Diff 303136

llvm/include/llvm/Transforms/Utils/SimplifyIndVar.h

Show All 9 Lines
// not define any actual pass or policy, but provides a single function to		// not define any actual pass or policy, but provides a single function to
// simplify a loop's induction variables based on ScalarEvolution.		// simplify a loop's induction variables based on ScalarEvolution.
//		//
//===----------------------------------------------------------------------===//		//===----------------------------------------------------------------------===//

#ifndef LLVM_TRANSFORMS_UTILS_SIMPLIFYINDVAR_H		#ifndef LLVM_TRANSFORMS_UTILS_SIMPLIFYINDVAR_H
#define LLVM_TRANSFORMS_UTILS_SIMPLIFYINDVAR_H		#define LLVM_TRANSFORMS_UTILS_SIMPLIFYINDVAR_H

		#include "llvm/Analysis/ScalarEvolutionExpressions.h"
		#include "llvm/IR/ConstantRange.h"
		fhahnUnsubmitted Not Done Reply Inline Actions those includes are not needed? fhahn: those includes are not needed?
#include "llvm/IR/ValueHandle.h"		#include "llvm/IR/ValueHandle.h"

namespace llvm {		namespace llvm {

class CastInst;		class CastInst;
class DominatorTree;		class DominatorTree;
class Loop;		class Loop;
class LoopInfo;		class LoopInfo;
Show All 26 Lines	bool simplifyUsersOfIV(PHINode CurrIV, ScalarEvolution SE, DominatorTree *DT,
SCEVExpander &Rewriter, IVVisitor *V = nullptr);		SCEVExpander &Rewriter, IVVisitor *V = nullptr);

/// SimplifyLoopIVs - Simplify users of induction variables within this		/// SimplifyLoopIVs - Simplify users of induction variables within this
/// loop. This does not actually change or add IVs.		/// loop. This does not actually change or add IVs.
bool simplifyLoopIVs(Loop L, ScalarEvolution SE, DominatorTree *DT,		bool simplifyLoopIVs(Loop L, ScalarEvolution SE, DominatorTree *DT,
LoopInfo LI, const TargetTransformInfo TTI,		LoopInfo LI, const TargetTransformInfo TTI,
SmallVectorImpl<WeakTrackingVH> &Dead);		SmallVectorImpl<WeakTrackingVH> &Dead);

		/// Collect information about induction variables that are used by sign/zero
		fhahnUnsubmitted Not Done Reply Inline Actions It seems like this comment needs updating. It seems to mentioned some implementation details. Probably better to just state that it contains information about a widened IV or something along those lines. fhahn: It seems like this comment needs updating. It seems to mentioned some implementation details.
		/// extend operations. This information is recorded by CollectExtend and provides
		/// the input to WidenIV.
		struct WideIVInfo {
		PHINode *NarrowIV = nullptr;

		// Widest integer type created [sz]ext
		Type *WidestNativeType = nullptr;

		// Was a sext user seen before a zext?
		bool IsSigned = false;
		};

		/// Widen Induction Variables - Extend the width of an IV to cover its
		/// widest uses.
		PHINode *createWideIV(WideIVInfo &WI,
		LoopInfo LI, ScalarEvolution SE, SCEVExpander &Rewriter,
		DominatorTree *DT, SmallVectorImpl<WeakTrackingVH> &DeadInsts,
		unsigned &NumElimExt, unsigned &NumWidened,
		bool HasGuards, bool UsePostIncrementRanges);

} // end namespace llvm		} // end namespace llvm

#endif // LLVM_TRANSFORMS_UTILS_SIMPLIFYINDVAR_H		#endif // LLVM_TRANSFORMS_UTILS_SIMPLIFYINDVAR_H

llvm/lib/Transforms/Scalar/IndVarSimplify.cpp

Show First 20 Lines • Show All 176 Lines • ▼ Show 20 Lines	if (MSSA)
MSSAU = std::make_unique<MemorySSAUpdater>(MSSA);		MSSAU = std::make_unique<MemorySSAUpdater>(MSSA);
}		}

bool run(Loop *L);		bool run(Loop *L);
};		};

} // end anonymous namespace		} // end anonymous namespace

/// Determine the insertion point for this user. By default, insert immediately
/// before the user. SCEVExpander or LICM will hoist loop invariants out of the
/// loop. For PHI nodes, there may be multiple uses, so compute the nearest
/// common dominator for the incoming blocks. A nullptr can be returned if no
/// viable location is found: it may happen if User is a PHI and Def only comes
/// to this PHI from unreachable blocks.
static Instruction getInsertPointForUses(Instruction User, Value *Def,
DominatorTree DT, LoopInfo LI) {
PHINode *PHI = dyn_cast<PHINode>(User);
if (!PHI)
return User;

Instruction *InsertPt = nullptr;
for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i) {
if (PHI->getIncomingValue(i) != Def)
continue;

BasicBlock *InsertBB = PHI->getIncomingBlock(i);

if (!DT->isReachableFromEntry(InsertBB))
continue;

if (!InsertPt) {
InsertPt = InsertBB->getTerminator();
continue;
}
InsertBB = DT->findNearestCommonDominator(InsertPt->getParent(), InsertBB);
InsertPt = InsertBB->getTerminator();
}

// If we have skipped all inputs, it means that Def only comes to Phi from
// unreachable blocks.
if (!InsertPt)
return nullptr;

auto *DefI = dyn_cast<Instruction>(Def);
if (!DefI)
return InsertPt;

assert(DT->dominates(DefI, InsertPt) && "def does not dominate all uses");

auto *L = LI->getLoopFor(DefI->getParent());
assert(!L \|\| L->contains(LI->getLoopFor(InsertPt->getParent())));

for (auto DTN = (DT)[InsertPt->getParent()]; DTN; DTN = DTN->getIDom())
if (LI->getLoopFor(DTN->getBlock()) == L)
return DTN->getBlock()->getTerminator();

llvm_unreachable("DefI dominates InsertPt!");
}

//===----------------------------------------------------------------------===//		//===----------------------------------------------------------------------===//
// rewriteNonIntegerIVs and helpers. Prefer integer IVs.		// rewriteNonIntegerIVs and helpers. Prefer integer IVs.
//===----------------------------------------------------------------------===//		//===----------------------------------------------------------------------===//

/// Convert APF to an integer, if possible.		/// Convert APF to an integer, if possible.
static bool ConvertToSInt(const APFloat &APF, int64_t &IntVal) {		static bool ConvertToSInt(const APFloat &APF, int64_t &IntVal) {
bool isExact = false;		bool isExact = false;
// See if we can convert this to an int64_t		// See if we can convert this to an int64_t
▲ Show 20 Lines • Show All 305 Lines • ▼ Show 20 Lines	bool IndVarSimplify::rewriteFirstIterationLoopExitValues(Loop *L) {
}		}
return MadeAnyChanges;		return MadeAnyChanges;
}		}

//===----------------------------------------------------------------------===//		//===----------------------------------------------------------------------===//
// IV Widening - Extend the width of an IV to cover its widest uses.		// IV Widening - Extend the width of an IV to cover its widest uses.
//===----------------------------------------------------------------------===//		//===----------------------------------------------------------------------===//

namespace {

// Collect information about induction variables that are used by sign/zero
// extend operations. This information is recorded by CollectExtend and provides
// the input to WidenIV.
struct WideIVInfo {
PHINode *NarrowIV = nullptr;

// Widest integer type created [sz]ext
Type *WidestNativeType = nullptr;

// Was a sext user seen before a zext?
bool IsSigned = false;
};

} // end anonymous namespace

/// Update information about the induction variable that is extended by this		/// Update information about the induction variable that is extended by this
/// sign or zero extend operation. This is used to determine the final width of		/// sign or zero extend operation. This is used to determine the final width of
/// the IV before actually widening it.		/// the IV before actually widening it.
static void visitIVCast(CastInst Cast, WideIVInfo &WI, ScalarEvolution SE,		static void visitIVCast(CastInst *Cast, WideIVInfo &WI,
		ScalarEvolution *SE,
const TargetTransformInfo *TTI) {		const TargetTransformInfo *TTI) {
bool IsSigned = Cast->getOpcode() == Instruction::SExt;		bool IsSigned = Cast->getOpcode() == Instruction::SExt;
if (!IsSigned && Cast->getOpcode() != Instruction::ZExt)		if (!IsSigned && Cast->getOpcode() != Instruction::ZExt)
return;		return;

Type *Ty = Cast->getType();		Type *Ty = Cast->getType();
uint64_t Width = SE->getTypeSizeInBits(Ty);		uint64_t Width = SE->getTypeSizeInBits(Ty);
if (!Cast->getModule()->getDataLayout().isLegalInteger(Width))		if (!Cast->getModule()->getDataLayout().isLegalInteger(Width))
Show All 29 Lines	static void visitIVCast(CastInst *Cast, WideIVInfo &WI,
// We extend the IV to satisfy the sign of its first user, arbitrarily.		// We extend the IV to satisfy the sign of its first user, arbitrarily.
if (WI.IsSigned != IsSigned)		if (WI.IsSigned != IsSigned)
return;		return;

if (Width > SE->getTypeSizeInBits(WI.WidestNativeType))		if (Width > SE->getTypeSizeInBits(WI.WidestNativeType))
WI.WidestNativeType = SE->getEffectiveSCEVType(Ty);		WI.WidestNativeType = SE->getEffectiveSCEVType(Ty);
}		}

namespace {

/// Record a link in the Narrow IV def-use chain along with the WideIV that
/// computes the same value as the Narrow IV def. This avoids caching Use*
/// pointers.
struct NarrowIVDefUse {
Instruction *NarrowDef = nullptr;
Instruction *NarrowUse = nullptr;
Instruction *WideDef = nullptr;

// True if the narrow def is never negative. Tracking this information lets
// us use a sign extension instead of a zero extension or vice versa, when
// profitable and legal.
bool NeverNegative = false;

NarrowIVDefUse(Instruction ND, Instruction NU, Instruction *WD,
bool NeverNegative)
: NarrowDef(ND), NarrowUse(NU), WideDef(WD),
NeverNegative(NeverNegative) {}
};

/// The goal of this transform is to remove sign and zero extends without
/// creating any new induction variables. To do this, it creates a new phi of
/// the wider type and redirects all users, either removing extends or inserting
/// truncs whenever we stop propagating the type.
class WidenIV {
// Parameters
PHINode *OrigPhi;
Type *WideType;

// Context
LoopInfo *LI;
Loop *L;
ScalarEvolution *SE;
DominatorTree *DT;

// Does the module have any calls to the llvm.experimental.guard intrinsic
// at all? If not we can avoid scanning instructions looking for guards.
bool HasGuards;

// Result
PHINode *WidePhi = nullptr;
Instruction *WideInc = nullptr;
const SCEV *WideIncExpr = nullptr;
SmallVectorImpl<WeakTrackingVH> &DeadInsts;

SmallPtrSet<Instruction *,16> Widened;
SmallVector<NarrowIVDefUse, 8> NarrowIVUsers;

enum ExtendKind { ZeroExtended, SignExtended, Unknown };

// A map tracking the kind of extension used to widen each narrow IV
// and narrow IV user.
// Key: pointer to a narrow IV or IV user.
// Value: the kind of extension used to widen this Instruction.
DenseMap<AssertingVH<Instruction>, ExtendKind> ExtendKindMap;

using DefUserPair = std::pair<AssertingVH<Value>, AssertingVH<Instruction>>;

// A map with control-dependent ranges for post increment IV uses. The key is
// a pair of IV def and a use of this def denoting the context. The value is
// a ConstantRange representing possible values of the def at the given
// context.
DenseMap<DefUserPair, ConstantRange> PostIncRangeInfos;

Optional<ConstantRange> getPostIncRangeInfo(Value *Def,
Instruction *UseI) {
DefUserPair Key(Def, UseI);
auto It = PostIncRangeInfos.find(Key);
return It == PostIncRangeInfos.end()
? Optional<ConstantRange>(None)
: Optional<ConstantRange>(It->second);
}

void calculatePostIncRanges(PHINode *OrigPhi);
void calculatePostIncRange(Instruction NarrowDef, Instruction NarrowUser);

void updatePostIncRangeInfo(Value Def, Instruction UseI, ConstantRange R) {
DefUserPair Key(Def, UseI);
auto It = PostIncRangeInfos.find(Key);
if (It == PostIncRangeInfos.end())
PostIncRangeInfos.insert({Key, R});
else
It->second = R.intersectWith(It->second);
}

public:
WidenIV(const WideIVInfo &WI, LoopInfo LInfo, ScalarEvolution SEv,
DominatorTree *DTree, SmallVectorImpl<WeakTrackingVH> &DI,
bool HasGuards)
: OrigPhi(WI.NarrowIV), WideType(WI.WidestNativeType), LI(LInfo),
L(LI->getLoopFor(OrigPhi->getParent())), SE(SEv), DT(DTree),
HasGuards(HasGuards), DeadInsts(DI) {
assert(L->getHeader() == OrigPhi->getParent() && "Phi must be an IV");
ExtendKindMap[OrigPhi] = WI.IsSigned ? SignExtended : ZeroExtended;
}

PHINode *createWideIV(SCEVExpander &Rewriter);

protected:
Value createExtendInst(Value NarrowOper, Type *WideType, bool IsSigned,
Instruction *Use);

Instruction cloneIVUser(NarrowIVDefUse DU, const SCEVAddRecExpr WideAR);
Instruction *cloneArithmeticIVUser(NarrowIVDefUse DU,
const SCEVAddRecExpr *WideAR);
Instruction *cloneBitwiseIVUser(NarrowIVDefUse DU);

ExtendKind getExtendKind(Instruction *I);

using WidenedRecTy = std::pair<const SCEVAddRecExpr *, ExtendKind>;

WidenedRecTy getWideRecurrence(NarrowIVDefUse DU);

WidenedRecTy getExtendedOperandRecurrence(NarrowIVDefUse DU);

const SCEV getSCEVByOpCode(const SCEV LHS, const SCEV *RHS,
unsigned OpCode) const;

Instruction *widenIVUse(NarrowIVDefUse DU, SCEVExpander &Rewriter);

bool widenLoopCompare(NarrowIVDefUse DU);
bool widenWithVariantUse(NarrowIVDefUse DU);

void pushNarrowIVUsers(Instruction NarrowDef, Instruction WideDef);
};

} // end anonymous namespace

Value WidenIV::createExtendInst(Value NarrowOper, Type *WideType,
bool IsSigned, Instruction *Use) {
// Set the debug location and conservative insertion point.
IRBuilder<> Builder(Use);
// Hoist the insertion point into loop preheaders as far as possible.
for (const Loop *L = LI->getLoopFor(Use->getParent());
L && L->getLoopPreheader() && L->isLoopInvariant(NarrowOper);
L = L->getParentLoop())
Builder.SetInsertPoint(L->getLoopPreheader()->getTerminator());

return IsSigned ? Builder.CreateSExt(NarrowOper, WideType) :
Builder.CreateZExt(NarrowOper, WideType);
}

/// Instantiate a wide operation to replace a narrow operation. This only needs
/// to handle operations that can evaluation to SCEVAddRec. It can safely return
/// 0 for any operation we decide not to clone.
Instruction *WidenIV::cloneIVUser(NarrowIVDefUse DU,
const SCEVAddRecExpr *WideAR) {
unsigned Opcode = DU.NarrowUse->getOpcode();
switch (Opcode) {
default:
return nullptr;
case Instruction::Add:
case Instruction::Mul:
case Instruction::UDiv:
case Instruction::Sub:
return cloneArithmeticIVUser(DU, WideAR);

case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
return cloneBitwiseIVUser(DU);
}
}

Instruction *WidenIV::cloneBitwiseIVUser(NarrowIVDefUse DU) {
Instruction *NarrowUse = DU.NarrowUse;
Instruction *NarrowDef = DU.NarrowDef;
Instruction *WideDef = DU.WideDef;

LLVM_DEBUG(dbgs() << "Cloning bitwise IVUser: " << *NarrowUse << "\n");

// Replace NarrowDef operands with WideDef. Otherwise, we don't know anything
// about the narrow operand yet so must insert a [sz]ext. It is probably loop
// invariant and will be folded or hoisted. If it actually comes from a
// widened IV, it should be removed during a future call to widenIVUse.
bool IsSigned = getExtendKind(NarrowDef) == SignExtended;
Value *LHS = (NarrowUse->getOperand(0) == NarrowDef)
? WideDef
: createExtendInst(NarrowUse->getOperand(0), WideType,
IsSigned, NarrowUse);
Value *RHS = (NarrowUse->getOperand(1) == NarrowDef)
? WideDef
: createExtendInst(NarrowUse->getOperand(1), WideType,
IsSigned, NarrowUse);

auto *NarrowBO = cast<BinaryOperator>(NarrowUse);
auto *WideBO = BinaryOperator::Create(NarrowBO->getOpcode(), LHS, RHS,
NarrowBO->getName());
IRBuilder<> Builder(NarrowUse);
Builder.Insert(WideBO);
WideBO->copyIRFlags(NarrowBO);
return WideBO;
}

Instruction *WidenIV::cloneArithmeticIVUser(NarrowIVDefUse DU,
const SCEVAddRecExpr *WideAR) {
Instruction *NarrowUse = DU.NarrowUse;
Instruction *NarrowDef = DU.NarrowDef;
Instruction *WideDef = DU.WideDef;

LLVM_DEBUG(dbgs() << "Cloning arithmetic IVUser: " << *NarrowUse << "\n");

unsigned IVOpIdx = (NarrowUse->getOperand(0) == NarrowDef) ? 0 : 1;

// We're trying to find X such that
//
// Widen(NarrowDef `op` NonIVNarrowDef) == WideAR == WideDef `op.wide` X
//
// We guess two solutions to X, sext(NonIVNarrowDef) and zext(NonIVNarrowDef),
// and check using SCEV if any of them are correct.

// Returns true if extending NonIVNarrowDef according to `SignExt` is a
// correct solution to X.
auto GuessNonIVOperand = [&](bool SignExt) {
const SCEV *WideLHS;
const SCEV *WideRHS;

auto GetExtend = [this, SignExt](const SCEV S, Type Ty) {
if (SignExt)
return SE->getSignExtendExpr(S, Ty);
return SE->getZeroExtendExpr(S, Ty);
};

if (IVOpIdx == 0) {
WideLHS = SE->getSCEV(WideDef);
const SCEV *NarrowRHS = SE->getSCEV(NarrowUse->getOperand(1));
WideRHS = GetExtend(NarrowRHS, WideType);
} else {
const SCEV *NarrowLHS = SE->getSCEV(NarrowUse->getOperand(0));
WideLHS = GetExtend(NarrowLHS, WideType);
WideRHS = SE->getSCEV(WideDef);
}

// WideUse is "WideDef `op.wide` X" as described in the comment.
const SCEV *WideUse = nullptr;

switch (NarrowUse->getOpcode()) {
default:
llvm_unreachable("No other possibility!");

case Instruction::Add:
WideUse = SE->getAddExpr(WideLHS, WideRHS);
break;

case Instruction::Mul:
WideUse = SE->getMulExpr(WideLHS, WideRHS);
break;

case Instruction::UDiv:
WideUse = SE->getUDivExpr(WideLHS, WideRHS);
break;

case Instruction::Sub:
WideUse = SE->getMinusSCEV(WideLHS, WideRHS);
break;
}

return WideUse == WideAR;
};

bool SignExtend = getExtendKind(NarrowDef) == SignExtended;
if (!GuessNonIVOperand(SignExtend)) {
SignExtend = !SignExtend;
if (!GuessNonIVOperand(SignExtend))
return nullptr;
}

Value *LHS = (NarrowUse->getOperand(0) == NarrowDef)
? WideDef
: createExtendInst(NarrowUse->getOperand(0), WideType,
SignExtend, NarrowUse);
Value *RHS = (NarrowUse->getOperand(1) == NarrowDef)
? WideDef
: createExtendInst(NarrowUse->getOperand(1), WideType,
SignExtend, NarrowUse);

auto *NarrowBO = cast<BinaryOperator>(NarrowUse);
auto *WideBO = BinaryOperator::Create(NarrowBO->getOpcode(), LHS, RHS,
NarrowBO->getName());

IRBuilder<> Builder(NarrowUse);
Builder.Insert(WideBO);
WideBO->copyIRFlags(NarrowBO);
return WideBO;
}

WidenIV::ExtendKind WidenIV::getExtendKind(Instruction *I) {
auto It = ExtendKindMap.find(I);
assert(It != ExtendKindMap.end() && "Instruction not yet extended!");
return It->second;
}

const SCEV WidenIV::getSCEVByOpCode(const SCEV LHS, const SCEV *RHS,
unsigned OpCode) const {
if (OpCode == Instruction::Add)
return SE->getAddExpr(LHS, RHS);
if (OpCode == Instruction::Sub)
return SE->getMinusSCEV(LHS, RHS);
if (OpCode == Instruction::Mul)
return SE->getMulExpr(LHS, RHS);

llvm_unreachable("Unsupported opcode.");
}

/// No-wrap operations can transfer sign extension of their result to their
/// operands. Generate the SCEV value for the widened operation without
/// actually modifying the IR yet. If the expression after extending the
/// operands is an AddRec for this loop, return the AddRec and the kind of
/// extension used.
WidenIV::WidenedRecTy WidenIV::getExtendedOperandRecurrence(NarrowIVDefUse DU) {
// Handle the common case of add<nsw/nuw>
const unsigned OpCode = DU.NarrowUse->getOpcode();
// Only Add/Sub/Mul instructions supported yet.
if (OpCode != Instruction::Add && OpCode != Instruction::Sub &&
OpCode != Instruction::Mul)
return {nullptr, Unknown};

// One operand (NarrowDef) has already been extended to WideDef. Now determine
// if extending the other will lead to a recurrence.
const unsigned ExtendOperIdx =
DU.NarrowUse->getOperand(0) == DU.NarrowDef ? 1 : 0;
assert(DU.NarrowUse->getOperand(1-ExtendOperIdx) == DU.NarrowDef && "bad DU");

const SCEV *ExtendOperExpr = nullptr;
const OverflowingBinaryOperator *OBO =
cast<OverflowingBinaryOperator>(DU.NarrowUse);
ExtendKind ExtKind = getExtendKind(DU.NarrowDef);
if (ExtKind == SignExtended && OBO->hasNoSignedWrap())
ExtendOperExpr = SE->getSignExtendExpr(
SE->getSCEV(DU.NarrowUse->getOperand(ExtendOperIdx)), WideType);
else if(ExtKind == ZeroExtended && OBO->hasNoUnsignedWrap())
ExtendOperExpr = SE->getZeroExtendExpr(
SE->getSCEV(DU.NarrowUse->getOperand(ExtendOperIdx)), WideType);
else
return {nullptr, Unknown};

// When creating this SCEV expr, don't apply the current operations NSW or NUW
// flags. This instruction may be guarded by control flow that the no-wrap
// behavior depends on. Non-control-equivalent instructions can be mapped to
// the same SCEV expression, and it would be incorrect to transfer NSW/NUW
// semantics to those operations.
const SCEV *lhs = SE->getSCEV(DU.WideDef);
const SCEV *rhs = ExtendOperExpr;

// Let's swap operands to the initial order for the case of non-commutative
// operations, like SUB. See PR21014.
if (ExtendOperIdx == 0)
std::swap(lhs, rhs);
const SCEVAddRecExpr *AddRec =
dyn_cast<SCEVAddRecExpr>(getSCEVByOpCode(lhs, rhs, OpCode));

if (!AddRec \|\| AddRec->getLoop() != L)
return {nullptr, Unknown};

return {AddRec, ExtKind};
}

/// Is this instruction potentially interesting for further simplification after
/// widening it's type? In other words, can the extend be safely hoisted out of
/// the loop with SCEV reducing the value to a recurrence on the same loop. If
/// so, return the extended recurrence and the kind of extension used. Otherwise
/// return {nullptr, Unknown}.
WidenIV::WidenedRecTy WidenIV::getWideRecurrence(NarrowIVDefUse DU) {
if (!SE->isSCEVable(DU.NarrowUse->getType()))
return {nullptr, Unknown};

const SCEV *NarrowExpr = SE->getSCEV(DU.NarrowUse);
if (SE->getTypeSizeInBits(NarrowExpr->getType()) >=
SE->getTypeSizeInBits(WideType)) {
// NarrowUse implicitly widens its operand. e.g. a gep with a narrow
// index. So don't follow this use.
return {nullptr, Unknown};
}

const SCEV *WideExpr;
ExtendKind ExtKind;
if (DU.NeverNegative) {
WideExpr = SE->getSignExtendExpr(NarrowExpr, WideType);
if (isa<SCEVAddRecExpr>(WideExpr))
ExtKind = SignExtended;
else {
WideExpr = SE->getZeroExtendExpr(NarrowExpr, WideType);
ExtKind = ZeroExtended;
}
} else if (getExtendKind(DU.NarrowDef) == SignExtended) {
WideExpr = SE->getSignExtendExpr(NarrowExpr, WideType);
ExtKind = SignExtended;
} else {
WideExpr = SE->getZeroExtendExpr(NarrowExpr, WideType);
ExtKind = ZeroExtended;
}
const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(WideExpr);
if (!AddRec \|\| AddRec->getLoop() != L)
return {nullptr, Unknown};
return {AddRec, ExtKind};
}

/// This IV user cannot be widened. Replace this use of the original narrow IV
/// with a truncation of the new wide IV to isolate and eliminate the narrow IV.
static void truncateIVUse(NarrowIVDefUse DU, DominatorTree DT, LoopInfo LI) {
auto *InsertPt = getInsertPointForUses(DU.NarrowUse, DU.NarrowDef, DT, LI);
if (!InsertPt)
return;
LLVM_DEBUG(dbgs() << "INDVARS: Truncate IV " << *DU.WideDef << " for user "
<< *DU.NarrowUse << "\n");
IRBuilder<> Builder(InsertPt);
Value *Trunc = Builder.CreateTrunc(DU.WideDef, DU.NarrowDef->getType());
DU.NarrowUse->replaceUsesOfWith(DU.NarrowDef, Trunc);
}

/// If the narrow use is a compare instruction, then widen the compare
// (and possibly the other operand). The extend operation is hoisted into the
// loop preheader as far as possible.
bool WidenIV::widenLoopCompare(NarrowIVDefUse DU) {
ICmpInst *Cmp = dyn_cast<ICmpInst>(DU.NarrowUse);
if (!Cmp)
return false;

// We can legally widen the comparison in the following two cases:
//
// - The signedness of the IV extension and comparison match
//
// - The narrow IV is always positive (and thus its sign extension is equal
// to its zero extension). For instance, let's say we're zero extending
// %narrow for the following use
//
// icmp slt i32 %narrow, %val ... (A)
//
// and %narrow is always positive. Then
//
// (A) == icmp slt i32 sext(%narrow), sext(%val)
// == icmp slt i32 zext(%narrow), sext(%val)
bool IsSigned = getExtendKind(DU.NarrowDef) == SignExtended;
if (!(DU.NeverNegative \|\| IsSigned == Cmp->isSigned()))
return false;

Value *Op = Cmp->getOperand(Cmp->getOperand(0) == DU.NarrowDef ? 1 : 0);
unsigned CastWidth = SE->getTypeSizeInBits(Op->getType());
unsigned IVWidth = SE->getTypeSizeInBits(WideType);
assert(CastWidth <= IVWidth && "Unexpected width while widening compare.");

// Widen the compare instruction.
auto *InsertPt = getInsertPointForUses(DU.NarrowUse, DU.NarrowDef, DT, LI);
if (!InsertPt)
return false;
IRBuilder<> Builder(InsertPt);
DU.NarrowUse->replaceUsesOfWith(DU.NarrowDef, DU.WideDef);

// Widen the other operand of the compare, if necessary.
if (CastWidth < IVWidth) {
Value *ExtOp = createExtendInst(Op, WideType, Cmp->isSigned(), Cmp);
DU.NarrowUse->replaceUsesOfWith(Op, ExtOp);
}
return true;
}

// The widenIVUse avoids generating trunc by evaluating the use as AddRec, this
// will not work when:
// 1) SCEV traces back to an instruction inside the loop that SCEV can not
// expand, eg. add %indvar, (load %addr)
// 2) SCEV finds a loop variant, eg. add %indvar, %loopvariant
// While SCEV fails to avoid trunc, we can still try to use instruction
// combining approach to prove trunc is not required. This can be further
// extended with other instruction combining checks, but for now we handle the
// following case (sub can be "add" and "mul", "nsw + sext" can be "nus + zext")
//
// Src:
// %c = sub nsw %b, %indvar
// %d = sext %c to i64
// Dst:
// %indvar.ext1 = sext %indvar to i64
// %m = sext %b to i64
// %d = sub nsw i64 %m, %indvar.ext1
// Therefore, as long as the result of add/sub/mul is extended to wide type, no
// trunc is required regardless of how %b is generated. This pattern is common
// when calculating address in 64 bit architecture
bool WidenIV::widenWithVariantUse(NarrowIVDefUse DU) {
Instruction *NarrowUse = DU.NarrowUse;
Instruction *NarrowDef = DU.NarrowDef;
Instruction *WideDef = DU.WideDef;

// Handle the common case of add<nsw/nuw>
const unsigned OpCode = NarrowUse->getOpcode();
// Only Add/Sub/Mul instructions are supported.
if (OpCode != Instruction::Add && OpCode != Instruction::Sub &&
OpCode != Instruction::Mul)
return false;

// The operand that is not defined by NarrowDef of DU. Let's call it the
// other operand.
assert((NarrowUse->getOperand(0) == NarrowDef \|\|
NarrowUse->getOperand(1) == NarrowDef) &&
"bad DU");

const OverflowingBinaryOperator *OBO =
cast<OverflowingBinaryOperator>(NarrowUse);
ExtendKind ExtKind = getExtendKind(NarrowDef);
bool CanSignExtend = ExtKind == SignExtended && OBO->hasNoSignedWrap();
bool CanZeroExtend = ExtKind == ZeroExtended && OBO->hasNoUnsignedWrap();
if (!CanSignExtend && !CanZeroExtend)
return false;

// Verifying that Defining operand is an AddRec
const SCEV *Op1 = SE->getSCEV(WideDef);
const SCEVAddRecExpr *AddRecOp1 = dyn_cast<SCEVAddRecExpr>(Op1);
if (!AddRecOp1 \|\| AddRecOp1->getLoop() != L)
return false;

for (Use &U : NarrowUse->uses()) {
Instruction *User = nullptr;
if (ExtKind == SignExtended)
User = dyn_cast<SExtInst>(U.getUser());
else
User = dyn_cast<ZExtInst>(U.getUser());
if (!User \|\| User->getType() != WideType)
return false;
}

LLVM_DEBUG(dbgs() << "Cloning arithmetic IVUser: " << *NarrowUse << "\n");

// Generating a widening use instruction.
Value *LHS = (NarrowUse->getOperand(0) == NarrowDef)
? WideDef
: createExtendInst(NarrowUse->getOperand(0), WideType,
ExtKind, NarrowUse);
Value *RHS = (NarrowUse->getOperand(1) == NarrowDef)
? WideDef
: createExtendInst(NarrowUse->getOperand(1), WideType,
ExtKind, NarrowUse);

auto *NarrowBO = cast<BinaryOperator>(NarrowUse);
auto *WideBO = BinaryOperator::Create(NarrowBO->getOpcode(), LHS, RHS,
NarrowBO->getName());
IRBuilder<> Builder(NarrowUse);
Builder.Insert(WideBO);
WideBO->copyIRFlags(NarrowBO);
ExtendKindMap[NarrowUse] = ExtKind;

for (Use &U : NarrowUse->uses()) {
Instruction *User = nullptr;
if (ExtKind == SignExtended)
User = cast<SExtInst>(U.getUser());
else
User = cast<ZExtInst>(U.getUser());
assert(User->getType() == WideType && "Checked before!");
LLVM_DEBUG(dbgs() << "INDVARS: eliminating " << *User << " replaced by "
<< *WideBO << "\n");
++NumElimExt;
User->replaceAllUsesWith(WideBO);
DeadInsts.emplace_back(User);
}
return true;
}

/// Determine whether an individual user of the narrow IV can be widened. If so,
/// return the wide clone of the user.
Instruction *WidenIV::widenIVUse(NarrowIVDefUse DU, SCEVExpander &Rewriter) {
assert(ExtendKindMap.count(DU.NarrowDef) &&
"Should already know the kind of extension used to widen NarrowDef");

// Stop traversing the def-use chain at inner-loop phis or post-loop phis.
if (PHINode *UsePhi = dyn_cast<PHINode>(DU.NarrowUse)) {
if (LI->getLoopFor(UsePhi->getParent()) != L) {
// For LCSSA phis, sink the truncate outside the loop.
// After SimplifyCFG most loop exit targets have a single predecessor.
// Otherwise fall back to a truncate within the loop.
if (UsePhi->getNumOperands() != 1)
truncateIVUse(DU, DT, LI);
else {
// Widening the PHI requires us to insert a trunc. The logical place
// for this trunc is in the same BB as the PHI. This is not possible if
// the BB is terminated by a catchswitch.
if (isa<CatchSwitchInst>(UsePhi->getParent()->getTerminator()))
return nullptr;

PHINode *WidePhi =
PHINode::Create(DU.WideDef->getType(), 1, UsePhi->getName() + ".wide",
UsePhi);
WidePhi->addIncoming(DU.WideDef, UsePhi->getIncomingBlock(0));
IRBuilder<> Builder(&*WidePhi->getParent()->getFirstInsertionPt());
Value *Trunc = Builder.CreateTrunc(WidePhi, DU.NarrowDef->getType());
UsePhi->replaceAllUsesWith(Trunc);
DeadInsts.emplace_back(UsePhi);
LLVM_DEBUG(dbgs() << "INDVARS: Widen lcssa phi " << *UsePhi << " to "
<< *WidePhi << "\n");
}
return nullptr;
}
}

// This narrow use can be widened by a sext if it's non-negative or its narrow
// def was widended by a sext. Same for zext.
auto canWidenBySExt = [&]() {
return DU.NeverNegative \|\| getExtendKind(DU.NarrowDef) == SignExtended;
};
auto canWidenByZExt = [&]() {
return DU.NeverNegative \|\| getExtendKind(DU.NarrowDef) == ZeroExtended;
};

// Our raison d'etre! Eliminate sign and zero extension.
if ((isa<SExtInst>(DU.NarrowUse) && canWidenBySExt()) \|\|
(isa<ZExtInst>(DU.NarrowUse) && canWidenByZExt())) {
Value *NewDef = DU.WideDef;
if (DU.NarrowUse->getType() != WideType) {
unsigned CastWidth = SE->getTypeSizeInBits(DU.NarrowUse->getType());
unsigned IVWidth = SE->getTypeSizeInBits(WideType);
if (CastWidth < IVWidth) {
// The cast isn't as wide as the IV, so insert a Trunc.
IRBuilder<> Builder(DU.NarrowUse);
NewDef = Builder.CreateTrunc(DU.WideDef, DU.NarrowUse->getType());
}
else {
// A wider extend was hidden behind a narrower one. This may induce
// another round of IV widening in which the intermediate IV becomes
// dead. It should be very rare.
LLVM_DEBUG(dbgs() << "INDVARS: New IV " << *WidePhi
<< " not wide enough to subsume " << *DU.NarrowUse
<< "\n");
DU.NarrowUse->replaceUsesOfWith(DU.NarrowDef, DU.WideDef);
NewDef = DU.NarrowUse;
}
}
if (NewDef != DU.NarrowUse) {
LLVM_DEBUG(dbgs() << "INDVARS: eliminating " << *DU.NarrowUse
<< " replaced by " << *DU.WideDef << "\n");
++NumElimExt;
DU.NarrowUse->replaceAllUsesWith(NewDef);
DeadInsts.emplace_back(DU.NarrowUse);
}
// Now that the extend is gone, we want to expose it's uses for potential
// further simplification. We don't need to directly inform SimplifyIVUsers
// of the new users, because their parent IV will be processed later as a
// new loop phi. If we preserved IVUsers analysis, we would also want to
// push the uses of WideDef here.

// No further widening is needed. The deceased [sz]ext had done it for us.
return nullptr;
}

// Does this user itself evaluate to a recurrence after widening?
WidenedRecTy WideAddRec = getExtendedOperandRecurrence(DU);
if (!WideAddRec.first)
WideAddRec = getWideRecurrence(DU);

assert((WideAddRec.first == nullptr) == (WideAddRec.second == Unknown));
if (!WideAddRec.first) {
// If use is a loop condition, try to promote the condition instead of
// truncating the IV first.
if (widenLoopCompare(DU))
return nullptr;

// We are here about to generate a truncate instruction that may hurt
// performance because the scalar evolution expression computed earlier
// in WideAddRec.first does not indicate a polynomial induction expression.
// In that case, look at the operands of the use instruction to determine
// if we can still widen the use instead of truncating its operand.
if (widenWithVariantUse(DU))
return nullptr;

// This user does not evaluate to a recurrence after widening, so don't
// follow it. Instead insert a Trunc to kill off the original use,
// eventually isolating the original narrow IV so it can be removed.
truncateIVUse(DU, DT, LI);
return nullptr;
}
// Assume block terminators cannot evaluate to a recurrence. We can't to
// insert a Trunc after a terminator if there happens to be a critical edge.
assert(DU.NarrowUse != DU.NarrowUse->getParent()->getTerminator() &&
"SCEV is not expected to evaluate a block terminator");

// Reuse the IV increment that SCEVExpander created as long as it dominates
// NarrowUse.
Instruction *WideUse = nullptr;
if (WideAddRec.first == WideIncExpr &&
Rewriter.hoistIVInc(WideInc, DU.NarrowUse))
WideUse = WideInc;
else {
WideUse = cloneIVUser(DU, WideAddRec.first);
if (!WideUse)
return nullptr;
}
// Evaluation of WideAddRec ensured that the narrow expression could be
// extended outside the loop without overflow. This suggests that the wide use
// evaluates to the same expression as the extended narrow use, but doesn't
// absolutely guarantee it. Hence the following failsafe check. In rare cases
// where it fails, we simply throw away the newly created wide use.
if (WideAddRec.first != SE->getSCEV(WideUse)) {
LLVM_DEBUG(dbgs() << "Wide use expression mismatch: " << *WideUse << ": "
<< SE->getSCEV(WideUse) << " != " << WideAddRec.first
<< "\n");
DeadInsts.emplace_back(WideUse);
return nullptr;
}

// if we reached this point then we are going to replace
// DU.NarrowUse with WideUse. Reattach DbgValue then.
replaceAllDbgUsesWith(DU.NarrowUse, WideUse, WideUse, DT);

ExtendKindMap[DU.NarrowUse] = WideAddRec.second;
// Returning WideUse pushes it on the worklist.
return WideUse;
}

/// Add eligible users of NarrowDef to NarrowIVUsers.
void WidenIV::pushNarrowIVUsers(Instruction NarrowDef, Instruction WideDef) {
const SCEV *NarrowSCEV = SE->getSCEV(NarrowDef);
bool NonNegativeDef =
SE->isKnownPredicate(ICmpInst::ICMP_SGE, NarrowSCEV,
SE->getZero(NarrowSCEV->getType()));
for (User *U : NarrowDef->users()) {
Instruction *NarrowUser = cast<Instruction>(U);

// Handle data flow merges and bizarre phi cycles.
if (!Widened.insert(NarrowUser).second)
continue;

bool NonNegativeUse = false;
if (!NonNegativeDef) {
// We might have a control-dependent range information for this context.
if (auto RangeInfo = getPostIncRangeInfo(NarrowDef, NarrowUser))
NonNegativeUse = RangeInfo->getSignedMin().isNonNegative();
}

NarrowIVUsers.emplace_back(NarrowDef, NarrowUser, WideDef,
NonNegativeDef \|\| NonNegativeUse);
}
}

/// Process a single induction variable. First use the SCEVExpander to create a
/// wide induction variable that evaluates to the same recurrence as the
/// original narrow IV. Then use a worklist to forward traverse the narrow IV's
/// def-use chain. After widenIVUse has processed all interesting IV users, the
/// narrow IV will be isolated for removal by DeleteDeadPHIs.
///
/// It would be simpler to delete uses as they are processed, but we must avoid
/// invalidating SCEV expressions.
PHINode *WidenIV::createWideIV(SCEVExpander &Rewriter) {
// Bail if we disallowed widening.
if(!AllowIVWidening)
return nullptr;

// Is this phi an induction variable?
const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(OrigPhi));
if (!AddRec)
return nullptr;

// Widen the induction variable expression.
const SCEV *WideIVExpr = getExtendKind(OrigPhi) == SignExtended
? SE->getSignExtendExpr(AddRec, WideType)
: SE->getZeroExtendExpr(AddRec, WideType);

assert(SE->getEffectiveSCEVType(WideIVExpr->getType()) == WideType &&
"Expect the new IV expression to preserve its type");

// Can the IV be extended outside the loop without overflow?
AddRec = dyn_cast<SCEVAddRecExpr>(WideIVExpr);
if (!AddRec \|\| AddRec->getLoop() != L)
return nullptr;

// An AddRec must have loop-invariant operands. Since this AddRec is
// materialized by a loop header phi, the expression cannot have any post-loop
// operands, so they must dominate the loop header.
assert(
SE->properlyDominates(AddRec->getStart(), L->getHeader()) &&
SE->properlyDominates(AddRec->getStepRecurrence(*SE), L->getHeader()) &&
"Loop header phi recurrence inputs do not dominate the loop");

// Iterate over IV uses (including transitive ones) looking for IV increments
// of the form 'add nsw %iv, <const>'. For each increment and each use of
// the increment calculate control-dependent range information basing on
// dominating conditions inside of the loop (e.g. a range check inside of the
// loop). Calculated ranges are stored in PostIncRangeInfos map.
//
// Control-dependent range information is later used to prove that a narrow
// definition is not negative (see pushNarrowIVUsers). It's difficult to do
// this on demand because when pushNarrowIVUsers needs this information some
// of the dominating conditions might be already widened.
if (UsePostIncrementRanges)
calculatePostIncRanges(OrigPhi);

// The rewriter provides a value for the desired IV expression. This may
// either find an existing phi or materialize a new one. Either way, we
// expect a well-formed cyclic phi-with-increments. i.e. any operand not part
// of the phi-SCC dominates the loop entry.
Instruction InsertPt = &L->getHeader()->getFirstInsertionPt();
Value *ExpandInst = Rewriter.expandCodeFor(AddRec, WideType, InsertPt);
// If the wide phi is not a phi node, for example a cast node, like bitcast,
// inttoptr, ptrtoint, just skip for now.
if (!(WidePhi = dyn_cast<PHINode>(ExpandInst))) {
// if the cast node is an inserted instruction without any user, we should
// remove it to make sure the pass don't touch the function as we can not
// wide the phi.
if (ExpandInst->hasNUses(0) &&
Rewriter.isInsertedInstruction(cast<Instruction>(ExpandInst)))
DeadInsts.emplace_back(ExpandInst);
return nullptr;
}

// Remembering the WideIV increment generated by SCEVExpander allows
// widenIVUse to reuse it when widening the narrow IV's increment. We don't
// employ a general reuse mechanism because the call above is the only call to
// SCEVExpander. Henceforth, we produce 1-to-1 narrow to wide uses.
if (BasicBlock *LatchBlock = L->getLoopLatch()) {
WideInc =
cast<Instruction>(WidePhi->getIncomingValueForBlock(LatchBlock));
WideIncExpr = SE->getSCEV(WideInc);
// Propagate the debug location associated with the original loop increment
// to the new (widened) increment.
auto *OrigInc =
cast<Instruction>(OrigPhi->getIncomingValueForBlock(LatchBlock));
WideInc->setDebugLoc(OrigInc->getDebugLoc());
}

LLVM_DEBUG(dbgs() << "Wide IV: " << *WidePhi << "\n");
++NumWidened;

// Traverse the def-use chain using a worklist starting at the original IV.
assert(Widened.empty() && NarrowIVUsers.empty() && "expect initial state" );

Widened.insert(OrigPhi);
pushNarrowIVUsers(OrigPhi, WidePhi);

while (!NarrowIVUsers.empty()) {
NarrowIVDefUse DU = NarrowIVUsers.pop_back_val();

// Process a def-use edge. This may replace the use, so don't hold a
// use_iterator across it.
Instruction *WideUse = widenIVUse(DU, Rewriter);

// Follow all def-use edges from the previous narrow use.
if (WideUse)
pushNarrowIVUsers(DU.NarrowUse, WideUse);

// widenIVUse may have removed the def-use edge.
if (DU.NarrowDef->use_empty())
DeadInsts.emplace_back(DU.NarrowDef);
}

// Attach any debug information to the new PHI.
replaceAllDbgUsesWith(OrigPhi, WidePhi, WidePhi, DT);

return WidePhi;
}

/// Calculates control-dependent range for the given def at the given context
/// by looking at dominating conditions inside of the loop
void WidenIV::calculatePostIncRange(Instruction *NarrowDef,
Instruction *NarrowUser) {
using namespace llvm::PatternMatch;

Value *NarrowDefLHS;
const APInt *NarrowDefRHS;
if (!match(NarrowDef, m_NSWAdd(m_Value(NarrowDefLHS),
m_APInt(NarrowDefRHS))) \|\|
!NarrowDefRHS->isNonNegative())
return;

auto UpdateRangeFromCondition = [&] (Value *Condition,
bool TrueDest) {
CmpInst::Predicate Pred;
Value *CmpRHS;
if (!match(Condition, m_ICmp(Pred, m_Specific(NarrowDefLHS),
m_Value(CmpRHS))))
return;

CmpInst::Predicate P =
TrueDest ? Pred : CmpInst::getInversePredicate(Pred);

auto CmpRHSRange = SE->getSignedRange(SE->getSCEV(CmpRHS));
auto CmpConstrainedLHSRange =
ConstantRange::makeAllowedICmpRegion(P, CmpRHSRange);
auto NarrowDefRange = CmpConstrainedLHSRange.addWithNoWrap(
*NarrowDefRHS, OverflowingBinaryOperator::NoSignedWrap);

updatePostIncRangeInfo(NarrowDef, NarrowUser, NarrowDefRange);
};

auto UpdateRangeFromGuards = [&](Instruction *Ctx) {
if (!HasGuards)
return;

for (Instruction &I : make_range(Ctx->getIterator().getReverse(),
Ctx->getParent()->rend())) {
Value *C = nullptr;
if (match(&I, m_Intrinsic<Intrinsic::experimental_guard>(m_Value(C))))
UpdateRangeFromCondition(C, /TrueDest=/true);
}
};

UpdateRangeFromGuards(NarrowUser);

BasicBlock *NarrowUserBB = NarrowUser->getParent();
// If NarrowUserBB is statically unreachable asking dominator queries may
// yield surprising results. (e.g. the block may not have a dom tree node)
if (!DT->isReachableFromEntry(NarrowUserBB))
return;

for (auto DTB = (DT)[NarrowUserBB]->getIDom();
L->contains(DTB->getBlock());
DTB = DTB->getIDom()) {
auto *BB = DTB->getBlock();
auto *TI = BB->getTerminator();
UpdateRangeFromGuards(TI);

auto *BI = dyn_cast<BranchInst>(TI);
if (!BI \|\| !BI->isConditional())
continue;

auto *TrueSuccessor = BI->getSuccessor(0);
auto *FalseSuccessor = BI->getSuccessor(1);

auto DominatesNarrowUser = [this, NarrowUser] (BasicBlockEdge BBE) {
return BBE.isSingleEdge() &&
DT->dominates(BBE, NarrowUser->getParent());
};

if (DominatesNarrowUser(BasicBlockEdge(BB, TrueSuccessor)))
UpdateRangeFromCondition(BI->getCondition(), /TrueDest=/true);

if (DominatesNarrowUser(BasicBlockEdge(BB, FalseSuccessor)))
UpdateRangeFromCondition(BI->getCondition(), /TrueDest=/false);
}
}

/// Calculates PostIncRangeInfos map for the given IV
void WidenIV::calculatePostIncRanges(PHINode *OrigPhi) {
SmallPtrSet<Instruction *, 16> Visited;
SmallVector<Instruction *, 6> Worklist;
Worklist.push_back(OrigPhi);
Visited.insert(OrigPhi);

while (!Worklist.empty()) {
Instruction *NarrowDef = Worklist.pop_back_val();

for (Use &U : NarrowDef->uses()) {
auto *NarrowUser = cast<Instruction>(U.getUser());

// Don't go looking outside the current loop.
auto NarrowUserLoop = (LI)[NarrowUser->getParent()];
if (!NarrowUserLoop \|\| !L->contains(NarrowUserLoop))
continue;

if (!Visited.insert(NarrowUser).second)
continue;

Worklist.push_back(NarrowUser);

calculatePostIncRange(NarrowDef, NarrowUser);
}
}
}

//===----------------------------------------------------------------------===//		//===----------------------------------------------------------------------===//
// Live IV Reduction - Minimize IVs live across the loop.		// Live IV Reduction - Minimize IVs live across the loop.
//===----------------------------------------------------------------------===//		//===----------------------------------------------------------------------===//

//===----------------------------------------------------------------------===//		//===----------------------------------------------------------------------===//
// Simplification of IV users based on SCEV evaluation.		// Simplification of IV users based on SCEV evaluation.
//===----------------------------------------------------------------------===//		//===----------------------------------------------------------------------===//

▲ Show 20 Lines • Show All 60 Lines • ▼ Show 20 Lines	do {
Changed \|= simplifyUsersOfIV(CurrIV, SE, DT, LI, TTI, DeadInsts, Rewriter,		Changed \|= simplifyUsersOfIV(CurrIV, SE, DT, LI, TTI, DeadInsts, Rewriter,
&Visitor);		&Visitor);

if (Visitor.WI.WidestNativeType) {		if (Visitor.WI.WidestNativeType) {
WideIVs.push_back(Visitor.WI);		WideIVs.push_back(Visitor.WI);
}		}
} while(!LoopPhis.empty());		} while(!LoopPhis.empty());

		// Continue if we disallowed widening.
		if (!AllowIVWidening)
		continue;

for (; !WideIVs.empty(); WideIVs.pop_back()) {		for (; !WideIVs.empty(); WideIVs.pop_back()) {
WidenIV Widener(WideIVs.back(), LI, SE, DT, DeadInsts, HasGuards);		unsigned ElimExt;
if (PHINode *WidePhi = Widener.createWideIV(Rewriter)) {		unsigned Widened;
		dmgreenUnsubmitted Not Done Reply Inline Actions UsePostIncrementRanges could be set in the constructor of WidenIV. Or the option could be moved to LoopUtils? dmgreen: UsePostIncrementRanges could be set in the constructor of WidenIV. Or the option could be moved…
		if (PHINode *WidePhi = createWideIV(WideIVs.back(), LI, SE, Rewriter,
		DT, DeadInsts, ElimExt, Widened,
		HasGuards, UsePostIncrementRanges)) {
		NumElimExt += ElimExt;
		NumWidened += Widened;
Changed = true;		Changed = true;
LoopPhis.push_back(WidePhi);		LoopPhis.push_back(WidePhi);
}		}
}		}
}		}
return Changed;		return Changed;
}		}

▲ Show 20 Lines • Show All 1,310 Lines • Show Last 20 Lines

llvm/lib/Transforms/Utils/SimplifyIndVar.cpp

Show First 20 Lines • Show All 962 Lines • ▼ Show 20 Lines	#endif
for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I) {		for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I) {
Changed \|=		Changed \|=
simplifyUsersOfIV(cast<PHINode>(I), SE, DT, LI, TTI, Dead, Rewriter);		simplifyUsersOfIV(cast<PHINode>(I), SE, DT, LI, TTI, Dead, Rewriter);
}		}
return Changed;		return Changed;
}		}

} // namespace llvm		} // namespace llvm

		//===----------------------------------------------------------------------===//
		// Widen Induction Variables - Extend the width of an IV to cover its
		// widest uses.
		//===----------------------------------------------------------------------===//

		class WidenIV {
		// Parameters
		PHINode *OrigPhi;
		Type *WideType;

		// Context
		LoopInfo *LI;
		Loop *L;
		ScalarEvolution *SE;
		DominatorTree *DT;

		// Does the module have any calls to the llvm.experimental.guard intrinsic
		// at all? If not we can avoid scanning instructions looking for guards.
		bool HasGuards;

		bool UsePostIncrementRanges;

		// Statistics
		unsigned NumElimExt = 0;
		unsigned NumWidened = 0;

		// Result
		PHINode *WidePhi = nullptr;
		Instruction *WideInc = nullptr;
		const SCEV *WideIncExpr = nullptr;
		SmallVectorImpl<WeakTrackingVH> &DeadInsts;

		SmallPtrSet<Instruction *,16> Widened;

		enum ExtendKind { ZeroExtended, SignExtended, Unknown };

		// A map tracking the kind of extension used to widen each narrow IV
		// and narrow IV user.
		// Key: pointer to a narrow IV or IV user.
		// Value: the kind of extension used to widen this Instruction.
		DenseMap<AssertingVH<Instruction>, ExtendKind> ExtendKindMap;

		using DefUserPair = std::pair<AssertingVH<Value>, AssertingVH<Instruction>>;

		// A map with control-dependent ranges for post increment IV uses. The key is
		// a pair of IV def and a use of this def denoting the context. The value is
		// a ConstantRange representing possible values of the def at the given
		// context.
		DenseMap<DefUserPair, ConstantRange> PostIncRangeInfos;

		Optional<ConstantRange> getPostIncRangeInfo(Value *Def,
		Instruction *UseI) {
		DefUserPair Key(Def, UseI);
		auto It = PostIncRangeInfos.find(Key);
		return It == PostIncRangeInfos.end()
		? Optional<ConstantRange>(None)
		: Optional<ConstantRange>(It->second);
		}

		void calculatePostIncRanges(PHINode *OrigPhi);
		void calculatePostIncRange(Instruction NarrowDef, Instruction NarrowUser);

		void updatePostIncRangeInfo(Value Def, Instruction UseI, ConstantRange R) {
		DefUserPair Key(Def, UseI);
		auto It = PostIncRangeInfos.find(Key);
		if (It == PostIncRangeInfos.end())
		PostIncRangeInfos.insert({Key, R});
		else
		It->second = R.intersectWith(It->second);
		}

		public:
		/// Record a link in the Narrow IV def-use chain along with the WideIV that
		/// computes the same value as the Narrow IV def. This avoids caching Use*
		/// pointers.
		struct NarrowIVDefUse {
		Instruction *NarrowDef = nullptr;
		Instruction *NarrowUse = nullptr;
		Instruction *WideDef = nullptr;

		// True if the narrow def is never negative. Tracking this information lets
		// us use a sign extension instead of a zero extension or vice versa, when
		// profitable and legal.
		bool NeverNegative = false;

		NarrowIVDefUse(Instruction ND, Instruction NU, Instruction *WD,
		bool NeverNegative)
		: NarrowDef(ND), NarrowUse(NU), WideDef(WD),
		NeverNegative(NeverNegative) {}
		};

		WidenIV(const WideIVInfo &WI, LoopInfo LInfo, ScalarEvolution SEv,
		DominatorTree *DTree, SmallVectorImpl<WeakTrackingVH> &DI,
		bool HasGuards, bool UsePostIncrementRanges = true);

		PHINode *createWideIV(SCEVExpander &Rewriter);

		unsigned getNumElimExt() { return NumElimExt; };
		unsigned getNumWidened() { return NumWidened; };

		protected:
		Value createExtendInst(Value NarrowOper, Type *WideType, bool IsSigned,
		Instruction *Use);

		Instruction cloneIVUser(NarrowIVDefUse DU, const SCEVAddRecExpr WideAR);
		Instruction *cloneArithmeticIVUser(NarrowIVDefUse DU,
		const SCEVAddRecExpr *WideAR);
		Instruction *cloneBitwiseIVUser(NarrowIVDefUse DU);

		ExtendKind getExtendKind(Instruction *I);

		using WidenedRecTy = std::pair<const SCEVAddRecExpr *, ExtendKind>;

		WidenedRecTy getWideRecurrence(NarrowIVDefUse DU);

		WidenedRecTy getExtendedOperandRecurrence(NarrowIVDefUse DU);

		const SCEV getSCEVByOpCode(const SCEV LHS, const SCEV *RHS,
		unsigned OpCode) const;

		Instruction *widenIVUse(NarrowIVDefUse DU, SCEVExpander &Rewriter);

		bool widenLoopCompare(NarrowIVDefUse DU);
		bool widenWithVariantUse(NarrowIVDefUse DU);

		void pushNarrowIVUsers(Instruction NarrowDef, Instruction WideDef);

		private:
		SmallVector<NarrowIVDefUse, 8> NarrowIVUsers;
		};


		/// Determine the insertion point for this user. By default, insert immediately
		/// before the user. SCEVExpander or LICM will hoist loop invariants out of the
		/// loop. For PHI nodes, there may be multiple uses, so compute the nearest
		/// common dominator for the incoming blocks. A nullptr can be returned if no
		/// viable location is found: it may happen if User is a PHI and Def only comes
		/// to this PHI from unreachable blocks.
		static Instruction getInsertPointForUses(Instruction User, Value *Def,
		DominatorTree DT, LoopInfo LI) {
		PHINode *PHI = dyn_cast<PHINode>(User);
		if (!PHI)
		return User;

		Instruction *InsertPt = nullptr;
		for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i) {
		if (PHI->getIncomingValue(i) != Def)
		continue;

		BasicBlock *InsertBB = PHI->getIncomingBlock(i);

		if (!DT->isReachableFromEntry(InsertBB))
		continue;

		if (!InsertPt) {
		InsertPt = InsertBB->getTerminator();
		continue;
		}
		InsertBB = DT->findNearestCommonDominator(InsertPt->getParent(), InsertBB);
		InsertPt = InsertBB->getTerminator();
		}

		// If we have skipped all inputs, it means that Def only comes to Phi from
		// unreachable blocks.
		if (!InsertPt)
		return nullptr;

		auto *DefI = dyn_cast<Instruction>(Def);
		if (!DefI)
		return InsertPt;

		assert(DT->dominates(DefI, InsertPt) && "def does not dominate all uses");

		auto *L = LI->getLoopFor(DefI->getParent());
		assert(!L \|\| L->contains(LI->getLoopFor(InsertPt->getParent())));

		for (auto DTN = (DT)[InsertPt->getParent()]; DTN; DTN = DTN->getIDom())
		if (LI->getLoopFor(DTN->getBlock()) == L)
		return DTN->getBlock()->getTerminator();

		llvm_unreachable("DefI dominates InsertPt!");
		}

		WidenIV::WidenIV(const WideIVInfo &WI, LoopInfo LInfo, ScalarEvolution SEv,
		DominatorTree *DTree, SmallVectorImpl<WeakTrackingVH> &DI,
		bool HasGuards, bool UsePostIncrementRanges)
		: OrigPhi(WI.NarrowIV), WideType(WI.WidestNativeType), LI(LInfo),
		L(LI->getLoopFor(OrigPhi->getParent())), SE(SEv), DT(DTree),
		HasGuards(HasGuards), UsePostIncrementRanges(UsePostIncrementRanges),
		DeadInsts(DI) {
		assert(L->getHeader() == OrigPhi->getParent() && "Phi must be an IV");
		ExtendKindMap[OrigPhi] = WI.IsSigned ? SignExtended : ZeroExtended;
		}

		Value WidenIV::createExtendInst(Value NarrowOper, Type *WideType,
		bool IsSigned, Instruction *Use) {
		// Set the debug location and conservative insertion point.
		IRBuilder<> Builder(Use);
		// Hoist the insertion point into loop preheaders as far as possible.
		for (const Loop *L = LI->getLoopFor(Use->getParent());
		L && L->getLoopPreheader() && L->isLoopInvariant(NarrowOper);
		L = L->getParentLoop())
		Builder.SetInsertPoint(L->getLoopPreheader()->getTerminator());

		return IsSigned ? Builder.CreateSExt(NarrowOper, WideType) :
		Builder.CreateZExt(NarrowOper, WideType);
		}

		/// Instantiate a wide operation to replace a narrow operation. This only needs
		/// to handle operations that can evaluation to SCEVAddRec. It can safely return
		/// 0 for any operation we decide not to clone.
		Instruction *WidenIV::cloneIVUser(WidenIV::NarrowIVDefUse DU,
		const SCEVAddRecExpr *WideAR) {
		unsigned Opcode = DU.NarrowUse->getOpcode();
		switch (Opcode) {
		default:
		return nullptr;
		case Instruction::Add:
		case Instruction::Mul:
		case Instruction::UDiv:
		case Instruction::Sub:
		return cloneArithmeticIVUser(DU, WideAR);

		case Instruction::And:
		case Instruction::Or:
		case Instruction::Xor:
		case Instruction::Shl:
		case Instruction::LShr:
		case Instruction::AShr:
		return cloneBitwiseIVUser(DU);
		}
		}

		Instruction *WidenIV::cloneBitwiseIVUser(WidenIV::NarrowIVDefUse DU) {
		Instruction *NarrowUse = DU.NarrowUse;
		Instruction *NarrowDef = DU.NarrowDef;
		Instruction *WideDef = DU.WideDef;

		LLVM_DEBUG(dbgs() << "Cloning bitwise IVUser: " << *NarrowUse << "\n");

		// Replace NarrowDef operands with WideDef. Otherwise, we don't know anything
		// about the narrow operand yet so must insert a [sz]ext. It is probably loop
		// invariant and will be folded or hoisted. If it actually comes from a
		// widened IV, it should be removed during a future call to widenIVUse.
		bool IsSigned = getExtendKind(NarrowDef) == SignExtended;
		Value *LHS = (NarrowUse->getOperand(0) == NarrowDef)
		? WideDef
		: createExtendInst(NarrowUse->getOperand(0), WideType,
		IsSigned, NarrowUse);
		Value *RHS = (NarrowUse->getOperand(1) == NarrowDef)
		? WideDef
		: createExtendInst(NarrowUse->getOperand(1), WideType,
		IsSigned, NarrowUse);

		auto *NarrowBO = cast<BinaryOperator>(NarrowUse);
		auto *WideBO = BinaryOperator::Create(NarrowBO->getOpcode(), LHS, RHS,
		NarrowBO->getName());
		IRBuilder<> Builder(NarrowUse);
		Builder.Insert(WideBO);
		WideBO->copyIRFlags(NarrowBO);
		return WideBO;
		}

		Instruction *WidenIV::cloneArithmeticIVUser(WidenIV::NarrowIVDefUse DU,
		const SCEVAddRecExpr *WideAR) {
		Instruction *NarrowUse = DU.NarrowUse;
		Instruction *NarrowDef = DU.NarrowDef;
		Instruction *WideDef = DU.WideDef;

		LLVM_DEBUG(dbgs() << "Cloning arithmetic IVUser: " << *NarrowUse << "\n");

		unsigned IVOpIdx = (NarrowUse->getOperand(0) == NarrowDef) ? 0 : 1;

		// We're trying to find X such that
		//
		// Widen(NarrowDef `op` NonIVNarrowDef) == WideAR == WideDef `op.wide` X
		//
		// We guess two solutions to X, sext(NonIVNarrowDef) and zext(NonIVNarrowDef),
		// and check using SCEV if any of them are correct.

		// Returns true if extending NonIVNarrowDef according to `SignExt` is a
		// correct solution to X.
		auto GuessNonIVOperand = [&](bool SignExt) {
		const SCEV *WideLHS;
		const SCEV *WideRHS;

		auto GetExtend = [this, SignExt](const SCEV S, Type Ty) {
		if (SignExt)
		return SE->getSignExtendExpr(S, Ty);
		return SE->getZeroExtendExpr(S, Ty);
		};

		if (IVOpIdx == 0) {
		WideLHS = SE->getSCEV(WideDef);
		const SCEV *NarrowRHS = SE->getSCEV(NarrowUse->getOperand(1));
		WideRHS = GetExtend(NarrowRHS, WideType);
		} else {
		const SCEV *NarrowLHS = SE->getSCEV(NarrowUse->getOperand(0));
		WideLHS = GetExtend(NarrowLHS, WideType);
		WideRHS = SE->getSCEV(WideDef);
		}

		// WideUse is "WideDef `op.wide` X" as described in the comment.
		const SCEV *WideUse = nullptr;

		switch (NarrowUse->getOpcode()) {
		default:
		llvm_unreachable("No other possibility!");

		case Instruction::Add:
		WideUse = SE->getAddExpr(WideLHS, WideRHS);
		break;

		case Instruction::Mul:
		WideUse = SE->getMulExpr(WideLHS, WideRHS);
		break;

		case Instruction::UDiv:
		WideUse = SE->getUDivExpr(WideLHS, WideRHS);
		break;

		case Instruction::Sub:
		WideUse = SE->getMinusSCEV(WideLHS, WideRHS);
		break;
		}

		return WideUse == WideAR;
		};

		bool SignExtend = getExtendKind(NarrowDef) == SignExtended;
		if (!GuessNonIVOperand(SignExtend)) {
		SignExtend = !SignExtend;
		if (!GuessNonIVOperand(SignExtend))
		return nullptr;
		}

		Value *LHS = (NarrowUse->getOperand(0) == NarrowDef)
		? WideDef
		: createExtendInst(NarrowUse->getOperand(0), WideType,
		SignExtend, NarrowUse);
		Value *RHS = (NarrowUse->getOperand(1) == NarrowDef)
		? WideDef
		: createExtendInst(NarrowUse->getOperand(1), WideType,
		SignExtend, NarrowUse);

		auto *NarrowBO = cast<BinaryOperator>(NarrowUse);
		auto *WideBO = BinaryOperator::Create(NarrowBO->getOpcode(), LHS, RHS,
		NarrowBO->getName());

		IRBuilder<> Builder(NarrowUse);
		Builder.Insert(WideBO);
		WideBO->copyIRFlags(NarrowBO);
		return WideBO;
		}

		WidenIV::ExtendKind WidenIV::getExtendKind(Instruction *I) {
		auto It = ExtendKindMap.find(I);
		assert(It != ExtendKindMap.end() && "Instruction not yet extended!");
		return It->second;
		}

		const SCEV WidenIV::getSCEVByOpCode(const SCEV LHS, const SCEV *RHS,
		unsigned OpCode) const {
		if (OpCode == Instruction::Add)
		return SE->getAddExpr(LHS, RHS);
		if (OpCode == Instruction::Sub)
		return SE->getMinusSCEV(LHS, RHS);
		if (OpCode == Instruction::Mul)
		return SE->getMulExpr(LHS, RHS);

		llvm_unreachable("Unsupported opcode.");
		}

		/// No-wrap operations can transfer sign extension of their result to their
		/// operands. Generate the SCEV value for the widened operation without
		/// actually modifying the IR yet. If the expression after extending the
		/// operands is an AddRec for this loop, return the AddRec and the kind of
		/// extension used.
		WidenIV::WidenedRecTy
		WidenIV::getExtendedOperandRecurrence(WidenIV::NarrowIVDefUse DU) {
		// Handle the common case of add<nsw/nuw>
		const unsigned OpCode = DU.NarrowUse->getOpcode();
		// Only Add/Sub/Mul instructions supported yet.
		if (OpCode != Instruction::Add && OpCode != Instruction::Sub &&
		OpCode != Instruction::Mul)
		return {nullptr, Unknown};

		// One operand (NarrowDef) has already been extended to WideDef. Now determine
		// if extending the other will lead to a recurrence.
		const unsigned ExtendOperIdx =
		DU.NarrowUse->getOperand(0) == DU.NarrowDef ? 1 : 0;
		assert(DU.NarrowUse->getOperand(1-ExtendOperIdx) == DU.NarrowDef && "bad DU");

		const SCEV *ExtendOperExpr = nullptr;
		const OverflowingBinaryOperator *OBO =
		cast<OverflowingBinaryOperator>(DU.NarrowUse);
		ExtendKind ExtKind = getExtendKind(DU.NarrowDef);
		if (ExtKind == SignExtended && OBO->hasNoSignedWrap())
		ExtendOperExpr = SE->getSignExtendExpr(
		SE->getSCEV(DU.NarrowUse->getOperand(ExtendOperIdx)), WideType);
		else if(ExtKind == ZeroExtended && OBO->hasNoUnsignedWrap())
		ExtendOperExpr = SE->getZeroExtendExpr(
		SE->getSCEV(DU.NarrowUse->getOperand(ExtendOperIdx)), WideType);
		else
		return {nullptr, Unknown};

		// When creating this SCEV expr, don't apply the current operations NSW or NUW
		// flags. This instruction may be guarded by control flow that the no-wrap
		// behavior depends on. Non-control-equivalent instructions can be mapped to
		// the same SCEV expression, and it would be incorrect to transfer NSW/NUW
		// semantics to those operations.
		const SCEV *lhs = SE->getSCEV(DU.WideDef);
		const SCEV *rhs = ExtendOperExpr;

		// Let's swap operands to the initial order for the case of non-commutative
		// operations, like SUB. See PR21014.
		if (ExtendOperIdx == 0)
		std::swap(lhs, rhs);
		const SCEVAddRecExpr *AddRec =
		dyn_cast<SCEVAddRecExpr>(getSCEVByOpCode(lhs, rhs, OpCode));

		if (!AddRec \|\| AddRec->getLoop() != L)
		return {nullptr, Unknown};

		return {AddRec, ExtKind};
		}

		/// Is this instruction potentially interesting for further simplification after
		/// widening it's type? In other words, can the extend be safely hoisted out of
		/// the loop with SCEV reducing the value to a recurrence on the same loop. If
		/// so, return the extended recurrence and the kind of extension used. Otherwise
		/// return {nullptr, Unknown}.
		WidenIV::WidenedRecTy WidenIV::getWideRecurrence(WidenIV::NarrowIVDefUse DU) {
		if (!SE->isSCEVable(DU.NarrowUse->getType()))
		return {nullptr, Unknown};

		const SCEV *NarrowExpr = SE->getSCEV(DU.NarrowUse);
		if (SE->getTypeSizeInBits(NarrowExpr->getType()) >=
		SE->getTypeSizeInBits(WideType)) {
		// NarrowUse implicitly widens its operand. e.g. a gep with a narrow
		// index. So don't follow this use.
		return {nullptr, Unknown};
		}

		const SCEV *WideExpr;
		ExtendKind ExtKind;
		if (DU.NeverNegative) {
		WideExpr = SE->getSignExtendExpr(NarrowExpr, WideType);
		if (isa<SCEVAddRecExpr>(WideExpr))
		ExtKind = SignExtended;
		else {
		WideExpr = SE->getZeroExtendExpr(NarrowExpr, WideType);
		ExtKind = ZeroExtended;
		}
		} else if (getExtendKind(DU.NarrowDef) == SignExtended) {
		WideExpr = SE->getSignExtendExpr(NarrowExpr, WideType);
		ExtKind = SignExtended;
		} else {
		WideExpr = SE->getZeroExtendExpr(NarrowExpr, WideType);
		ExtKind = ZeroExtended;
		}
		const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(WideExpr);
		if (!AddRec \|\| AddRec->getLoop() != L)
		return {nullptr, Unknown};
		return {AddRec, ExtKind};
		}

		/// This IV user cannot be widened. Replace this use of the original narrow IV
		/// with a truncation of the new wide IV to isolate and eliminate the narrow IV.
		static void truncateIVUse(WidenIV::NarrowIVDefUse DU, DominatorTree *DT,
		LoopInfo *LI) {
		auto *InsertPt = getInsertPointForUses(DU.NarrowUse, DU.NarrowDef, DT, LI);
		if (!InsertPt)
		return;
		LLVM_DEBUG(dbgs() << "INDVARS: Truncate IV " << *DU.WideDef << " for user "
		<< *DU.NarrowUse << "\n");
		IRBuilder<> Builder(InsertPt);
		Value *Trunc = Builder.CreateTrunc(DU.WideDef, DU.NarrowDef->getType());
		DU.NarrowUse->replaceUsesOfWith(DU.NarrowDef, Trunc);
		}

		/// If the narrow use is a compare instruction, then widen the compare
		// (and possibly the other operand). The extend operation is hoisted into the
		// loop preheader as far as possible.
		bool WidenIV::widenLoopCompare(WidenIV::NarrowIVDefUse DU) {
		ICmpInst *Cmp = dyn_cast<ICmpInst>(DU.NarrowUse);
		if (!Cmp)
		return false;

		// We can legally widen the comparison in the following two cases:
		//
		// - The signedness of the IV extension and comparison match
		//
		// - The narrow IV is always positive (and thus its sign extension is equal
		// to its zero extension). For instance, let's say we're zero extending
		// %narrow for the following use
		//
		// icmp slt i32 %narrow, %val ... (A)
		//
		// and %narrow is always positive. Then
		//
		// (A) == icmp slt i32 sext(%narrow), sext(%val)
		// == icmp slt i32 zext(%narrow), sext(%val)
		bool IsSigned = getExtendKind(DU.NarrowDef) == SignExtended;
		if (!(DU.NeverNegative \|\| IsSigned == Cmp->isSigned()))
		return false;

		Value *Op = Cmp->getOperand(Cmp->getOperand(0) == DU.NarrowDef ? 1 : 0);
		unsigned CastWidth = SE->getTypeSizeInBits(Op->getType());
		unsigned IVWidth = SE->getTypeSizeInBits(WideType);
		assert(CastWidth <= IVWidth && "Unexpected width while widening compare.");

		// Widen the compare instruction.
		auto *InsertPt = getInsertPointForUses(DU.NarrowUse, DU.NarrowDef, DT, LI);
		if (!InsertPt)
		return false;
		IRBuilder<> Builder(InsertPt);
		DU.NarrowUse->replaceUsesOfWith(DU.NarrowDef, DU.WideDef);

		// Widen the other operand of the compare, if necessary.
		if (CastWidth < IVWidth) {
		Value *ExtOp = createExtendInst(Op, WideType, Cmp->isSigned(), Cmp);
		DU.NarrowUse->replaceUsesOfWith(Op, ExtOp);
		}
		return true;
		}

		// The widenIVUse avoids generating trunc by evaluating the use as AddRec, this
		// will not work when:
		// 1) SCEV traces back to an instruction inside the loop that SCEV can not
		// expand, eg. add %indvar, (load %addr)
		// 2) SCEV finds a loop variant, eg. add %indvar, %loopvariant
		// While SCEV fails to avoid trunc, we can still try to use instruction
		// combining approach to prove trunc is not required. This can be further
		// extended with other instruction combining checks, but for now we handle the
		// following case (sub can be "add" and "mul", "nsw + sext" can be "nus + zext")
		//
		// Src:
		// %c = sub nsw %b, %indvar
		// %d = sext %c to i64
		// Dst:
		// %indvar.ext1 = sext %indvar to i64
		// %m = sext %b to i64
		// %d = sub nsw i64 %m, %indvar.ext1
		// Therefore, as long as the result of add/sub/mul is extended to wide type, no
		// trunc is required regardless of how %b is generated. This pattern is common
		// when calculating address in 64 bit architecture
		bool WidenIV::widenWithVariantUse(WidenIV::NarrowIVDefUse DU) {
		Instruction *NarrowUse = DU.NarrowUse;
		Instruction *NarrowDef = DU.NarrowDef;
		Instruction *WideDef = DU.WideDef;

		// Handle the common case of add<nsw/nuw>
		const unsigned OpCode = NarrowUse->getOpcode();
		// Only Add/Sub/Mul instructions are supported.
		if (OpCode != Instruction::Add && OpCode != Instruction::Sub &&
		OpCode != Instruction::Mul)
		return false;

		// The operand that is not defined by NarrowDef of DU. Let's call it the
		// other operand.
		assert((NarrowUse->getOperand(0) == NarrowDef \|\|
		NarrowUse->getOperand(1) == NarrowDef) &&
		"bad DU");

		const OverflowingBinaryOperator *OBO =
		cast<OverflowingBinaryOperator>(NarrowUse);
		ExtendKind ExtKind = getExtendKind(NarrowDef);
		bool CanSignExtend = ExtKind == SignExtended && OBO->hasNoSignedWrap();
		bool CanZeroExtend = ExtKind == ZeroExtended && OBO->hasNoUnsignedWrap();
		if (!CanSignExtend && !CanZeroExtend)
		return false;

		// Verifying that Defining operand is an AddRec
		const SCEV *Op1 = SE->getSCEV(WideDef);
		const SCEVAddRecExpr *AddRecOp1 = dyn_cast<SCEVAddRecExpr>(Op1);
		if (!AddRecOp1 \|\| AddRecOp1->getLoop() != L)
		return false;

		for (Use &U : NarrowUse->uses()) {
		Instruction *User = nullptr;
		if (ExtKind == SignExtended)
		User = dyn_cast<SExtInst>(U.getUser());
		else
		User = dyn_cast<ZExtInst>(U.getUser());
		if (!User \|\| User->getType() != WideType)
		return false;
		}

		LLVM_DEBUG(dbgs() << "Cloning arithmetic IVUser: " << *NarrowUse << "\n");

		// Generating a widening use instruction.
		Value *LHS = (NarrowUse->getOperand(0) == NarrowDef)
		? WideDef
		: createExtendInst(NarrowUse->getOperand(0), WideType,
		ExtKind, NarrowUse);
		Value *RHS = (NarrowUse->getOperand(1) == NarrowDef)
		? WideDef
		: createExtendInst(NarrowUse->getOperand(1), WideType,
		ExtKind, NarrowUse);

		auto *NarrowBO = cast<BinaryOperator>(NarrowUse);
		auto *WideBO = BinaryOperator::Create(NarrowBO->getOpcode(), LHS, RHS,
		NarrowBO->getName());
		IRBuilder<> Builder(NarrowUse);
		Builder.Insert(WideBO);
		WideBO->copyIRFlags(NarrowBO);
		ExtendKindMap[NarrowUse] = ExtKind;

		for (Use &U : NarrowUse->uses()) {
		Instruction *User = nullptr;
		if (ExtKind == SignExtended)
		User = cast<SExtInst>(U.getUser());
		else
		User = cast<ZExtInst>(U.getUser());
		assert(User->getType() == WideType && "Checked before!");
		LLVM_DEBUG(dbgs() << "INDVARS: eliminating " << *User << " replaced by "
		<< *WideBO << "\n");
		++NumElimExt;
		User->replaceAllUsesWith(WideBO);
		DeadInsts.emplace_back(User);
		}
		return true;
		}

		/// Determine whether an individual user of the narrow IV can be widened. If so,
		/// return the wide clone of the user.
		Instruction *WidenIV::widenIVUse(WidenIV::NarrowIVDefUse DU, SCEVExpander &Rewriter) {
		assert(ExtendKindMap.count(DU.NarrowDef) &&
		"Should already know the kind of extension used to widen NarrowDef");

		// Stop traversing the def-use chain at inner-loop phis or post-loop phis.
		if (PHINode *UsePhi = dyn_cast<PHINode>(DU.NarrowUse)) {
		if (LI->getLoopFor(UsePhi->getParent()) != L) {
		// For LCSSA phis, sink the truncate outside the loop.
		// After SimplifyCFG most loop exit targets have a single predecessor.
		// Otherwise fall back to a truncate within the loop.
		if (UsePhi->getNumOperands() != 1)
		truncateIVUse(DU, DT, LI);
		else {
		// Widening the PHI requires us to insert a trunc. The logical place
		// for this trunc is in the same BB as the PHI. This is not possible if
		// the BB is terminated by a catchswitch.
		if (isa<CatchSwitchInst>(UsePhi->getParent()->getTerminator()))
		return nullptr;

		PHINode *WidePhi =
		PHINode::Create(DU.WideDef->getType(), 1, UsePhi->getName() + ".wide",
		UsePhi);
		WidePhi->addIncoming(DU.WideDef, UsePhi->getIncomingBlock(0));
		IRBuilder<> Builder(&*WidePhi->getParent()->getFirstInsertionPt());
		Value *Trunc = Builder.CreateTrunc(WidePhi, DU.NarrowDef->getType());
		UsePhi->replaceAllUsesWith(Trunc);
		DeadInsts.emplace_back(UsePhi);
		LLVM_DEBUG(dbgs() << "INDVARS: Widen lcssa phi " << *UsePhi << " to "
		<< *WidePhi << "\n");
		}
		return nullptr;
		}
		}

		// This narrow use can be widened by a sext if it's non-negative or its narrow
		// def was widended by a sext. Same for zext.
		auto canWidenBySExt = [&]() {
		return DU.NeverNegative \|\| getExtendKind(DU.NarrowDef) == SignExtended;
		};
		auto canWidenByZExt = [&]() {
		return DU.NeverNegative \|\| getExtendKind(DU.NarrowDef) == ZeroExtended;
		};

		// Our raison d'etre! Eliminate sign and zero extension.
		if ((isa<SExtInst>(DU.NarrowUse) && canWidenBySExt()) \|\|
		(isa<ZExtInst>(DU.NarrowUse) && canWidenByZExt())) {
		Value *NewDef = DU.WideDef;
		if (DU.NarrowUse->getType() != WideType) {
		unsigned CastWidth = SE->getTypeSizeInBits(DU.NarrowUse->getType());
		unsigned IVWidth = SE->getTypeSizeInBits(WideType);
		if (CastWidth < IVWidth) {
		// The cast isn't as wide as the IV, so insert a Trunc.
		IRBuilder<> Builder(DU.NarrowUse);
		NewDef = Builder.CreateTrunc(DU.WideDef, DU.NarrowUse->getType());
		}
		else {
		// A wider extend was hidden behind a narrower one. This may induce
		// another round of IV widening in which the intermediate IV becomes
		// dead. It should be very rare.
		LLVM_DEBUG(dbgs() << "INDVARS: New IV " << *WidePhi
		<< " not wide enough to subsume " << *DU.NarrowUse
		<< "\n");
		DU.NarrowUse->replaceUsesOfWith(DU.NarrowDef, DU.WideDef);
		NewDef = DU.NarrowUse;
		}
		}
		if (NewDef != DU.NarrowUse) {
		LLVM_DEBUG(dbgs() << "INDVARS: eliminating " << *DU.NarrowUse
		<< " replaced by " << *DU.WideDef << "\n");
		++NumElimExt;
		DU.NarrowUse->replaceAllUsesWith(NewDef);
		DeadInsts.emplace_back(DU.NarrowUse);
		}
		// Now that the extend is gone, we want to expose it's uses for potential
		// further simplification. We don't need to directly inform SimplifyIVUsers
		// of the new users, because their parent IV will be processed later as a
		// new loop phi. If we preserved IVUsers analysis, we would also want to
		// push the uses of WideDef here.

		// No further widening is needed. The deceased [sz]ext had done it for us.
		return nullptr;
		}

		// Does this user itself evaluate to a recurrence after widening?
		WidenedRecTy WideAddRec = getExtendedOperandRecurrence(DU);
		if (!WideAddRec.first)
		WideAddRec = getWideRecurrence(DU);

		assert((WideAddRec.first == nullptr) == (WideAddRec.second == Unknown));
		if (!WideAddRec.first) {
		// If use is a loop condition, try to promote the condition instead of
		// truncating the IV first.
		if (widenLoopCompare(DU))
		return nullptr;

		// We are here about to generate a truncate instruction that may hurt
		// performance because the scalar evolution expression computed earlier
		// in WideAddRec.first does not indicate a polynomial induction expression.
		// In that case, look at the operands of the use instruction to determine
		// if we can still widen the use instead of truncating its operand.
		if (widenWithVariantUse(DU))
		return nullptr;

		// This user does not evaluate to a recurrence after widening, so don't
		// follow it. Instead insert a Trunc to kill off the original use,
		// eventually isolating the original narrow IV so it can be removed.
		truncateIVUse(DU, DT, LI);
		return nullptr;
		}
		// Assume block terminators cannot evaluate to a recurrence. We can't to
		// insert a Trunc after a terminator if there happens to be a critical edge.
		assert(DU.NarrowUse != DU.NarrowUse->getParent()->getTerminator() &&
		"SCEV is not expected to evaluate a block terminator");

		// Reuse the IV increment that SCEVExpander created as long as it dominates
		// NarrowUse.
		Instruction *WideUse = nullptr;
		if (WideAddRec.first == WideIncExpr &&
		Rewriter.hoistIVInc(WideInc, DU.NarrowUse))
		WideUse = WideInc;
		else {
		WideUse = cloneIVUser(DU, WideAddRec.first);
		if (!WideUse)
		return nullptr;
		}
		// Evaluation of WideAddRec ensured that the narrow expression could be
		// extended outside the loop without overflow. This suggests that the wide use
		// evaluates to the same expression as the extended narrow use, but doesn't
		// absolutely guarantee it. Hence the following failsafe check. In rare cases
		// where it fails, we simply throw away the newly created wide use.
		if (WideAddRec.first != SE->getSCEV(WideUse)) {
		LLVM_DEBUG(dbgs() << "Wide use expression mismatch: " << *WideUse << ": "
		<< SE->getSCEV(WideUse) << " != " << WideAddRec.first
		<< "\n");
		DeadInsts.emplace_back(WideUse);
		return nullptr;
		}

		// if we reached this point then we are going to replace
		// DU.NarrowUse with WideUse. Reattach DbgValue then.
		replaceAllDbgUsesWith(DU.NarrowUse, WideUse, WideUse, DT);

		ExtendKindMap[DU.NarrowUse] = WideAddRec.second;
		// Returning WideUse pushes it on the worklist.
		return WideUse;
		}

		/// Add eligible users of NarrowDef to NarrowIVUsers.
		void WidenIV::pushNarrowIVUsers(Instruction NarrowDef, Instruction WideDef) {
		const SCEV *NarrowSCEV = SE->getSCEV(NarrowDef);
		bool NonNegativeDef =
		SE->isKnownPredicate(ICmpInst::ICMP_SGE, NarrowSCEV,
		SE->getZero(NarrowSCEV->getType()));
		for (User *U : NarrowDef->users()) {
		Instruction *NarrowUser = cast<Instruction>(U);

		// Handle data flow merges and bizarre phi cycles.
		if (!Widened.insert(NarrowUser).second)
		continue;

		bool NonNegativeUse = false;
		if (!NonNegativeDef) {
		// We might have a control-dependent range information for this context.
		if (auto RangeInfo = getPostIncRangeInfo(NarrowDef, NarrowUser))
		NonNegativeUse = RangeInfo->getSignedMin().isNonNegative();
		}

		NarrowIVUsers.emplace_back(NarrowDef, NarrowUser, WideDef,
		NonNegativeDef \|\| NonNegativeUse);
		}
		}

		/// Process a single induction variable. First use the SCEVExpander to create a
		/// wide induction variable that evaluates to the same recurrence as the
		/// original narrow IV. Then use a worklist to forward traverse the narrow IV's
		/// def-use chain. After widenIVUse has processed all interesting IV users, the
		/// narrow IV will be isolated for removal by DeleteDeadPHIs.
		///
		/// It would be simpler to delete uses as they are processed, but we must avoid
		/// invalidating SCEV expressions.
		PHINode *WidenIV::createWideIV(SCEVExpander &Rewriter) {
		// Is this phi an induction variable?
		const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(OrigPhi));
		if (!AddRec)
		return nullptr;

		// Widen the induction variable expression.
		const SCEV *WideIVExpr = getExtendKind(OrigPhi) == SignExtended
		? SE->getSignExtendExpr(AddRec, WideType)
		: SE->getZeroExtendExpr(AddRec, WideType);

		assert(SE->getEffectiveSCEVType(WideIVExpr->getType()) == WideType &&
		"Expect the new IV expression to preserve its type");

		// Can the IV be extended outside the loop without overflow?
		AddRec = dyn_cast<SCEVAddRecExpr>(WideIVExpr);
		if (!AddRec \|\| AddRec->getLoop() != L)
		return nullptr;

		// An AddRec must have loop-invariant operands. Since this AddRec is
		// materialized by a loop header phi, the expression cannot have any post-loop
		// operands, so they must dominate the loop header.
		assert(
		SE->properlyDominates(AddRec->getStart(), L->getHeader()) &&
		SE->properlyDominates(AddRec->getStepRecurrence(*SE), L->getHeader()) &&
		"Loop header phi recurrence inputs do not dominate the loop");

		// Iterate over IV uses (including transitive ones) looking for IV increments
		// of the form 'add nsw %iv, <const>'. For each increment and each use of
		// the increment calculate control-dependent range information basing on
		// dominating conditions inside of the loop (e.g. a range check inside of the
		// loop). Calculated ranges are stored in PostIncRangeInfos map.
		//
		// Control-dependent range information is later used to prove that a narrow
		// definition is not negative (see pushNarrowIVUsers). It's difficult to do
		// this on demand because when pushNarrowIVUsers needs this information some
		// of the dominating conditions might be already widened.
		if (UsePostIncrementRanges)
		calculatePostIncRanges(OrigPhi);

		// The rewriter provides a value for the desired IV expression. This may
		// either find an existing phi or materialize a new one. Either way, we
		// expect a well-formed cyclic phi-with-increments. i.e. any operand not part
		// of the phi-SCC dominates the loop entry.
		Instruction InsertPt = &L->getHeader()->getFirstInsertionPt();
		Value *ExpandInst = Rewriter.expandCodeFor(AddRec, WideType, InsertPt);
		// If the wide phi is not a phi node, for example a cast node, like bitcast,
		// inttoptr, ptrtoint, just skip for now.
		if (!(WidePhi = dyn_cast<PHINode>(ExpandInst))) {
		// if the cast node is an inserted instruction without any user, we should
		// remove it to make sure the pass don't touch the function as we can not
		// wide the phi.
		if (ExpandInst->hasNUses(0) &&
		Rewriter.isInsertedInstruction(cast<Instruction>(ExpandInst)))
		DeadInsts.emplace_back(ExpandInst);
		return nullptr;
		}

		// Remembering the WideIV increment generated by SCEVExpander allows
		// widenIVUse to reuse it when widening the narrow IV's increment. We don't
		// employ a general reuse mechanism because the call above is the only call to
		// SCEVExpander. Henceforth, we produce 1-to-1 narrow to wide uses.
		if (BasicBlock *LatchBlock = L->getLoopLatch()) {
		WideInc =
		cast<Instruction>(WidePhi->getIncomingValueForBlock(LatchBlock));
		WideIncExpr = SE->getSCEV(WideInc);
		// Propagate the debug location associated with the original loop increment
		// to the new (widened) increment.
		auto *OrigInc =
		cast<Instruction>(OrigPhi->getIncomingValueForBlock(LatchBlock));
		WideInc->setDebugLoc(OrigInc->getDebugLoc());
		}

		LLVM_DEBUG(dbgs() << "Wide IV: " << *WidePhi << "\n");
		++NumWidened;

		// Traverse the def-use chain using a worklist starting at the original IV.
		assert(Widened.empty() && NarrowIVUsers.empty() && "expect initial state" );

		Widened.insert(OrigPhi);
		pushNarrowIVUsers(OrigPhi, WidePhi);

		while (!NarrowIVUsers.empty()) {
		WidenIV::NarrowIVDefUse DU = NarrowIVUsers.pop_back_val();

		// Process a def-use edge. This may replace the use, so don't hold a
		// use_iterator across it.
		Instruction *WideUse = widenIVUse(DU, Rewriter);

		// Follow all def-use edges from the previous narrow use.
		if (WideUse)
		pushNarrowIVUsers(DU.NarrowUse, WideUse);

		// widenIVUse may have removed the def-use edge.
		if (DU.NarrowDef->use_empty())
		DeadInsts.emplace_back(DU.NarrowDef);
		}

		// Attach any debug information to the new PHI.
		replaceAllDbgUsesWith(OrigPhi, WidePhi, WidePhi, DT);

		return WidePhi;
		}

		/// Calculates control-dependent range for the given def at the given context
		/// by looking at dominating conditions inside of the loop
		void WidenIV::calculatePostIncRange(Instruction *NarrowDef,
		Instruction *NarrowUser) {
		using namespace llvm::PatternMatch;

		Value *NarrowDefLHS;
		const APInt *NarrowDefRHS;
		if (!match(NarrowDef, m_NSWAdd(m_Value(NarrowDefLHS),
		m_APInt(NarrowDefRHS))) \|\|
		!NarrowDefRHS->isNonNegative())
		return;

		auto UpdateRangeFromCondition = [&] (Value *Condition,
		bool TrueDest) {
		CmpInst::Predicate Pred;
		Value *CmpRHS;
		if (!match(Condition, m_ICmp(Pred, m_Specific(NarrowDefLHS),
		m_Value(CmpRHS))))
		return;

		CmpInst::Predicate P =
		TrueDest ? Pred : CmpInst::getInversePredicate(Pred);

		auto CmpRHSRange = SE->getSignedRange(SE->getSCEV(CmpRHS));
		auto CmpConstrainedLHSRange =
		ConstantRange::makeAllowedICmpRegion(P, CmpRHSRange);
		auto NarrowDefRange = CmpConstrainedLHSRange.addWithNoWrap(
		*NarrowDefRHS, OverflowingBinaryOperator::NoSignedWrap);

		updatePostIncRangeInfo(NarrowDef, NarrowUser, NarrowDefRange);
		};

		auto UpdateRangeFromGuards = [&](Instruction *Ctx) {
		if (!HasGuards)
		return;

		for (Instruction &I : make_range(Ctx->getIterator().getReverse(),
		Ctx->getParent()->rend())) {
		Value *C = nullptr;
		if (match(&I, m_Intrinsic<Intrinsic::experimental_guard>(m_Value(C))))
		UpdateRangeFromCondition(C, /TrueDest=/true);
		}
		};

		UpdateRangeFromGuards(NarrowUser);

		BasicBlock *NarrowUserBB = NarrowUser->getParent();
		// If NarrowUserBB is statically unreachable asking dominator queries may
		// yield surprising results. (e.g. the block may not have a dom tree node)
		if (!DT->isReachableFromEntry(NarrowUserBB))
		return;

		for (auto DTB = (DT)[NarrowUserBB]->getIDom();
		L->contains(DTB->getBlock());
		DTB = DTB->getIDom()) {
		auto *BB = DTB->getBlock();
		auto *TI = BB->getTerminator();
		UpdateRangeFromGuards(TI);

		auto *BI = dyn_cast<BranchInst>(TI);
		if (!BI \|\| !BI->isConditional())
		continue;

		auto *TrueSuccessor = BI->getSuccessor(0);
		auto *FalseSuccessor = BI->getSuccessor(1);

		auto DominatesNarrowUser = [this, NarrowUser] (BasicBlockEdge BBE) {
		return BBE.isSingleEdge() &&
		DT->dominates(BBE, NarrowUser->getParent());
		};

		if (DominatesNarrowUser(BasicBlockEdge(BB, TrueSuccessor)))
		UpdateRangeFromCondition(BI->getCondition(), /TrueDest=/true);

		if (DominatesNarrowUser(BasicBlockEdge(BB, FalseSuccessor)))
		UpdateRangeFromCondition(BI->getCondition(), /TrueDest=/false);
		}
		}

		/// Calculates PostIncRangeInfos map for the given IV
		void WidenIV::calculatePostIncRanges(PHINode *OrigPhi) {
		SmallPtrSet<Instruction *, 16> Visited;
		SmallVector<Instruction *, 6> Worklist;
		Worklist.push_back(OrigPhi);
		Visited.insert(OrigPhi);

		while (!Worklist.empty()) {
		Instruction *NarrowDef = Worklist.pop_back_val();

		for (Use &U : NarrowDef->uses()) {
		auto *NarrowUser = cast<Instruction>(U.getUser());

		// Don't go looking outside the current loop.
		auto NarrowUserLoop = (LI)[NarrowUser->getParent()];
		if (!NarrowUserLoop \|\| !L->contains(NarrowUserLoop))
		continue;

		if (!Visited.insert(NarrowUser).second)
		continue;

		Worklist.push_back(NarrowUser);

		calculatePostIncRange(NarrowDef, NarrowUser);
		}
		}
		}

		PHINode *llvm::createWideIV(WideIVInfo &WI,
		LoopInfo LI, ScalarEvolution SE, SCEVExpander &Rewriter,
		DominatorTree *DT, SmallVectorImpl<WeakTrackingVH> &DeadInsts,
		unsigned &NumElimExt, unsigned &NumWidened,
		bool HasGuards, bool UsePostIncrementRanges) {
		WidenIV Widener(WI, LI, SE, DT, DeadInsts, HasGuards, UsePostIncrementRanges);
		PHINode *WidePHI = Widener.createWideIV(Rewriter);
		NumElimExt = Widener.getNumElimExt();
		NumWidened = Widener.getNumWidened();
		return WidePHI;
		}

This is an archive of the discontinued LLVM Phabricator instance.

[IndVarSimplify][SimplifyIndVar] Move WidenIV to Utils/SimplifyIndVar. NFCI.
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llvm/include/llvm/Transforms/Utils/SimplifyIndVar.h

llvm/lib/Transforms/Scalar/IndVarSimplify.cpp

llvm/lib/Transforms/Utils/SimplifyIndVar.cpp

This is an archive of the discontinued LLVM Phabricator instance.

[IndVarSimplify][SimplifyIndVar] Move WidenIV to Utils/SimplifyIndVar. NFCI.ClosedPublic

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llvm/include/llvm/Transforms/Utils/SimplifyIndVar.h

llvm/lib/Transforms/Scalar/IndVarSimplify.cpp

llvm/lib/Transforms/Utils/SimplifyIndVar.cpp

[IndVarSimplify][SimplifyIndVar] Move WidenIV to Utils/SimplifyIndVar. NFCI.
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