LLVM  13.0.0git
Classes | Macros | Functions | Variables
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/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.

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 ValuegetIdentityValue (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 ValuefoldOperationIntoSelectOperand (Instruction &I, Value *SO, InstCombiner::BuilderTy &Builder)
 
static ValuefoldOperationIntoPhiValue (BinaryOperator *I, Value *InV, InstCombiner::BuilderTy &Builder)
 
static bool shouldMergeGEPs (GEPOperator &GEP, GEPOperator &Src)
 
static bool isMergedGEPInBounds (GEPOperator &GEP1, GEPOperator &GEP2)
 
static InstructionfoldSelectGEP (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 isAllocSiteRemovable (Instruction *AI, SmallVectorImpl< WeakTrackingVH > &Users, const TargetLibraryInfo *TLI)
 
static InstructiontryToMoveFreeBeforeNullTest (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 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 prepareICWorklistFromFunction (Function &F, const DataLayout &DL, const TargetLibraryInfo *TLI, InstCombineWorklist &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, InstCombineWorklist &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 115 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 294 of file InstructionCombining.cpp.

References I.

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

◆ combineInstructionsOverFunction()

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

◆ DEBUG_COUNTER()

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

◆ foldOperationIntoPhiValue()

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

◆ foldOperationIntoSelectOperand()

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

◆ foldSelectGEP()

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

◆ 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 578 of file InstructionCombining.cpp.

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

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 565 of file InstructionCombining.cpp.

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

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

◆ hasNoSignedWrap()

static bool hasNoSignedWrap ( BinaryOperator I)
static

◆ hasNoUnsignedWrap()

static bool hasNoUnsignedWrap ( BinaryOperator I)
static

◆ 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

◆ isCatchAll()

static bool isCatchAll ( EHPersonality  Personality,
Constant TypeInfo 
)
static

◆ isMergedGEPInBounds()

static bool isMergedGEPInBounds ( GEPOperator GEP1,
GEPOperator GEP2 
)
static

◆ isMustTailCall()

static bool isMustTailCall ( Value V)
static

◆ isNeverEqualToUnescapedAlloc()

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

Definition at line 2514 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 529 of file InstructionCombining.cpp.

References llvm::MCID::Add.

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

◆ maintainNoSignedWrap()

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

◆ prepareICWorklistFromFunction()

static bool prepareICWorklistFromFunction ( Function F,
const DataLayout DL,
const TargetLibraryInfo TLI,
InstCombineWorklist 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 3838 of file InstructionCombining.cpp.

References AliasScopeTracker::analyse(), llvm::append_range(), BB, Cond, llvm::ConstantFoldConstant(), llvm::ConstantFoldInstruction(), llvm::SmallPtrSetImpl< PtrType >::count(), llvm::dbgs(), DL, E, llvm::Instruction::eraseFromParent(), F, llvm::User::getNumOperands(), llvm::User::getOperand(), llvm::SmallPtrSetImpl< PtrType >::insert(), llvm::Instruction::isDebugOrPseudoInst(), llvm::isInstructionTriviallyDead(), AliasScopeTracker::isNoAliasScopeDeclDead(), LLVM_DEBUG, llvm::User::operands(), llvm::SmallVectorImpl< T >::pop_back_val(), llvm::InstCombineWorklist::push(), llvm::removeAllNonTerminatorAndEHPadInstructions(), llvm::Value::replaceAllUsesWith(), llvm::InstCombineWorklist::reserve(), llvm::reverse(), llvm::salvageDebugInfo(), SI, llvm::successors(), and llvm::Value::use_empty().

Referenced by combineInstructionsOverFunction().

◆ rightDistributesOverLeft()

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

◆ shorter_filter()

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

◆ shouldMergeGEPs()

static bool shouldMergeGEPs ( GEPOperator GEP,
GEPOperator Src 
)
static

◆ 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 310 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().

◆ 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 2727 of file InstructionCombining.cpp.

References assert(), llvm::BasicBlock::begin(), DL, llvm::CallBase::getArgOperand(), llvm::Instruction::getParent(), llvm::BasicBlock::getSinglePredecessor(), llvm::BasicBlock::getTerminator(), llvm::CmpInst::ICMP_EQ, llvm::CmpInst::ICMP_NE, llvm::BasicBlock::instructionsWithoutDebug(), 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(), and llvm::BasicBlock::size().

Referenced by llvm::InstCombinerImpl::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.

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

Definition at line 3513 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(), 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

◆ false

Combine redundant false

Definition at line 4123 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

◆ instcombine

instcombine

Definition at line 4122 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 4123 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

◆ MaxArraySize

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

◆ ShouldLowerDbgDeclare

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