This class emits a version of the loop where run-time checks ensure that may-alias pointers can't overlap. More...

#include "llvm/Transforms/Utils/LoopVersioning.h"

Public Member Functions
	LoopVersioning (const LoopAccessInfo &LAI, Loop L, LoopInfo LI, DominatorTree DT, ScalarEvolution SE, bool UseLAIChecks=true)
	Expects LoopAccessInfo, Loop, LoopInfo, DominatorTree as input. More...

void	versionLoop ()
	Performs the CFG manipulation part of versioning the loop including the DominatorTree and LoopInfo updates. More...

void	versionLoop (const SmallVectorImpl< Instruction *> &DefsUsedOutside)
	Same but if the client has already precomputed the set of values used outside the loop, this API will allows passing that. More...

Loop *	getVersionedLoop ()
	Returns the versioned loop. More...

Loop *	getNonVersionedLoop ()
	Returns the fall-back loop. More...

void	setAliasChecks (SmallVector< RuntimePointerChecking::PointerCheck, 4 > Checks)
	Sets the runtime alias checks for versioning the loop. More...

void	setSCEVChecks (SCEVUnionPredicate Check)
	Sets the runtime SCEV checks for versioning the loop. More...

void	annotateLoopWithNoAlias ()
	Annotate memory instructions in the versioned loop with no-alias metadata based on the memchecks issued. More...

void	prepareNoAliasMetadata ()
	Set up the aliasing scopes based on the memchecks. More...

void	annotateInstWithNoAlias (Instruction VersionedInst, const Instruction OrigInst)
	Add the noalias annotations to `VersionedInst`. More...

Detailed Description

This class emits a version of the loop where run-time checks ensure that may-alias pointers can't overlap.

It currently only supports single-exit loops and assumes that the loop already has a preheader.

Definition at line 36 of file LoopVersioning.h.

Constructor & Destructor Documentation

◆ LoopVersioning()

LoopVersioning::LoopVersioning	(	const LoopAccessInfo &	LAI,
		Loop *	L,
		LoopInfo *	LI,
		DominatorTree *	DT,
		ScalarEvolution *	SE,
		bool	UseLAIChecks = `true`
	)

Expects LoopAccessInfo, Loop, LoopInfo, DominatorTree as input.

It uses runtime check provided by the user. If UseLAIChecks is true, we will retain the default checks made by LAI. Otherwise, construct an object having no checks and we expect the user to add them.

Definition at line 33 of file LoopVersioning.cpp.

References assert(), llvm::RuntimePointerChecking::getChecks(), llvm::LoopBase< BlockT, LoopT >::getExitBlock(), llvm::LoopAccessInfo::getPSE(), llvm::LoopAccessInfo::getRuntimePointerChecking(), llvm::PredicatedScalarEvolution::getUnionPredicate(), llvm::Loop::isLoopSimplifyForm(), setAliasChecks(), and setSCEVChecks().

Member Function Documentation

◆ annotateInstWithNoAlias()

void LoopVersioning::annotateInstWithNoAlias	(	Instruction *	VersionedInst,
		const Instruction *	OrigInst
	)

Add the noalias annotations to VersionedInst.

OrigInst is the instruction corresponding to VersionedInst in the original loop. Initialize the aliasing scopes with prepareNoAliasMetadata once before this can be called.

Definition at line 223 of file LoopVersioning.cpp.

References llvm::AnalysisUsage::addPreserved(), llvm::AnalysisUsage::addRequired(), annotateLoopWithNoAlias(), AnnotateNoAlias, llvm::MDNode::concatenate(), Context, llvm::depth_first(), F(), llvm::MDNode::get(), llvm::BasicBlock::getContext(), llvm::LoopBase< BlockT, LoopT >::getHeader(), llvm::Instruction::getMetadata(), llvm::LoopAccessInfo::getNumRuntimePointerChecks(), llvm::PassRegistry::getPassRegistry(), llvm::getPointerOperand(), llvm::LoopAccessInfo::getPSE(), llvm::PredicatedScalarEvolution::getUnionPredicate(), llvm::initializeLoopVersioningPassPass(), llvm::SCEVUnionPredicate::isAlwaysTrue(), llvm::LLVMContext::MD_alias_scope, llvm::LLVMContext::MD_noalias, llvm::SmallVectorTemplateBase< T >::push_back(), runOnFunction(), llvm::Instruction::setMetadata(), and versionLoop().

Referenced by annotateLoopWithNoAlias(), and getNonVersionedLoop().

◆ annotateLoopWithNoAlias()

void LoopVersioning::annotateLoopWithNoAlias ( )

Annotate memory instructions in the versioned loop with no-alias metadata based on the memchecks issued.

This is just wrapper that calls prepareNoAliasMetadata and annotateInstWithNoAlias on the instructions of the versioned loop.

Definition at line 210 of file LoopVersioning.cpp.

References annotateInstWithNoAlias(), AnnotateNoAlias, llvm::LoopAccessInfo::getDepChecker(), llvm::MemoryDepChecker::getMemoryInstructions(), I, and prepareNoAliasMetadata().

Referenced by annotateInstWithNoAlias(), and getNonVersionedLoop().

◆ getNonVersionedLoop()

Loop* llvm::LoopVersioning::getNonVersionedLoop ( )

inline

Returns the fall-back loop.

Control flows here if pointers in the loop may alias (i.e. one of the memchecks failed).

Definition at line 72 of file LoopVersioning.h.

References annotateInstWithNoAlias(), annotateLoopWithNoAlias(), Check(), I, prepareNoAliasMetadata(), setAliasChecks(), and setSCEVChecks().

◆ getVersionedLoop()

Loop* llvm::LoopVersioning::getVersionedLoop ( )

inline

Returns the versioned loop.

Control flows here if pointers in the loop don't alias (i.e. all memchecks passed). (This loop is actually the same as the original loop that we got constructed with.)

Definition at line 68 of file LoopVersioning.h.