true;
}
bool isDone() const { return !IndexIsConstant; }
};
class UnrollAnalyzer : public InstVisitor<UnrollAnalyzer, bool> {
typedef SetVector<BasicBlock *, SmallVector<BasicBlock *, 16>,
SmallPtrSet<BasicBlock *, 16>> BBSetVector;
typedef InstVisitor<UnrollAnalyzer, bool> Base;
friend class InstVisitor<UnrollAnalyzer, bool>;
typedef struct {
Value *BaseAddr;
uint64_t Start;
uint64_t Step;
} SCEVGEPDescriptor;
const Loop *L;
unsigned TripCount;
ScalarEvolution &SE;
const TargetTransformInfo &TTI;
DenseMap<Value *, Constant *> SimplifiedValues;
SmallPtrSet<Instruction *, 16> DeadInstructions;
SmallDenseMap<Value *, SCEVGEPDescriptor> SCEVCache;
unsigned Iteration;
unsigned MaxUnrolledLoopSize;
bool visitInstruction(Instruction &I) { return false; };
bool visitBinaryOperator(BinaryOperator &I) {
Value *LHS = lookupSimplifiedValue(I.getOperand(0));
Value *RHS = lookupSimplifiedValue(I.getOperand(1));
Value *SimpleV = nullptr;
const DataLayout &DL = I.getModule()->getDataLayout();
if (auto FI = dyn_cast<FPMathOperator>(&I))
SimpleV =
SimplifyFPBinOp(I.getOpcode(), LHS, RHS, FI->getFastMathFlags(), DL);
else
SimpleV = SimplifyBinOp(I.getOpcode(), LHS, RHS, DL);
if (SimpleV)
NumberOfOptimizedInstructions += TTI.getUserCost(&I);
if (Constant *C = dyn_cast_or_null<Constant>(SimpleV)) {
SimplifiedValues[&I] = C;
return true;
}
return false;
}
bool visitLoad(LoadInst &I) {
Value *AddrOp = lookupSimplifiedValue(I.getPointerOperand());
auto It = SCEVCache.find(AddrOp);
if (It == SCEVCache.end())
return false;
SCEVGEPDescriptor d = It->second;
auto GV = dyn_cast<GlobalVariable>(d.BaseAddr);
if (!GV || !GV->hasInitializer())
return false;
ConstantDataSequential *CDS =
dyn_cast<ConstantDataSequential>(GV->getInitializer());
if (!CDS)
return false;
unsigned ElemSize = CDS->getElementType()->getPrimitiveSizeInBits() / 8U;
uint64_t Index = (d.Start + d.Step * Iteration) / ElemSize;
if (Index >= CDS->getNumElements())
return false;
Constant *CV = CDS->getElementAsConstant(Index);
assert(CV && "Constant expected.");
SimplifiedValues[&I] = CV;
NumberOfOptimizedInstructions += TTI.getUserCost(&I);
return true;
}
void cacheSCEVResults() {
for (auto BB : L->getBlocks()) {
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
Value *V = cast<Value>(GEP);
if (!SE.isSCEVable(V->getType()))
continue;
const SCEV *S = SE.getSCEV(V);
FindConstantPointers Visitor(L, SE);
SCEVTraversal<FindConstantPointers> T(Visitor);
T.visitAll(S);
if (!Visitor.IndexIsConstant || !Visitor.BaseAddress)
continue;
SCEVGEPDescriptor d;
d.BaseAddr = Visitor.BaseAddress;
const SCEV *BaseAddrSE = SE.getSCEV(d.BaseAddr);
if (BaseAddrSE->getType() != S->getType())
continue;
const SCEV *OffSE = SE.getMinusSCEV(S, BaseAddrSE);
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(OffSE);
if (!AR)
continue;
const SCEVConstant *StepSE =
dyn_cast<SCEVConstant>(AR->getStepRecurrence(SE));
const SCEVConstant *StartSE = dyn_cast<SCEVConstant>(AR->getStart());
if (!StepSE || !StartSE)
continue;
APInt StepAP = StepSE->getValue()->getValue();
APInt StartAP = StartSE->getValue()->getValue();
if (StartAP.getActiveBits() > 32 || StepAP.getActiveBits() > 32)
continue;
d.Start = StartAP.getLimitedValue();
d.Step = StepAP.getLimitedValue();
SCEVCache[V] = d;
}
}
}
}
Value *lookupSimplifiedValue(Value *V) {
if (isa<Constant>(V))
return V;
if (Constant *SimplifiedV = SimplifiedValues.lookup(V))
return SimplifiedV;
return V;
}
public:
UnrollAnalyzer(const Loop *L, unsigned TripCount, ScalarEvolution &SE,
const TargetTransformInfo &TTI, unsigned MaxUnrolledLoopSize)
: L(L), TripCount(TripCount), SE(SE), TTI(TTI),
MaxUnrolledLoopSize(MaxUnrolledLoopSize) {}
unsigned NumberOfOptimizedInstructions;
unsigned UnrolledLoopSize;
bool analyzeLoop() {
BBSetVector BBWorklist;
UnrolledLoopSize = 0;
NumberOfOptimizedInstructions = 0;
if (!UnrollMaxIterationsCountToAnalyze || !TripCount ||
TripCount > UnrollMaxIterationsCountToAnalyze)
return false;
cacheSCEVResults();
for (Iteration = 0; Iteration < TripCount; ++Iteration) {
SimplifiedValues.clear();
DeadInstructions.clear();
BBWorklist.clear();
BBWorklist.insert(L->getHeader());
for (unsigned Idx = 0; Idx != BBWorklist.size(); ++Idx) {
BasicBlock *BB = BBWorklist[Idx];
if (BB->empty())
continue;
for (Instruction &I : *BB) {
UnrolledLoopSize += TTI.getUserCost(&I);
Base::visit(I);
if (UnrolledLoopSize - NumberOfOptimizedInstructions >
MaxUnrolledLoopSize)
return false;
}
for (BasicBlock *Succ : successors(BB))
if (L->contains(Succ))
BBWorklist.insert(Succ);
}
if (!NumberOfOptimizedInstructions)
return false;
for (unsigned Idx = BBWorklist.size() - 1; Idx != 0; --Idx) {
BasicBlock *BB = BBWorklist[Idx];
if (BB->empty())
continue;
for (BasicBlock::reverse_iterator I = BB->rbegin(), E = BB->rend(); I != E; ++I) {
if (SimplifiedValues.count(&*I))
continue;
if (DeadInstructions.count(&*I))
continue;
if (std::all_of(I->user_begin(), I->user_end(), [&](User *U) {
return SimplifiedValues.count(cast<Instruction>(U)) +
DeadInstructions.count(cast<Instruction>(U));
})) {
NumberOfOptimizedInstructions += TTI.getUserCost(&*I);
DeadInstructions.insert(&*I);
}
}
}
}
return true;
}
};
}
static unsigned ApproximateLoopSize(const Loop *L, unsigned &NumCalls,
bool &NotDuplicatable,
const TargetTransformInfo &TTI,
AssumptionCache *AC) {
SmallPtrSet<const Value *, 32> EphValues;
CodeMetrics::collectEphemeralValues(L, AC, EphValues);
CodeMetrics Metrics;
for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
I != E; ++I)
Metrics.analyzeBasicBlock(*I, TTI, EphValues);
NumCalls = Metrics.NumInlineCandidates;
NotDuplicatable = Metrics.notDuplicatable;
unsigned LoopSize = Metrics.NumInsts;
LoopSize = std::max(LoopSize, 3u);
return LoopSize;
}
static MDNode *GetUnrollMetadataForLoop(const Loop *L, StringRef Name) {
if (MDNode *LoopID = L->getLoopID())
return GetUnrollMetadata(LoopID, Name);
return nullptr;
}
static bool HasUnrollFullPragma(const Loop *L) {
return GetUnrollMetadataForLoop(L, "llvm.loop.unroll.full");
}
static bool HasUnrollDisablePragma(const Loop *L) {
return GetUnrollMetadataForLoop(L, "llvm.loop.unroll.disable");
}
static unsigned UnrollCountPragmaValue(const Loop *L) {
MDNode *MD = GetUnrollMetadataForLoop(L, "llvm.loop.unroll.count");
if (MD) {
assert(MD->getNumOperands() == 2 &&
"Unroll count hint metadata should have two operands.");
unsigned Count =
mdconst::extract<ConstantInt>(MD->getOperand(1))->getZExtValue();
assert(Count >= 1 && "Unroll count must be positive.");
return Count;
}
return 0;
}
static void SetLoopAlreadyUnrolled(Loop *L) {
MDNode *LoopID = L->getLoopID();
if (!LoopID) return;
SmallVector<Metadata *, 4> MDs;
MDs.push_back(nullptr);
for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
bool IsUnrollMetadata = false;
MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
if (MD) {
const MDString *S = dyn_cast<MDString>(MD->getOperand(0));
IsUnrollMetadata = S && S->getString().startswith("llvm.loop.unroll.");
}
if (!IsUnrollMetadata)
MDs.push_back(LoopID->getOperand(i));
}
LLVMContext &Context = L->getHeader()->getContext();
SmallVector<Metadata *, 1> DisableOperands;
DisableOperands.push_back(MDString::get(Context, "llvm.loop.unroll.disable"));
MDNode *DisableNode = MDNode::get(Context, DisableOperands);
MDs.push_back(DisableNode);
MDNode *NewLoopID = MDNode::get(Context, MDs);
NewLoopID->replaceOperandWith(0, NewLoopID);
L->setLoopID(NewLoopID);
}
bool LoopUnroll::canUnrollCompletely(
Loop *L, unsigned Threshold, unsigned AbsoluteThreshold,
uint64_t UnrolledSize, unsigned NumberOfOptimizedInstructions,
unsigned PercentOfOptimizedForCompleteUnroll) {
if (Threshold == NoThreshold) {
DEBUG(dbgs() << " Can fully unroll, because no threshold is set.\n");
return true;
}
if (UnrolledSize <= Threshold) {
DEBUG(dbgs() << " Can fully unroll, because unrolled size: "
<< UnrolledSize << "<" << Threshold << "\n");
return true;
}
if (NumberOfOptimizedInstructions > UINT_MAX / 100)
NumberOfOptimizedInstructions = 0;
unsigned PercentOfOptimizedInstructions =
NumberOfOptimizedInstructions * 100 /
UnrolledSize; if (UnrolledSize <= AbsoluteThreshold &&
PercentOfOptimizedInstructions >= PercentOfOptimizedForCompleteUnroll) {
DEBUG(dbgs() << " Can fully unroll, because unrolling will help removing "
<< PercentOfOptimizedInstructions
<< "% instructions (threshold: "
<< PercentOfOptimizedForCompleteUnroll << "%)\n");
DEBUG(dbgs() << " Unrolled size (" << UnrolledSize
<< ") is less than the threshold (" << AbsoluteThreshold
<< ").\n");
return true;
}
DEBUG(dbgs() << " Too large to fully unroll:\n");
DEBUG(dbgs() << " Unrolled size: " << UnrolledSize << "\n");
DEBUG(dbgs() << " Estimated number of optimized instructions: "
<< NumberOfOptimizedInstructions << "\n");
DEBUG(dbgs() << " Absolute threshold: " << AbsoluteThreshold << "\n");
DEBUG(dbgs() << " Minimum percent of removed instructions: "
<< PercentOfOptimizedForCompleteUnroll << "\n");
DEBUG(dbgs() << " Threshold for small loops: " << Threshold << "\n");
return false;
}
unsigned LoopUnroll::selectUnrollCount(
const Loop *L, unsigned TripCount, bool PragmaFullUnroll,
unsigned PragmaCount, const TargetTransformInfo::UnrollingPreferences &UP,
bool &SetExplicitly) {
SetExplicitly = true;
unsigned Count = UserCount ? CurrentCount : 0;
if (Count == 0) {
if (PragmaCount) {
Count = PragmaCount;
} else if (PragmaFullUnroll) {
Count = TripCount;
}
}
if (Count == 0)
Count = UP.Count;
if (Count == 0) {
SetExplicitly = false;
if (TripCount == 0)
Count = UnrollRuntimeCount;
else
Count = TripCount;
}
if (TripCount && Count > TripCount)
return TripCount;
return Count;
}
bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
if (skipOptnoneFunction(L))
return false;
Function &F = *L->getHeader()->getParent();
LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
ScalarEvolution *SE = &getAnalysis<ScalarEvolution>();
const TargetTransformInfo &TTI =
getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
BasicBlock *Header = L->getHeader();
DEBUG(dbgs() << "Loop Unroll: F[" << Header->getParent()->getName()
<< "] Loop %" << Header->getName() << "\n");
if (HasUnrollDisablePragma(L)) {
return false;
}
bool PragmaFullUnroll = HasUnrollFullPragma(L);
unsigned PragmaCount = UnrollCountPragmaValue(L);
bool HasPragma = PragmaFullUnroll || PragmaCount > 0;
TargetTransformInfo::UnrollingPreferences UP;
getUnrollingPreferences(L, TTI, UP);
unsigned TripCount = 0;
unsigned TripMultiple = 1;
BasicBlock *ExitingBlock = L->getLoopLatch();
if (!ExitingBlock || !L->isLoopExiting(ExitingBlock))
ExitingBlock = L->getExitingBlock();
if (ExitingBlock) {
TripCount = SE->getSmallConstantTripCount(L, ExitingBlock);
TripMultiple = SE->getSmallConstantTripMultiple(L, ExitingBlock);
}
bool CountSetExplicitly;
unsigned Count = selectUnrollCount(L, TripCount, PragmaFullUnroll,
PragmaCount, UP, CountSetExplicitly);
unsigned NumInlineCandidates;
bool notDuplicatable;
unsigned LoopSize =
ApproximateLoopSize(L, NumInlineCandidates, notDuplicatable, TTI, &AC);
DEBUG(dbgs() << " Loop Size = " << LoopSize << "\n");
uint64_t UnrolledSize = (uint64_t)(LoopSize-2) * Count + 2;
if (notDuplicatable) {
DEBUG(dbgs() << " Not unrolling loop which contains non-duplicatable"
<< " instructions.\n");
return false;
}
if (NumInlineCandidates != 0) {
DEBUG(dbgs() << " Not unrolling loop with inlinable calls.\n");
return false;
}
unsigned Threshold, PartialThreshold;
unsigned AbsoluteThreshold, PercentOfOptimizedForCompleteUnroll;
selectThresholds(L, HasPragma, UP, Threshold, PartialThreshold,
AbsoluteThreshold, PercentOfOptimizedForCompleteUnroll);
enum { Full = 0, Partial = 1, Runtime = 2 };
int Unrolling;
if (TripCount && Count == TripCount) {
Unrolling = Partial;
if (canUnrollCompletely(
L, Threshold, AbsoluteThreshold,
UnrolledSize, 0, 100)) {
Unrolling = Full;
} else {
UnrollAnalyzer UA(L, TripCount, *SE, TTI, AbsoluteThreshold);
if (UA.analyzeLoop() && canUnrollCompletely(
L, Threshold, AbsoluteThreshold,
std::min<uint64_t>(UnrolledSize, UA.UnrolledLoopSize),
UA.NumberOfOptimizedInstructions,
PercentOfOptimizedForCompleteUnroll)) {
Unrolling = Full;
}
}
} else if (TripCount && Count < TripCount) {
Unrolling = Partial;
} else {
Unrolling = Runtime;
}
unsigned OriginalCount = Count;
bool AllowRuntime = UserRuntime ? CurrentRuntime : UP.Runtime;
if (Unrolling == Partial) {
bool AllowPartial = UserAllowPartial ? CurrentAllowPartial : UP.Partial;
if (!AllowPartial && !CountSetExplicitly) {
DEBUG(dbgs() << " will not try to unroll partially because "
<< "-unroll-allow-partial not given\n");
return false;
}
if (PartialThreshold != NoThreshold && UnrolledSize > PartialThreshold) {
Count = (std::max(PartialThreshold, 3u)-2) / (LoopSize-2);
while (Count != 0 && TripCount % Count != 0)
Count--;
}
} else if (Unrolling == Runtime) {
if (!AllowRuntime && !CountSetExplicitly) {
DEBUG(dbgs() << " will not try to unroll loop with runtime trip count "
<< "-unroll-runtime not given\n");
return false;
}
while (Count != 0 && UnrolledSize > PartialThreshold) {
Count >>= 1;
UnrolledSize = (LoopSize-2) * Count + 2;
}
if (Count > UP.MaxCount)
Count = UP.MaxCount;
DEBUG(dbgs() << " partially unrolling with count: " << Count << "\n");
}
if (HasPragma) {
if (PragmaCount != 0)
SetLoopAlreadyUnrolled(L);
DebugLoc LoopLoc = L->getStartLoc();
Function *F = Header->getParent();
LLVMContext &Ctx = F->getContext();
if (PragmaFullUnroll && PragmaCount == 0) {
if (TripCount && Count != TripCount) {
emitOptimizationRemarkMissed(
Ctx, DEBUG_TYPE, *F, LoopLoc,
"Unable to fully unroll loop as directed by unroll(full) pragma "
"because unrolled size is too large.");
} else if (!TripCount) {
emitOptimizationRemarkMissed(
Ctx, DEBUG_TYPE, *F, LoopLoc,
"Unable to fully unroll loop as directed by unroll(full) pragma "
"because loop has a runtime trip count.");
}
} else if (PragmaCount > 0 && Count != OriginalCount) {
emitOptimizationRemarkMissed(
Ctx, DEBUG_TYPE, *F, LoopLoc,
"Unable to unroll loop the number of times directed by "
"unroll_count pragma because unrolled size is too large.");
}
}
if (Unrolling != Full && Count < 2) {
return false;
}
if (!UnrollLoop(L, Count, TripCount, AllowRuntime, TripMultiple, LI, this,
&LPM, &AC))
return false;
return true;
}