#include "llvm/Transforms/Scalar.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Type.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/SimplifyIndVar.h"

Include dependency graph for IndVarSimplify.cpp:

Defines
#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")
	INITIALIZE_PASS_BEGIN (IndVarSimplify,"indvars","Induction Variable Simplification", false, false) INITIALIZE_PASS_END(IndVarSimplify
static Instruction *	getInsertPointForUses (Instruction User, Value Def, DominatorTree *DT)
static bool	ConvertToSInt (const APFloat &APF, int64_t &IntVal)
	ConvertToSInt - Convert APF to an integer, if possible.
static void	visitIVCast (CastInst Cast, WideIVInfo &WI, ScalarEvolution SE, const DataLayout *DL)
static bool	isLoopInvariant (Value V, const Loop L, const DominatorTree *DT)
static void	truncateIVUse (NarrowIVDefUse DU, DominatorTree *DT)
static bool	isHighCostExpansion (const SCEV S, BranchInst BI, SmallPtrSetImpl< const SCEV * > &Processed, ScalarEvolution *SE)
static bool	canExpandBackedgeTakenCount (Loop L, ScalarEvolution SE)
static PHINode *	getLoopPhiForCounter (Value IncV, Loop L, DominatorTree *DT)
static ICmpInst *	getLoopTest (Loop *L)
	Return the compare guarding the loop latch, or NULL for unrecognized tests.
static bool	needsLFTR (Loop L, DominatorTree DT)
static bool	hasConcreteDefImpl (Value V, SmallPtrSetImpl< Value > &Visited, unsigned Depth)
static bool	hasConcreteDef (Value *V)
static bool	AlmostDeadIV (PHINode Phi, BasicBlock LatchBlock, Value *Cond)
static PHINode *	FindLoopCounter (Loop L, const SCEV BECount, ScalarEvolution SE, DominatorTree DT, const DataLayout *DL)
static Value *	genLoopLimit (PHINode IndVar, const SCEV IVCount, Loop L, SCEVExpander &Rewriter, ScalarEvolution SE)
Variables
static cl::opt< bool >	VerifyIndvars ("verify-indvars", cl::Hidden, cl::desc("Verify the ScalarEvolution result after running indvars"))
static cl::opt< bool >	ReduceLiveIVs ("liv-reduce", cl::Hidden, cl::desc("Reduce live induction variables."))
	indvars
Induction Variable	Simplification
Induction Variable	false

Define Documentation

#define DEBUG_TYPE "indvars"

Definition at line 52 of file IndVarSimplify.cpp.

Function Documentation

static bool AlmostDeadIV	(	PHINode *	Phi,
		BasicBlock *	LatchBlock,
		Value *	Cond
	)		`[static]`

AlmostDeadIV - Return true if this IV has any uses other than the (soon to be rewritten) loop exit test.

Definition at line 1471 of file IndVarSimplify.cpp.

References llvm::PHINode::getBasicBlockIndex(), llvm::PHINode::getIncomingValue(), and llvm::Value::users().

Referenced by FindLoopCounter().

static bool canExpandBackedgeTakenCount	(	Loop *	L,
		ScalarEvolution *	SE
	)		`[static]`

canExpandBackedgeTakenCount - Return true if this loop's backedge taken count expression can be safely and cheaply expanded into an instruction sequence that can be used by LinearFunctionTestReplace.

TODO: This fails for pointer-type loop counters with greater than one byte strides, consequently preventing LFTR from running. For the purpose of LFTR we could skip this check in the case that the LFTR loop counter (chosen by FindLoopCounter) is also pointer type. Instead, we could directly convert the loop test to an inequality test by checking the target data's alignment of element types (given that the initial pointer value originates from or is used by ABI constrained operation, as opposed to inttoptr/ptrtoint). However, we don't yet have a strong motivation for converting loop tests into inequality tests.

Definition at line 1315 of file IndVarSimplify.cpp.

References llvm::dyn_cast(), llvm::ScalarEvolution::getBackedgeTakenCount(), llvm::LoopBase< BlockT, LoopT >::getExitingBlock(), llvm::BasicBlock::getTerminator(), isHighCostExpansion(), and llvm::SCEV::isZero().

static bool ConvertToSInt	(	const APFloat &	APF,
		int64_t &	IntVal
	)		`[static]`

ConvertToSInt - Convert APF to an integer, if possible.

Definition at line 225 of file IndVarSimplify.cpp.

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

static PHINode* FindLoopCounter	(	Loop *	L,
		const SCEV *	BECount,
		ScalarEvolution *	SE,
		DominatorTree *	DT,
		const DataLayout *	DL
	)		`[static]`

FindLoopCounter - Find an affine IV in canonical form.

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.

Currently only valid for LFTR. See the comments on hasConcreteDef below.

FIXME: Accept -1 stride and set IVLimit = IVInit - BECount

FIXME: Accept non-unit stride as long as SCEV can reduce BECount * Stride. This is difficult in general for SCEV because of potential overflow. But we could at least handle constant BECounts.

Definition at line 1497 of file IndVarSimplify.cpp.

References AlmostDeadIV(), llvm::BasicBlock::begin(), llvm::dyn_cast(), llvm::PHINode::getBasicBlockIndex(), llvm::LoopBase< BlockT, LoopT >::getExitingBlock(), llvm::LoopBase< BlockT, LoopT >::getHeader(), llvm::PHINode::getIncomingValue(), llvm::SCEVAddRecExpr::getLoop(), llvm::LoopBase< BlockT, LoopT >::getLoopLatch(), getLoopPhiForCounter(), getLoopTest(), llvm::ScalarEvolution::getSCEV(), llvm::SCEVAddRecExpr::getStart(), llvm::SCEVAddRecExpr::getStepRecurrence(), llvm::BasicBlock::getTerminator(), llvm::SCEV::getType(), llvm::SCEVNAryExpr::getType(), llvm::Value::getType(), llvm::ScalarEvolution::getTypeSizeInBits(), hasConcreteDef(), I, llvm::SCEVAddRecExpr::isAffine(), llvm::DataLayout::isLegalInteger(), llvm::SCEV::isOne(), llvm::Type::isPointerTy(), llvm::ScalarEvolution::isSCEVable(), and llvm::SCEV::isZero().

static Value* genLoopLimit	(	PHINode *	IndVar,
		const SCEV *	IVCount,
		Loop *	L,
		SCEVExpander &	Rewriter,
		ScalarEvolution *	SE
	)		`[static]`

genLoopLimit - Help LinearFunctionTestReplace by generating a value that holds the RHS of the new loop test.

Definition at line 1579 of file IndVarSimplify.cpp.

References llvm::IRBuilder< preserveNames, T, Inserter >::CreateGEP(), llvm::dyn_cast(), llvm::SCEVExpander::expandCodeFor(), llvm::ScalarEvolution::getAddExpr(), llvm::Value::getContext(), llvm::ScalarEvolution::getEffectiveSCEVType(), llvm::LoopBase< BlockT, LoopT >::getExitingBlock(), llvm::PHINode::getIncomingValueForBlock(), llvm::Type::getInt64Ty(), llvm::SCEVAddRecExpr::getLoop(), llvm::LoopBase< BlockT, LoopT >::getLoopPreheader(), llvm::ScalarEvolution::getSCEV(), llvm::ScalarEvolution::getSizeOfExpr(), llvm::SCEVAddRecExpr::getStart(), llvm::SCEVAddRecExpr::getStepRecurrence(), llvm::BasicBlock::getTerminator(), llvm::ScalarEvolution::getTruncateExpr(), llvm::ScalarEvolution::getTruncateOrZeroExtend(), llvm::SCEV::getType(), llvm::Value::getType(), llvm::ScalarEvolution::getTypeSizeInBits(), llvm::SCEVAddRecExpr::isAffine(), llvm::ScalarEvolution::isLoopInvariant(), llvm::SCEV::isOne(), llvm::Type::isPointerTy(), and llvm::SCEV::isZero().

static Instruction* getInsertPointForUses	(	Instruction *	User,
		Value *	Def,
		DominatorTree *	DT
	)		`[static]`

Determine the insertion point for this user. By default, insert immediately before the user. SCEVExpander or LICM will hoist loop invariants out of the loop. For PHI nodes, there may be multiple uses, so compute the nearest common dominator for the incoming blocks.

Definition at line 194 of file IndVarSimplify.cpp.

References llvm::tgtok::Def, llvm::DominatorTree::dominates(), llvm::dyn_cast(), llvm::DominatorTreeBase< NodeT >::findNearestCommonDominator(), llvm::PHINode::getIncomingBlock(), llvm::PHINode::getIncomingValue(), llvm::PHINode::getNumIncomingValues(), llvm::Instruction::getParent(), llvm::BasicBlock::getTerminator(), and llvm::TargetOpcode::PHI.

Referenced by truncateIVUse().

static PHINode* getLoopPhiForCounter	(	Value *	IncV,
		Loop *	L,
		DominatorTree *	DT
	)		`[static]`

getLoopPhiForCounter - Return the loop header phi IFF IncV adds a loop invariant value to the phi.

Definition at line 1338 of file IndVarSimplify.cpp.

References llvm::dyn_cast(), llvm::LoopBase< BlockT, LoopT >::getHeader(), llvm::User::getNumOperands(), llvm::Instruction::getOpcode(), llvm::User::getOperand(), llvm::Instruction::getParent(), and isLoopInvariant().

Referenced by FindLoopCounter(), and needsLFTR().

static ICmpInst* getLoopTest ( Loop * L ) [static]

Return the compare guarding the loop latch, or NULL for unrecognized tests.

Definition at line 1374 of file IndVarSimplify.cpp.

References llvm::dyn_cast(), llvm::BranchInst::getCondition(), llvm::LoopBase< BlockT, LoopT >::getExitingBlock(), llvm::LoopBase< BlockT, LoopT >::getLoopLatch(), and llvm::BasicBlock::getTerminator().

Referenced by FindLoopCounter(), and needsLFTR().

static 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 1463 of file IndVarSimplify.cpp.

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

Referenced by FindLoopCounter().

static 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 1430 of file IndVarSimplify.cpp.

References llvm::dyn_cast(), I, llvm::SmallPtrSetImpl< PtrType >::insert(), llvm::Instruction::mayReadFromMemory(), llvm::User::op_begin(), and llvm::User::op_end().

Referenced by hasConcreteDef().

INITIALIZE_PASS_BEGIN	(	IndVarSimplify	,
		"indvars"	,
		"Induction Variable Simplification"	,
		false	,
		false
	)

static bool isHighCostExpansion	(	const SCEV *	S,
		BranchInst *	BI,
		SmallPtrSetImpl< const SCEV * > &	Processed,
		ScalarEvolution *	SE
	)		`[static]`

Check for expressions that ScalarEvolution generates to compute BackedgeTakenInfo. If these expressions have not been reduced, then expanding them may incur additional cost (albeit in the loop preheader).

Definition at line 1256 of file IndVarSimplify.cpp.

References llvm::dyn_cast(), llvm::BranchInst::getCondition(), llvm::ScalarEvolution::getConstant(), llvm::ScalarEvolution::getMinusSCEV(), llvm::User::getOperand(), llvm::ScalarEvolution::getSCEV(), llvm::SCEV::getType(), I, and llvm::SmallPtrSetImpl< PtrType >::insert().

Referenced by canExpandBackedgeTakenCount().

static bool isLoopInvariant	(	Value *	V,
		const Loop *	L,
		const DominatorTree *	DT
	)		`[static]`

isLoopInvariant - Perform a quick domtree based check for loop invariance assuming that V is used within the loop. LoopInfo::isLoopInvariant() seems gratuitous for this purpose.

Definition at line 774 of file IndVarSimplify.cpp.

References llvm::dyn_cast(), llvm::LoopBase< BlockT, LoopT >::getHeader(), llvm::Instruction::getParent(), and llvm::DominatorTreeBase< NodeT >::properlyDominates().

Referenced by llvm::DependenceAnalysis::depends(), getLoopPhiForCounter(), llvm::DependenceAnalysis::getSplitIteration(), and needsLFTR().

static bool needsLFTR	(	Loop *	L,
		DominatorTree *	DT
	)		`[static]`

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

Definition at line 1390 of file IndVarSimplify.cpp.

References llvm::dyn_cast(), llvm::PHINode::getBasicBlockIndex(), llvm::PHINode::getIncomingValue(), llvm::LoopBase< BlockT, LoopT >::getLoopLatch(), getLoopPhiForCounter(), getLoopTest(), llvm::User::getOperand(), llvm::CmpInst::getPredicate(), llvm::CmpInst::ICMP_EQ, llvm::CmpInst::ICMP_NE, isLoopInvariant(), and std::swap().

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 void truncateIVUse	(	NarrowIVDefUse	DU,
		DominatorTree *	DT
	)		`[static]`

This IV user cannot be widen. Replace this use of the original narrow IV with a truncation of the new wide IV to isolate and eliminate the narrow IV.

Definition at line 923 of file IndVarSimplify.cpp.

References llvm::IRBuilder< preserveNames, T, Inserter >::CreateTrunc(), llvm::dbgs(), DEBUG, getInsertPointForUses(), and llvm::Trunc.

static void visitIVCast	(	CastInst *	Cast,
		WideIVInfo &	WI,
		ScalarEvolution *	SE,
		const DataLayout *	DL
	)		`[static]`

visitCast - 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 663 of file IndVarSimplify.cpp.

References llvm::ScalarEvolution::getEffectiveSCEVType(), llvm::CastInst::getOpcode(), llvm::Value::getType(), llvm::ScalarEvolution::getTypeSizeInBits(), llvm::DataLayout::isLegalInteger(), and llvm::SExt.

Variable Documentation

Induction Variable false

Definition at line 131 of file IndVarSimplify.cpp.

indvars

Definition at line 131 of file IndVarSimplify.cpp.

cl::opt<bool> ReduceLiveIVs("liv-reduce", cl::Hidden, cl::desc("Reduce live induction variables.")) [static]

Induction Variable Simplification

Definition at line 131 of file IndVarSimplify.cpp.

cl::opt<bool> VerifyIndvars("verify-indvars", cl::Hidden, cl::desc("Verify the ScalarEvolution result after running indvars")) [static]

Defines

Functions

Variables

Define Documentation

Function Documentation

Variable Documentation