InstCombineShifts.cpp File Reference

#include "InstCombineInternal.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/PatternMatch.h"

Include dependency graph for InstCombineShifts.cpp:

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Macros
#define	DEBUG_TYPE   "instcombine"

Functions
static bool	canEvaluateShiftedShift (unsigned OuterShAmt, bool IsOuterShl, Instruction *InnerShift, InstCombiner &IC, Instruction *CxtI)
	Return true if we can simplify two logical (either left or right) shifts that have constant shift amounts: OuterShift (InnerShift X, C1), C2. More...
static bool	canEvaluateShifted (Value *V, unsigned NumBits, bool IsLeftShift, InstCombiner &IC, Instruction *CxtI)
	See if we can compute the specified value, but shifted logically to the left or right by some number of bits. More...
static Value *	foldShiftedShift (BinaryOperator *InnerShift, unsigned OuterShAmt, bool IsOuterShl, InstCombiner::BuilderTy &Builder)
	Fold OuterShift (InnerShift X, C1), C2. More...
static Value *	getShiftedValue (Value *V, unsigned NumBits, bool isLeftShift, InstCombiner &IC, const DataLayout &DL)
	When canEvaluateShifted() returns true for an expression, this function inserts the new computation that produces the shifted value. More...
static bool	canShiftBinOpWithConstantRHS (BinaryOperator &Shift, BinaryOperator *BO, const APInt &C)

Macro Definition Documentation

DEBUG_TYPE

#define DEBUG_TYPE   "instcombine"

Definition at line 22 of file InstCombineShifts.cpp.

Function Documentation

canEvaluateShifted()

static bool canEvaluateShifted ( Value *  V, unsigned  NumBits, bool  IsLeftShift, InstCombiner &  IC, Instruction *  CxtI  )

static

See if we can compute the specified value, but shifted logically to the left or right by some number of bits.

This should return true if the expression can be computed for the same cost as the current expression tree. This is used to eliminate extraneous shifting from things like: C = shl i128 A, 64 D = shl i128 B, 96 E = or i128 C, D F = lshr i128 E, 64 where the client will ask if E can be computed shifted right by 64-bits. If this succeeds, getShiftedValue() will be called to produce the value.

Definition at line 122 of file InstCombineShifts.cpp.

References canEvaluateShiftedShift(), llvm::dyn_cast(), llvm::SelectInst::getFalseValue(), llvm::APInt::getHighBitsSet(), llvm::ConstantInt::getLimitedValue(), llvm::Instruction::getOpcode(), llvm::User::getOperand(), llvm::SelectInst::getTrueValue(), llvm::ConstantInt::getValue(), llvm::Value::hasOneUse(), I, llvm::PHINode::incoming_values(), llvm::PatternMatch::m_ConstantInt(), llvm::PatternMatch::m_LShr(), llvm::PatternMatch::m_Shl(), llvm::PatternMatch::m_Value(), llvm::MaskedValueIsZero(), llvm::PatternMatch::match(), llvm::MCID::Select, and SI.

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

canEvaluateShiftedShift()

static bool canEvaluateShiftedShift ( unsigned  OuterShAmt, bool  IsOuterShl, Instruction *  InnerShift, InstCombiner &  IC, Instruction *  CxtI  )

static

Return true if we can simplify two logical (either left or right) shifts that have constant shift amounts: OuterShift (InnerShift X, C1), C2.

Definition at line 70 of file InstCombineShifts.cpp.

References assert(), llvm::APInt::getLowBitsSet(), llvm::Instruction::getOpcode(), llvm::User::getOperand(), llvm::Type::getScalarSizeInBits(), llvm::Value::getType(), llvm::Instruction::isLogicalShift(), llvm::PatternMatch::m_APInt(), llvm::BitmaskEnumDetail::Mask(), llvm::InstCombiner::MaskedValueIsZero(), and llvm::PatternMatch::match().

Referenced by canEvaluateShifted().

canShiftBinOpWithConstantRHS()

static bool canShiftBinOpWithConstantRHS ( BinaryOperator &  Shift, BinaryOperator *  BO, const APInt &  C  )

static

Definition at line 315 of file InstCombineShifts.cpp.

References llvm::MCID::Add, llvm::BinaryOperator::getOpcode(), and llvm::APInt::isNegative().

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

foldShiftedShift()

static Value* foldShiftedShift ( BinaryOperator *  InnerShift, unsigned  OuterShAmt, bool  IsOuterShl, InstCombiner::BuilderTy &  Builder  )

static

Fold OuterShift (InnerShift X, C1), C2.

See canEvaluateShiftedShift() for the constraints on these instructions.

Definition at line 195 of file InstCombineShifts.cpp.

References assert(), llvm::IRBuilder< T, Inserter >::CreateAnd(), llvm::ConstantInt::get(), llvm::APInt::getHighBitsSet(), llvm::APInt::getLowBitsSet(), llvm::Constant::getNullValue(), llvm::BinaryOperator::getOpcode(), llvm::User::getOperand(), llvm::Type::getScalarSizeInBits(), llvm::Value::getType(), llvm::APInt::getZExtValue(), llvm::PatternMatch::m_APInt(), llvm::BitmaskEnumDetail::Mask(), llvm::PatternMatch::match(), llvm::Instruction::setHasNoSignedWrap(), llvm::Instruction::setHasNoUnsignedWrap(), llvm::Instruction::setIsExact(), llvm::User::setOperand(), and llvm::Value::takeName().

Referenced by getShiftedValue().

getShiftedValue()

static Value* getShiftedValue ( Value *  V, unsigned  NumBits, bool  isLeftShift, InstCombiner &  IC, const DataLayout &  DL  )

static

When canEvaluateShifted() returns true for an expression, this function inserts the new computation that produces the shifted value.

Definition at line 258 of file InstCombineShifts.cpp.

References llvm::InstCombineWorklist::Add(), llvm::InstCombiner::Builder, C, llvm::ConstantFoldConstant(), llvm::IRBuilder< T, Inserter >::CreateLShr(), llvm::IRBuilder< T, Inserter >::CreateShl(), foldShiftedShift(), llvm::PHINode::getIncomingValue(), llvm::PHINode::getNumIncomingValues(), llvm::Instruction::getOpcode(), llvm::User::getOperand(), llvm::InstCombiner::getTargetLibraryInfo(), I, llvm_unreachable, llvm::MCID::Select, llvm::PHINode::setIncomingValue(), llvm::User::setOperand(), and llvm::InstCombiner::Worklist.

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