#include <DependenceAnalysis.h>

Inheritance diagram for llvm::DependenceAnalysis:

Collaboration diagram for llvm::DependenceAnalysis:

Public Member Functions
Dependence *	depends (Instruction Src, Instruction Dst, bool PossiblyLoopIndependent)

const SCEV *	getSplitIteration (const Dependence *Dep, unsigned Level)

	DependenceAnalysis ()

bool	runOnFunction (Function &F)

void	releaseMemory ()

void	getAnalysisUsage (AnalysisUsage &) const

void	print (raw_ostream &, const Module *=0) const

Public Member Functions inherited from llvm::FunctionPass
	FunctionPass (char &pid)

Pass *	createPrinterPass (raw_ostream &O, const std::string &Banner) const
	createPrinterPass - Get a function printer pass. More...

virtual void	assignPassManager (PMStack &PMS, PassManagerType T)

virtual PassManagerType	getPotentialPassManagerType () const
	Return what kind of Pass Manager can manage this pass. More...

Public Member Functions inherited from llvm::Pass
	Pass (PassKind K, char &pid)

virtual	~Pass ()

PassKind	getPassKind () const

virtual const char *	getPassName () const

AnalysisID	getPassID () const
	getPassID - Return the PassID number that corresponds to this pass. More...

virtual bool	doInitialization (Module &)

virtual bool	doFinalization (Module &)

void	dump () const

virtual void	preparePassManager (PMStack &)
	Check if available pass managers are suitable for this pass or not. More...

void	setResolver (AnalysisResolver *AR)

AnalysisResolver *	getResolver () const

virtual void *	getAdjustedAnalysisPointer (AnalysisID ID)

virtual ImmutablePass *	getAsImmutablePass ()

virtual PMDataManager *	getAsPMDataManager ()

virtual void	verifyAnalysis () const

virtual void	dumpPassStructure (unsigned Offset=0)

template<typename AnalysisType >
AnalysisType *	getAnalysisIfAvailable () const

bool	mustPreserveAnalysisID (char &AID) const

template<typename AnalysisType >
AnalysisType &	getAnalysis () const

template<typename AnalysisType >
AnalysisType &	getAnalysis (Function &F)

template<typename AnalysisType >
AnalysisType &	getAnalysisID (AnalysisID PI) const

template<typename AnalysisType >
AnalysisType &	getAnalysisID (AnalysisID PI, Function &F)

Static Public Attributes
static char	ID = 0

Additional Inherited Members
Static Public Member Functions inherited from llvm::Pass
static const PassInfo *	lookupPassInfo (const void *TI)

static const PassInfo *	lookupPassInfo (StringRef Arg)

static Pass *	createPass (AnalysisID ID)

Detailed Description

DependenceAnalysis - This class is the main dependence-analysis driver.

Definition at line 280 of file DependenceAnalysis.h.

Constructor & Destructor Documentation

llvm::DependenceAnalysis::DependenceAnalysis ( )

inline

Definition at line 917 of file DependenceAnalysis.h.

References llvm::PassRegistry::getPassRegistry(), and llvm::initializeDependenceAnalysisPass().

Member Function Documentation

Dependence * DependenceAnalysis::depends	(	Instruction *	Src,
		Instruction *	Dst,
		bool	PossiblyLoopIndependent
	)

depends - Tests for a dependence between the Src and Dst instructions. Returns NULL if no dependence; otherwise, returns a Dependence (or a FullDependence) with as much information as can be gleaned. The flag PossiblyLoopIndependent should be set by the caller if it appears that control flow can reach from Src to Dst without traversing a loop back edge.

Definition at line 3256 of file DependenceAnalysis.cpp.

References llvm::SmallBitVector::any(), llvm::SmallBitVector::count(), llvm::dbgs(), DEBUG, Delinearize, llvm::Dependence::DVEntry::Direction, dumpSmallBitVector(), llvm::dyn_cast(), llvm::Dependence::DVEntry::EQ, llvm::SmallBitVector::find_first(), llvm::SmallBitVector::find_next(), llvm::FullDependence::getDirection(), llvm::Instruction::getParent(), llvm::GEPOperator::getPointerOperand(), getPointerOperand(), llvm::GEPOperator::getPointerOperandType(), llvm::ScalarEvolution::getSCEV(), llvm::GEPOperator::idx_begin(), llvm::GEPOperator::idx_end(), isLoadOrStore(), isLoopInvariant(), LI, llvm_unreachable, llvm::AliasAnalysis::MayAlias, llvm::Instruction::mayReadFromMemory(), llvm::Instruction::mayWriteToMemory(), llvm::AliasAnalysis::MustAlias, llvm::AliasAnalysis::NoAlias, llvm::Dependence::DVEntry::NONE, P, llvm::AliasAnalysis::PartialAlias, llvm::SmallBitVector::reset(), llvm::SmallVectorImpl< T >::resize(), llvm::Dependence::DVEntry::Scalar, llvm::SmallBitVector::set(), llvm::SmallVectorTemplateCommon< T >::size(), and underlyingObjectsAlias().

Referenced by dumpExampleDependence().

void DependenceAnalysis::getAnalysisUsage ( AnalysisUsage & ) const

virtual

getAnalysisUsage - This function should be overriden by passes that need analysis information to do their job. If a pass specifies that it uses a particular analysis result to this function, it can then use the getAnalysis<AnalysisType>() function, below.

Reimplemented from llvm::Pass.

Definition at line 144 of file DependenceAnalysis.cpp.

References llvm::AnalysisUsage::addRequiredTransitive(), and llvm::AnalysisUsage::setPreservesAll().

const SCEV * DependenceAnalysis::getSplitIteration	(	const Dependence *	Dep,
		unsigned	Level
	)

getSplitIteration - Give a dependence that's splittable at some particular level, return the iteration that should be used to split the loop.

Generally, the dependence analyzer will be used to build a dependence graph for a function (basically a map from instructions to dependences). Looking for cycles in the graph shows us loops that cannot be trivially vectorized/parallelized.

We can try to improve the situation by examining all the dependences that make up the cycle, looking for ones we can break. Sometimes, peeling the first or last iteration of a loop will break dependences, and there are flags for those possibilities. Sometimes, splitting a loop at some other iteration will do the trick, and we've got a flag for that case. Rather than waste the space to record the exact iteration (since we rarely know), we provide a method that calculates the iteration. It's a drag that it must work from scratch, but wonderful in that it's possible.

Here's an example:

for (i = 0; i < 10; i++) A[i] = ... ... = A[11 - i]

There's a loop-carried flow dependence from the store to the load, found by the weak-crossing SIV test. The dependence will have a flag, indicating that the dependence can be broken by splitting the loop. Calling getSplitIteration will return 5. Splitting the loop breaks the dependence, like so:

for (i = 0; i <= 5; i++) A[i] = ... ... = A[11 - i] for (i = 6; i < 10; i++) A[i] = ... ... = A[11 - i]

breaks the dependence and allows us to vectorize/parallelize both loops.

Definition at line 3708 of file DependenceAnalysis.cpp.

References llvm::SmallBitVector::any(), llvm::SmallBitVector::count(), llvm::dbgs(), DEBUG, Delinearize, llvm::dyn_cast(), llvm::SmallBitVector::find_first(), llvm::SmallBitVector::find_next(), llvm::Dependence::getDst(), llvm::Instruction::getParent(), llvm::GEPOperator::getPointerOperand(), getPointerOperand(), llvm::GEPOperator::getPointerOperandType(), llvm::ScalarEvolution::getSCEV(), llvm::Dependence::getSrc(), llvm::GEPOperator::idx_begin(), llvm::GEPOperator::idx_end(), isLoadOrStore(), isLoopInvariant(), llvm::Dependence::isSplitable(), LI, llvm_unreachable, llvm::Instruction::mayReadFromMemory(), llvm::Instruction::mayWriteToMemory(), llvm::AliasAnalysis::MustAlias, P, llvm::SmallBitVector::reset(), llvm::SmallVectorImpl< T >::resize(), llvm::SmallBitVector::set(), llvm::SmallVectorTemplateCommon< T >::size(), and underlyingObjectsAlias().

Referenced by dumpExampleDependence().

void DependenceAnalysis::print	(	raw_ostream &	O,
		const Module *	M = `0`
	)		const

virtual

print - Print out the internal state of the pass. This is called by Analyze to print out the contents of an analysis. Otherwise it is not necessary to implement this method. Beware that the module pointer MAY be null. This automatically forwards to a virtual function that does not provide the Module* in case the analysis doesn't need it it can just be ignored.

Reimplemented from llvm::Pass.

Definition at line 186 of file DependenceAnalysis.cpp.

References dumpExampleDependence(), and F().

void DependenceAnalysis::releaseMemory ( )

virtual

releaseMemory() - This member can be implemented by a pass if it wants to be able to release its memory when it is no longer needed. The default behavior of passes is to hold onto memory for the entire duration of their lifetime (which is the entire compile time). For pipelined passes, this is not a big deal because that memory gets recycled every time the pass is invoked on another program unit. For IP passes, it is more important to free memory when it is unused.

Optionally implement this function to release pass memory when it is no longer used.

Reimplemented from llvm::Pass.

Definition at line 140 of file DependenceAnalysis.cpp.

bool DependenceAnalysis::runOnFunction ( Function & F )

virtual

runOnFunction - Virtual method overriden by subclasses to do the per-function processing of the pass.

Implements llvm::FunctionPass.

Definition at line 131 of file DependenceAnalysis.cpp.

References F(), and LI.

Member Data Documentation

Dependence true char DependenceAnalysis::ID = 0

static

Definition at line 916 of file DependenceAnalysis.h.

The documentation for this class was generated from the following files:

Public Member Functions

Static Public Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation