Analysis providing branch probability information. More...

#include "llvm/Analysis/BranchProbabilityInfo.h"

Classes
struct	SccInfo

Public Types
using	SccMap = DenseMap< const BasicBlock *, int >

using	SccHeaderMap = DenseMap< const BasicBlock *, bool >

using	SccHeaderMaps = std::vector< SccHeaderMap >

Public Member Functions
	BranchProbabilityInfo ()=default

	BranchProbabilityInfo (const Function &F, const LoopInfo &LI, const TargetLibraryInfo *TLI=nullptr)

	BranchProbabilityInfo (BranchProbabilityInfo &&Arg)

	BranchProbabilityInfo (const BranchProbabilityInfo &)=delete

BranchProbabilityInfo &	operator= (const BranchProbabilityInfo &)=delete

BranchProbabilityInfo &	operator= (BranchProbabilityInfo &&RHS)

void	releaseMemory ()

void	print (raw_ostream &OS) const

BranchProbability	getEdgeProbability (const BasicBlock *Src, unsigned IndexInSuccessors) const
	Get an edge's probability, relative to other out-edges of the Src. More...

BranchProbability	getEdgeProbability (const BasicBlock Src, const BasicBlock Dst) const
	Get the probability of going from Src to Dst. More...

BranchProbability	getEdgeProbability (const BasicBlock *Src, succ_const_iterator Dst) const

bool	isEdgeHot (const BasicBlock Src, const BasicBlock Dst) const
	Test if an edge is hot relative to other out-edges of the Src. More...

const BasicBlock *	getHotSucc (const BasicBlock *BB) const
	Retrieve the hot successor of a block if one exists. More...

raw_ostream &	printEdgeProbability (raw_ostream &OS, const BasicBlock Src, const BasicBlock Dst) const
	Print an edge's probability. More...

void	setEdgeProbability (const BasicBlock *Src, unsigned IndexInSuccessors, BranchProbability Prob)
	Set the raw edge probability for the given edge. More...

void	calculate (const Function &F, const LoopInfo &LI, const TargetLibraryInfo *TLI=nullptr)

void	eraseBlock (const BasicBlock *BB)
	Forget analysis results for the given basic block. More...

Static Public Member Functions
static BranchProbability	getBranchProbStackProtector (bool IsLikely)

Detailed Description

Analysis providing branch probability information.

This is a function analysis which provides information on the relative probabilities of each "edge" in the function's CFG where such an edge is defined by a pair (PredBlock and an index in the successors). The probability of an edge from one block is always relative to the probabilities of other edges from the block. The probabilites of all edges from a block sum to exactly one (100%). We use a pair (PredBlock and an index in the successors) to uniquely identify an edge, since we can have multiple edges from Src to Dst. As an example, we can have a switch which jumps to Dst with value 0 and value 10.

Definition at line 53 of file BranchProbabilityInfo.h.

Member Typedef Documentation

◆ SccHeaderMap

using llvm::BranchProbabilityInfo::SccHeaderMap = DenseMap<const BasicBlock *, bool>

Definition at line 142 of file BranchProbabilityInfo.h.

◆ SccHeaderMaps

using llvm::BranchProbabilityInfo::SccHeaderMaps = std::vector<SccHeaderMap>

Definition at line 143 of file BranchProbabilityInfo.h.

◆ SccMap

using llvm::BranchProbabilityInfo::SccMap = DenseMap<const BasicBlock *, int>

Definition at line 141 of file BranchProbabilityInfo.h.

Constructor & Destructor Documentation

◆ BranchProbabilityInfo() [1/4]

llvm::BranchProbabilityInfo::BranchProbabilityInfo ( )

default

Referenced by BranchProbabilityInfo().

◆ BranchProbabilityInfo() [2/4]

llvm::BranchProbabilityInfo::BranchProbabilityInfo	(	const Function &	F,
		const LoopInfo &	LI,
		const TargetLibraryInfo *	TLI = `nullptr`
	)

inline

Definition at line 57 of file BranchProbabilityInfo.h.

References calculate().

◆ BranchProbabilityInfo() [3/4]

llvm::BranchProbabilityInfo::BranchProbabilityInfo ( BranchProbabilityInfo && Arg )

inline

Definition at line 62 of file BranchProbabilityInfo.h.

References BranchProbabilityInfo(), and operator=().

◆ BranchProbabilityInfo() [4/4]

llvm::BranchProbabilityInfo::BranchProbabilityInfo ( const BranchProbabilityInfo & )

delete

Member Function Documentation

◆ calculate()

void BranchProbabilityInfo::calculate	(	const Function &	F,
		const LoopInfo &	LI,
		const TargetLibraryInfo *	TLI = `nullptr`
	)

Definition at line 932 of file BranchProbabilityInfo.cpp.

References assert(), llvm::dbgs(), llvm::StringRef::equals(), F(), llvm::Function::getEntryBlock(), llvm::Value::getName(), LLVM_DEBUG, llvm::post_order(), print(), PrintBranchProb, PrintBranchProbFuncName, llvm::scc_begin(), and llvm::BranchProbabilityInfo::SccInfo::SccNums.

Referenced by BranchProbabilityInfo(), getBranchProbStackProtector(), llvm::OptimizationRemarkEmitter::OptimizationRemarkEmitter(), and llvm::BranchProbabilityAnalysis::run().

◆ eraseBlock()

void BranchProbabilityInfo::eraseBlock ( const BasicBlock * BB )

Forget analysis results for the given basic block.

Definition at line 924 of file BranchProbabilityInfo.cpp.

References E, and I.

Referenced by getBranchProbStackProtector(), and llvm::SplitIndirectBrCriticalEdges().

◆ getBranchProbStackProtector()

static BranchProbability llvm::BranchProbabilityInfo::getBranchProbStackProtector ( bool IsLikely )

inlinestatic

Definition at line 129 of file BranchProbabilityInfo.h.

References calculate(), eraseBlock(), F(), and llvm::BranchProbability::getCompl().

Referenced by CreatePrologue(), and tryToElideArgumentCopy().

◆ getEdgeProbability() [1/3]

BranchProbability BranchProbabilityInfo::getEdgeProbability	(	const BasicBlock *	Src,
		unsigned	IndexInSuccessors
	)		const

Get an edge's probability, relative to other out-edges of the Src.

Get the raw edge probability for the edge.

This routine provides access to the fractional probability between zero (0%) and one (100%) of this edge executing, relative to other edges leaving the 'Src' block. The returned probability is never zero, and can only be one if the source block has only one successor.

If can't find it, return a default probability 1/N where N is the number of successors. Here an edge is specified using PredBlock and an index to the successors.

Definition at line 865 of file BranchProbabilityInfo.cpp.

References I, and llvm::succ_size().

Referenced by llvm::CFGMST< Edge, BBInfo >::buildEdges(), llvm::CodeExtractor::extractCodeRegion(), findUnwindDestinations(), getBranchHint(), getEdgeProbability(), getHotSucc(), isEdgeHot(), llvm::SelectionDAGBuilder::isExportableFromCurrentBlock(), operator=(), printEdgeProbability(), scaleCaseProbality(), llvm::SplitIndirectBrCriticalEdges(), tryToElideArgumentCopy(), and llvm::SelectionDAGBuilder::visitBitTestCase().

◆ getEdgeProbability() [2/3]

BranchProbability BranchProbabilityInfo::getEdgeProbability	(	const BasicBlock *	Src,
		const BasicBlock *	Dst
	)		const

Get the probability of going from Src to Dst.

Get the raw edge probability calculated for the block pair.

It returns the sum of all probabilities for edges from Src to Dst.

This returns the sum of all raw edge probabilities from Src to Dst.

Definition at line 884 of file BranchProbabilityInfo.cpp.

References E, llvm::BranchProbability::getZero(), I, llvm::succ_begin(), and llvm::succ_end().

◆ getEdgeProbability() [3/3]

BranchProbability BranchProbabilityInfo::getEdgeProbability	(	const BasicBlock *	Src,
		succ_const_iterator	Dst
	)		const

Definition at line 876 of file BranchProbabilityInfo.cpp.

References getEdgeProbability(), and llvm::SuccIterator< InstructionT, BlockT >::getSuccessorIndex().

◆ getHotSucc()

const BasicBlock * BranchProbabilityInfo::getHotSucc ( const BasicBlock * BB ) const

Retrieve the hot successor of a block if one exists.

Given a basic block, look through its successors and if one exists for which

See also: isEdgeHot would return true, return that successor block.

Definition at line 840 of file BranchProbabilityInfo.cpp.

References E, getEdgeProbability(), llvm::BranchProbability::getZero(), I, llvm::succ_begin(), and llvm::succ_end().

Referenced by operator=().

◆ isEdgeHot()

bool BranchProbabilityInfo::isEdgeHot	(	const BasicBlock *	Src,
		const BasicBlock *	Dst
	)		const

Test if an edge is hot relative to other out-edges of the Src.

Check whether this edge out of the source block is 'hot'. We define hot as having a relative probability >= 80%.

Definition at line 833 of file BranchProbabilityInfo.cpp.

References getEdgeProbability().

Referenced by operator=(), print(), and printEdgeProbability().

◆ operator=() [1/2]

BranchProbabilityInfo& llvm::BranchProbabilityInfo::operator= ( const BranchProbabilityInfo & )

delete

Referenced by BranchProbabilityInfo().

◆ operator=() [2/2]

BranchProbabilityInfo& llvm::BranchProbabilityInfo::operator= ( BranchProbabilityInfo && RHS )

inline

Definition at line 70 of file BranchProbabilityInfo.h.

References getEdgeProbability(), getHotSucc(), isEdgeHot(), print(), printEdgeProbability(), releaseMemory(), and setEdgeProbability().

◆ print()

void BranchProbabilityInfo::print ( raw_ostream & OS ) const

Definition at line 819 of file BranchProbabilityInfo.cpp.

References assert(), isEdgeHot(), printEdgeProbability(), SI, llvm::succ_begin(), and llvm::succ_end().

Referenced by calculate(), llvm::BranchProbabilityInfoWrapperPass::getBPI(), operator=(), and llvm::BranchProbabilityPrinterPass::run().

◆ printEdgeProbability()

raw_ostream & BranchProbabilityInfo::printEdgeProbability	(	raw_ostream &	OS,
		const BasicBlock *	Src,
		const BasicBlock *	Dst
	)		const

Print an edge's probability.

Retrieves an edge's probability similarly to

See also: getEdgeProbability, but then prints that probability to the provided stream. That stream is then returned.

Definition at line 913 of file BranchProbabilityInfo.cpp.

References getEdgeProbability(), llvm::Value::getName(), and isEdgeHot().

Referenced by operator=(), and print().

◆ releaseMemory()

void BranchProbabilityInfo::releaseMemory ( )

Definition at line 815 of file BranchProbabilityInfo.cpp.

Referenced by llvm::BranchProbabilityInfoWrapperPass::getBPI(), and operator=().

◆ setEdgeProbability()

void BranchProbabilityInfo::setEdgeProbability	(	const BasicBlock *	Src,
		unsigned	IndexInSuccessors,
		BranchProbability	Prob
	)

Set the raw edge probability for the given edge.

Set the edge probability for a given edge specified by PredBlock and an index to the successors.

This allows a pass to explicitly set the edge probability for an edge. It can be used when updating the CFG to update and preserve the branch probability information. Read the implementation of how these edge probabilities are calculated carefully before using!

Definition at line 902 of file BranchProbabilityInfo.cpp.

References llvm::dbgs(), llvm::Value::getName(), and LLVM_DEBUG.

Referenced by computeUnlikelySuccessors(), llvm::CodeExtractor::findInputsOutputs(), operator=(), and llvm::SplitIndirectBrCriticalEdges().

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

include/llvm/Analysis/BranchProbabilityInfo.h
lib/Analysis/BranchProbabilityInfo.cpp

Classes

Public Types

Public Member Functions

Static Public Member Functions

Detailed Description

Member Typedef Documentation

◆ SccHeaderMap

◆ SccHeaderMaps

◆ SccMap

Constructor & Destructor Documentation

◆ BranchProbabilityInfo() [1/4]

◆ BranchProbabilityInfo() [2/4]

◆ BranchProbabilityInfo() [3/4]

◆ BranchProbabilityInfo() [4/4]

Member Function Documentation

◆ calculate()

◆ eraseBlock()

◆ getBranchProbStackProtector()

◆ getEdgeProbability() [1/3]

◆ getEdgeProbability() [2/3]

◆ getEdgeProbability() [3/3]

◆ getHotSucc()

◆ isEdgeHot()

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ print()

◆ printEdgeProbability()

◆ releaseMemory()

◆ setEdgeProbability()