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llvm-6502/lib/Transforms/InstCombine/InstCombine.h
Chandler Carruth 5761a8e4f3 [PM] Clean up a bunch of the doxygen / API docs on the InstCombiner pass 
prior to refactoring it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226594 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-20 19:27:58 +00:00

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//===- InstCombine.h - Main InstCombine pass definition ---------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIB_TRANSFORMS_INSTCOMBINE_INSTCOMBINE_H
#define LLVM_LIB_TRANSFORMS_INSTCOMBINE_INSTCOMBINE_H
#include "InstCombineWorklist.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/TargetFolder.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Utils/SimplifyLibCalls.h"
#define DEBUG_TYPE "instcombine"
namespace llvm {
class CallSite;
class DataLayout;
class DominatorTree;
class TargetLibraryInfo;
class DbgDeclareInst;
class MemIntrinsic;
class MemSetInst;
/// \brief Specific patterns of select instructions we can match.
enum SelectPatternFlavor {
SPF_UNKNOWN = 0,
SPF_SMIN,
SPF_UMIN,
SPF_SMAX,
SPF_UMAX,
SPF_ABS,
SPF_NABS
};
/// \brief Assign a complexity or rank value to LLVM Values.
///
/// This routine maps IR values to various complexity ranks:
/// 0 -> undef
/// 1 -> Constants
/// 2 -> Other non-instructions
/// 3 -> Arguments
/// 3 -> Unary operations
/// 4 -> Other instructions
static inline unsigned getComplexity(Value *V) {
if (isa<Instruction>(V)) {
if (BinaryOperator::isNeg(V) || BinaryOperator::isFNeg(V) ||
BinaryOperator::isNot(V))
return 3;
return 4;
}
if (isa<Argument>(V))
return 3;
return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
}
/// \brief Add one to a Constant
static inline Constant *AddOne(Constant *C) {
return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1));
}
/// \brief Subtract one from a Constant
static inline Constant *SubOne(Constant *C) {
return ConstantExpr::getSub(C, ConstantInt::get(C->getType(), 1));
}
/// \brief An IRBuilder inserter that adds new instructions to the instcombine
/// worklist.
class LLVM_LIBRARY_VISIBILITY InstCombineIRInserter
: public IRBuilderDefaultInserter<true> {
InstCombineWorklist &Worklist;
AssumptionCache *AC;
public:
InstCombineIRInserter(InstCombineWorklist &WL, AssumptionCache *AC)
: Worklist(WL), AC(AC) {}
void InsertHelper(Instruction *I, const Twine &Name, BasicBlock *BB,
BasicBlock::iterator InsertPt) const {
IRBuilderDefaultInserter<true>::InsertHelper(I, Name, BB, InsertPt);
Worklist.Add(I);
using namespace llvm::PatternMatch;
if (match(I, m_Intrinsic<Intrinsic::assume>()))
AC->registerAssumption(cast<CallInst>(I));
}
};
/// \brief The core instruction combiner logic.
///
/// This class provides both the logic to recursively visit instructions and
/// combine them, as well as the pass infrastructure for running this as part
/// of the LLVM pass pipeline.
class LLVM_LIBRARY_VISIBILITY InstCombiner
: public FunctionPass,
public InstVisitor<InstCombiner, Instruction *> {
AssumptionCache *AC;
const DataLayout *DL;
TargetLibraryInfo *TLI;
DominatorTree *DT;
LoopInfo *LI;
bool MadeIRChange;
LibCallSimplifier *Simplifier;
bool MinimizeSize;
public:
/// \brief A worklist of the instructions that need to be simplified.
InstCombineWorklist Worklist;
/// \brief An IRBuilder that automatically inserts new instructions into the
/// worklist.
typedef IRBuilder<true, TargetFolder, InstCombineIRInserter> BuilderTy;
BuilderTy *Builder;
static char ID; // Pass identification, replacement for typeid
InstCombiner()
: FunctionPass(ID), DL(nullptr), DT(nullptr), LI(nullptr),
Builder(nullptr) {
MinimizeSize = false;
initializeInstCombinerPass(*PassRegistry::getPassRegistry());
}
public:
bool runOnFunction(Function &F) override;
bool DoOneIteration(Function &F, unsigned ItNum);
void getAnalysisUsage(AnalysisUsage &AU) const override;
AssumptionCache *getAssumptionCache() const { return AC; }
const DataLayout *getDataLayout() const { return DL; }
DominatorTree *getDominatorTree() const { return DT; }
LoopInfo *getLoopInfo() const { return LI; }
TargetLibraryInfo *getTargetLibraryInfo() const { return TLI; }
// Visitation implementation - Implement instruction combining for different
// instruction types. The semantics are as follows:
// Return Value:
// null - No change was made
// I - Change was made, I is still valid, I may be dead though
// otherwise - Change was made, replace I with returned instruction
//
Instruction *visitAdd(BinaryOperator &I);
Instruction *visitFAdd(BinaryOperator &I);
Value *OptimizePointerDifference(Value *LHS, Value *RHS, Type *Ty);
Instruction *visitSub(BinaryOperator &I);
Instruction *visitFSub(BinaryOperator &I);
Instruction *visitMul(BinaryOperator &I);
Value *foldFMulConst(Instruction *FMulOrDiv, Constant *C,
Instruction *InsertBefore);
Instruction *visitFMul(BinaryOperator &I);
Instruction *visitURem(BinaryOperator &I);
Instruction *visitSRem(BinaryOperator &I);
Instruction *visitFRem(BinaryOperator &I);
bool SimplifyDivRemOfSelect(BinaryOperator &I);
Instruction *commonRemTransforms(BinaryOperator &I);
Instruction *commonIRemTransforms(BinaryOperator &I);
Instruction *commonDivTransforms(BinaryOperator &I);
Instruction *commonIDivTransforms(BinaryOperator &I);
Instruction *visitUDiv(BinaryOperator &I);
Instruction *visitSDiv(BinaryOperator &I);
Instruction *visitFDiv(BinaryOperator &I);
Value *simplifyRangeCheck(ICmpInst *Cmp0, ICmpInst *Cmp1, bool Inverted);
Value *FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS);
Value *FoldAndOfFCmps(FCmpInst *LHS, FCmpInst *RHS);
Instruction *visitAnd(BinaryOperator &I);
Value *FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS, Instruction *CxtI);
Value *FoldOrOfFCmps(FCmpInst *LHS, FCmpInst *RHS);
Instruction *FoldOrWithConstants(BinaryOperator &I, Value *Op, Value *A,
Value *B, Value *C);
Instruction *FoldXorWithConstants(BinaryOperator &I, Value *Op, Value *A,
Value *B, Value *C);
Instruction *visitOr(BinaryOperator &I);
Instruction *visitXor(BinaryOperator &I);
Instruction *visitShl(BinaryOperator &I);
Instruction *visitAShr(BinaryOperator &I);
Instruction *visitLShr(BinaryOperator &I);
Instruction *commonShiftTransforms(BinaryOperator &I);
Instruction *FoldFCmp_IntToFP_Cst(FCmpInst &I, Instruction *LHSI,
Constant *RHSC);
Instruction *FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
GlobalVariable *GV, CmpInst &ICI,
ConstantInt *AndCst = nullptr);
Instruction *visitFCmpInst(FCmpInst &I);
Instruction *visitICmpInst(ICmpInst &I);
Instruction *visitICmpInstWithCastAndCast(ICmpInst &ICI);
Instruction *visitICmpInstWithInstAndIntCst(ICmpInst &ICI, Instruction *LHS,
ConstantInt *RHS);
Instruction *FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
ConstantInt *DivRHS);
Instruction *FoldICmpShrCst(ICmpInst &ICI, BinaryOperator *DivI,
ConstantInt *DivRHS);
Instruction *FoldICmpCstShrCst(ICmpInst &I, Value *Op, Value *A,
ConstantInt *CI1, ConstantInt *CI2);
Instruction *FoldICmpCstShlCst(ICmpInst &I, Value *Op, Value *A,
ConstantInt *CI1, ConstantInt *CI2);
Instruction *FoldICmpAddOpCst(Instruction &ICI, Value *X, ConstantInt *CI,
ICmpInst::Predicate Pred);
Instruction *FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
ICmpInst::Predicate Cond, Instruction &I);
Instruction *FoldShiftByConstant(Value *Op0, Constant *Op1,
BinaryOperator &I);
Instruction *commonCastTransforms(CastInst &CI);
Instruction *commonPointerCastTransforms(CastInst &CI);
Instruction *visitTrunc(TruncInst &CI);
Instruction *visitZExt(ZExtInst &CI);
Instruction *visitSExt(SExtInst &CI);
Instruction *visitFPTrunc(FPTruncInst &CI);
Instruction *visitFPExt(CastInst &CI);
Instruction *visitFPToUI(FPToUIInst &FI);
Instruction *visitFPToSI(FPToSIInst &FI);
Instruction *visitUIToFP(CastInst &CI);
Instruction *visitSIToFP(CastInst &CI);
Instruction *visitPtrToInt(PtrToIntInst &CI);
Instruction *visitIntToPtr(IntToPtrInst &CI);
Instruction *visitBitCast(BitCastInst &CI);
Instruction *visitAddrSpaceCast(AddrSpaceCastInst &CI);
Instruction *FoldSelectOpOp(SelectInst &SI, Instruction *TI, Instruction *FI);
Instruction *FoldSelectIntoOp(SelectInst &SI, Value *, Value *);
Instruction *FoldSPFofSPF(Instruction *Inner, SelectPatternFlavor SPF1,
Value *A, Value *B, Instruction &Outer,
SelectPatternFlavor SPF2, Value *C);
Instruction *visitSelectInst(SelectInst &SI);
Instruction *visitSelectInstWithICmp(SelectInst &SI, ICmpInst *ICI);
Instruction *visitCallInst(CallInst &CI);
Instruction *visitInvokeInst(InvokeInst &II);
Instruction *SliceUpIllegalIntegerPHI(PHINode &PN);
Instruction *visitPHINode(PHINode &PN);
Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
Instruction *visitAllocaInst(AllocaInst &AI);
Instruction *visitAllocSite(Instruction &FI);
Instruction *visitFree(CallInst &FI);
Instruction *visitLoadInst(LoadInst &LI);
Instruction *visitStoreInst(StoreInst &SI);
Instruction *visitBranchInst(BranchInst &BI);
Instruction *visitSwitchInst(SwitchInst &SI);
Instruction *visitReturnInst(ReturnInst &RI);
Instruction *visitInsertValueInst(InsertValueInst &IV);
Instruction *visitInsertElementInst(InsertElementInst &IE);
Instruction *visitExtractElementInst(ExtractElementInst &EI);
Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI);
Instruction *visitExtractValueInst(ExtractValueInst &EV);
Instruction *visitLandingPadInst(LandingPadInst &LI);
// visitInstruction - Specify what to return for unhandled instructions...
Instruction *visitInstruction(Instruction &I) { return nullptr; }
// True when DB dominates all uses of DI execpt UI.
// UI must be in the same block as DI.
// The routine checks that the DI parent and DB are different.
bool dominatesAllUses(const Instruction *DI, const Instruction *UI,
const BasicBlock *DB) const;
// Replace select with select operand SIOpd in SI-ICmp sequence when possible
bool replacedSelectWithOperand(SelectInst *SI, const ICmpInst *Icmp,
const unsigned SIOpd);
private:
bool ShouldChangeType(Type *From, Type *To) const;
Value *dyn_castNegVal(Value *V) const;
Value *dyn_castFNegVal(Value *V, bool NoSignedZero = false) const;
Type *FindElementAtOffset(Type *PtrTy, int64_t Offset,
SmallVectorImpl<Value *> &NewIndices);
Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI);
/// \brief Classify whether a cast is worth optimizing.
///
/// Returns true if the cast from "V to Ty" actually results in any code
/// being generated and is interesting to optimize out. If the cast can be
/// eliminated by some other simple transformation, we prefer to do the
/// simplification first.
bool ShouldOptimizeCast(Instruction::CastOps opcode, const Value *V,
Type *Ty);
Instruction *visitCallSite(CallSite CS);
Instruction *tryOptimizeCall(CallInst *CI, const DataLayout *DL);
bool transformConstExprCastCall(CallSite CS);
Instruction *transformCallThroughTrampoline(CallSite CS,
IntrinsicInst *Tramp);
Instruction *transformZExtICmp(ICmpInst *ICI, Instruction &CI,
bool DoXform = true);
Instruction *transformSExtICmp(ICmpInst *ICI, Instruction &CI);
bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS, Instruction *CxtI);
bool WillNotOverflowSignedSub(Value *LHS, Value *RHS, Instruction *CxtI);
bool WillNotOverflowUnsignedSub(Value *LHS, Value *RHS, Instruction *CxtI);
bool WillNotOverflowSignedMul(Value *LHS, Value *RHS, Instruction *CxtI);
Value *EmitGEPOffset(User *GEP);
Instruction *scalarizePHI(ExtractElementInst &EI, PHINode *PN);
Value *EvaluateInDifferentElementOrder(Value *V, ArrayRef<int> Mask);
public:
/// \brief Inserts an instruction \p New before instruction \p Old
///
/// Also adds the new instruction to the worklist and returns \p New so that
/// it is suitable for use as the return from the visitation patterns.
Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) {
assert(New && !New->getParent() &&
"New instruction already inserted into a basic block!");
BasicBlock *BB = Old.getParent();
BB->getInstList().insert(&Old, New); // Insert inst
Worklist.Add(New);
return New;
}
/// \brief Same as InsertNewInstBefore, but also sets the debug loc.
Instruction *InsertNewInstWith(Instruction *New, Instruction &Old) {
New->setDebugLoc(Old.getDebugLoc());
return InsertNewInstBefore(New, Old);
}
/// \brief A combiner-aware RAUW-like routine.
///
/// This method is to be used when an instruction is found to be dead,
/// replacable with another preexisting expression. Here we add all uses of
/// I to the worklist, replace all uses of I with the new value, then return
/// I, so that the inst combiner will know that I was modified.
Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
Worklist.AddUsersToWorkList(I); // Add all modified instrs to worklist.
// If we are replacing the instruction with itself, this must be in a
// segment of unreachable code, so just clobber the instruction.
if (&I == V)
V = UndefValue::get(I.getType());
DEBUG(dbgs() << "IC: Replacing " << I << "\n"
" with " << *V << '\n');
I.replaceAllUsesWith(V);
return &I;
}
/// Creates a result tuple for an overflow intrinsic \p II with a given
/// \p Result and a constant \p Overflow value. If \p ReUseName is true the
/// \p Result's name is taken from \p II.
Instruction *CreateOverflowTuple(IntrinsicInst *II, Value *Result,
bool Overflow, bool ReUseName = true) {
if (ReUseName)
Result->takeName(II);
Constant *V[] = { UndefValue::get(Result->getType()),
Overflow ? Builder->getTrue() : Builder->getFalse() };
StructType *ST = cast<StructType>(II->getType());
Constant *Struct = ConstantStruct::get(ST, V);
return InsertValueInst::Create(Struct, Result, 0);
}
/// \brief Combiner aware instruction erasure.
///
/// When dealing with an instruction that has side effects or produces a void
/// value, we can't rely on DCE to delete the instruction. Instead, visit
/// methods should return the value returned by this function.
Instruction *EraseInstFromFunction(Instruction &I) {
DEBUG(dbgs() << "IC: ERASE " << I << '\n');
assert(I.use_empty() && "Cannot erase instruction that is used!");
// Make sure that we reprocess all operands now that we reduced their
// use counts.
if (I.getNumOperands() < 8) {
for (User::op_iterator i = I.op_begin(), e = I.op_end(); i != e; ++i)
if (Instruction *Op = dyn_cast<Instruction>(*i))
Worklist.Add(Op);
}
Worklist.Remove(&I);
I.eraseFromParent();
MadeIRChange = true;
return nullptr; // Don't do anything with FI
}
void computeKnownBits(Value *V, APInt &KnownZero, APInt &KnownOne,
unsigned Depth = 0, Instruction *CxtI = nullptr) const {
return llvm::computeKnownBits(V, KnownZero, KnownOne, DL, Depth, AC, CxtI,
DT);
}
bool MaskedValueIsZero(Value *V, const APInt &Mask,
unsigned Depth = 0,
Instruction *CxtI = nullptr) const {
return llvm::MaskedValueIsZero(V, Mask, DL, Depth, AC, CxtI, DT);
}
unsigned ComputeNumSignBits(Value *Op, unsigned Depth = 0,
Instruction *CxtI = nullptr) const {
return llvm::ComputeNumSignBits(Op, DL, Depth, AC, CxtI, DT);
}
void ComputeSignBit(Value *V, bool &KnownZero, bool &KnownOne,
unsigned Depth = 0, Instruction *CxtI = nullptr) const {
return llvm::ComputeSignBit(V, KnownZero, KnownOne, DL, Depth, AC, CxtI,
DT);
}
OverflowResult computeOverflowForUnsignedMul(Value *LHS, Value *RHS,
const Instruction *CxtI) {
return llvm::computeOverflowForUnsignedMul(LHS, RHS, DL, AC, CxtI, DT);
}
OverflowResult computeOverflowForUnsignedAdd(Value *LHS, Value *RHS,
const Instruction *CxtI) {
return llvm::computeOverflowForUnsignedAdd(LHS, RHS, DL, AC, CxtI, DT);
}
private:
/// \brief Performs a few simplifications for operators which are associative
/// or commutative.
bool SimplifyAssociativeOrCommutative(BinaryOperator &I);
/// \brief Tries to simplify binary operations which some other binary operation distributes over.
///
/// It does this by either by factorizing out common terms (eg "(A*B)+(A*C)"
/// -> "A*(B+C)") or expanding out if this results in simplifications (eg: "A
/// & (B | C) -> (A&B) | (A&C)" if this is a win). Returns the simplified
/// value, or null if it didn't simplify.
Value *SimplifyUsingDistributiveLaws(BinaryOperator &I);
/// \brief Attempts to replace V with a simpler value based on the demanded
/// bits.
Value *SimplifyDemandedUseBits(Value *V, APInt DemandedMask, APInt &KnownZero,
APInt &KnownOne, unsigned Depth,
Instruction *CxtI = nullptr);
bool SimplifyDemandedBits(Use &U, APInt DemandedMask, APInt &KnownZero,
APInt &KnownOne, unsigned Depth = 0);
/// Helper routine of SimplifyDemandedUseBits. It tries to simplify demanded
/// bit for "r1 = shr x, c1; r2 = shl r1, c2" instruction sequence.
Value *SimplifyShrShlDemandedBits(Instruction *Lsr, Instruction *Sftl,
APInt DemandedMask, APInt &KnownZero,
APInt &KnownOne);
/// \brief Tries to simplify operands to an integer instruction based on its
/// demanded bits.
bool SimplifyDemandedInstructionBits(Instruction &Inst);
Value *SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
APInt &UndefElts, unsigned Depth = 0);
Value *SimplifyVectorOp(BinaryOperator &Inst);
Value *SimplifyBSwap(BinaryOperator &Inst);
// FoldOpIntoPhi - Given a binary operator, cast instruction, or select
// which has a PHI node as operand #0, see if we can fold the instruction
// into the PHI (which is only possible if all operands to the PHI are
// constants).
//
Instruction *FoldOpIntoPhi(Instruction &I);
/// \brief Try to rotate an operation below a PHI node, using PHI nodes for
/// its operands.
Instruction *FoldPHIArgOpIntoPHI(PHINode &PN);
Instruction *FoldPHIArgBinOpIntoPHI(PHINode &PN);
Instruction *FoldPHIArgGEPIntoPHI(PHINode &PN);
Instruction *FoldPHIArgLoadIntoPHI(PHINode &PN);
Instruction *OptAndOp(Instruction *Op, ConstantInt *OpRHS,
ConstantInt *AndRHS, BinaryOperator &TheAnd);
Value *FoldLogicalPlusAnd(Value *LHS, Value *RHS, ConstantInt *Mask,
bool isSub, Instruction &I);
Value *InsertRangeTest(Value *V, Constant *Lo, Constant *Hi, bool isSigned,
bool Inside);
Instruction *PromoteCastOfAllocation(BitCastInst &CI, AllocaInst &AI);
Instruction *MatchBSwap(BinaryOperator &I);
bool SimplifyStoreAtEndOfBlock(StoreInst &SI);
Instruction *SimplifyMemTransfer(MemIntrinsic *MI);
Instruction *SimplifyMemSet(MemSetInst *MI);
Value *EvaluateInDifferentType(Value *V, Type *Ty, bool isSigned);
/// \brief Returns a value X such that Val = X * Scale, or null if none.
///
/// If the multiplication is known not to overflow then NoSignedWrap is set.
Value *Descale(Value *Val, APInt Scale, bool &NoSignedWrap);
};
} // end namespace llvm.
#undef DEBUG_TYPE
#endif
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