LLVM  mainline
Defines | Functions
InstCombineCompares.cpp File Reference
#include "InstCombineInternal.h"
#include "llvm/ADT/APSInt.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
Include dependency graph for InstCombineCompares.cpp:

Go to the source code of this file.

Defines

#define DEBUG_TYPE   "instcombine"

Functions

 STATISTIC (NumSel,"Number of select opts")
static ConstantIntgetOne (Constant *C)
static ConstantIntExtractElement (Constant *V, Constant *Idx)
static bool HasAddOverflow (ConstantInt *Result, ConstantInt *In1, ConstantInt *In2, bool IsSigned)
static bool AddWithOverflow (Constant *&Result, Constant *In1, Constant *In2, bool IsSigned=false)
 AddWithOverflow - Compute Result = In1+In2, returning true if the result overflowed for this type.
static bool HasSubOverflow (ConstantInt *Result, ConstantInt *In1, ConstantInt *In2, bool IsSigned)
static bool SubWithOverflow (Constant *&Result, Constant *In1, Constant *In2, bool IsSigned=false)
 SubWithOverflow - Compute Result = In1-In2, returning true if the result overflowed for this type.
static bool isSignBitCheck (ICmpInst::Predicate pred, ConstantInt *RHS, bool &TrueIfSigned)
 isSignBitCheck - Given an exploded icmp instruction, return true if the comparison only checks the sign bit.
static bool isSignTest (ICmpInst::Predicate &pred, const ConstantInt *RHS)
 Returns true if the exploded icmp can be expressed as a signed comparison to zero and updates the predicate accordingly.
static bool isHighOnes (const ConstantInt *CI)
static void ComputeSignedMinMaxValuesFromKnownBits (const APInt &KnownZero, const APInt &KnownOne, APInt &Min, APInt &Max)
 ComputeSignedMinMaxValuesFromKnownBits - Given a signed integer type and a set of known zero and one bits, compute the maximum and minimum values that could have the specified known zero and known one bits, returning them in min/max.
static void ComputeUnsignedMinMaxValuesFromKnownBits (const APInt &KnownZero, const APInt &KnownOne, APInt &Min, APInt &Max)
static ValueEvaluateGEPOffsetExpression (User *GEP, InstCombiner &IC, const DataLayout &DL)
 EvaluateGEPOffsetExpression - Return a value that can be used to compare the *offset* implied by a GEP to zero.
static bool canRewriteGEPAsOffset (Value *Start, Value *Base, const DataLayout &DL, SetVector< Value * > &Explored)
 Returns true if we can rewrite Start as a GEP with pointer Base and some integer offset.
static void setInsertionPoint (IRBuilder<> &Builder, Value *V, bool Before=true)
static ValuerewriteGEPAsOffset (Value *Start, Value *Base, const DataLayout &DL, SetVector< Value * > &Explored)
 Returns a re-written value of Start as an indexed GEP using Base as a pointer.
static std::pair< Value
*, Value * > 
getAsConstantIndexedAddress (Value *V, const DataLayout &DL)
 Looks through GEPs, IntToPtrInsts and PtrToIntInsts in order to express the input Value as a constant indexed GEP.
static InstructiontransformToIndexedCompare (GEPOperator *GEPLHS, Value *RHS, ICmpInst::Predicate Cond, const DataLayout &DL)
static InstructionProcessUGT_ADDCST_ADD (ICmpInst &I, Value *A, Value *B, ConstantInt *CI2, ConstantInt *CI1, InstCombiner &IC)
 ProcessUGT_ADDCST_ADD - The caller has matched a pattern of the form: I = icmp ugt (add (add A, B), CI2), CI1 If this is of the form: sum = a + b if (sum+128 >u 255) Then replace it with llvm.sadd.with.overflow.i8.
static InstructionProcessUMulZExtIdiom (ICmpInst &I, Value *MulVal, Value *OtherVal, InstCombiner &IC)
 Recognize and process idiom involving test for multiplication overflow.
static APInt DemandedBitsLHSMask (ICmpInst &I, unsigned BitWidth, bool isSignCheck)
static bool swapMayExposeCSEOpportunities (const Value *Op0, const Value *Op1)
 Check if the order of Op0 and Op1 as operand in an ICmpInst should be swapped.
static bool isChainSelectCmpBranch (const SelectInst *SI)
 true when the instruction sequence within a block is select-cmp-br.

Define Documentation

#define DEBUG_TYPE   "instcombine"

Definition at line 33 of file InstCombineCompares.cpp.


Function Documentation

static bool AddWithOverflow ( Constant *&  Result,
Constant In1,
Constant In2,
bool  IsSigned = false 
) [static]

AddWithOverflow - Compute Result = In1+In2, returning true if the result overflowed for this type.

Definition at line 61 of file InstCombineCompares.cpp.

References ExtractElement(), llvm::ConstantInt::get(), llvm::ConstantExpr::getAdd(), llvm::Value::getContext(), llvm::Type::getInt32Ty(), llvm::Value::getType(), and HasAddOverflow().

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

static bool canRewriteGEPAsOffset ( Value Start,
Value Base,
const DataLayout DL,
SetVector< Value * > &  Explored 
) [static]
static void ComputeSignedMinMaxValuesFromKnownBits ( const APInt KnownZero,
const APInt KnownOne,
APInt Min,
APInt Max 
) [static]

ComputeSignedMinMaxValuesFromKnownBits - Given a signed integer type and a set of known zero and one bits, compute the maximum and minimum values that could have the specified known zero and known one bits, returning them in min/max.

Definition at line 181 of file InstCombineCompares.cpp.

References llvm::APInt::clearBit(), llvm::APInt::getBitWidth(), and llvm::APInt::setBit().

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

static void ComputeUnsignedMinMaxValuesFromKnownBits ( const APInt KnownZero,
const APInt KnownOne,
APInt Min,
APInt Max 
) [static]

Definition at line 205 of file InstCombineCompares.cpp.

References llvm::APInt::getBitWidth().

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

static APInt DemandedBitsLHSMask ( ICmpInst I,
unsigned  BitWidth,
bool  isSignCheck 
) [static]
static Value* EvaluateGEPOffsetExpression ( User GEP,
InstCombiner IC,
const DataLayout DL 
) [static]

EvaluateGEPOffsetExpression - Return a value that can be used to compare the *offset* implied by a GEP to zero.

For example, if we have &A[i], we want to return 'i' for "icmp ne i, 0". Note that, in general, indices can be complex, and scales are involved. The above expression would also be legal to codegen as "icmp ne (i*4), 0" (assuming A is a pointer to i32). This later form is less amenable to optimization though, and we are allowed to generate the first by knowing that pointer arithmetic doesn't overflow.

If we can't emit an optimized form for this expression, this returns null.

Definition at line 506 of file InstCombineCompares.cpp.

References llvm::InstCombiner::Builder, llvm::IRBuilder< preserveNames, T, Inserter >::CreateAdd(), llvm::IRBuilder< preserveNames, T, Inserter >::CreateIntCast(), llvm::IRBuilder< preserveNames, T, Inserter >::CreateTrunc(), llvm::dyn_cast(), llvm::gep_type_begin(), llvm::ConstantInt::get(), llvm::StructLayout::getElementOffset(), llvm::generic_gep_type_iterator< ItTy >::getIndexedType(), llvm::Type::getIntegerBitWidth(), llvm::DataLayout::getIntPtrType(), llvm::User::getNumOperands(), llvm::User::getOperand(), llvm::Type::getPrimitiveSizeInBits(), llvm::ConstantInt::getSExtValue(), llvm::DataLayout::getStructLayout(), llvm::Value::getType(), llvm::DataLayout::getTypeAllocSize(), llvm::ConstantInt::getZExtValue(), llvm::ConstantInt::isZero(), and Offset.

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

static ConstantInt* ExtractElement ( Constant V,
Constant Idx 
) [static]
static std::pair<Value *, Value *> getAsConstantIndexedAddress ( Value V,
const DataLayout DL 
) [static]

Looks through GEPs, IntToPtrInsts and PtrToIntInsts in order to express the input Value as a constant indexed GEP.

Returns a pair containing the GEPs Pointer and Index.

Definition at line 840 of file InstCombineCompares.cpp.

References GEP, llvm::IntegerType::get(), llvm::ConstantExpr::getAdd(), llvm::Value::getContext(), llvm::Constant::getNullValue(), llvm::DataLayout::getPointerTypeSizeInBits(), llvm::ConstantExpr::getSExtOrBitCast(), llvm::Value::getType(), and llvm::codeview::Index.

Referenced by transformToIndexedCompare().

static ConstantInt* getOne ( Constant C) [static]
static bool HasAddOverflow ( ConstantInt Result,
ConstantInt In1,
ConstantInt In2,
bool  IsSigned 
) [static]
static bool HasSubOverflow ( ConstantInt Result,
ConstantInt In1,
ConstantInt In2,
bool  IsSigned 
) [static]
static bool isChainSelectCmpBranch ( const SelectInst SI) [static]

true when the instruction sequence within a block is select-cmp-br.

Definition at line 2979 of file InstCombineCompares.cpp.

References llvm::dyn_cast(), llvm::User::getOperand(), llvm::Instruction::getParent(), llvm::BasicBlock::getTerminator(), and llvm::SI.

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

static bool isHighOnes ( const ConstantInt CI) [static]
static bool isSignBitCheck ( ICmpInst::Predicate  pred,
ConstantInt RHS,
bool TrueIfSigned 
) [static]

isSignBitCheck - Given an exploded icmp instruction, return true if the comparison only checks the sign bit.

If it only checks the sign bit, set TrueIfSigned if the result of the comparison is true when the input value is signed.

Definition at line 121 of file InstCombineCompares.cpp.

References llvm::ConstantInt::getValue(), llvm::CmpInst::ICMP_SGT, llvm::CmpInst::ICMP_SLE, llvm::CmpInst::ICMP_SLT, llvm::CmpInst::ICMP_UGE, llvm::CmpInst::ICMP_UGT, llvm::Constant::isAllOnesValue(), llvm::ConstantInt::isMaxValue(), llvm::APInt::isSignBit(), and llvm::ConstantInt::isZero().

Referenced by llvm::InstCombiner::visitICmpInst(), and llvm::InstCombiner::visitICmpInstWithInstAndIntCst().

static bool isSignTest ( ICmpInst::Predicate &  pred,
const ConstantInt RHS 
) [static]

Returns true if the exploded icmp can be expressed as a signed comparison to zero and updates the predicate accordingly.

The signedness of the comparison is preserved.

Definition at line 149 of file InstCombineCompares.cpp.

References fuzzer::ICMP_SGE, llvm::CmpInst::ICMP_SGT, fuzzer::ICMP_SLE, llvm::CmpInst::ICMP_SLT, llvm::Constant::isAllOnesValue(), llvm::ConstantInt::isOne(), llvm::ICmpInst::isRelational(), llvm::CmpInst::isSigned(), and llvm::ConstantInt::isZero().

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

static Instruction* ProcessUGT_ADDCST_ADD ( ICmpInst I,
Value A,
Value B,
ConstantInt CI2,
ConstantInt CI1,
InstCombiner IC 
) [static]
static Instruction* ProcessUMulZExtIdiom ( ICmpInst I,
Value MulVal,
Value OtherVal,
InstCombiner IC 
) [static]

Recognize and process idiom involving test for multiplication overflow.

The caller has matched a pattern of the form: I = cmp u (mul(zext A, zext B), V The function checks if this is a test for overflow and if so replaces multiplication with call to 'mul.with.overflow' intrinsic.

Parameters:
ICompare instruction.
MulValResult of 'mult' instruction. It is one of the arguments of the compare instruction. Must be of integer type.
OtherValThe other argument of compare instruction.
Returns:
Instruction which must replace the compare instruction, NULL if no replacement required.

Definition at line 2644 of file InstCombineCompares.cpp.

References A, llvm::InstCombineWorklist::Add(), llvm::APIntOps::And(), B, llvm::InstCombiner::Builder, llvm::Call, llvm::APInt::countLeadingZeros(), llvm::ExtractValueInst::Create(), llvm::IRBuilder< preserveNames, T, Inserter >::CreateAnd(), llvm::IRBuilder< preserveNames, T, Inserter >::CreateCall(), llvm::IRBuilder< preserveNames, T, Inserter >::CreateExtractValue(), llvm::BinaryOperator::CreateNot(), llvm::IRBuilder< preserveNames, T, Inserter >::CreateZExt(), llvm::dyn_cast(), llvm::APInt::eq(), F, llvm::ConstantInt::getBitWidth(), llvm::APInt::getBitWidth(), llvm::Intrinsic::getDeclaration(), llvm::HexagonMCInstrInfo::getMaxValue(), llvm::Instruction::getModule(), llvm::APInt::getOneBitSet(), llvm::User::getOperand(), llvm::CmpInst::getPredicate(), llvm::Type::getPrimitiveSizeInBits(), llvm::Value::getType(), llvm::ConstantInt::getValue(), llvm::Value::hasNUsesOrMore(), llvm::CmpInst::ICMP_EQ, llvm::CmpInst::ICMP_NE, llvm::CmpInst::ICMP_UGE, llvm::CmpInst::ICMP_UGT, llvm::CmpInst::ICMP_ULE, llvm::CmpInst::ICMP_ULT, llvm::APInt::isPowerOf2(), llvm_unreachable, llvm::APInt::logBase2(), llvm::PatternMatch::m_And(), llvm::PatternMatch::m_ConstantInt(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::match(), llvm::InstCombiner::ReplaceInstUsesWith(), llvm::IRBuilderBase::SetInsertPoint(), llvm::User::setOperand(), llvm::Trunc, llvm::APInt::trunc(), llvm::Value::users(), llvm::InstCombiner::Worklist, and llvm::APInt::zext().

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

static Value* rewriteGEPAsOffset ( Value Start,
Value Base,
const DataLayout DL,
SetVector< Value * > &  Explored 
) [static]
static void setInsertionPoint ( IRBuilder<> &  Builder,
Value V,
bool  Before = true 
) [static]
STATISTIC ( NumSel  ,
"Number of select opts  
)
static bool SubWithOverflow ( Constant *&  Result,
Constant In1,
Constant In2,
bool  IsSigned = false 
) [static]

SubWithOverflow - Compute Result = In1-In2, returning true if the result overflowed for this type.

Definition at line 96 of file InstCombineCompares.cpp.

References ExtractElement(), llvm::ConstantInt::get(), llvm::Value::getContext(), llvm::Type::getInt32Ty(), llvm::ConstantExpr::getSub(), llvm::Value::getType(), and HasSubOverflow().

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

static bool swapMayExposeCSEOpportunities ( const Value Op0,
const Value Op1 
) [static]

Check if the order of Op0 and Op1 as operand in an ICmpInst should be swapped.

The decision is based on how many times these two operands are reused as subtract operands and their positions in those instructions. The rational is that several architectures use the same instruction for both subtract and cmp, thus it is better if the order of those operands match.

Returns:
true if Op0 and Op1 should be swapped.

Definition at line 2909 of file InstCombineCompares.cpp.

References llvm::dyn_cast(), llvm::BinaryOperator::getOpcode(), llvm::User::getOperand(), llvm::Value::getType(), llvm::Type::isPointerTy(), and llvm::Value::users().

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

static Instruction* transformToIndexedCompare ( GEPOperator GEPLHS,
Value RHS,
ICmpInst::Predicate  Cond,
const DataLayout DL 
) [static]