llvm::UnrollRuntimeLoopRemainder

Insert a runtime prolog or epilog so L can be unrolled by Count.

Synopsis

Declared in <llvm/Transforms/Utils/UnrollLoop.h>

bool
UnrollRuntimeLoopRemainder(
    Loop* L,
    unsigned int Count,
    bool AllowExpensiveTripCount,
    bool UseEpilogRemainder,
    bool UnrollRemainder,
    bool ForgetAllSCEV,
    LoopInfo* LI,
    ScalarEvolution* SE,
    DominatorTree* DT,
    AssumptionCache* AC,
    TargetTransformInfo const* TTI,
    bool PreserveLCSSA,
    unsigned int SCEVExpansionBudget,
    bool RuntimeUnrollMultiExit,
    Loop** ResultLoop = nullptr,
    std::optional<unsigned int> OriginalTripCount = std::nullopt,
    BranchProbability OriginalLoopProb = BranchProbability::getUnknown());

Description

Ensures the latch trip count is a multiple of Count when the trip count is not known statically. May create and optionally unroll a remainder loop.

Return Value

True if the remainder transformation succeeded.

Parameters

Name

Description

Loop to prepare for runtime unrolling.

Count

Unroll factor that the remainder logic must satisfy.

AllowExpensiveTripCount

Allow costly run‐time trip‐count computation.

UseEpilogRemainder

Prefer an epilog remainder over a prolog.

UnrollRemainder

Unroll the generated remainder loop when profitable.

ForgetAllSCEV

Forget all SCEV expressions for the loop after rewrite.

LoopInfo to keep consistent.

ScalarEvolution used to compute the trip count.

Dominator tree to update.

Assumption cache used by subsequent simplifications.

TTI

Target transform info for cost checks.

PreserveLCSSA

Whether to preserve LCSSA form.

SCEVExpansionBudget

Budget for expanding the trip‐count SCEV.

RuntimeUnrollMultiExit

Allow runtime unrolling with multiple exits.

ResultLoop

If non‐null, receives the remainder loop when created.

OriginalTripCount

Optional original trip count used for probabilities.

OriginalLoopProb

Optional original loop‐latch branch probability.

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