ConstraintElimination.cpp File Reference

#include "llvm/Transforms/Scalar/ConstraintElimination.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/ScopeExit.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/ConstraintSystem.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Verifier.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/DebugCounter.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/ValueMapper.h"
#include <cmath>
#include <optional>
#include <string>

Go to the source code of this file.

Macros
#define	DEBUG_TYPE   "constraint-elimination"

Functions
	STATISTIC (NumCondsRemoved, "Number of instructions removed")
	DEBUG_COUNTER (EliminatedCounter, "conds-eliminated", "Controls which conditions are eliminated")
static int64_t	multiplyWithOverflow (int64_t A, int64_t B)
static int64_t	addWithOverflow (int64_t A, int64_t B)
static Instruction *	getContextInstForUse (Use &U)
static Decomposition	decompose (Value *V, SmallVectorImpl< ConditionTy > &Preconditions, bool IsSigned, const DataLayout &DL)
static bool	canUseSExt (ConstantInt *CI)
static Decomposition	decomposeGEP (GEPOperator &GEP, SmallVectorImpl< ConditionTy > &Preconditions, bool IsSigned, const DataLayout &DL)
static void	dumpConstraint (ArrayRef< int64_t > C, const DenseMap< Value *, unsigned > &Value2Index)
static void	generateReproducer (CmpInst *Cond, Module *M, ArrayRef< ReproducerEntry > Stack, ConstraintInfo &Info, DominatorTree &DT)
	Helper function to generate a reproducer function for simplifying Cond.
static std::optional< bool >	checkCondition (CmpInst *Cmp, ConstraintInfo &Info, unsigned NumIn, unsigned NumOut, Instruction *ContextInst)
static bool	checkAndReplaceCondition (CmpInst *Cmp, ConstraintInfo &Info, unsigned NumIn, unsigned NumOut, Instruction *ContextInst, Module *ReproducerModule, ArrayRef< ReproducerEntry > ReproducerCondStack, DominatorTree &DT, SmallVectorImpl< Instruction * > &ToRemove)
static void	removeEntryFromStack (const StackEntry &E, ConstraintInfo &Info, Module *ReproducerModule, SmallVectorImpl< ReproducerEntry > &ReproducerCondStack, SmallVectorImpl< StackEntry > &DFSInStack)
static bool	checkAndSecondOpImpliedByFirst (FactOrCheck &CB, ConstraintInfo &Info, Module *ReproducerModule, SmallVectorImpl< ReproducerEntry > &ReproducerCondStack, SmallVectorImpl< StackEntry > &DFSInStack)
	Check if the first condition for an AND implies the second.
static bool	replaceSubOverflowUses (IntrinsicInst *II, Value *A, Value *B, SmallVectorImpl< Instruction * > &ToRemove)
static bool	tryToSimplifyOverflowMath (IntrinsicInst *II, ConstraintInfo &Info, SmallVectorImpl< Instruction * > &ToRemove)
static bool	eliminateConstraints (Function &F, DominatorTree &DT, OptimizationRemarkEmitter &ORE)

Variables
static cl::opt< unsigned >	MaxRows ("constraint-elimination-max-rows", cl::init(500), cl::Hidden, cl::desc("Maximum number of rows to keep in constraint system"))
static cl::opt< bool >	DumpReproducers ("constraint-elimination-dump-reproducers", cl::init(false), cl::Hidden, cl::desc("Dump IR to reproduce successful transformations."))
static int64_t	MaxConstraintValue = std::numeric_limits<int64_t>::max()
static int64_t	MinSignedConstraintValue = std::numeric_limits<int64_t>::min()

Macro Definition Documentation

DEBUG_TYPE

#define DEBUG_TYPE   "constraint-elimination"

Definition at line 47 of file ConstraintElimination.cpp.

Function Documentation

addWithOverflow()

static int64_t addWithOverflow ( int64_t  A, int64_t  B  )

static

Definition at line 72 of file ConstraintElimination.cpp.

References A, llvm::AddOverflow(), and B.

canUseSExt()

static bool canUseSExt ( ConstantInt *  CI )

static

Definition at line 360 of file ConstraintElimination.cpp.

References llvm::ConstantInt::getValue(), MaxConstraintValue, MinSignedConstraintValue, llvm::APInt::sgt(), and llvm::APInt::slt().

Referenced by decompose().

checkAndReplaceCondition()

static bool checkAndReplaceCondition ( CmpInst *  Cmp, ConstraintInfo &  Info, unsigned  NumIn, unsigned  NumOut, Instruction *  ContextInst, Module *  ReproducerModule, ArrayRef< ReproducerEntry >  ReproducerCondStack, DominatorTree &  DT, SmallVectorImpl< Instruction * > &  ToRemove  )

static

Definition at line 1112 of file ConstraintElimination.cpp.

References checkCondition(), generateReproducer(), llvm::ConstantInt::getBool(), getContextInstForUse(), llvm::DominatorTreeBase< NodeT, IsPostDom >::getNode(), llvm::Instruction::getParent(), Info, llvm::CmpInst::makeCmpResultType(), and ToRemove.

checkAndSecondOpImpliedByFirst()

static bool checkAndSecondOpImpliedByFirst ( FactOrCheck &  CB, ConstraintInfo &  Info, Module *  ReproducerModule, SmallVectorImpl< ReproducerEntry > &  ReproducerCondStack, SmallVectorImpl< StackEntry > &  DFSInStack  )

static

Check if the first condition for an AND implies the second.

Definition at line 1165 of file ConstraintElimination.cpp.

References A, llvm::And, B, llvm::SmallVectorTemplateCommon< T, typename >::back(), checkCondition(), E, llvm::ConstantInt::getBool(), Info, llvm::PatternMatch::m_ICmp(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::match(), removeEntryFromStack(), and llvm::SmallVectorBase< Size_T >::size().

checkCondition()

static std::optional< bool > checkCondition ( CmpInst *  Cmp, ConstraintInfo &  Info, unsigned  NumIn, unsigned  NumOut, Instruction *  ContextInst  )

static

Definition at line 1064 of file ConstraintElimination.cpp.

References A, B, llvm::dbgs(), llvm::CmpInst::getPredicateName(), I, Info, LLVM_DEBUG, llvm::make_scope_exit(), and llvm::DebugCounter::shouldExecute().

Referenced by checkAndReplaceCondition(), and checkAndSecondOpImpliedByFirst().

DEBUG_COUNTER()

DEBUG_COUNTER	(	EliminatedCounter	,
		"conds-eliminated"	,
		"Controls which conditions are eliminated"
	)

decompose()

static Decomposition decompose ( Value *  V, SmallVectorImpl< ConditionTy > &  Preconditions, bool  IsSigned, const DataLayout &  DL  )

static

Definition at line 427 of file ConstraintElimination.cpp.

References A, B, canUseSExt(), decompose(), decomposeGEP(), DL, llvm::SmallVectorImpl< T >::emplace_back(), GEP, llvm::ConstantInt::get(), llvm::ConstantInt::getSExtValue(), llvm::Value::getType(), llvm::haveNoCommonBitsSet(), llvm::CmpInst::ICMP_SGE, llvm::CmpInst::ICMP_UGE, llvm::isKnownNonNegative(), llvm::ConstantInt::isNegative(), llvm::PatternMatch::m_Add(), llvm::PatternMatch::m_ConstantInt(), llvm::PatternMatch::m_NSWAdd(), llvm::PatternMatch::m_NSWMul(), llvm::PatternMatch::m_NUWAdd(), llvm::PatternMatch::m_NUWMul(), llvm::PatternMatch::m_NUWShl(), llvm::PatternMatch::m_NUWSub(), llvm::PatternMatch::m_Or(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::m_ZExt(), llvm::PatternMatch::match(), llvm::MaxAnalysisRecursionDepth, and MaxConstraintValue.

Referenced by decompose(), and decomposeGEP().

decomposeGEP()

static Decomposition decomposeGEP ( GEPOperator &  GEP, SmallVectorImpl< ConditionTy > &  Preconditions, bool  IsSigned, const DataLayout &  DL  )

static

Definition at line 365 of file ConstraintElimination.cpp.

References assert(), llvm::BitWidth, decompose(), DL, llvm::SmallVectorImpl< T >::emplace_back(), llvm::MapVector< KeyT, ValueT, MapType, VectorType >::empty(), GEP, llvm::ConstantInt::get(), llvm::APInt::getSExtValue(), llvm::CmpInst::ICMP_SGE, llvm::isKnownNonNegative(), llvm::APInt::isNegative(), and llvm::MaxAnalysisRecursionDepth.

Referenced by decompose().

dumpConstraint()

static void dumpConstraint ( ArrayRef< int64_t >  C, const DenseMap< Value *, unsigned > &  Value2Index  )

static

Definition at line 781 of file ConstraintElimination.cpp.

References llvm::ConstraintSystem::addVariableRowFill(), llvm::CallingConv::C, and llvm::ConstraintSystem::dump().

eliminateConstraints()

static bool eliminateConstraints ( Function &  F, DominatorTree &  DT, OptimizationRemarkEmitter &  ORE  )

static

Definition at line 1312 of file ConstraintElimination.cpp.

References A, B, DumpReproducers, F, llvm::DominatorTreeBase< NodeT, IsPostDom >::getNode(), if(), Info, llvm::SmallVectorTemplateBase< T, bool >::push_back(), llvm::stable_sort(), and llvm::DominatorTreeBase< NodeT, IsPostDom >::updateDFSNumbers().

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

generateReproducer()

static void generateReproducer ( CmpInst *  Cond, Module *  M, ArrayRef< ReproducerEntry >  Stack, ConstraintInfo &  Info, DominatorTree &  DT  )

static

Helper function to generate a reproducer function for simplifying Cond.

The reproducer function contains a series of @llvm.assume calls, one for each condition in Stack. For each condition, the operand instruction are cloned until we reach operands that have an entry in Value2Index. Those will then be added as function arguments. DT is used to order cloned instructions. The reproducer function will get added to M, if it is non-null. Otherwise no reproducer function is generated.

Definition at line 935 of file ConstraintElimination.cpp.

References A, llvm::append_range(), assert(), B, Builder, Cond, llvm::Function::Create(), llvm::BasicBlock::Create(), llvm::dbgs(), llvm::DominatorTree::dominates(), llvm::Instruction::dropUnknownNonDebugMetadata(), llvm::SmallVectorBase< Size_T >::empty(), llvm::ValueMap< KeyT, ValueT, Config >::end(), F, llvm::ValueMap< KeyT, ValueT, Config >::find(), getName(), I, Info, llvm::SmallPtrSetImpl< PtrType >::insert(), llvm::Instruction::insertBefore(), llvm::CmpInst::isSigned(), LLVM_DEBUG, P, llvm::SmallVectorImpl< T >::pop_back_val(), llvm::SmallVectorTemplateBase< T, bool >::push_back(), llvm::remapInstructionsInBlocks(), llvm::Instruction::setDebugLoc(), llvm::sort(), and llvm::verifyFunction().

Referenced by checkAndReplaceCondition().

getContextInstForUse()

static Instruction * getContextInstForUse ( Use &  U )

static

Definition at line 78 of file ConstraintElimination.cpp.

Referenced by checkAndReplaceCondition().

multiplyWithOverflow()

static int64_t multiplyWithOverflow ( int64_t  A, int64_t  B  )

static

Definition at line 65 of file ConstraintElimination.cpp.

References A, B, and llvm::MulOverflow().

removeEntryFromStack()

static void removeEntryFromStack ( const StackEntry &  E, ConstraintInfo &  Info, Module *  ReproducerModule, SmallVectorImpl< ReproducerEntry > &  ReproducerCondStack, SmallVectorImpl< StackEntry > &  DFSInStack  )

static

Definition at line 1149 of file ConstraintElimination.cpp.

References E, Info, and llvm::SmallVectorTemplateBase< T, bool >::pop_back().

Referenced by checkAndSecondOpImpliedByFirst().

replaceSubOverflowUses()

static bool replaceSubOverflowUses ( IntrinsicInst *  II, Value *  A, Value *  B, SmallVectorImpl< Instruction * > &  ToRemove  )

static

Definition at line 1252 of file ConstraintElimination.cpp.

References A, B, Builder, llvm::Instruction::eraseFromParent(), llvm::PoisonValue::get(), llvm::ilist_node_impl< OptionsT >::getIterator(), llvm::Instruction::getParent(), llvm::Value::getType(), I, llvm::PatternMatch::m_Value(), llvm::make_early_inc_range(), llvm::PatternMatch::match(), ToRemove, llvm::Value::use_empty(), and llvm::Value::users().

Referenced by tryToSimplifyOverflowMath().

STATISTIC()

STATISTIC	(	NumCondsRemoved	,
		"Number of instructions removed"
	)

tryToSimplifyOverflowMath()

static bool tryToSimplifyOverflowMath ( IntrinsicInst *  II, ConstraintInfo &  Info, SmallVectorImpl< Instruction * > &  ToRemove  )

static

Definition at line 1285 of file ConstraintElimination.cpp.

References A, B, llvm::ConstantInt::get(), llvm::CallBase::getArgOperand(), llvm::IntrinsicInst::getIntrinsicID(), llvm::CmpInst::ICMP_SGE, Info, replaceSubOverflowUses(), and ToRemove.

Variable Documentation

DumpReproducers

cl::opt< bool > DumpReproducers("constraint-elimination-dump-reproducers", cl::init(false), cl::Hidden, cl::desc("Dump IR to reproduce successful transformations.")) ( "constraint-elimination-dump-reproducers"  , cl::init(false)  , cl::Hidden  , cl::desc("Dump IR to reproduce successful transformations.")    )

static

Referenced by eliminateConstraints().

MaxConstraintValue

int64_t MaxConstraintValue = std::numeric_limits<int64_t>::max()

static

Definition at line 61 of file ConstraintElimination.cpp.

Referenced by canUseSExt(), and decompose().

MaxRows

cl::opt< unsigned > MaxRows("constraint-elimination-max-rows", cl::init(500), cl::Hidden, cl::desc("Maximum number of rows to keep in constraint system")) ( "constraint-elimination-max-rows"  , cl::init(500)  , cl::Hidden  , cl::desc("Maximum number of rows to keep in constraint system")    )

static

MinSignedConstraintValue

int64_t MinSignedConstraintValue = std::numeric_limits<int64_t>::min()

static

Definition at line 62 of file ConstraintElimination.cpp.

Referenced by canUseSExt().