InstructionCombining.cpp File Reference

#include "InstCombineInternal.h"
#include "llvm-c/Initialization.h"
#include "llvm-c/Transforms/InstCombine.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BasicAliasAnalysis.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/EHPersonalities.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LazyBlockFrequencyInfo.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TargetFolder.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Operator.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/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/CBindingWrapping.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/DebugCounter.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/InstCombine/InstCombine.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <memory>
#include <string>
#include <utility>
#include "llvm/Transforms/Utils/InstructionWorklist.h"

Go to the source code of this file.

Classes
class	AliasScopeTracker

Macros
#define	DEBUG_TYPE   "instcombine"

Functions
	STATISTIC (NumWorklistIterations, "Number of instruction combining iterations performed")
	STATISTIC (NumCombined, "Number of insts combined")
	STATISTIC (NumConstProp, "Number of constant folds")
	STATISTIC (NumDeadInst, "Number of dead inst eliminated")
	STATISTIC (NumSunkInst, "Number of instructions sunk")
	STATISTIC (NumExpand, "Number of expansions")
	STATISTIC (NumFactor, "Number of factorizations")
	STATISTIC (NumReassoc, "Number of reassociations")
	DEBUG_COUNTER (VisitCounter, "instcombine-visit", "Controls which instructions are visited")
static bool	maintainNoSignedWrap (BinaryOperator &I, Value *B, Value *C)
static bool	hasNoUnsignedWrap (BinaryOperator &I)
static bool	hasNoSignedWrap (BinaryOperator &I)
static void	ClearSubclassDataAfterReassociation (BinaryOperator &I)
	Conservatively clears subclassOptionalData after a reassociation or commutation. More...
static bool	simplifyAssocCastAssoc (BinaryOperator *BinOp1, InstCombinerImpl &IC)
	Combine constant operands of associative operations either before or after a cast to eliminate one of the associative operations: (op (cast (op X, C2)), C1) --> (cast (op X, op (C1, C2))) (op (cast (op X, C2)), C1) --> (op (cast X), op (C1, C2)) More...
static bool	leftDistributesOverRight (Instruction::BinaryOps LOp, Instruction::BinaryOps ROp)
	Return whether "X LOp (Y ROp Z)" is always equal to "(X LOp Y) ROp (X LOp Z)". More...
static bool	rightDistributesOverLeft (Instruction::BinaryOps LOp, Instruction::BinaryOps ROp)
	Return whether "(X LOp Y) ROp Z" is always equal to "(X ROp Z) LOp (Y ROp Z)". More...
static Value *	getIdentityValue (Instruction::BinaryOps Opcode, Value *V)
	This function returns identity value for given opcode, which can be used to factor patterns like (X * 2) + X ==> (X * 2) + (X * 1) ==> X * (2 + 1). More...
static Instruction::BinaryOps	getBinOpsForFactorization (Instruction::BinaryOps TopOpcode, BinaryOperator *Op, Value *&LHS, Value *&RHS)
	This function predicates factorization using distributive laws. More...
static Value *	foldOperationIntoSelectOperand (Instruction &I, Value *SO, InstCombiner::BuilderTy &Builder)
static Value *	foldOperationIntoPhiValue (BinaryOperator *I, Value *InV, InstCombiner::BuilderTy &Builder)
static bool	shouldMergeGEPs (GEPOperator &GEP, GEPOperator &Src)
static bool	isMergedGEPInBounds (GEPOperator &GEP1, GEPOperator &GEP2)
static Instruction *	foldSelectGEP (GetElementPtrInst &GEP, InstCombiner::BuilderTy &Builder)
	Thread a GEP operation with constant indices through the constant true/false arms of a select. More...
static bool	isNeverEqualToUnescapedAlloc (Value *V, const TargetLibraryInfo &TLI, Instruction *AI)
static bool	isRemovableWrite (CallBase &CB, Value *UsedV, const TargetLibraryInfo &TLI)
	Given a call CB which uses an address UsedV, return true if we can prove the call's only possible effect is storing to V. More...
static bool	isAllocSiteRemovable (Instruction *AI, SmallVectorImpl< WeakTrackingVH > &Users, const TargetLibraryInfo &TLI)
static Instruction *	tryToMoveFreeBeforeNullTest (CallInst &FI, const DataLayout &DL)
	Move the call to free before a NULL test. More...
static bool	isMustTailCall (Value *V)
static bool	isCatchAll (EHPersonality Personality, Constant *TypeInfo)
	Return 'true' if the given typeinfo will match anything. More...
static bool	shorter_filter (const Value *LHS, const Value *RHS)
static bool	SoleWriteToDeadLocal (Instruction *I, TargetLibraryInfo &TLI)
	Check for case where the call writes to an otherwise dead alloca. More...
static bool	TryToSinkInstruction (Instruction *I, BasicBlock *DestBlock, TargetLibraryInfo &TLI)
	Try to move the specified instruction from its current block into the beginning of DestBlock, which can only happen if it's safe to move the instruction past all of the instructions between it and the end of its block. More...
static bool	prepareICWorklistFromFunction (Function &F, const DataLayout &DL, const TargetLibraryInfo *TLI, InstructionWorklist &ICWorklist)
	Populate the IC worklist from a function, by walking it in depth-first order and adding all reachable code to the worklist. More...
static bool	combineInstructionsOverFunction (Function &F, InstructionWorklist &Worklist, AliasAnalysis *AA, AssumptionCache &AC, TargetLibraryInfo &TLI, TargetTransformInfo &TTI, DominatorTree &DT, OptimizationRemarkEmitter &ORE, BlockFrequencyInfo *BFI, ProfileSummaryInfo *PSI, unsigned MaxIterations, LoopInfo *LI)
	INITIALIZE_PASS_BEGIN (InstructionCombiningPass, "instcombine", "Combine redundant instructions", false, false) INITIALIZE_PASS_END(InstructionCombiningPass
void	LLVMInitializeInstCombine (LLVMPassRegistryRef R)
void	LLVMAddInstructionCombiningPass (LLVMPassManagerRef PM)
	See llvm::createInstructionCombiningPass function. More...

Variables
static constexpr unsigned	InstCombineDefaultMaxIterations = 1000
static constexpr unsigned	InstCombineDefaultInfiniteLoopThreshold = 100
static cl::opt< bool >	EnableCodeSinking ("instcombine-code-sinking", cl::desc("Enable code sinking"), cl::init(true))
static cl::opt< unsigned >	LimitMaxIterations ("instcombine-max-iterations", cl::desc("Limit the maximum number of instruction combining iterations"), cl::init(InstCombineDefaultMaxIterations))
static cl::opt< unsigned >	InfiniteLoopDetectionThreshold ("instcombine-infinite-loop-threshold", cl::desc("Number of instruction combining iterations considered an " "infinite loop"), cl::init(InstCombineDefaultInfiniteLoopThreshold), cl::Hidden)
static cl::opt< unsigned >	MaxArraySize ("instcombine-maxarray-size", cl::init(1024), cl::desc("Maximum array size considered when doing a combine"))
static cl::opt< unsigned >	ShouldLowerDbgDeclare ("instcombine-lower-dbg-declare", cl::Hidden, cl::init(true))
	instcombine
Combine redundant	instructions
Combine redundant	false

Macro Definition Documentation

DEBUG_TYPE

#define DEBUG_TYPE   "instcombine"

Definition at line 111 of file InstructionCombining.cpp.

Function Documentation

ClearSubclassDataAfterReassociation()

static void ClearSubclassDataAfterReassociation ( BinaryOperator &  I )

static

Conservatively clears subclassOptionalData after a reassociation or commutation.

We preserve fast-math flags when applicable as they can be preserved.

Definition at line 308 of file InstructionCombining.cpp.

References I.

Referenced by llvm::InstCombinerImpl::SimplifyAssociativeOrCommutative().

combineInstructionsOverFunction()

static bool combineInstructionsOverFunction ( Function &  F, InstructionWorklist &  Worklist, AliasAnalysis *  AA, AssumptionCache &  AC, TargetLibraryInfo &  TLI, TargetTransformInfo &  TTI, DominatorTree &  DT, OptimizationRemarkEmitter &  ORE, BlockFrequencyInfo *  BFI, ProfileSummaryInfo *  PSI, unsigned  MaxIterations, LoopInfo *  LI  )

static

Builder - This is an IRBuilder that automatically inserts new instructions into the worklist when they are created.

Definition at line 4244 of file InstructionCombining.cpp.

References llvm::InstructionWorklist::add(), llvm::AMDGPUISD::BFI, Builder, llvm::dbgs(), DL, F, I, InfiniteLoopDetectionThreshold, LimitMaxIterations, LLVM_DEBUG, llvm::LowerDbgDeclare(), MaxArraySize, llvm::InstCombiner::MaxArraySizeForCombine, llvm::min(), prepareICWorklistFromFunction(), llvm::AssumptionCache::registerAssumption(), llvm::report_fatal_error(), llvm::InstCombinerImpl::run(), and ShouldLowerDbgDeclare.

Referenced by llvm::InstCombinePass::run(), and llvm::InstructionCombiningPass::runOnFunction().

DEBUG_COUNTER()

DEBUG_COUNTER	(	VisitCounter	,
		"instcombine-visit"	,
		"Controls which instructions are visited"
	)

foldOperationIntoPhiValue()

static Value* foldOperationIntoPhiValue ( BinaryOperator *  I, Value *  InV, InstCombiner::BuilderTy &  Builder  )

static

Definition at line 1111 of file InstructionCombining.cpp.

References Builder, llvm::ConstantExpr::get(), I, and std::swap().

Referenced by llvm::InstCombinerImpl::foldOpIntoPhi().

foldOperationIntoSelectOperand()

static Value* foldOperationIntoSelectOperand ( Instruction &  I, Value *  SO, InstCombiner::BuilderTy &  Builder  )

static

Definition at line 993 of file InstructionCombining.cpp.

References llvm::CallBase::arg_size(), assert(), Builder, llvm::canConstantFoldCallTo(), llvm::ConstantExpr::get(), llvm::CallBase::getArgOperand(), llvm::CallBase::getCalledOperand(), llvm::IntrinsicInst::getIntrinsicID(), llvm::Value::getName(), getOpcode(), I, and std::swap().

Referenced by llvm::InstCombinerImpl::FoldOpIntoSelect().

foldSelectGEP()

static Instruction* foldSelectGEP ( GetElementPtrInst &  GEP, InstCombiner::BuilderTy &  Builder  )

static

Thread a GEP operation with constant indices through the constant true/false arms of a select.

Definition at line 1859 of file InstructionCombining.cpp.

References Builder, Cond, llvm::SelectInst::Create(), GEP, llvm::PatternMatch::m_Constant(), llvm::PatternMatch::m_Instruction(), llvm::PatternMatch::m_Select(), llvm::PatternMatch::m_Value(), and llvm::PatternMatch::match().

Referenced by llvm::InstCombinerImpl::visitGetElementPtrInst().

getBinOpsForFactorization()

static Instruction::BinaryOps getBinOpsForFactorization ( Instruction::BinaryOps  TopOpcode, BinaryOperator *  Op, Value *&  LHS, Value *&  RHS  )

static

This function predicates factorization using distributive laws.

By default, it just returns the 'Op' inputs. But for special-cases like 'add(shl(X, 5), ...)', this function will have TopOpcode == Instruction::Add and Op = shl(X, 5). The 'shl' is treated as the more general 'mul X, 32' to allow more factorization opportunities.

Definition at line 612 of file InstructionCombining.cpp.

References llvm::MCID::Add, assert(), llvm::ConstantInt::get(), llvm::ConstantExpr::getShl(), LHS, llvm::PatternMatch::m_Constant(), llvm::PatternMatch::m_Shl(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::match(), Mul, and RHS.

Referenced by llvm::InstCombinerImpl::SimplifyUsingDistributiveLaws().

getIdentityValue()

static Value* getIdentityValue ( Instruction::BinaryOps  Opcode, Value *  V  )

static

This function returns identity value for given opcode, which can be used to factor patterns like (X * 2) + X ==> (X * 2) + (X * 1) ==> X * (2 + 1).

Definition at line 599 of file InstructionCombining.cpp.

References llvm::ConstantExpr::getBinOpIdentity(), and llvm::Value::getType().

Referenced by llvm::InstCombinerImpl::SimplifyUsingDistributiveLaws().

hasNoSignedWrap()

static bool hasNoSignedWrap ( BinaryOperator &  I )

static

Definition at line 300 of file InstructionCombining.cpp.

References I.

Referenced by llvm::SDNode::print_details(), and llvm::InstCombinerImpl::SimplifyAssociativeOrCommutative().

hasNoUnsignedWrap()

static bool hasNoUnsignedWrap ( BinaryOperator &  I )

static

Definition at line 295 of file InstructionCombining.cpp.

References I.

Referenced by llvm::SDNode::print_details(), llvm::InstCombinerImpl::SimplifyAssociativeOrCommutative(), and llvm::InstCombinerImpl::visitLShr().

INITIALIZE_PASS_BEGIN()

INITIALIZE_PASS_BEGIN	(	InstructionCombiningPass	,
		"instcombine"	,
		"Combine redundant instructions"	,
		false	,
		false
	)

isAllocSiteRemovable()

static bool isAllocSiteRemovable ( Instruction *  AI, SmallVectorImpl< WeakTrackingVH > &  Users, const TargetLibraryInfo &  TLI  )

static

Definition at line 2590 of file InstructionCombining.cpp.

References llvm::MCID::Call, llvm::IntrinsicInst::getIntrinsicID(), llvm::User::getOperand(), I, llvm::ICmpInst::isEquality(), llvm::isFreeCall(), isNeverEqualToUnescapedAlloc(), llvm::isReallocLikeFn(), isRemovableWrite(), LLVM_FALLTHROUGH, llvm_unreachable, memcpy(), MI, llvm::SmallVectorImpl< T >::pop_back_val(), SI, llvm::SPII::Store, Users, and llvm::Value::users().

Referenced by llvm::InstCombinerImpl::visitAllocSite().

isCatchAll()

static bool isCatchAll ( EHPersonality  Personality, Constant *  TypeInfo  )

static

Return 'true' if the given typeinfo will match anything.

Definition at line 3250 of file InstructionCombining.cpp.

References llvm::CoreCLR, llvm::GNU_Ada, llvm::GNU_C, llvm::GNU_C_SjLj, llvm::GNU_CXX, llvm::GNU_CXX_SjLj, llvm::GNU_ObjC, llvm::Constant::isNullValue(), llvm_unreachable, llvm::MSVC_CXX, llvm::MSVC_TableSEH, llvm::MSVC_X86SEH, llvm::Rust, llvm::Unknown, llvm::Wasm_CXX, and llvm::XL_CXX.

Referenced by llvm::InstCombinerImpl::visitLandingPadInst().

isMergedGEPInBounds()

static bool isMergedGEPInBounds ( GEPOperator &  GEP1, GEPOperator &  GEP2  )

static

Definition at line 1848 of file InstructionCombining.cpp.

References llvm::GEPOperator::hasAllZeroIndices(), and llvm::GEPOperator::isInBounds().

Referenced by llvm::InstCombinerImpl::visitGEPOfGEP().

isMustTailCall()

static bool isMustTailCall ( Value *  V )

static

Definition at line 2936 of file InstructionCombining.cpp.

Referenced by llvm::SelectionDAGBuilder::LowerCallTo(), and llvm::InstCombinerImpl::visitReturnInst().

isNeverEqualToUnescapedAlloc()

static bool isNeverEqualToUnescapedAlloc ( Value *  V, const TargetLibraryInfo &  TLI, Instruction *  AI  )

static

Definition at line 2558 of file InstructionCombining.cpp.

References llvm::isAllocLikeFn().

Referenced by isAllocSiteRemovable().

isRemovableWrite()

static bool isRemovableWrite ( CallBase &  CB, Value *  UsedV, const TargetLibraryInfo &  TLI  )

static

Given a call CB which uses an address UsedV, return true if we can prove the call's only possible effect is storing to V.

Definition at line 2570 of file InstructionCombining.cpp.

References llvm::CallBase::doesNotThrow(), llvm::MemoryLocation::getForDest(), llvm::Instruction::isTerminator(), llvm::MemoryLocation::Ptr, llvm::Value::use_empty(), and llvm::Instruction::willReturn().

Referenced by isAllocSiteRemovable().

leftDistributesOverRight()

static bool leftDistributesOverRight ( Instruction::BinaryOps  LOp, Instruction::BinaryOps  ROp  )

static

Return whether "X LOp (Y ROp Z)" is always equal to "(X LOp Y) ROp (X LOp Z)".

Definition at line 563 of file InstructionCombining.cpp.

References llvm::MCID::Add, and Mul.

Referenced by rightDistributesOverLeft(), llvm::InstCombinerImpl::SimplifyUsingDistributiveLaws(), and llvm::InstCombinerImpl::tryFactorization().

maintainNoSignedWrap()

static bool maintainNoSignedWrap ( BinaryOperator &  I, Value *  B, Value *  C  )

static

Definition at line 272 of file InstructionCombining.cpp.

References llvm::MCID::Add, B, I, llvm::PatternMatch::m_APInt(), llvm::PatternMatch::match(), llvm::APInt::sadd_ov(), and llvm::APInt::ssub_ov().

Referenced by llvm::InstCombinerImpl::SimplifyAssociativeOrCommutative().

prepareICWorklistFromFunction()

static bool prepareICWorklistFromFunction ( Function &  F, const DataLayout &  DL, const TargetLibraryInfo *  TLI, InstructionWorklist &  ICWorklist  )

static

Populate the IC worklist from a function, by walking it in depth-first order and adding all reachable code to the worklist.

This has a couple of tricks to make the code faster and more powerful. In particular, we constant fold and DCE instructions as we go, to avoid adding them to the worklist (this significantly speeds up instcombine on code where many instructions are dead or constant). Additionally, if we find a branch whose condition is a known constant, we only visit the reachable successors.

Definition at line 4121 of file InstructionCombining.cpp.

References AliasScopeTracker::analyse(), llvm::append_range(), BB, Cond, llvm::ConstantFoldConstant(), llvm::ConstantFoldInstruction(), llvm::SmallPtrSetImpl< PtrType >::count(), llvm::dbgs(), DL, F, llvm::SmallPtrSetImpl< PtrType >::insert(), llvm::isInstructionTriviallyDead(), AliasScopeTracker::isNoAliasScopeDeclDead(), LLVM_DEBUG, llvm::make_early_inc_range(), llvm::SmallVectorImpl< T >::pop_back_val(), llvm::InstructionWorklist::push(), llvm::removeAllNonTerminatorAndEHPadInstructions(), llvm::InstructionWorklist::reserve(), llvm::reverse(), llvm::salvageDebugInfo(), SI, and llvm::successors().

Referenced by combineInstructionsOverFunction().

rightDistributesOverLeft()

static bool rightDistributesOverLeft ( Instruction::BinaryOps  LOp, Instruction::BinaryOps  ROp  )

static

Return whether "(X LOp Y) ROp Z" is always equal to "(X ROp Z) LOp (Y ROp Z)".

Definition at line 584 of file InstructionCombining.cpp.

References llvm::Instruction::isBitwiseLogicOp(), llvm::Instruction::isCommutative(), llvm::Instruction::isShift(), and leftDistributesOverRight().

Referenced by llvm::InstCombinerImpl::SimplifyUsingDistributiveLaws(), and llvm::InstCombinerImpl::tryFactorization().

shorter_filter()

static bool shorter_filter ( const Value *  LHS, const Value *  RHS  )

static

Definition at line 3278 of file InstructionCombining.cpp.

References llvm::Value::getType(), LHS, and RHS.

Referenced by llvm::InstCombinerImpl::visitLandingPadInst().

shouldMergeGEPs()

static bool shouldMergeGEPs ( GEPOperator &  GEP, GEPOperator &  Src  )

static

Definition at line 1325 of file InstructionCombining.cpp.

References GEP.

Referenced by llvm::InstCombinerImpl::visitGEPOfGEP().

simplifyAssocCastAssoc()

static bool simplifyAssocCastAssoc ( BinaryOperator *  BinOp1, InstCombinerImpl &  IC  )

static

Combine constant operands of associative operations either before or after a cast to eliminate one of the associative operations: (op (cast (op X, C2)), C1) --> (cast (op X, op (C1, C2))) (op (cast (op X, C2)), C1) --> (op (cast X), op (C1, C2))

Definition at line 324 of file InstructionCombining.cpp.

References C1, llvm::ConstantExpr::get(), llvm::ConstantExpr::getCast(), llvm::BinaryOperator::getOpcode(), llvm::User::getOperand(), llvm::Instruction::isBitwiseLogicOp(), llvm::PatternMatch::m_Constant(), llvm::PatternMatch::match(), and llvm::InstCombinerImpl::replaceOperand().

Referenced by llvm::InstCombinerImpl::SimplifyAssociativeOrCommutative().

SoleWriteToDeadLocal()

static bool SoleWriteToDeadLocal ( Instruction *  I, TargetLibraryInfo &  TLI  )

static

Check for case where the call writes to an otherwise dead alloca.

This shows up for unused out-params in idiomatic C/C++ code. Note that this helper only analyzes the write; doesn't check any other legality aspect.

Definition at line 3722 of file InstructionCombining.cpp.

References llvm::MemoryLocation::getForDest(), llvm::getUnderlyingObject(), I, llvm::SmallPtrSetImpl< PtrType >::insert(), llvm::SmallVectorImpl< T >::pop_back_val(), and llvm::MemoryLocation::Ptr.

Referenced by TryToSinkInstruction().

STATISTIC() [1/8]

STATISTIC	(	NumCombined	,
		"Number of insts combined"
	)

STATISTIC() [2/8]

STATISTIC	(	NumConstProp	,
		"Number of constant folds"
	)

STATISTIC() [3/8]

STATISTIC	(	NumDeadInst	,
		"Number of dead inst eliminated"
	)

STATISTIC() [4/8]

STATISTIC	(	NumExpand	,
		"Number of expansions"
	)

STATISTIC() [5/8]

STATISTIC	(	NumFactor	,
		"Number of factorizations"
	)

STATISTIC() [6/8]

STATISTIC	(	NumReassoc	,
		"Number of reassociations"
	)

STATISTIC() [7/8]

STATISTIC	(	NumSunkInst	,
		"Number of instructions sunk"
	)

STATISTIC() [8/8]

STATISTIC	(	NumWorklistIterations	,
		"Number of instruction combining iterations performed"
	)

tryToMoveFreeBeforeNullTest()

static Instruction* tryToMoveFreeBeforeNullTest ( CallInst &  FI, const DataLayout &  DL  )

static

Move the call to free before a NULL test.

Check if this free is accessed after its argument has been test against NULL (property 0). If yes, it is legal to move this call in its predecessor block.

The move is performed only if the block containing the call to free will be removed, i.e.:

1. it has only one predecessor P, and P has two successors
2. it contains the call, noops, and an unconditional branch
3. its successor is the same as its predecessor's successor

The profitability is out-of concern here and this function should be called only if the caller knows this transformation would be profitable (e.g., for code size).

Definition at line 2808 of file InstructionCombining.cpp.

References llvm::Function::addDereferenceableOrNullParamAttr(), assert(), Attrs, DL, llvm::CallBase::getArgOperand(), llvm::CallBase::getAttributes(), llvm::Value::getContext(), llvm::Attribute::getDereferenceableBytes(), llvm::Instruction::getParent(), llvm::BasicBlock::getSinglePredecessor(), llvm::BasicBlock::getTerminator(), llvm::CmpInst::ICMP_EQ, llvm::CmpInst::ICMP_NE, llvm::BasicBlock::instructionsWithoutDebug(), llvm::Attribute::isValid(), llvm::PatternMatch::m_Br(), llvm::PatternMatch::m_CombineOr(), llvm::PatternMatch::m_ICmp(), llvm::PatternMatch::m_Specific(), llvm::PatternMatch::m_UnconditionalBr(), llvm::PatternMatch::m_Zero(), llvm::make_early_inc_range(), llvm::PatternMatch::match(), llvm::CallBase::setAttributes(), and llvm::BasicBlock::size().

Referenced by llvm::InstCombinerImpl::visitFree().

TryToSinkInstruction()

static bool TryToSinkInstruction ( Instruction *  I, BasicBlock *  DestBlock, TargetLibraryInfo &  TLI  )

static

Try to move the specified instruction from its current block into the beginning of DestBlock, which can only happen if it's safe to move the instruction past all of the instructions between it and the end of its block.

FIXME: We could remove droppable uses that are not dominated by the new position.

Definition at line 3767 of file InstructionCombining.cpp.

References assert(), B, llvm::dbgs(), E, llvm::findDbgUsers(), llvm::BasicBlock::getFirstInsertionPt(), llvm::BasicBlock::getTerminator(), llvm::BasicBlock::getUniquePredecessor(), I, llvm::SmallSet< T, N, C >::insert(), LLVM_DEBUG, llvm::reverse(), llvm::salvageDebugInfoForDbgValues(), SoleWriteToDeadLocal(), and llvm::sort().

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

Variable Documentation

EnableCodeSinking

cl::opt<bool> EnableCodeSinking("instcombine-code-sinking", cl::desc("Enable code sinking"), cl::init(true))

static

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

false

Combine redundant false

Definition at line 4404 of file InstructionCombining.cpp.

InfiniteLoopDetectionThreshold

cl::opt<unsigned> InfiniteLoopDetectionThreshold("instcombine-infinite-loop-threshold", cl::desc("Number of instruction combining iterations considered an " "infinite loop"), cl::init(InstCombineDefaultInfiniteLoopThreshold), cl::Hidden)

static

Referenced by combineInstructionsOverFunction().

instcombine

instcombine

Definition at line 4403 of file InstructionCombining.cpp.

InstCombineDefaultInfiniteLoopThreshold

constexpr unsigned InstCombineDefaultInfiniteLoopThreshold = 100

staticconstexpr

Definition at line 133 of file InstructionCombining.cpp.

InstCombineDefaultMaxIterations

constexpr unsigned InstCombineDefaultMaxIterations = 1000

staticconstexpr

Definition at line 131 of file InstructionCombining.cpp.

instructions

Combine redundant instructions

Definition at line 4404 of file InstructionCombining.cpp.

LimitMaxIterations

cl::opt<unsigned> LimitMaxIterations("instcombine-max-iterations", cl::desc("Limit the maximum number of instruction combining iterations"), cl::init(InstCombineDefaultMaxIterations))

static

Referenced by combineInstructionsOverFunction().

MaxArraySize

cl::opt<unsigned> MaxArraySize("instcombine-maxarray-size", cl::init(1024), cl::desc("Maximum array size considered when doing a combine"))

static

Referenced by combineInstructionsOverFunction().

ShouldLowerDbgDeclare

cl::opt<unsigned> ShouldLowerDbgDeclare("instcombine-lower-dbg-declare", cl::Hidden, cl::init(true))

static

Referenced by combineInstructionsOverFunction().