LLVM 20.0.0git
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llvm::TargetTransformInfo::UnrollingPreferences Struct Reference

Parameters that control the generic loop unrolling transformation. More...

#include "llvm/Analysis/TargetTransformInfo.h"

Public Attributes

unsigned Threshold
 The cost threshold for the unrolled loop.
 
unsigned MaxPercentThresholdBoost
 If complete unrolling will reduce the cost of the loop, we will boost the Threshold by a certain percent to allow more aggressive complete unrolling.
 
unsigned OptSizeThreshold
 The cost threshold for the unrolled loop when optimizing for size (set to UINT_MAX to disable).
 
unsigned PartialThreshold
 The cost threshold for the unrolled loop, like Threshold, but used for partial/runtime unrolling (set to UINT_MAX to disable).
 
unsigned PartialOptSizeThreshold
 The cost threshold for the unrolled loop when optimizing for size, like OptSizeThreshold, but used for partial/runtime unrolling (set to UINT_MAX to disable).
 
unsigned Count
 A forced unrolling factor (the number of concatenated bodies of the original loop in the unrolled loop body).
 
unsigned DefaultUnrollRuntimeCount
 Default unroll count for loops with run-time trip count.
 
unsigned MaxCount
 
unsigned MaxUpperBound
 Set the maximum upper bound of trip count.
 
unsigned FullUnrollMaxCount
 Set the maximum unrolling factor for full unrolling.
 
unsigned BEInsns
 
bool Partial
 Allow partial unrolling (unrolling of loops to expand the size of the loop body, not only to eliminate small constant-trip-count loops).
 
bool Runtime
 Allow runtime unrolling (unrolling of loops to expand the size of the loop body even when the number of loop iterations is not known at compile time).
 
bool AllowRemainder
 Allow generation of a loop remainder (extra iterations after unroll).
 
bool AllowExpensiveTripCount
 Allow emitting expensive instructions (such as divisions) when computing the trip count of a loop for runtime unrolling.
 
bool Force
 Apply loop unroll on any kind of loop (mainly to loops that fail runtime unrolling).
 
bool UpperBound
 Allow using trip count upper bound to unroll loops.
 
bool UnrollRemainder
 Allow unrolling of all the iterations of the runtime loop remainder.
 
bool UnrollAndJam
 Allow unroll and jam. Used to enable unroll and jam for the target.
 
unsigned UnrollAndJamInnerLoopThreshold
 Threshold for unroll and jam, for inner loop size.
 
unsigned MaxIterationsCountToAnalyze
 Don't allow loop unrolling to simulate more than this number of iterations when checking full unroll profitability.
 
bool UnrollVectorizedLoop = false
 Don't disable runtime unroll for the loops which were vectorized.
 

Detailed Description

Parameters that control the generic loop unrolling transformation.

Definition at line 531 of file TargetTransformInfo.h.

Member Data Documentation

◆ AllowExpensiveTripCount

bool llvm::TargetTransformInfo::UnrollingPreferences::AllowExpensiveTripCount

Allow emitting expensive instructions (such as divisions) when computing the trip count of a loop for runtime unrolling.

Definition at line 597 of file TargetTransformInfo.h.

Referenced by llvm::computeUnrollCount(), llvm::gatherUnrollingPreferences(), llvm::PPCTTIImpl::getUnrollingPreferences(), llvm::SystemZTTIImpl::getUnrollingPreferences(), and tryToUnrollLoop().

◆ AllowRemainder

bool llvm::TargetTransformInfo::UnrollingPreferences::AllowRemainder

Allow generation of a loop remainder (extra iterations after unroll).

Definition at line 594 of file TargetTransformInfo.h.

Referenced by computeUnrollAndJamCount(), llvm::computeUnrollCount(), llvm::gatherUnrollingPreferences(), shouldPartialUnroll(), shouldPragmaUnroll(), and tryToUnrollLoop().

◆ BEInsns

unsigned llvm::TargetTransformInfo::UnrollingPreferences::BEInsns

◆ Count

unsigned llvm::TargetTransformInfo::UnrollingPreferences::Count

A forced unrolling factor (the number of concatenated bodies of the original loop in the unrolled loop body).

When set to 0, the unrolling transformation will select an unrolling factor based on the current cost threshold and other factors.

Definition at line 565 of file TargetTransformInfo.h.

Referenced by computeHeuristicUnrollFactor(), computeUnrollAndJamCount(), llvm::computeUnrollCount(), llvm::gatherUnrollingPreferences(), getUnrollAndJammedLoopSize(), llvm::UnrollCostEstimator::getUnrolledLoopSize(), shouldPartialUnroll(), tryToUnrollAndJamLoop(), and tryToUnrollLoop().

◆ DefaultUnrollRuntimeCount

unsigned llvm::TargetTransformInfo::UnrollingPreferences::DefaultUnrollRuntimeCount

◆ Force

bool llvm::TargetTransformInfo::UnrollingPreferences::Force

◆ FullUnrollMaxCount

unsigned llvm::TargetTransformInfo::UnrollingPreferences::FullUnrollMaxCount

Set the maximum unrolling factor for full unrolling.

Like MaxCount, but applies even if full unrolling is selected. This allows a target to fall back to Partial unrolling if full unrolling is above FullUnrollMaxCount.

Definition at line 580 of file TargetTransformInfo.h.

Referenced by llvm::gatherUnrollingPreferences(), llvm::SystemZTTIImpl::getUnrollingPreferences(), and shouldFullUnroll().

◆ MaxCount

unsigned llvm::TargetTransformInfo::UnrollingPreferences::MaxCount

◆ MaxIterationsCountToAnalyze

unsigned llvm::TargetTransformInfo::UnrollingPreferences::MaxIterationsCountToAnalyze

Don't allow loop unrolling to simulate more than this number of iterations when checking full unroll profitability.

Definition at line 614 of file TargetTransformInfo.h.

Referenced by llvm::gatherUnrollingPreferences(), llvm::AMDGPUTTIImpl::getUnrollingPreferences(), and shouldFullUnroll().

◆ MaxPercentThresholdBoost

unsigned llvm::TargetTransformInfo::UnrollingPreferences::MaxPercentThresholdBoost

If complete unrolling will reduce the cost of the loop, we will boost the Threshold by a certain percent to allow more aggressive complete unrolling.

This value provides the maximum boost percentage that we can apply to Threshold (The value should be no less than 100). BoostedThreshold = Threshold * min(RolledCost / UnrolledCost, MaxPercentThresholdBoost / 100) E.g. if complete unrolling reduces the loop execution time by 50% then we boost the threshold by the factor of 2x. If unrolling is not expected to reduce the running time, then we do not increase the threshold.

Definition at line 550 of file TargetTransformInfo.h.

Referenced by llvm::gatherUnrollingPreferences(), and shouldFullUnroll().

◆ MaxUpperBound

unsigned llvm::TargetTransformInfo::UnrollingPreferences::MaxUpperBound

Set the maximum upper bound of trip count.

Allowing the MaxUpperBound to be overrided by a target gives more flexiblity on certain cases. By default, MaxUpperBound uses UnrollMaxUpperBound which value is 8.

Definition at line 576 of file TargetTransformInfo.h.

Referenced by llvm::computeUnrollCount(), llvm::gatherUnrollingPreferences(), and shouldPragmaUnroll().

◆ OptSizeThreshold

unsigned llvm::TargetTransformInfo::UnrollingPreferences::OptSizeThreshold

◆ Partial

bool llvm::TargetTransformInfo::UnrollingPreferences::Partial

◆ PartialOptSizeThreshold

unsigned llvm::TargetTransformInfo::UnrollingPreferences::PartialOptSizeThreshold

The cost threshold for the unrolled loop when optimizing for size, like OptSizeThreshold, but used for partial/runtime unrolling (set to UINT_MAX to disable).

Definition at line 560 of file TargetTransformInfo.h.

Referenced by computeHeuristicUnrollFactor(), llvm::gatherUnrollingPreferences(), llvm::BasicTTIImplBase< T >::getUnrollingPreferences(), llvm::AArch64TTIImpl::getUnrollingPreferences(), llvm::ARMTTIImpl::getUnrollingPreferences(), llvm::RISCVTTIImpl::getUnrollingPreferences(), and llvm::WebAssemblyTTIImpl::getUnrollingPreferences().

◆ PartialThreshold

unsigned llvm::TargetTransformInfo::UnrollingPreferences::PartialThreshold

◆ Runtime

bool llvm::TargetTransformInfo::UnrollingPreferences::Runtime

◆ Threshold

unsigned llvm::TargetTransformInfo::UnrollingPreferences::Threshold

The cost threshold for the unrolled loop.

Should be relative to the getInstructionCost values returned by this API, and the expectation is that the unrolled loop's instructions when run through that interface should not exceed this cost. However, this is only an estimate. Also, specific loops may be unrolled even with a cost above this threshold if deemed profitable. Set this to UINT_MAX to disable the loop body cost restriction.

Definition at line 539 of file TargetTransformInfo.h.

Referenced by computeHeuristicUnrollFactor(), computeUnrollAndJamCount(), llvm::computeUnrollCount(), llvm::gatherUnrollingPreferences(), llvm::AMDGPUTTIImpl::getUnrollingPreferences(), llvm::NVPTXTTIImpl::getUnrollingPreferences(), shouldFullUnroll(), shouldPragmaUnroll(), and tryToUnrollLoop().

◆ UnrollAndJam

bool llvm::TargetTransformInfo::UnrollingPreferences::UnrollAndJam

◆ UnrollAndJamInnerLoopThreshold

unsigned llvm::TargetTransformInfo::UnrollingPreferences::UnrollAndJamInnerLoopThreshold

Threshold for unroll and jam, for inner loop size.

The 'Threshold' value above is used during unroll and jam for the outer loop size. This value is used in the same manner to limit the size of the inner loop.

Definition at line 611 of file TargetTransformInfo.h.

Referenced by computeUnrollAndJamCount(), llvm::gatherUnrollingPreferences(), llvm::AArch64TTIImpl::getUnrollingPreferences(), llvm::ARMTTIImpl::getUnrollingPreferences(), llvm::RISCVTTIImpl::getUnrollingPreferences(), and tryToUnrollAndJamLoop().

◆ UnrollRemainder

bool llvm::TargetTransformInfo::UnrollingPreferences::UnrollRemainder

◆ UnrollVectorizedLoop

bool llvm::TargetTransformInfo::UnrollingPreferences::UnrollVectorizedLoop = false

Don't disable runtime unroll for the loops which were vectorized.

Definition at line 616 of file TargetTransformInfo.h.

Referenced by llvm::LoopVectorizationPlanner::executePlan(), and llvm::AMDGPUTTIImpl::getUnrollingPreferences().

◆ UpperBound

bool llvm::TargetTransformInfo::UnrollingPreferences::UpperBound

The documentation for this struct was generated from the following file: