InstCombineSelect.cpp File Reference

#include "InstCombineInternal.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/CmpInstAnalysis.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/OverflowInstAnalysis.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.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/Operator.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Transforms/InstCombine/InstCombiner.h"
#include <cassert>
#include <utility>
#include "llvm/Transforms/Utils/InstructionWorklist.h"

Go to the source code of this file.

Macros
#define	DEBUG_TYPE   "instcombine"

Functions
static Instruction *	foldSelectBinOpIdentity (SelectInst &Sel, const TargetLibraryInfo &TLI, InstCombinerImpl &IC)
	Replace a select operand based on an equality comparison with the identity constant of a binop.
static Value *	foldSelectICmpAnd (SelectInst &Sel, ICmpInst *Cmp, InstCombiner::BuilderTy &Builder)
	This folds: select (icmp eq (and X, C1)), TC, FC iff C1 is a power 2 and the difference between TC and FC is a power-of-2.
static unsigned	getSelectFoldableOperands (BinaryOperator *I)
	We want to turn code that looks like this: C = or A, B D = select cond, C, A into: C = select cond, B, 0 D = or A, C.
static bool	isSelect01 (const APInt &C1I, const APInt &C2I)
static Instruction *	foldSelectICmpAndAnd (Type *SelType, const ICmpInst *Cmp, Value *TVal, Value *FVal, InstCombiner::BuilderTy &Builder)
	We want to turn: (select (icmp eq (and X, Y), 0), (and (lshr X, Z), 1), 1) into: zext (icmp ne i32 (and X, (or Y, (shl 1, Z))), 0) Note: Z may be 0 if lshr is missing.
static Value *	foldSelectICmpAndZeroShl (const ICmpInst *Cmp, Value *TVal, Value *FVal, InstCombiner::BuilderTy &Builder)
	We want to turn: (select (icmp eq (and X, C1), 0), 0, (shl [nsw/nuw] X, C2)); iff C1 is a mask and the number of its leading zeros is equal to C2 into: shl X, C2.
static Value *	foldSelectICmpLshrAshr (const ICmpInst *IC, Value *TrueVal, Value *FalseVal, InstCombiner::BuilderTy &Builder)
	We want to turn: (select (icmp sgt x, C), lshr (X, Y), ashr (X, Y)); iff C s>= -1 (select (icmp slt x, C), ashr (X, Y), lshr (X, Y)); iff C s>= 0 into: ashr (X, Y)
static Value *	foldSelectICmpAndBinOp (const ICmpInst *IC, Value *TrueVal, Value *FalseVal, InstCombiner::BuilderTy &Builder)
	We want to turn: (select (icmp eq (and X, C1), 0), Y, (BinOp Y, C2)) into: IF C2 u>= C1 (BinOp Y, (shl (and X, C1), C3)) ELSE (BinOp Y, (lshr (and X, C1), C3)) iff: 0 on the RHS is the identity value (i.e add, xor, shl, etc...) C1 and C2 are both powers of 2 where: IF C2 u>= C1 C3 = Log(C2) - Log(C1) ELSE C3 = Log(C1) - Log(C2)
static Instruction *	foldSetClearBits (SelectInst &Sel, InstCombiner::BuilderTy &Builder)
	Canonicalize a set or clear of a masked set of constant bits to select-of-constants form.
static Instruction *	foldSelectZeroOrMul (SelectInst &SI, InstCombinerImpl &IC)
static Value *	canonicalizeSaturatedSubtract (const ICmpInst *ICI, const Value *TrueVal, const Value *FalseVal, InstCombiner::BuilderTy &Builder)
	Transform patterns such as (a > b) ? a - b : 0 into usub.sat(a, b).
static Value *	canonicalizeSaturatedAdd (ICmpInst *Cmp, Value *TVal, Value *FVal, InstCombiner::BuilderTy &Builder)
static Value *	foldAbsDiff (ICmpInst *Cmp, Value *TVal, Value *FVal, InstCombiner::BuilderTy &Builder)
	Try to match patterns with select and subtract as absolute difference.

Macro Definition Documentation

DEBUG_TYPE

#define DEBUG_TYPE   "instcombine"

Definition at line 46 of file InstCombineSelect.cpp.

Function Documentation

canonicalizeSaturatedAdd()

static Value * canonicalizeSaturatedAdd ( ICmpInst *  Cmp, Value *  TVal, Value *  FVal, InstCombiner::BuilderTy &  Builder  )

static

Definition at line 954 of file InstCombineSelect.cpp.

References Builder, llvm::CallingConv::C, llvm::ConstantInt::get(), llvm::CmpInst::getInversePredicate(), llvm::User::getOperand(), llvm::CmpInst::getSwappedPredicate(), llvm::CmpInst::ICMP_UGE, llvm::CmpInst::ICMP_UGT, llvm::CmpInst::ICMP_ULE, llvm::CmpInst::ICMP_ULT, llvm::PatternMatch::m_Add(), llvm::PatternMatch::m_AllOnes(), llvm::PatternMatch::m_APInt(), llvm::PatternMatch::m_c_Add(), llvm::PatternMatch::m_Not(), llvm::PatternMatch::m_Specific(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::match(), std::swap(), X, and Y.

canonicalizeSaturatedSubtract()

static Value * canonicalizeSaturatedSubtract ( const ICmpInst *  ICI, const Value *  TrueVal, const Value *  FalseVal, InstCombiner::BuilderTy &  Builder  )

static

Transform patterns such as (a > b) ? a - b : 0 into usub.sat(a, b).

There are 8 commuted/swapped variants of this pattern. TODO: Also support a - UMIN(a,b) patterns.

Definition at line 887 of file InstCombineSelect.cpp.

References A, assert(), B, Builder, llvm::CallingConv::C, llvm::ConstantInt::get(), llvm::CmpInst::getInversePredicate(), llvm::User::getOperand(), llvm::CmpInst::getPredicate(), llvm::CmpInst::getSwappedPredicate(), llvm::Value::hasOneUse(), llvm::CmpInst::ICMP_NE, llvm::CmpInst::ICMP_UGE, llvm::CmpInst::ICMP_UGT, llvm::CmpInst::ICMP_ULE, llvm::CmpInst::ICMP_ULT, llvm::CmpInst::isUnsigned(), llvm::PatternMatch::m_Add(), llvm::PatternMatch::m_AllOnes(), llvm::PatternMatch::m_APInt(), llvm::PatternMatch::m_Specific(), llvm::PatternMatch::m_SpecificInt(), llvm::PatternMatch::m_Sub(), llvm::PatternMatch::m_Zero(), llvm::PatternMatch::match(), and std::swap().

foldAbsDiff()

static Value * foldAbsDiff ( ICmpInst *  Cmp, Value *  TVal, Value *  FVal, InstCombiner::BuilderTy &  Builder  )

static

Try to match patterns with select and subtract as absolute difference.

Definition at line 1025 of file InstCombineSelect.cpp.

References A, B, Builder, llvm::CmpInst::getSwappedPredicate(), llvm::CmpInst::ICMP_SGT, llvm::PatternMatch::m_Specific(), llvm::PatternMatch::m_Sub(), llvm::PatternMatch::match(), and std::swap().

foldSelectBinOpIdentity()

static Instruction * foldSelectBinOpIdentity ( SelectInst &  Sel, const TargetLibraryInfo &  TLI, InstCombinerImpl &  IC  )

static

Replace a select operand based on an equality comparison with the identity constant of a binop.

Definition at line 55 of file InstCombineSelect.cpp.

References llvm::CallingConv::C, llvm::cannotBeNegativeZero(), llvm::ConstantExpr::getBinOpIdentity(), llvm::SelectInst::getCondition(), llvm::InstCombiner::getDataLayout(), llvm::BinaryOperator::getOpcode(), llvm::User::getOperand(), llvm::Value::getType(), llvm::Instruction::hasNoSignedZeros(), llvm::Instruction::isCommutative(), llvm::ICmpInst::isEquality(), llvm::CmpInst::isFPPredicate(), llvm::PatternMatch::m_AnyZeroFP(), llvm::PatternMatch::m_BinOp(), llvm::PatternMatch::m_c_BinOp(), llvm::PatternMatch::m_Cmp(), llvm::PatternMatch::m_Constant(), llvm::PatternMatch::m_Specific(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::match(), llvm::InstCombiner::replaceOperand(), X, and Y.

foldSelectICmpAnd()

static Value * foldSelectICmpAnd ( SelectInst &  Sel, ICmpInst *  Cmp, InstCombiner::BuilderTy &  Builder  )

static

This folds: select (icmp eq (and X, C1)), TC, FC iff C1 is a power 2 and the difference between TC and FC is a power-of-2.

To something like: (shr (and (X, C1)), (log2(C1) - log2(TC-FC))) + FC Or: (shl (and (X, C1)), (log2(TC-FC) - log2(C1))) + FC With some variations depending if FC is larger than TC, or the shift isn't needed, or the bit widths don't match.

Definition at line 121 of file InstCombineSelect.cpp.

References assert(), Builder, llvm::CallingConv::C, llvm::decomposeBitTestICmp(), llvm::ConstantInt::get(), llvm::APInt::getBitWidth(), llvm::SelectInst::getFalseValue(), llvm::SelectInst::getTrueValue(), llvm::Value::getType(), llvm::ICmpInst::isEquality(), llvm::APInt::isPowerOf2(), llvm::Type::isVectorTy(), llvm::APInt::isZero(), llvm_unreachable, llvm::APInt::logBase2(), llvm::PatternMatch::m_And(), llvm::PatternMatch::m_APInt(), llvm::PatternMatch::m_Power2(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::m_Zero(), llvm::PatternMatch::match(), and llvm::APInt::ugt().

foldSelectICmpAndAnd()

static Instruction * foldSelectICmpAndAnd ( Type *  SelType, const ICmpInst *  Cmp, Value *  TVal, Value *  FVal, InstCombiner::BuilderTy &  Builder  )

static

We want to turn: (select (icmp eq (and X, Y), 0), (and (lshr X, Z), 1), 1) into: zext (icmp ne i32 (and X, (or Y, (shl 1, Z))), 0) Note: Z may be 0 if lshr is missing.

Worst-case scenario is that we will replace 5 instructions with 5 different instructions, but we got rid of select.

Definition at line 570 of file InstCombineSelect.cpp.

References B, Builder, llvm::ConstantInt::get(), llvm::Type::getScalarSizeInBits(), llvm::CmpInst::ICMP_EQ, llvm::CmpInst::ICMP_ULT, llvm::PatternMatch::m_And(), llvm::PatternMatch::m_c_And(), llvm::PatternMatch::m_LShr(), llvm::PatternMatch::m_One(), llvm::PatternMatch::m_OneUse(), llvm::PatternMatch::m_Specific(), llvm::PatternMatch::m_SpecificInt_ICMP(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::m_Zero(), llvm::PatternMatch::match(), X, and Y.

foldSelectICmpAndBinOp()

static Value * foldSelectICmpAndBinOp ( const ICmpInst *  IC, Value *  TrueVal, Value *  FalseVal, InstCombiner::BuilderTy &  Builder  )

static

We want to turn: (select (icmp eq (and X, C1), 0), Y, (BinOp Y, C2)) into: IF C2 u>= C1 (BinOp Y, (shl (and X, C1), C3)) ELSE (BinOp Y, (lshr (and X, C1), C3)) iff: 0 on the RHS is the identity value (i.e add, xor, shl, etc...) C1 and C2 are both powers of 2 where: IF C2 u>= C1 C3 = Log(C2) - Log(C1) ELSE C3 = Log(C1) - Log(C2)

This transform handles cases where:

1. The icmp predicate is inverted
2. The select operands are reversed
3. The magnitude of C2 and C1 are flipped

Definition at line 711 of file InstCombineSelect.cpp.

References Builder, llvm::decomposeBitTestICmp(), llvm::ConstantInt::get(), llvm::ConstantExpr::getBinOpIdentity(), llvm::APInt::getOneBitSet(), llvm::BinaryOperator::getOpcode(), llvm::User::getOperand(), llvm::CmpInst::getPredicate(), llvm::Value::getType(), llvm::Value::hasOneUse(), llvm::CmpInst::ICMP_EQ, llvm::CmpInst::ICMP_NE, llvm::ICmpInst::isEquality(), llvm::APInt::isPowerOf2(), llvm::Type::isVectorTy(), llvm::APInt::logBase2(), llvm::PatternMatch::m_And(), llvm::PatternMatch::m_BinOp(), llvm::PatternMatch::m_Power2(), llvm::PatternMatch::m_Specific(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::m_Zero(), llvm::PatternMatch::match(), NeedAnd, and Y.

foldSelectICmpAndZeroShl()

static Value * foldSelectICmpAndZeroShl ( const ICmpInst *  Cmp, Value *  TVal, Value *  FVal, InstCombiner::BuilderTy &  Builder  )

static

We want to turn: (select (icmp eq (and X, C1), 0), 0, (shl [nsw/nuw] X, C2)); iff C1 is a mask and the number of its leading zeros is equal to C2 into: shl X, C2.

Definition at line 618 of file InstCombineSelect.cpp.

References llvm::APInt::countLeadingZeros(), llvm::APInt::getZExtValue(), llvm::CmpInst::ICMP_EQ, llvm::CmpInst::ICMP_NE, llvm::APInt::isMask(), llvm::PatternMatch::m_And(), llvm::PatternMatch::m_APInt(), llvm::PatternMatch::m_ICmp(), llvm::PatternMatch::m_Shl(), llvm::PatternMatch::m_Specific(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::m_Zero(), llvm::PatternMatch::match(), std::swap(), and X.

foldSelectICmpLshrAshr()

static Value * foldSelectICmpLshrAshr ( const ICmpInst *  IC, Value *  TrueVal, Value *  FalseVal, InstCombiner::BuilderTy &  Builder  )

static

We want to turn: (select (icmp sgt x, C), lshr (X, Y), ashr (X, Y)); iff C s>= -1 (select (icmp slt x, C), ashr (X, Y), lshr (X, Y)); iff C s>= 0 into: ashr (X, Y)

Definition at line 656 of file InstCombineSelect.cpp.

References Builder, llvm::Value::getName(), llvm::User::getOperand(), llvm::CmpInst::getPredicate(), llvm::Type::getScalarSizeInBits(), llvm::Value::getType(), llvm::CmpInst::ICMP_SGE, llvm::CmpInst::ICMP_SGT, llvm::CmpInst::ICMP_SLT, llvm::Type::isIntOrIntVectorTy(), llvm::PatternMatch::m_AShr(), llvm::PatternMatch::m_LShr(), llvm::PatternMatch::m_Specific(), llvm::PatternMatch::m_SpecificInt_ICMP(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::match(), std::swap(), X, and Y.

foldSelectZeroOrMul()

static Instruction * foldSelectZeroOrMul ( SelectInst &  SI, InstCombinerImpl &  IC  )

static

Definition at line 842 of file InstCombineSelect.cpp.

References llvm::ilist_node_impl< OptionsT >::getIterator(), llvm::CmpInst::ICMP_NE, llvm::InstCombiner::InsertNewInstBefore(), llvm::ICmpInst::isEquality(), llvm::PatternMatch::m_c_Mul(), llvm::PatternMatch::m_ICmp(), llvm::PatternMatch::m_Specific(), llvm::PatternMatch::m_Undef(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::m_Zero(), llvm::PatternMatch::match(), llvm::Constant::mergeUndefsWith(), llvm::InstCombiner::replaceInstUsesWith(), llvm::InstCombiner::replaceOperand(), std::swap(), X, and Y.

foldSetClearBits()

static Instruction * foldSetClearBits ( SelectInst &  Sel, InstCombiner::BuilderTy &  Builder  )

static

Canonicalize a set or clear of a masked set of constant bits to select-of-constants form.

Definition at line 802 of file InstCombineSelect.cpp.

References Builder, llvm::CallingConv::C, Cond, F, llvm::ConstantInt::get(), llvm::SelectInst::getCondition(), llvm::SelectInst::getFalseValue(), llvm::Constant::getNullValue(), llvm::SelectInst::getTrueValue(), llvm::Value::getType(), llvm::PatternMatch::m_And(), llvm::PatternMatch::m_APInt(), llvm::PatternMatch::m_OneUse(), llvm::PatternMatch::m_Or(), llvm::PatternMatch::m_Specific(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::match(), and X.

getSelectFoldableOperands()

static unsigned getSelectFoldableOperands ( BinaryOperator *  I )

static

We want to turn code that looks like this: C = or A, B D = select cond, C, A into: C = select cond, B, 0 D = or A, C.

Assuming that the specified instruction is an operand to the select, return a bitmask indicating which operands of this instruction are foldable if they equal the other incoming value of the select.

Definition at line 241 of file InstCombineSelect.cpp.

References I.

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

isSelect01()

static bool isSelect01 ( const APInt &  C1I, const APInt &  C2I  )

static

Definition at line 496 of file InstCombineSelect.cpp.

References llvm::APInt::isAllOnes(), llvm::APInt::isOne(), and llvm::APInt::isZero().

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