class LoopVersioning

Declaration

class LoopVersioning { /* full declaration omitted */ };

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.

Declared at: llvm/include/llvm/Transforms/Utils/LoopVersioning.h:35

Method Overview

Methods

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

Description

Expects LoopAccessInfo, Loop, LoopInfo, DominatorTree as input. It uses runtime check provided by the user. If \p 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.

Declared at: llvm/include/llvm/Transforms/Utils/LoopVersioning.h:41

Parameters

const llvm::LoopAccessInfo& LAI
llvm::Loop* L
llvm::LoopInfo* LI
llvm::DominatorTree* DT
llvm::ScalarEvolution* SE
bool UseLAIChecks = true

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

Description

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

Declared at: llvm/include/llvm/Transforms/Utils/LoopVersioning.h:96

Parameters

llvm::Instruction* VersionedInst
const llvm::Instruction* OrigInst

void annotateLoopWithNoAlias()

Description

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.

Declared at: llvm/include/llvm/Transforms/Utils/LoopVersioning.h:85

llvm::Loop* getNonVersionedLoop()

Description

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

Declared at: llvm/include/llvm/Transforms/Utils/LoopVersioning.h:71

llvm::Loop* getVersionedLoop()

Description

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.)

Declared at: llvm/include/llvm/Transforms/Utils/LoopVersioning.h:67

void prepareNoAliasMetadata()

Description

Set up the aliasing scopes based on the memchecks. This needs to be called before the first call to annotateInstWithNoAlias.

Declared at: llvm/include/llvm/Transforms/Utils/LoopVersioning.h:89

void setAliasChecks(
    SmallVector<
        RuntimePointerChecking::PointerCheck,
        4> Checks)

Description

Sets the runtime alias checks for versioning the loop.

Declared at: llvm/include/llvm/Transforms/Utils/LoopVersioning.h:74

Parameters

SmallVector<RuntimePointerChecking::PointerCheck, 4> Checks

void setSCEVChecks(llvm::SCEVUnionPredicate Check)

Description

Sets the runtime SCEV checks for versioning the loop.

Declared at: llvm/include/llvm/Transforms/Utils/LoopVersioning.h:78

Parameters

llvm::SCEVUnionPredicate Check

void versionLoop()

Description

Performs the CFG manipulation part of versioning the loop including the DominatorTree and LoopInfo updates. The loop that was used to construct the class will be the "versioned" loop i.e. the loop that will receive control if all the memchecks pass. This allows the loop transform pass to operate on the same loop regardless of whether versioning was necessary or not: for each loop L: analyze L if versioning is necessary version L transform L

Declared at: llvm/include/llvm/Transforms/Utils/LoopVersioning.h:58

void versionLoop(
    const SmallVectorImpl<llvm::Instruction*>&
        DefsUsedOutside)

Description

Same but if the client has already precomputed the set of values used outside the loop, this API will allows passing that.

Declared at: llvm/include/llvm/Transforms/Utils/LoopVersioning.h:62

Parameters

const SmallVectorImpl<llvm::Instruction*>& DefsUsedOutside