IndVarSimplify.cpp File Reference

#include "llvm/Transforms/Scalar/IndVarSimplify.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/MemorySSA.h"
#include "llvm/Analysis/MemorySSAUpdater.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ScalarEvolutionPatternMatch.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Use.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Scalar/SimpleLoopUnswitch.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/LoopUtils.h"
#include "llvm/Transforms/Utils/ScalarEvolutionExpander.h"
#include "llvm/Transforms/Utils/SimplifyIndVar.h"
#include <cassert>
#include <cstdint>
#include <utility>

Go to the source code of this file.

Macros
#define	DEBUG_TYPE   "indvars"

Functions
	STATISTIC (NumWidened, "Number of indvars widened")
	STATISTIC (NumReplaced, "Number of exit values replaced")
	STATISTIC (NumLFTR, "Number of loop exit tests replaced")
	STATISTIC (NumElimExt, "Number of IV sign/zero extends eliminated")
	STATISTIC (NumElimIV, "Number of congruent IVs eliminated")
static bool	ConvertToSInt (const APFloat &APF, int64_t &IntVal)
	Convert APF to an integer, if possible.
static void	visitIVCast (CastInst *Cast, WideIVInfo &WI, ScalarEvolution *SE, const TargetTransformInfo *TTI)
	Update information about the induction variable that is extended by this sign or zero extend operation.
static PHINode *	getLoopPhiForCounter (Value *IncV, Loop *L)
	Given an Value which is hoped to be part of an add recurance in the given loop, return the associated Phi node if so.
static bool	isLoopExitTestBasedOn (Value *V, BasicBlock *ExitingBB)
	Whether the current loop exit test is based on this value.
static bool	needsLFTR (Loop *L, BasicBlock *ExitingBB)
	linearFunctionTestReplace policy.
static bool	hasConcreteDefImpl (Value *V, SmallPtrSetImpl< Value * > &Visited, unsigned Depth)
	Recursive helper for hasConcreteDef().
static bool	hasConcreteDef (Value *V)
	Return true if the given value is concrete.
static bool	isLoopCounter (PHINode *Phi, Loop *L, ScalarEvolution *SE)
	Return true if the given phi is a "counter" in L.
static PHINode *	FindLoopCounter (Loop *L, BasicBlock *ExitingBB, const SCEV *BECount, ScalarEvolution *SE, DominatorTree *DT)
	Search the loop header for a loop counter (anadd rec w/step of one) suitable for use by LFTR.
static Value *	genLoopLimit (PHINode *IndVar, BasicBlock *ExitingBB, const SCEV *ExitCount, bool UsePostInc, Loop *L, SCEVExpander &Rewriter, ScalarEvolution *SE)
	Insert an IR expression which computes the value held by the IV IndVar (which must be an loop counter w/unit stride) after the backedge of loop L is taken ExitCount times.
static void	replaceExitCond (BranchInst *BI, Value *NewCond, SmallVectorImpl< WeakTrackingVH > &DeadInsts)
static Constant *	createFoldedExitCond (const Loop *L, BasicBlock *ExitingBB, bool IsTaken)
static void	foldExit (const Loop *L, BasicBlock *ExitingBB, bool IsTaken, SmallVectorImpl< WeakTrackingVH > &DeadInsts)
static void	replaceLoopPHINodesWithPreheaderValues (LoopInfo *LI, Loop *L, SmallVectorImpl< WeakTrackingVH > &DeadInsts, ScalarEvolution &SE)
static Value *	createInvariantCond (const Loop *L, BasicBlock *ExitingBB, const ScalarEvolution::LoopInvariantPredicate &LIP, SCEVExpander &Rewriter)
static std::optional< Value * >	createReplacement (ICmpInst *ICmp, const Loop *L, BasicBlock *ExitingBB, const SCEV *MaxIter, bool Inverted, bool SkipLastIter, ScalarEvolution *SE, SCEVExpander &Rewriter)
static bool	optimizeLoopExitWithUnknownExitCount (const Loop *L, BranchInst *BI, BasicBlock *ExitingBB, const SCEV *MaxIter, bool SkipLastIter, ScalarEvolution *SE, SCEVExpander &Rewriter, SmallVectorImpl< WeakTrackingVH > &DeadInsts)

Variables
static cl::opt< ReplaceExitVal >	ReplaceExitValue ("replexitval", cl::Hidden, cl::init(OnlyCheapRepl), cl::desc("Choose the strategy to replace exit value in IndVarSimplify"), cl::values(clEnumValN(NeverRepl, "never", "never replace exit value"), clEnumValN(OnlyCheapRepl, "cheap", "only replace exit value when the cost is cheap"), clEnumValN(UnusedIndVarInLoop, "unusedindvarinloop", "only replace exit value when it is an unused " "induction variable in the loop and has cheap replacement cost"), clEnumValN(NoHardUse, "noharduse", "only replace exit values when loop def likely dead"), clEnumValN(AlwaysRepl, "always", "always replace exit value whenever possible")))
static cl::opt< bool >	UsePostIncrementRanges ("indvars-post-increment-ranges", cl::Hidden, cl::desc("Use post increment control-dependent ranges in IndVarSimplify"), cl::init(true))
static cl::opt< bool >	DisableLFTR ("disable-lftr", cl::Hidden, cl::init(false), cl::desc("Disable Linear Function Test Replace optimization"))
static cl::opt< bool >	LoopPredication ("indvars-predicate-loops", cl::Hidden, cl::init(true), cl::desc("Predicate conditions in read only loops"))
static cl::opt< bool >	AllowIVWidening ("indvars-widen-indvars", cl::Hidden, cl::init(true), cl::desc("Allow widening of indvars to eliminate s/zext"))

Macro Definition Documentation

DEBUG_TYPE

#define DEBUG_TYPE   "indvars"

Definition at line 83 of file IndVarSimplify.cpp.

Function Documentation

ConvertToSInt()

bool ConvertToSInt ( const APFloat & APF, int64_t & IntVal )

static

Convert APF to an integer, if possible.

Definition at line 184 of file IndVarSimplify.cpp.

References llvm::APFloat::convertToInteger(), llvm::APFloatBase::opOK, and llvm::APFloatBase::rmTowardZero.

createFoldedExitCond()

Constant * createFoldedExitCond ( const Loop * L, BasicBlock * ExitingBB, bool IsTaken )

static

Definition at line 1166 of file IndVarSimplify.cpp.

References llvm::cast(), llvm::BranchInst::getCondition(), llvm::BasicBlock::getTerminator(), and llvm::succ_begin().

Referenced by createReplacement(), and foldExit().

createInvariantCond()

Value * createInvariantCond ( const Loop * L, BasicBlock * ExitingBB, const ScalarEvolution::LoopInvariantPredicate & LIP, SCEVExpander & Rewriter )

static

Definition at line 1221 of file IndVarSimplify.cpp.

References assert(), llvm::cast(), llvm::BranchInst::getCondition(), llvm::CmpInst::getInversePredicate(), llvm::Value::getName(), llvm::BasicBlock::getTerminator(), llvm::ScalarEvolution::LoopInvariantPredicate::LHS, llvm::ScalarEvolution::LoopInvariantPredicate::Pred, llvm::ScalarEvolution::LoopInvariantPredicate::RHS, and llvm::succ_begin().

Referenced by createReplacement().

createReplacement()

std::optional< Value * > createReplacement ( ICmpInst * ICmp, const Loop * L, BasicBlock * ExitingBB, const SCEV * MaxIter, bool Inverted, bool SkipLastIter, ScalarEvolution * SE, SCEVExpander & Rewriter )

static

Definition at line 1240 of file IndVarSimplify.cpp.

References llvm::cast(), createFoldedExitCond(), createInvariantCond(), llvm::dyn_cast(), llvm::ScalarEvolution::evaluatePredicateAt(), llvm::ICmpInst::getCmpPredicate(), llvm::ICmpInst::getInverseCmpPredicate(), llvm::ScalarEvolution::getLoopInvariantExitCondDuringFirstIterations(), llvm::ScalarEvolution::getMinusOne(), llvm::ScalarEvolution::getMinusSCEV(), llvm::ScalarEvolution::getOne(), llvm::User::getOperand(), llvm::ScalarEvolution::getSCEVAtScope(), llvm::BasicBlock::getTerminator(), llvm::ScalarEvolution::getTruncateExpr(), llvm::SCEV::getType(), llvm::ScalarEvolution::getTypeSizeInBits(), llvm::ScalarEvolution::getUMinFromMismatchedTypes(), llvm::ScalarEvolution::getZeroExtendExpr(), llvm::CmpInst::ICMP_ULE, llvm::ScalarEvolution::isKnownPredicateAt(), LHS, RHS, and llvm::UMin.

Referenced by optimizeLoopExitWithUnknownExitCount().

FindLoopCounter()

PHINode * FindLoopCounter ( Loop * L, BasicBlock * ExitingBB, const SCEV * BECount, ScalarEvolution * SE, DominatorTree * DT )

static

Search the loop header for a loop counter (anadd rec w/step of one) suitable for use by LFTR.

If multiple counters are available, select the "best" one based profitable heuristics.

BECount may be an i8* pointer type. The pointer difference is already valid count without scaling the address stride, so it remains a pointer expression as far as SCEV is concerned.

Definition at line 826 of file IndVarSimplify.cpp.

References assert(), llvm::cast(), Cond, DL, llvm::ScalarEvolution::getSCEV(), llvm::BasicBlock::getTerminator(), llvm::SCEV::getType(), llvm::Value::getType(), llvm::ScalarEvolution::getTypeSizeInBits(), hasConcreteDef(), I, llvm::isa(), llvm::isAlmostDeadIV(), isLoopCounter(), isLoopExitTestBasedOn(), llvm::SCEV::isZero(), and llvm::mustExecuteUBIfPoisonOnPathTo().

foldExit()

void foldExit ( const Loop * L, BasicBlock * ExitingBB, bool IsTaken, SmallVectorImpl< WeakTrackingVH > & DeadInsts )

static

Definition at line 1175 of file IndVarSimplify.cpp.

References llvm::cast(), createFoldedExitCond(), llvm::BasicBlock::getTerminator(), and replaceExitCond().

genLoopLimit()

Value * genLoopLimit ( PHINode * IndVar, BasicBlock * ExitingBB, const SCEV * ExitCount, bool UsePostInc, Loop * L, SCEVExpander & Rewriter, ScalarEvolution * SE )

static

Insert an IR expression which computes the value held by the IV IndVar (which must be an loop counter w/unit stride) after the backedge of loop L is taken ExitCount times.

Definition at line 906 of file IndVarSimplify.cpp.

References assert(), llvm::cast(), llvm::SCEVAddRecExpr::evaluateAtIteration(), llvm::SCEVAddRecExpr::getPostIncExpr(), llvm::ScalarEvolution::getSCEV(), llvm::SCEVAddRecExpr::getStart(), llvm::SCEVAddRecExpr::getStepRecurrence(), llvm::BasicBlock::getTerminator(), llvm::ScalarEvolution::getTruncateExpr(), llvm::SCEV::getType(), llvm::SCEVAddRecExpr::getType(), llvm::Value::getType(), llvm::ScalarEvolution::getTypeSizeInBits(), llvm::isa(), llvm::Type::isIntegerTy(), isLoopCounter(), llvm::ScalarEvolution::isLoopInvariant(), and llvm::SCEV::isOne().

getLoopPhiForCounter()

PHINode * getLoopPhiForCounter ( Value * IncV, Loop * L )

static

Given an Value which is hoped to be part of an add recurance in the given loop, return the associated Phi node if so.

Otherwise, return null. Note that this is less general than SCEVs AddRec checking.

Definition at line 658 of file IndVarSimplify.cpp.

References llvm::dyn_cast(), llvm::User::getNumOperands(), llvm::Instruction::getOpcode(), and llvm::User::getOperand().

Referenced by isLoopCounter(), and needsLFTR().

hasConcreteDef()

bool hasConcreteDef ( Value * V )

static

Return true if the given value is concrete.

We must prove that undef can never reach it.

TODO: If we decide that this is a good approach to checking for undef, we may factor it into a common location.

Definition at line 792 of file IndVarSimplify.cpp.

References hasConcreteDefImpl(), and llvm::SmallPtrSetImpl< PtrType >::insert().

Referenced by FindLoopCounter().

hasConcreteDefImpl()

bool hasConcreteDefImpl ( Value * V, SmallPtrSetImpl< Value * > & Visited, unsigned Depth )

static

Recursive helper for hasConcreteDef().

Unfortunately, this currently boils down to checking that all operands are constant and listing instructions that may hide undef.

Definition at line 759 of file IndVarSimplify.cpp.

References llvm::Depth, llvm::dyn_cast(), hasConcreteDefImpl(), I, llvm::SmallPtrSetImpl< PtrType >::insert(), and llvm::isa().

Referenced by hasConcreteDef(), and hasConcreteDefImpl().

isLoopCounter()

bool isLoopCounter ( PHINode * Phi, Loop * L, ScalarEvolution * SE )

static

Return true if the given phi is a "counter" in L.

A counter is an add recurance (of integer or pointer type) with an arbitrary start, and a step of 1. Note that L must have exactly one latch.

Definition at line 801 of file IndVarSimplify.cpp.

References assert(), getLoopPhiForCounter(), llvm::ScalarEvolution::getSCEV(), llvm::isa(), llvm::ScalarEvolution::isSCEVable(), llvm::SCEVPatternMatch::m_SCEV(), llvm::SCEVPatternMatch::m_scev_AffineAddRec(), llvm::SCEVPatternMatch::m_scev_One(), llvm::SCEVPatternMatch::m_SpecificLoop(), and llvm::SCEVPatternMatch::match().

Referenced by FindLoopCounter(), and genLoopLimit().

isLoopExitTestBasedOn()

bool isLoopExitTestBasedOn ( Value * V, BasicBlock * ExitingBB )

static

Whether the current loop exit test is based on this value.

Currently this is limited to a direct use in the loop condition.

Definition at line 696 of file IndVarSimplify.cpp.

References llvm::cast(), llvm::dyn_cast(), llvm::BranchInst::getCondition(), llvm::User::getOperand(), and llvm::BasicBlock::getTerminator().

Referenced by FindLoopCounter().

needsLFTR()

bool needsLFTR ( Loop * L, BasicBlock * ExitingBB )

static

linearFunctionTestReplace policy.

Return true unless we can show that the current exit test is already sufficiently canonical.

Definition at line 709 of file IndVarSimplify.cpp.

References assert(), llvm::cast(), Cond, llvm::dyn_cast(), llvm::BranchInst::getCondition(), getLoopPhiForCounter(), llvm::BasicBlock::getTerminator(), llvm::CmpInst::ICMP_EQ, llvm::CmpInst::ICMP_NE, LHS, RHS, and std::swap().

optimizeLoopExitWithUnknownExitCount()

bool optimizeLoopExitWithUnknownExitCount ( const Loop * L, BranchInst * BI, BasicBlock * ExitingBB, const SCEV * MaxIter, bool SkipLastIter, ScalarEvolution * SE, SCEVExpander & Rewriter, SmallVectorImpl< WeakTrackingVH > & DeadInsts )

static

Definition at line 1297 of file IndVarSimplify.cpp.

References assert(), Changed, llvm::ScalarEvolution::computeExitLimitFromCond(), llvm::SmallPtrSetImpl< PtrType >::count(), createReplacement(), llvm::dbgs(), llvm::dyn_cast(), llvm::SmallVectorTemplateCommon< T, typename >::empty(), llvm::SmallPtrSetImpl< PtrType >::erase(), llvm::BranchInst::getCondition(), llvm::ScalarEvolution::getExitCount(), llvm::Value::getName(), llvm::ScalarEvolution::getNoopOrZeroExtend(), llvm::BranchInst::getSuccessor(), llvm::SCEV::getType(), llvm::ScalarEvolution::getWiderType(), llvm::Value::hasOneUse(), llvm::SmallPtrSetImpl< PtrType >::insert(), llvm::isa(), LHS, LLVM_DEBUG, llvm::PatternMatch::m_LogicalAnd(), llvm::PatternMatch::m_LogicalOr(), llvm::PatternMatch::m_Value(), llvm::SCEVPatternMatch::match(), llvm::SmallVectorImpl< T >::pop_back_val(), llvm::SmallVectorTemplateBase< T, bool >::push_back(), llvm::Value::replaceAllUsesWith(), RHS, llvm::SmallPtrSetImplBase::size(), llvm::SmallVectorTemplateCommon< T, typename >::size(), and llvm::ScalarEvolution::SymbolicMaximum.

replaceExitCond()

void replaceExitCond ( BranchInst * BI, Value * NewCond, SmallVectorImpl< WeakTrackingVH > & DeadInsts )

static

Definition at line 1156 of file IndVarSimplify.cpp.

References llvm::dbgs(), llvm::SmallVectorImpl< T >::emplace_back(), llvm::BranchInst::getCondition(), LLVM_DEBUG, and llvm::BranchInst::setCondition().

Referenced by foldExit().

replaceLoopPHINodesWithPreheaderValues()

void replaceLoopPHINodesWithPreheaderValues ( LoopInfo * LI, Loop * L, SmallVectorImpl< WeakTrackingVH > & DeadInsts, ScalarEvolution & SE )

static

Definition at line 1182 of file IndVarSimplify.cpp.

References assert(), llvm::cast(), llvm::SmallVectorImpl< T >::emplace_back(), llvm::SmallVectorTemplateCommon< T, typename >::empty(), llvm::ScalarEvolution::forgetValue(), llvm::PHINode::getIncomingValueForBlock(), I, llvm::SmallPtrSetImpl< PtrType >::insert(), llvm::SmallVectorImpl< T >::pop_back_val(), llvm::SmallVectorTemplateBase< T, bool >::push_back(), llvm::Value::replaceAllUsesWith(), llvm::LoopInfo::replacementPreservesLCSSAForm(), llvm::simplifyInstruction(), and llvm::Value::users().

STATISTIC() [1/5]

STATISTIC	(	NumElimExt	,
		"Number of IV sign/zero extends eliminated"	)

STATISTIC() [2/5]

STATISTIC	(	NumElimIV	,
		"Number of congruent IVs eliminated"	)

STATISTIC() [3/5]

STATISTIC	(	NumLFTR	,
		"Number of loop exit tests replaced"	)

STATISTIC() [4/5]

STATISTIC	(	NumReplaced	,
		"Number of exit values replaced"	)

STATISTIC() [5/5]

STATISTIC	(	NumWidened	,
		"Number of indvars widened"	)

visitIVCast()

void visitIVCast ( CastInst * Cast, WideIVInfo & WI, ScalarEvolution * SE, const TargetTransformInfo * TTI )

static

Update information about the induction variable that is extended by this sign or zero extend operation.

This is used to determine the final width of the IV before actually widening it.

Definition at line 507 of file IndVarSimplify.cpp.

References llvm::Instruction::getDataLayout(), llvm::ScalarEvolution::getEffectiveSCEVType(), llvm::CastInst::getOpcode(), llvm::User::getOperand(), llvm::Value::getType(), llvm::ScalarEvolution::getTypeSizeInBits(), llvm::DataLayout::isLegalInteger(), llvm::WideIVInfo::IsSigned, llvm::WideIVInfo::NarrowIV, and llvm::WideIVInfo::WidestNativeType.

Variable Documentation

AllowIVWidening

cl::opt< bool > AllowIVWidening("indvars-widen-indvars", cl::Hidden, cl::init(true), cl::desc("Allow widening of indvars to eliminate s/zext")) ( "indvars-widen-indvars" , cl::Hidden , cl::init(true) , cl::desc("Allow widening of indvars to eliminate s/zext")  )

static

Referenced by llvm::IndVarSimplifyPass::run().

DisableLFTR

cl::opt< bool > DisableLFTR("disable-lftr", cl::Hidden, cl::init(false), cl::desc("Disable Linear Function Test Replace optimization")) ( "disable-lftr" , cl::Hidden , cl::init(false) , cl::desc("Disable Linear Function Test Replace optimization")  )

static

LoopPredication

cl::opt< bool > LoopPredication("indvars-predicate-loops", cl::Hidden, cl::init(true), cl::desc("Predicate conditions in read only loops")) ( "indvars-predicate-loops" , cl::Hidden , cl::init(true) , cl::desc("Predicate conditions in read only loops")  )

static

ReplaceExitValue

cl::opt< ReplaceExitVal > ReplaceExitValue("replexitval", cl::Hidden, cl::init(OnlyCheapRepl), cl::desc("Choose the strategy to replace exit value in IndVarSimplify"), cl::values( clEnumValN(NeverRepl, "never", "never replace exit value"), clEnumValN(OnlyCheapRepl, "cheap", "only replace exit value when the cost is cheap"), clEnumValN( UnusedIndVarInLoop, "unusedindvarinloop", "only replace exit value when it is an unused " "induction variable in the loop and has cheap replacement cost"), clEnumValN(NoHardUse, "noharduse", "only replace exit values when loop def likely dead"), clEnumValN(AlwaysRepl, "always", "always replace exit value whenever possible"))) ( "replexitval" , cl::Hidden , cl::init(OnlyCheapRepl) , cl::desc("Choose the strategy to replace exit value in IndVarSimplify") , cl::values( clEnumValN(NeverRepl, "never", "never replace exit value"), clEnumValN(OnlyCheapRepl, "cheap", "only replace exit value when the cost is cheap"), clEnumValN( UnusedIndVarInLoop, "unusedindvarinloop", "only replace exit value when it is an unused " "induction variable in the loop and has cheap replacement cost"), clEnumValN(NoHardUse, "noharduse", "only replace exit values when loop def likely dead"), clEnumValN(AlwaysRepl, "always", "always replace exit value whenever possible"))  )

static

Referenced by llvm::rewriteLoopExitValues().

UsePostIncrementRanges

cl::opt< bool > UsePostIncrementRanges("indvars-post-increment-ranges", cl::Hidden, cl::desc("Use post increment control-dependent ranges in IndVarSimplify"), cl::init(true)) ( "indvars-post-increment-ranges" , cl::Hidden , cl::desc("Use post increment control-dependent ranges in IndVarSimplify") , cl::init(true)  )

static

Referenced by llvm::createWideIV().