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/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/LoopInfo.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/TargetFolder.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/ValueTracking.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/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/InstCombine/InstCombineWorklist.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <memory>
#include <string>
#include <utility>

Go to the source code of this file.

Macros
#define	DEBUG_TYPE   "instcombine"

Functions
	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 void	ClearSubclassDataAfterReassociation (BinaryOperator &I)
	Conservatively clears subclassOptionalData after a reassociation or commutation. More...
static bool	simplifyAssocCastAssoc (BinaryOperator *BinOp1)
	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	isNeverEqualToUnescapedAlloc (Value *V, const TargetLibraryInfo *TLI, Instruction *AI)
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	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	TryToSinkInstruction (Instruction *I, BasicBlock *DestBlock)
	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	AddReachableCodeToWorklist (BasicBlock *BB, const DataLayout &DL, SmallPtrSetImpl< BasicBlock *> &Visited, InstCombineWorklist &ICWorklist, const TargetLibraryInfo *TLI)
	Walk the function in depth-first order, adding all reachable code to the worklist. More...
static bool	prepareICWorklistFromFunction (Function &F, const DataLayout &DL, TargetLibraryInfo *TLI, InstCombineWorklist &ICWorklist)
	Populate the IC worklist from a function, and prune any dead basic blocks discovered in the process. More...
static bool	combineInstructionsOverFunction (Function &F, InstCombineWorklist &Worklist, AliasAnalysis *AA, AssumptionCache &AC, TargetLibraryInfo &TLI, DominatorTree &DT, OptimizationRemarkEmitter &ORE, bool ExpensiveCombines=true, LoopInfo *LI=nullptr)
	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 cl::opt< bool >	EnableCodeSinking ("instcombine-code-sinking", cl::desc("Enable code sinking"), cl::init(true))
static cl::opt< bool >	EnableExpensiveCombines ("expensive-combines", cl::desc("Enable expensive instruction combines"))
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 110 of file InstructionCombining.cpp.

Function Documentation

AddReachableCodeToWorklist()

static bool AddReachableCodeToWorklist ( BasicBlock *  BB, const DataLayout &  DL, SmallPtrSetImpl< BasicBlock *> &  Visited, InstCombineWorklist &  ICWorklist, const TargetLibraryInfo *  TLI  )

static

Walk the function in depth-first order, 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 3275 of file InstructionCombining.cpp.

References llvm::InstCombineWorklist::AddInitialGroup(), llvm::BasicBlock::begin(), C, llvm::ConstantFoldConstant(), llvm::ConstantFoldInstruction(), llvm::dbgs(), E, llvm::SmallVectorBase::empty(), llvm::BasicBlock::end(), llvm::Instruction::eraseFromParent(), llvm::SelectInst::getCondition(), llvm::User::getNumOperands(), llvm::User::getOperand(), llvm::BasicBlock::getTerminator(), llvm::SmallPtrSetImpl< PtrType >::insert(), llvm::isInstructionTriviallyDead(), LLVM_DEBUG, llvm::User::operands(), llvm::SmallVectorImpl< T >::pop_back_val(), llvm::SmallVectorTemplateBase< T >::push_back(), llvm::Value::replaceAllUsesWith(), llvm::salvageDebugInfo(), llvm::successors(), and llvm::Value::use_empty().

Referenced by prepareICWorklistFromFunction().

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 227 of file InstructionCombining.cpp.

References llvm::Value::clearSubclassOptionalData(), llvm::dyn_cast(), llvm::Instruction::getFastMathFlags(), I, and llvm::Instruction::setFastMathFlags().

Referenced by simplifyAssocCastAssoc().

combineInstructionsOverFunction()

static bool combineInstructionsOverFunction ( Function &  F, InstCombineWorklist &  Worklist, AliasAnalysis *  AA, AssumptionCache &  AC, TargetLibraryInfo &  TLI, DominatorTree &  DT, OptimizationRemarkEmitter &  ORE, bool  ExpensiveCombines = true, LoopInfo *  LI = nullptr  )

static

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

Definition at line 3410 of file InstructionCombining.cpp.

References llvm::InstCombineWorklist::Add(), llvm::dbgs(), EnableExpensiveCombines, llvm::Function::getContext(), llvm::Module::getDataLayout(), llvm::Value::getName(), llvm::GlobalValue::getParent(), LLVM_DEBUG, llvm::LowerDbgDeclare(), llvm::PatternMatch::match(), MaxArraySize, llvm::InstCombiner::MaxArraySizeForCombine, llvm::Function::optForMinSize(), prepareICWorklistFromFunction(), llvm::AssumptionCache::registerAssumption(), 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 867 of file InstructionCombining.cpp.

References llvm::PHINode::addIncoming(), assert(), C, llvm::Instruction::copyFastMathFlags(), llvm::PHINode::Create(), llvm::IRBuilder< T, Inserter >::CreateBinOp(), llvm::Value::DoPHITranslation(), llvm::dyn_cast(), E, llvm::ConstantInt::get(), llvm::ConstantExpr::get(), llvm::ConstantExpr::getCast(), llvm::ConstantExpr::getCompare(), llvm::Type::getContext(), llvm::StructLayout::getElementContainingOffset(), llvm::StructLayout::getElementOffset(), llvm::PointerType::getElementType(), llvm::SelectInst::getFalseValue(), llvm::PHINode::getIncomingBlock(), llvm::PHINode::getIncomingValue(), llvm::Type::getInt32Ty(), llvm::PHINode::getNumIncomingValues(), llvm::BinaryOperator::getOpcode(), llvm::CastInst::getOpcode(), llvm::User::getOperand(), llvm::Instruction::getParent(), llvm::StructLayout::getSizeInBytes(), llvm::BasicBlock::getTerminator(), llvm::SelectInst::getTrueValue(), llvm::Value::getType(), llvm::Value::hasOneUse(), I, llvm::Instruction::isIdenticalTo(), llvm::Constant::isNullValue(), llvm::isPotentiallyReachable(), llvm::Type::isSized(), llvm::BranchInst::isUnconditional(), llvm::SmallVectorTemplateBase< T, bool >::push_back(), std::swap(), llvm::Value::takeName(), llvm::Value::user_begin(), llvm::Value::user_end(), and llvm::Value::users().

foldOperationIntoSelectOperand()

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

static

Definition at line 787 of file InstructionCombining.cpp.

References assert(), llvm::Instruction::copyFastMathFlags(), llvm::SelectInst::Create(), llvm::IRBuilder< T, Inserter >::CreateBinOp(), llvm::IRBuilder< T, Inserter >::CreateCast(), llvm::dyn_cast(), llvm::ConstantExpr::get(), llvm::SelectInst::getCondition(), llvm::SelectInst::getFalseValue(), llvm::Value::getName(), llvm::SequentialType::getNumElements(), llvm::Instruction::getOpcode(), llvm::User::getOperand(), llvm::SelectInst::getTrueValue(), llvm::Value::getType(), llvm::Value::hasOneUse(), I, llvm::Instruction::isBinaryOp(), llvm::Type::isIntOrIntVectorTy(), SI, and std::swap().

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 498 of file InstructionCombining.cpp.

References llvm::MCID::Add, assert(), B, C, D, llvm::dyn_cast(), E, llvm::ConstantInt::get(), llvm::Constant::getAggregateElement(), llvm::ConstantExpr::getBinOpIdentity(), llvm::Instruction::getFastMathFlags(), getIdentityValue(), llvm::Value::getName(), llvm::ConstantExpr::getNeg(), llvm::BinaryOperator::getOpcode(), llvm::User::getOperand(), llvm::ConstantExpr::getShl(), llvm::Value::getType(), llvm::Instruction::hasNoSignedWrap(), llvm::Value::hasOneUse(), llvm::Instruction::isCommutative(), llvm::Type::isIntegerTy(), llvm::APInt::isMinSignedValue(), leftDistributesOverRight(), llvm::PatternMatch::m_APInt(), llvm::PatternMatch::m_Constant(), llvm::PatternMatch::m_Neg(), llvm::PatternMatch::m_Select(), llvm::PatternMatch::m_Shl(), llvm::PatternMatch::m_Specific(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::match(), rightDistributesOverLeft(), SI, llvm::SimplifyBinOp(), std::swap(), llvm::Value::takeName(), and llvm::NVPTX::PTXLdStInstCode::V2.

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 485 of file InstructionCombining.cpp.

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

Referenced by getBinOpsForFactorization().

INITIALIZE_PASS_BEGIN()

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

Referenced by llvm::InstructionCombiningPass::runOnFunction().

isAllocSiteRemovable()

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

static

Definition at line 2186 of file InstructionCombining.cpp.

References llvm::MCID::Call, llvm::SmallVectorImpl< T >::emplace_back(), llvm::SmallVectorBase::empty(), llvm::Instruction::getOpcode(), llvm::User::getOperand(), llvm::StoreInst::getPointerOperand(), llvm::MemIntrinsicBase< Derived >::getRawDest(), I, llvm::Intrinsic::invariant_end, llvm::Intrinsic::invariant_start, llvm::ICmpInst::isEquality(), llvm::isFreeCall(), isNeverEqualToUnescapedAlloc(), llvm::StoreInst::isVolatile(), llvm::MemIntrinsic::isVolatile(), llvm::Intrinsic::lifetime_end, llvm::Intrinsic::lifetime_start, LLVM_FALLTHROUGH, llvm_unreachable, llvm::Intrinsic::memcpy, llvm::Intrinsic::memmove, llvm::Intrinsic::memset, MI, llvm::Intrinsic::objectsize, llvm::SmallVectorImpl< T >::pop_back_val(), llvm::SmallVectorTemplateBase< T >::push_back(), llvm::SPII::Store, and llvm::Value::users().

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

isCatchAll()

static bool isCatchAll ( EHPersonality  Personality, Constant *  TypeInfo  )

static

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

Definition at line 2713 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_Win64SEH, llvm::MSVC_X86SEH, llvm::Rust, llvm::Unknown, and llvm::Wasm_CXX.

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

isNeverEqualToUnescapedAlloc()

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

static

Definition at line 2172 of file InstructionCombining.cpp.

References llvm::isAllocLikeFn().

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 449 of file InstructionCombining.cpp.

References llvm::MCID::Add.

Referenced by getBinOpsForFactorization(), and rightDistributesOverLeft().

MaintainNoSignedWrap()

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

static

Definition at line 201 of file InstructionCombining.cpp.

References llvm::MCID::Add, llvm::dyn_cast(), llvm::BinaryOperator::getOpcode(), llvm::OverflowingBinaryOperator::hasNoSignedWrap(), I, llvm::PatternMatch::m_APInt(), llvm::PatternMatch::match(), llvm::APInt::sadd_ov(), and llvm::APInt::ssub_ov().

Referenced by simplifyAssocCastAssoc().

prepareICWorklistFromFunction()

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

static

Populate the IC worklist from a function, and prune any dead basic blocks discovered in the process.

This also does basic constant propagation and other forward fixing to make the combiner itself run much faster.

Definition at line 3383 of file InstructionCombining.cpp.

References AddReachableCodeToWorklist(), llvm::Function::front(), and llvm::removeAllNonTerminatorAndEHPadInstructions().

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 470 of file InstructionCombining.cpp.

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

Referenced by getBinOpsForFactorization().

shorter_filter()

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

static

Definition at line 2740 of file InstructionCombining.cpp.

References llvm::Value::getType().

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

shouldMergeGEPs()

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

static

Definition at line 1110 of file InstructionCombining.cpp.

References assert(), C, llvm::CastInst::Create(), llvm::APInt::exactLogBase2(), llvm::ConstantInt::get(), llvm::ConstantVector::get(), llvm::ConstantExpr::get(), llvm::UndefValue::get(), llvm::Constant::getAggregateElement(), getBitWidth(), llvm::APInt::getBitWidth(), llvm::ConstantExpr::getCast(), llvm::Instruction::getOpcode(), getOpcode(), llvm::BinaryOperator::getOpcode(), llvm::User::getOperand(), llvm::getSafeVectorConstantForBinop(), llvm::Type::getScalarType(), llvm::ShuffleVectorInst::getShuffleMask(), llvm::ConstantExpr::getTrunc(), llvm::Value::getType(), llvm::Type::getVectorNumElements(), llvm::GEPOperator::hasAllZeroIndices(), llvm::Instruction::hasNoSignedWrap(), llvm::Value::hasOneUse(), I, llvm::Instruction::isIntDivRem(), llvm::APInt::isMinValue(), llvm::isSafeToSpeculativelyExecute(), llvm::Instruction::isShift(), llvm::Type::isVectorTy(), llvm::PatternMatch::m_c_BinOp(), llvm::PatternMatch::m_Constant(), llvm::PatternMatch::m_OneUse(), llvm::PatternMatch::m_SExt(), llvm::PatternMatch::m_ShuffleVector(), llvm::PatternMatch::m_Specific(), llvm::PatternMatch::m_Undef(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::m_Zero(), llvm::PatternMatch::m_ZExt(), llvm::PatternMatch::m_ZExtOrSExt(), llvm::BitmaskEnumDetail::Mask(), llvm::PatternMatch::match(), llvm::APInt::sdivrem(), llvm::APInt::sext(), std::swap(), llvm::APInt::trunc(), llvm::Instruction::user_back(), llvm::NVPTX::PTXLdStInstCode::V2, willNotOverflow(), X, and Y.

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

simplifyAssocCastAssoc()

static bool simplifyAssocCastAssoc ( BinaryOperator *  BinOp1 )

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 243 of file InstructionCombining.cpp.

References B, C, ClearSubclassDataAfterReassociation(), llvm::Value::clearSubclassOptionalData(), llvm::BinaryOperator::Create(), llvm::dyn_cast(), llvm::ConstantExpr::get(), llvm::ConstantExpr::getCast(), llvm::getComplexity(), llvm::Instruction::getFastMathFlags(), llvm::BinaryOperator::getOpcode(), llvm::CastInst::getOpcode(), llvm::User::getOperand(), llvm::Value::getType(), llvm::Instruction::hasNoSignedWrap(), I, llvm::Instruction::isAssociative(), llvm::Instruction::isBitwiseLogicOp(), llvm::Instruction::isCommutative(), llvm::PatternMatch::m_BinOp(), llvm::PatternMatch::m_Constant(), llvm::PatternMatch::m_OneUse(), llvm::PatternMatch::m_Value(), MaintainNoSignedWrap(), llvm::PatternMatch::match(), llvm::Instruction::setFastMathFlags(), llvm::Instruction::setHasNoSignedWrap(), llvm::User::setOperand(), llvm::SimplifyBinOp(), llvm::BinaryOperator::swapOperands(), and llvm::Value::takeName().

STATISTIC() [1/7]

STATISTIC	(	NumCombined	,
		"Number of insts combined"
	)

STATISTIC() [2/7]

STATISTIC	(	NumConstProp	,
		"Number of constant folds"
	)

STATISTIC() [3/7]

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

STATISTIC() [4/7]

STATISTIC	(	NumSunkInst	,
		"Number of instructions sunk"
	)

STATISTIC() [5/7]

STATISTIC	(	NumExpand	,
		"Number of expansions"
	)

STATISTIC() [6/7]

STATISTIC	(	NumFactor	,
		"Number of factorizations"
	)

STATISTIC() [7/7]

STATISTIC	(	NumReassoc	,
		"Number of reassociations"
	)

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 2359 of file InstructionCombining.cpp.

References assert(), llvm::BasicBlock::begin(), llvm::dyn_cast(), llvm::CallBase::getArgOperand(), llvm::Instruction::getParent(), llvm::BasicBlock::getSinglePredecessor(), llvm::BasicBlock::getTerminator(), llvm::CmpInst::ICMP_EQ, llvm::CmpInst::ICMP_NE, 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::PatternMatch::match(), llvm::BasicBlock::size(), and llvm::Value::stripPointerCasts().

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

TryToSinkInstruction()

static bool TryToSinkInstruction ( Instruction *  I, BasicBlock *  DestBlock  )

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.

Definition at line 3060 of file InstructionCombining.cpp.

References assert(), llvm::dbgs(), E, llvm::BasicBlock::end(), llvm::findDbgUsers(), llvm::BasicBlock::getFirstInsertionPt(), llvm::ilist_node_impl< OptionsT >::getIterator(), llvm::Instruction::getParent(), llvm::BasicBlock::getTerminator(), llvm::Value::hasOneUse(), llvm::Instruction::isEHPad(), llvm::Instruction::isTerminator(), LLVM_DEBUG, llvm::Instruction::mayHaveSideEffects(), llvm::Instruction::mayReadFromMemory(), and llvm::Instruction::moveBefore().

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

Variable Documentation

EnableCodeSinking

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

static

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

EnableExpensiveCombines

cl::opt<bool> EnableExpensiveCombines("expensive-combines", cl::desc("Enable expensive instruction combines"))

static

Referenced by combineInstructionsOverFunction().

false

Combine redundant false

Definition at line 3520 of file InstructionCombining.cpp.

instcombine

instcombine

Definition at line 3520 of file InstructionCombining.cpp.

instructions

Combine redundant instructions

Definition at line 3520 of file InstructionCombining.cpp.

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().