//
// The LLVM Compiler Infrastructure
//
-// This file was developed by Nate Begeman and is distributed under the
-// University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Target/TargetData.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Compiler.h"
#include <set>
using namespace llvm;
-STATISTIC(NumReduced , "Number of GEPs strength reduced");
-STATISTIC(NumInserted, "Number of PHIs inserted");
-STATISTIC(NumVariable, "Number of PHIs with variable strides");
+STATISTIC(NumReduced , "Number of GEPs strength reduced");
+STATISTIC(NumInserted, "Number of PHIs inserted");
+STATISTIC(NumVariable, "Number of PHIs with variable strides");
+STATISTIC(NumEliminated, "Number of strides eliminated");
+STATISTIC(NumShadow, "Number of Shadow IVs optimized");
namespace {
/// IVStrideUse - Keep track of one use of a strided induction variable, where
/// the stride is stored externally. The Offset member keeps track of the
- /// offset from the IV, User is the actual user of the operand, and 'Operand'
- /// is the operand # of the User that is the use.
+ /// offset from the IV, User is the actual user of the operand, and
+ /// 'OperandValToReplace' is the operand of the User that is the use.
struct VISIBILITY_HIDDEN IVStrideUse {
SCEVHandle Offset;
Instruction *User;
PHINode *PHI;
Value *IncV;
- IVExpr()
- : Stride(SCEVUnknown::getIntegerSCEV(0, Type::Int32Ty)),
- Base (SCEVUnknown::getIntegerSCEV(0, Type::Int32Ty)) {}
IVExpr(const SCEVHandle &stride, const SCEVHandle &base, PHINode *phi,
Value *incv)
: Stride(stride), Base(base), PHI(phi), IncV(incv) {}
/// StrideOrder - An ordering of the keys in IVUsesByStride that is stable:
/// We use this to iterate over the IVUsesByStride collection without being
/// dependent on random ordering of pointers in the process.
- std::vector<SCEVHandle> StrideOrder;
+ SmallVector<SCEVHandle, 16> StrideOrder;
/// CastedValues - As we need to cast values to uintptr_t, this keeps track
/// of the casted version of each value. This is accessed by
/// getCastedVersionOf.
- std::map<Value*, Value*> CastedPointers;
+ DenseMap<Value*, Value*> CastedPointers;
/// DeadInsts - Keep track of instructions we may have made dead, so that
/// we can remove them after we are done working.
- std::set<Instruction*> DeadInsts;
+ SetVector<Instruction*> DeadInsts;
/// TLI - Keep a pointer of a TargetLowering to consult for determining
/// transformation profitability.
public:
static char ID; // Pass ID, replacement for typeid
explicit LoopStrengthReduce(const TargetLowering *tli = NULL) :
- LoopPass((intptr_t)&ID), TLI(tli) {
+ LoopPass(&ID), TLI(tli) {
}
bool runOnLoop(Loop *L, LPPassManager &LPM);
AU.addRequired<DominatorTree>();
AU.addRequired<TargetData>();
AU.addRequired<ScalarEvolution>();
+ AU.addPreserved<ScalarEvolution>();
}
/// getCastedVersionOf - Return the specified value casted to uintptr_t.
Value *getCastedVersionOf(Instruction::CastOps opcode, Value *V);
private:
bool AddUsersIfInteresting(Instruction *I, Loop *L,
- std::set<Instruction*> &Processed);
- SCEVHandle GetExpressionSCEV(Instruction *E, Loop *L);
-
+ SmallPtrSet<Instruction*,16> &Processed);
+ SCEVHandle GetExpressionSCEV(Instruction *E);
+ ICmpInst *ChangeCompareStride(Loop *L, ICmpInst *Cond,
+ IVStrideUse* &CondUse,
+ const SCEVHandle* &CondStride);
void OptimizeIndvars(Loop *L);
- bool FindIVForUser(ICmpInst *Cond, IVStrideUse *&CondUse,
- const SCEVHandle *&CondStride);
- unsigned CheckForIVReuse(const SCEVHandle&, IVExpr&, const Type*,
- const std::vector<BasedUser>& UsersToProcess);
+ /// OptimizeShadowIV - If IV is used in a int-to-float cast
+ /// inside the loop then try to eliminate the cast opeation.
+ void OptimizeShadowIV(Loop *L);
- bool ValidStride(int64_t, const std::vector<BasedUser>& UsersToProcess);
+ /// OptimizeSMax - Rewrite the loop's terminating condition
+ /// if it uses an smax computation.
+ ICmpInst *OptimizeSMax(Loop *L, ICmpInst *Cond,
+ IVStrideUse* &CondUse);
+ bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
+ const SCEVHandle *&CondStride);
+ bool RequiresTypeConversion(const Type *Ty, const Type *NewTy);
+ unsigned CheckForIVReuse(bool, bool, const SCEVHandle&,
+ IVExpr&, const Type*,
+ const std::vector<BasedUser>& UsersToProcess);
+ bool ValidStride(bool, int64_t,
+ const std::vector<BasedUser>& UsersToProcess);
+ SCEVHandle CollectIVUsers(const SCEVHandle &Stride,
+ IVUsersOfOneStride &Uses,
+ Loop *L,
+ bool &AllUsesAreAddresses,
+ std::vector<BasedUser> &UsersToProcess);
void StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
IVUsersOfOneStride &Uses,
Loop *L, bool isOnlyStride);
- void DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts);
+ void DeleteTriviallyDeadInstructions(SetVector<Instruction*> &Insts);
};
- char LoopStrengthReduce::ID = 0;
- RegisterPass<LoopStrengthReduce> X("loop-reduce", "Loop Strength Reduction");
}
-LoopPass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
+char LoopStrengthReduce::ID = 0;
+static RegisterPass<LoopStrengthReduce>
+X("loop-reduce", "Loop Strength Reduction");
+
+Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
return new LoopStrengthReduce(TLI);
}
/// specified set are trivially dead, delete them and see if this makes any of
/// their operands subsequently dead.
void LoopStrengthReduce::
-DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts) {
+DeleteTriviallyDeadInstructions(SetVector<Instruction*> &Insts) {
while (!Insts.empty()) {
- Instruction *I = *Insts.begin();
- Insts.erase(Insts.begin());
+ Instruction *I = Insts.back();
+ Insts.pop_back();
+
+ if (PHINode *PN = dyn_cast<PHINode>(I)) {
+ // If all incoming values to the Phi are the same, we can replace the Phi
+ // with that value.
+ if (Value *PNV = PN->hasConstantValue()) {
+ if (Instruction *U = dyn_cast<Instruction>(PNV))
+ Insts.insert(U);
+ SE->deleteValueFromRecords(PN);
+ PN->replaceAllUsesWith(PNV);
+ PN->eraseFromParent();
+ Changed = true;
+ continue;
+ }
+ }
+
if (isInstructionTriviallyDead(I)) {
- for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
- if (Instruction *U = dyn_cast<Instruction>(I->getOperand(i)))
+ for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
+ if (Instruction *U = dyn_cast<Instruction>(*i))
Insts.insert(U);
SE->deleteValueFromRecords(I);
I->eraseFromParent();
/// GetExpressionSCEV - Compute and return the SCEV for the specified
/// instruction.
-SCEVHandle LoopStrengthReduce::GetExpressionSCEV(Instruction *Exp, Loop *L) {
+SCEVHandle LoopStrengthReduce::GetExpressionSCEV(Instruction *Exp) {
// Pointer to pointer bitcast instructions return the same value as their
// operand.
if (BitCastInst *BCI = dyn_cast<BitCastInst>(Exp)) {
if (SE->hasSCEV(BCI) || !isa<Instruction>(BCI->getOperand(0)))
return SE->getSCEV(BCI);
- SCEVHandle R = GetExpressionSCEV(cast<Instruction>(BCI->getOperand(0)), L);
+ SCEVHandle R = GetExpressionSCEV(cast<Instruction>(BCI->getOperand(0)));
SE->setSCEV(BCI, R);
return R;
}
return SE->getSCEV(Exp);
// Analyze all of the subscripts of this getelementptr instruction, looking
- // for uses that are determined by the trip count of L. First, skip all
- // operands the are not dependent on the IV.
+ // for uses that are determined by the trip count of the loop. First, skip
+ // all operands the are not dependent on the IV.
// Build up the base expression. Insert an LLVM cast of the pointer to
// uintptr_t first.
- SCEVHandle GEPVal = SCEVUnknown::get(
+ SCEVHandle GEPVal = SE->getUnknown(
getCastedVersionOf(Instruction::PtrToInt, GEP->getOperand(0)));
gep_type_iterator GTI = gep_type_begin(GEP);
- for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i, ++GTI) {
+ for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
+ i != e; ++i, ++GTI) {
// If this is a use of a recurrence that we can analyze, and it comes before
// Op does in the GEP operand list, we will handle this when we process this
// operand.
if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
const StructLayout *SL = TD->getStructLayout(STy);
- unsigned Idx = cast<ConstantInt>(GEP->getOperand(i))->getZExtValue();
+ unsigned Idx = cast<ConstantInt>(*i)->getZExtValue();
uint64_t Offset = SL->getElementOffset(Idx);
- GEPVal = SCEVAddExpr::get(GEPVal,
- SCEVUnknown::getIntegerSCEV(Offset, UIntPtrTy));
+ GEPVal = SE->getAddExpr(GEPVal,
+ SE->getIntegerSCEV(Offset, UIntPtrTy));
} else {
unsigned GEPOpiBits =
- GEP->getOperand(i)->getType()->getPrimitiveSizeInBits();
+ (*i)->getType()->getPrimitiveSizeInBits();
unsigned IntPtrBits = UIntPtrTy->getPrimitiveSizeInBits();
Instruction::CastOps opcode = (GEPOpiBits < IntPtrBits ?
Instruction::SExt : (GEPOpiBits > IntPtrBits ? Instruction::Trunc :
Instruction::BitCast));
- Value *OpVal = getCastedVersionOf(opcode, GEP->getOperand(i));
+ Value *OpVal = getCastedVersionOf(opcode, *i);
SCEVHandle Idx = SE->getSCEV(OpVal);
- uint64_t TypeSize = TD->getTypeSize(GTI.getIndexedType());
+ uint64_t TypeSize = TD->getABITypeSize(GTI.getIndexedType());
if (TypeSize != 1)
- Idx = SCEVMulExpr::get(Idx,
- SCEVConstant::get(ConstantInt::get(UIntPtrTy,
- TypeSize)));
- GEPVal = SCEVAddExpr::get(GEPVal, Idx);
+ Idx = SE->getMulExpr(Idx,
+ SE->getConstant(ConstantInt::get(UIntPtrTy,
+ TypeSize)));
+ GEPVal = SE->getAddExpr(GEPVal, Idx);
}
}
/// is. The stride must be a loop invariant expression, but the start may be
/// a mix of loop invariant and loop variant expressions.
static bool getSCEVStartAndStride(const SCEVHandle &SH, Loop *L,
- SCEVHandle &Start, SCEVHandle &Stride) {
+ SCEVHandle &Start, SCEVHandle &Stride,
+ ScalarEvolution *SE) {
SCEVHandle TheAddRec = Start; // Initialize to zero.
// If the outer level is an AddExpr, the operands are all start values except
if (SCEVAddRecExpr *AddRec =
dyn_cast<SCEVAddRecExpr>(AE->getOperand(i))) {
if (AddRec->getLoop() == L)
- TheAddRec = SCEVAddExpr::get(AddRec, TheAddRec);
+ TheAddRec = SE->getAddExpr(AddRec, TheAddRec);
else
return false; // Nested IV of some sort?
} else {
- Start = SCEVAddExpr::get(Start, AE->getOperand(i));
+ Start = SE->getAddExpr(Start, AE->getOperand(i));
}
} else if (isa<SCEVAddRecExpr>(SH)) {
// FIXME: Generalize to non-affine IV's.
if (!AddRec->isAffine()) return false;
- Start = SCEVAddExpr::get(Start, AddRec->getOperand(0));
+ Start = SE->getAddExpr(Start, AddRec->getOperand(0));
if (!isa<SCEVConstant>(AddRec->getOperand(1)))
DOUT << "[" << L->getHeader()->getName()
/// the loop, resulting in reg-reg copies (if we use the pre-inc value when we
/// should use the post-inc value).
static bool IVUseShouldUsePostIncValue(Instruction *User, Instruction *IV,
- Loop *L, DominatorTree *DT, Pass *P) {
+ Loop *L, DominatorTree *DT, Pass *P,
+ SetVector<Instruction*> &DeadInsts){
// If the user is in the loop, use the preinc value.
if (L->contains(User->getParent())) return false;
// post-incremented value.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingValue(i) == IV) {
- SplitCriticalEdge(PN->getIncomingBlock(i), PN->getParent(), P,
- true);
+ SplitCriticalEdge(PN->getIncomingBlock(i), PN->getParent(), P, false);
// Splitting the critical edge can reduce the number of entries in this
// PHI.
e = PN->getNumIncomingValues();
if (--NumUses == 0) break;
}
+
+ // PHI node might have become a constant value after SplitCriticalEdge.
+ DeadInsts.insert(User);
return true;
}
/// reducible SCEV, recursively add its users to the IVUsesByStride set and
/// return true. Otherwise, return false.
bool LoopStrengthReduce::AddUsersIfInteresting(Instruction *I, Loop *L,
- std::set<Instruction*> &Processed) {
+ SmallPtrSet<Instruction*,16> &Processed) {
if (!I->getType()->isInteger() && !isa<PointerType>(I->getType()))
- return false; // Void and FP expressions cannot be reduced.
- if (!Processed.insert(I).second)
+ return false; // Void and FP expressions cannot be reduced.
+ if (!Processed.insert(I))
return true; // Instruction already handled.
// Get the symbolic expression for this instruction.
- SCEVHandle ISE = GetExpressionSCEV(I, L);
+ SCEVHandle ISE = GetExpressionSCEV(I);
if (isa<SCEVCouldNotCompute>(ISE)) return false;
// Get the start and stride for this expression.
- SCEVHandle Start = SCEVUnknown::getIntegerSCEV(0, ISE->getType());
+ SCEVHandle Start = SE->getIntegerSCEV(0, ISE->getType());
SCEVHandle Stride = Start;
- if (!getSCEVStartAndStride(ISE, L, Start, Stride))
+ if (!getSCEVStartAndStride(ISE, L, Start, Stride, SE))
return false; // Non-reducible symbolic expression, bail out.
std::vector<Instruction *> IUsers;
// Okay, we found a user that we cannot reduce. Analyze the instruction
// and decide what to do with it. If we are a use inside of the loop, use
// the value before incrementation, otherwise use it after incrementation.
- if (IVUseShouldUsePostIncValue(User, I, L, DT, this)) {
+ if (IVUseShouldUsePostIncValue(User, I, L, DT, this, DeadInsts)) {
// The value used will be incremented by the stride more than we are
// expecting, so subtract this off.
- SCEVHandle NewStart = SCEV::getMinusSCEV(Start, Stride);
+ SCEVHandle NewStart = SE->getMinusSCEV(Start, Stride);
StrideUses.addUser(NewStart, User, I);
StrideUses.Users.back().isUseOfPostIncrementedValue = true;
DOUT << " USING POSTINC SCEV, START=" << *NewStart<< "\n";
/// BasedUser - For a particular base value, keep information about how we've
/// partitioned the expression so far.
struct BasedUser {
+ /// SE - The current ScalarEvolution object.
+ ScalarEvolution *SE;
+
/// Base - The Base value for the PHI node that needs to be inserted for
/// this use. As the use is processed, information gets moved from this
/// field to the Imm field (below). BasedUser values are sorted by this
// the loop.
bool isUseOfPostIncrementedValue;
- BasedUser(IVStrideUse &IVSU)
- : Base(IVSU.Offset), Inst(IVSU.User),
+ BasedUser(IVStrideUse &IVSU, ScalarEvolution *se)
+ : SE(se), Base(IVSU.Offset), Inst(IVSU.User),
OperandValToReplace(IVSU.OperandValToReplace),
- Imm(SCEVUnknown::getIntegerSCEV(0, Base->getType())), EmittedBase(0),
+ Imm(SE->getIntegerSCEV(0, Base->getType())), EmittedBase(0),
isUseOfPostIncrementedValue(IVSU.isUseOfPostIncrementedValue) {}
// Once we rewrite the code to insert the new IVs we want, update the
// operands of Inst to use the new expression 'NewBase', with 'Imm' added
// to it.
void RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
- SCEVExpander &Rewriter, Loop *L,
- Pass *P);
+ Instruction *InsertPt,
+ SCEVExpander &Rewriter, Loop *L, Pass *P,
+ SetVector<Instruction*> &DeadInsts);
Value *InsertCodeForBaseAtPosition(const SCEVHandle &NewBase,
SCEVExpander &Rewriter,
}
// If there is no immediate value, skip the next part.
- if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Imm))
- if (SC->getValue()->isZero())
- return Rewriter.expandCodeFor(NewBase, BaseInsertPt);
+ if (Imm->isZero())
+ return Rewriter.expandCodeFor(NewBase, BaseInsertPt);
Value *Base = Rewriter.expandCodeFor(NewBase, BaseInsertPt);
IP = Rewriter.getInsertionPoint();
// Always emit the immediate (if non-zero) into the same block as the user.
- SCEVHandle NewValSCEV = SCEVAddExpr::get(SCEVUnknown::get(Base), Imm);
+ SCEVHandle NewValSCEV = SE->getAddExpr(SE->getUnknown(Base), Imm);
return Rewriter.expandCodeFor(NewValSCEV, IP);
}
// Once we rewrite the code to insert the new IVs we want, update the
// operands of Inst to use the new expression 'NewBase', with 'Imm' added
-// to it.
+// to it. NewBasePt is the last instruction which contributes to the
+// value of NewBase in the case that it's a diffferent instruction from
+// the PHI that NewBase is computed from, or null otherwise.
+//
void BasedUser::RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
- SCEVExpander &Rewriter,
- Loop *L, Pass *P) {
+ Instruction *NewBasePt,
+ SCEVExpander &Rewriter, Loop *L, Pass *P,
+ SetVector<Instruction*> &DeadInsts) {
if (!isa<PHINode>(Inst)) {
// By default, insert code at the user instruction.
BasicBlock::iterator InsertPt = Inst;
// value will be pinned to live somewhere after the original computation.
// In this case, we have to back off.
if (!isUseOfPostIncrementedValue) {
- if (Instruction *OpInst = dyn_cast<Instruction>(OperandValToReplace)) {
+ if (NewBasePt && isa<PHINode>(OperandValToReplace)) {
+ InsertPt = NewBasePt;
+ ++InsertPt;
+ } else if (Instruction *OpInst
+ = dyn_cast<Instruction>(OperandValToReplace)) {
InsertPt = OpInst;
while (isa<PHINode>(InsertPt)) ++InsertPt;
}
// have multiple entries for the same predecessor. We use a map to make sure
// that a PHI node only has a single Value* for each predecessor (which also
// prevents us from inserting duplicate code in some blocks).
- std::map<BasicBlock*, Value*> InsertedCode;
+ DenseMap<BasicBlock*, Value*> InsertedCode;
PHINode *PN = cast<PHINode>(Inst);
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
if (PN->getIncomingValue(i) == OperandValToReplace) {
(PN->getParent() != L->getHeader() || !L->contains(PHIPred))) {
// First step, split the critical edge.
- SplitCriticalEdge(PHIPred, PN->getParent(), P, true);
+ SplitCriticalEdge(PHIPred, PN->getParent(), P, false);
// Next step: move the basic block. In particular, if the PHI node
// is outside of the loop, and PredTI is in the loop, we want to
Instruction *InsertPt = PN->getIncomingBlock(i)->getTerminator();
Code = InsertCodeForBaseAtPosition(NewBase, Rewriter, InsertPt, L);
- // Adjust the type back to match the PHI. Note that we can't use InsertPt
- // here because the SCEVExpander may have inserted its instructions after
- // that point, in its efforts to avoid inserting redundant expressions.
+ // Adjust the type back to match the PHI. Note that we can't use
+ // InsertPt here because the SCEVExpander may have inserted its
+ // instructions after that point, in its efforts to avoid inserting
+ // redundant expressions.
if (isa<PointerType>(PN->getType())) {
Code = SCEVExpander::InsertCastOfTo(Instruction::IntToPtr,
Code,
Rewriter.clear();
}
}
+
+ // PHI node might have become a constant value after SplitCriticalEdge.
+ DeadInsts.insert(Inst);
+
DOUT << " CHANGED: IMM =" << *Imm << " Inst = " << *Inst;
}
/// MoveLoopVariantsToImediateField - Move any subexpressions from Val that are
/// loop varying to the Imm operand.
static void MoveLoopVariantsToImediateField(SCEVHandle &Val, SCEVHandle &Imm,
- Loop *L) {
+ Loop *L, ScalarEvolution *SE) {
if (Val->isLoopInvariant(L)) return; // Nothing to do.
if (SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
if (!SAE->getOperand(i)->isLoopInvariant(L)) {
// If this is a loop-variant expression, it must stay in the immediate
// field of the expression.
- Imm = SCEVAddExpr::get(Imm, SAE->getOperand(i));
+ Imm = SE->getAddExpr(Imm, SAE->getOperand(i));
} else {
NewOps.push_back(SAE->getOperand(i));
}
if (NewOps.empty())
- Val = SCEVUnknown::getIntegerSCEV(0, Val->getType());
+ Val = SE->getIntegerSCEV(0, Val->getType());
else
- Val = SCEVAddExpr::get(NewOps);
+ Val = SE->getAddExpr(NewOps);
} else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
// Try to pull immediates out of the start value of nested addrec's.
SCEVHandle Start = SARE->getStart();
- MoveLoopVariantsToImediateField(Start, Imm, L);
+ MoveLoopVariantsToImediateField(Start, Imm, L, SE);
std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
Ops[0] = Start;
- Val = SCEVAddRecExpr::get(Ops, SARE->getLoop());
+ Val = SE->getAddRecExpr(Ops, SARE->getLoop());
} else {
// Otherwise, all of Val is variant, move the whole thing over.
- Imm = SCEVAddExpr::get(Imm, Val);
- Val = SCEVUnknown::getIntegerSCEV(0, Val->getType());
+ Imm = SE->getAddExpr(Imm, Val);
+ Val = SE->getIntegerSCEV(0, Val->getType());
}
}
static void MoveImmediateValues(const TargetLowering *TLI,
Instruction *User,
SCEVHandle &Val, SCEVHandle &Imm,
- bool isAddress, Loop *L) {
+ bool isAddress, Loop *L,
+ ScalarEvolution *SE) {
const Type *UseTy = User->getType();
if (StoreInst *SI = dyn_cast<StoreInst>(User))
UseTy = SI->getOperand(0)->getType();
for (unsigned i = 0; i != SAE->getNumOperands(); ++i) {
SCEVHandle NewOp = SAE->getOperand(i);
- MoveImmediateValues(TLI, User, NewOp, Imm, isAddress, L);
+ MoveImmediateValues(TLI, User, NewOp, Imm, isAddress, L, SE);
if (!NewOp->isLoopInvariant(L)) {
// If this is a loop-variant expression, it must stay in the immediate
// field of the expression.
- Imm = SCEVAddExpr::get(Imm, NewOp);
+ Imm = SE->getAddExpr(Imm, NewOp);
} else {
NewOps.push_back(NewOp);
}
}
if (NewOps.empty())
- Val = SCEVUnknown::getIntegerSCEV(0, Val->getType());
+ Val = SE->getIntegerSCEV(0, Val->getType());
else
- Val = SCEVAddExpr::get(NewOps);
+ Val = SE->getAddExpr(NewOps);
return;
} else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
// Try to pull immediates out of the start value of nested addrec's.
SCEVHandle Start = SARE->getStart();
- MoveImmediateValues(TLI, User, Start, Imm, isAddress, L);
+ MoveImmediateValues(TLI, User, Start, Imm, isAddress, L, SE);
if (Start != SARE->getStart()) {
std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
Ops[0] = Start;
- Val = SCEVAddRecExpr::get(Ops, SARE->getLoop());
+ Val = SE->getAddRecExpr(Ops, SARE->getLoop());
}
return;
} else if (SCEVMulExpr *SME = dyn_cast<SCEVMulExpr>(Val)) {
if (isAddress && isTargetConstant(SME->getOperand(0), UseTy, TLI) &&
SME->getNumOperands() == 2 && SME->isLoopInvariant(L)) {
- SCEVHandle SubImm = SCEVUnknown::getIntegerSCEV(0, Val->getType());
+ SCEVHandle SubImm = SE->getIntegerSCEV(0, Val->getType());
SCEVHandle NewOp = SME->getOperand(1);
- MoveImmediateValues(TLI, User, NewOp, SubImm, isAddress, L);
+ MoveImmediateValues(TLI, User, NewOp, SubImm, isAddress, L, SE);
// If we extracted something out of the subexpressions, see if we can
// simplify this!
if (NewOp != SME->getOperand(1)) {
// Scale SubImm up by "8". If the result is a target constant, we are
// good.
- SubImm = SCEVMulExpr::get(SubImm, SME->getOperand(0));
+ SubImm = SE->getMulExpr(SubImm, SME->getOperand(0));
if (isTargetConstant(SubImm, UseTy, TLI)) {
// Accumulate the immediate.
- Imm = SCEVAddExpr::get(Imm, SubImm);
+ Imm = SE->getAddExpr(Imm, SubImm);
// Update what is left of 'Val'.
- Val = SCEVMulExpr::get(SME->getOperand(0), NewOp);
+ Val = SE->getMulExpr(SME->getOperand(0), NewOp);
return;
}
}
// expression.
if ((isAddress && isTargetConstant(Val, UseTy, TLI)) ||
!Val->isLoopInvariant(L)) {
- Imm = SCEVAddExpr::get(Imm, Val);
- Val = SCEVUnknown::getIntegerSCEV(0, Val->getType());
+ Imm = SE->getAddExpr(Imm, Val);
+ Val = SE->getIntegerSCEV(0, Val->getType());
return;
}
/// added together. This is used to reassociate common addition subexprs
/// together for maximal sharing when rewriting bases.
static void SeparateSubExprs(std::vector<SCEVHandle> &SubExprs,
- SCEVHandle Expr) {
+ SCEVHandle Expr,
+ ScalarEvolution *SE) {
if (SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(Expr)) {
for (unsigned j = 0, e = AE->getNumOperands(); j != e; ++j)
- SeparateSubExprs(SubExprs, AE->getOperand(j));
+ SeparateSubExprs(SubExprs, AE->getOperand(j), SE);
} else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Expr)) {
- SCEVHandle Zero = SCEVUnknown::getIntegerSCEV(0, Expr->getType());
+ SCEVHandle Zero = SE->getIntegerSCEV(0, Expr->getType());
if (SARE->getOperand(0) == Zero) {
SubExprs.push_back(Expr);
} else {
// Compute the addrec with zero as its base.
std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
Ops[0] = Zero; // Start with zero base.
- SubExprs.push_back(SCEVAddRecExpr::get(Ops, SARE->getLoop()));
+ SubExprs.push_back(SE->getAddRecExpr(Ops, SARE->getLoop()));
- SeparateSubExprs(SubExprs, SARE->getOperand(0));
+ SeparateSubExprs(SubExprs, SARE->getOperand(0), SE);
}
- } else if (!isa<SCEVConstant>(Expr) ||
- !cast<SCEVConstant>(Expr)->getValue()->isZero()) {
+ } else if (!Expr->isZero()) {
// Do not add zero.
SubExprs.push_back(Expr);
}
/// removed, accumulated, and returned. This looks for things like (a+b+c) and
/// (a+c+d) -> (a+c). The common expression is *removed* from the Bases.
static SCEVHandle
-RemoveCommonExpressionsFromUseBases(std::vector<BasedUser> &Uses) {
+RemoveCommonExpressionsFromUseBases(std::vector<BasedUser> &Uses,
+ ScalarEvolution *SE) {
unsigned NumUses = Uses.size();
// Only one use? Use its base, regardless of what it is!
- SCEVHandle Zero = SCEVUnknown::getIntegerSCEV(0, Uses[0].Base->getType());
+ SCEVHandle Zero = SE->getIntegerSCEV(0, Uses[0].Base->getType());
SCEVHandle Result = Zero;
if (NumUses == 1) {
std::swap(Result, Uses[0].Base);
if (Uses[i].Base == Zero) return Zero;
// Split the expression into subexprs.
- SeparateSubExprs(SubExprs, Uses[i].Base);
+ SeparateSubExprs(SubExprs, Uses[i].Base, SE);
// Add one to SubExpressionUseCounts for each subexpr present.
for (unsigned j = 0, e = SubExprs.size(); j != e; ++j)
if (++SubExpressionUseCounts[SubExprs[j]] == 1)
SubExpressionUseCounts.find(UniqueSubExprs[i]);
assert(I != SubExpressionUseCounts.end() && "Entry not found?");
if (I->second == NumUses) { // Found CSE!
- Result = SCEVAddExpr::get(Result, I->first);
+ Result = SE->getAddExpr(Result, I->first);
} else {
// Remove non-cse's from SubExpressionUseCounts.
SubExpressionUseCounts.erase(I);
// Otherwise, remove all of the CSE's we found from each of the base values.
for (unsigned i = 0; i != NumUses; ++i) {
// Split the expression into subexprs.
- SeparateSubExprs(SubExprs, Uses[i].Base);
+ SeparateSubExprs(SubExprs, Uses[i].Base, SE);
// Remove any common subexpressions.
for (unsigned j = 0, e = SubExprs.size(); j != e; ++j)
if (SubExprs.empty())
Uses[i].Base = Zero;
else
- Uses[i].Base = SCEVAddExpr::get(SubExprs);
+ Uses[i].Base = SE->getAddExpr(SubExprs);
SubExprs.clear();
}
return Result;
}
-/// isZero - returns true if the scalar evolution expression is zero.
-///
-static bool isZero(SCEVHandle &V) {
- if (SCEVConstant *SC = dyn_cast<SCEVConstant>(V))
- return SC->getValue()->isZero();
- return false;
-}
-
/// ValidStride - Check whether the given Scale is valid for all loads and
/// stores in UsersToProcess.
///
-bool LoopStrengthReduce::ValidStride(int64_t Scale,
+bool LoopStrengthReduce::ValidStride(bool HasBaseReg,
+ int64_t Scale,
const std::vector<BasedUser>& UsersToProcess) {
+ if (!TLI)
+ return true;
+
for (unsigned i=0, e = UsersToProcess.size(); i!=e; ++i) {
// If this is a load or other access, pass the type of the access in.
const Type *AccessTy = Type::VoidTy;
AccessTy = SI->getOperand(0)->getType();
else if (LoadInst *LI = dyn_cast<LoadInst>(UsersToProcess[i].Inst))
AccessTy = LI->getType();
+ else if (isa<PHINode>(UsersToProcess[i].Inst))
+ continue;
TargetLowering::AddrMode AM;
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(UsersToProcess[i].Imm))
AM.BaseOffs = SC->getValue()->getSExtValue();
+ AM.HasBaseReg = HasBaseReg || !UsersToProcess[i].Base->isZero();
AM.Scale = Scale;
// If load[imm+r*scale] is illegal, bail out.
return true;
}
+/// RequiresTypeConversion - Returns true if converting Ty to NewTy is not
+/// a nop.
+bool LoopStrengthReduce::RequiresTypeConversion(const Type *Ty1,
+ const Type *Ty2) {
+ if (Ty1 == Ty2)
+ return false;
+ if (TLI && TLI->isTruncateFree(Ty1, Ty2))
+ return false;
+ return (!Ty1->canLosslesslyBitCastTo(Ty2) &&
+ !(isa<PointerType>(Ty2) &&
+ Ty1->canLosslesslyBitCastTo(UIntPtrTy)) &&
+ !(isa<PointerType>(Ty1) &&
+ Ty2->canLosslesslyBitCastTo(UIntPtrTy)));
+}
+
/// CheckForIVReuse - Returns the multiple if the stride is the multiple
/// of a previous stride and it is a legal value for the target addressing
-/// mode scale component. This allows the users of this stride to be rewritten
-/// as prev iv * factor. It returns 0 if no reuse is possible.
-unsigned LoopStrengthReduce::CheckForIVReuse(const SCEVHandle &Stride,
+/// mode scale component and optional base reg. This allows the users of
+/// this stride to be rewritten as prev iv * factor. It returns 0 if no
+/// reuse is possible.
+unsigned LoopStrengthReduce::CheckForIVReuse(bool HasBaseReg,
+ bool AllUsesAreAddresses,
+ const SCEVHandle &Stride,
IVExpr &IV, const Type *Ty,
const std::vector<BasedUser>& UsersToProcess) {
- if (!TLI) return 0;
-
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Stride)) {
int64_t SInt = SC->getValue()->getSExtValue();
- if (SInt == 1) return 0;
-
- for (std::map<SCEVHandle, IVsOfOneStride>::iterator SI= IVsByStride.begin(),
- SE = IVsByStride.end(); SI != SE; ++SI) {
+ for (unsigned NewStride = 0, e = StrideOrder.size(); NewStride != e;
+ ++NewStride) {
+ std::map<SCEVHandle, IVsOfOneStride>::iterator SI =
+ IVsByStride.find(StrideOrder[NewStride]);
+ if (SI == IVsByStride.end())
+ continue;
int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
- if (SInt != -SSInt &&
+ if (SI->first != Stride &&
(unsigned(abs(SInt)) < SSInt || (SInt % SSInt) != 0))
continue;
int64_t Scale = SInt / SSInt;
// Check that this stride is valid for all the types used for loads and
// stores; if it can be used for some and not others, we might as well use
// the original stride everywhere, since we have to create the IV for it
- // anyway.
- if (ValidStride(Scale, UsersToProcess))
+ // anyway. If the scale is 1, then we don't need to worry about folding
+ // multiplications.
+ if (Scale == 1 ||
+ (AllUsesAreAddresses &&
+ ValidStride(HasBaseReg, Scale, UsersToProcess)))
for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
IE = SI->second.IVs.end(); II != IE; ++II)
// FIXME: Only handle base == 0 for now.
// Only reuse previous IV if it would not require a type conversion.
- if (isZero(II->Base) && II->Base->getType() == Ty) {
+ if (II->Base->isZero() &&
+ !RequiresTypeConversion(II->Base->getType(), Ty)) {
IV = *II;
return Scale;
}
return Val.isUseOfPostIncrementedValue;
}
-/// isNonConstantNegative - REturn true if the specified scev is negated, but
+/// isNonConstantNegative - Return true if the specified scev is negated, but
/// not a constant.
static bool isNonConstantNegative(const SCEVHandle &Expr) {
SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Expr);
return SC->getValue()->getValue().isNegative();
}
-/// StrengthReduceStridedIVUsers - Strength reduce all of the users of a single
-/// stride of IV. All of the users may have different starting values, and this
-/// may not be the only stride (we know it is if isOnlyStride is true).
-void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
- IVUsersOfOneStride &Uses,
- Loop *L,
- bool isOnlyStride) {
- // Transform our list of users and offsets to a bit more complex table. In
- // this new vector, each 'BasedUser' contains 'Base' the base of the
- // strided accessas well as the old information from Uses. We progressively
- // move information from the Base field to the Imm field, until we eventually
- // have the full access expression to rewrite the use.
- std::vector<BasedUser> UsersToProcess;
+/// isAddress - Returns true if the specified instruction is using the
+/// specified value as an address.
+static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
+ bool isAddress = isa<LoadInst>(Inst);
+ if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+ if (SI->getOperand(1) == OperandVal)
+ isAddress = true;
+ } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
+ // Addressing modes can also be folded into prefetches and a variety
+ // of intrinsics.
+ switch (II->getIntrinsicID()) {
+ default: break;
+ case Intrinsic::prefetch:
+ case Intrinsic::x86_sse2_loadu_dq:
+ case Intrinsic::x86_sse2_loadu_pd:
+ case Intrinsic::x86_sse_loadu_ps:
+ case Intrinsic::x86_sse_storeu_ps:
+ case Intrinsic::x86_sse2_storeu_pd:
+ case Intrinsic::x86_sse2_storeu_dq:
+ case Intrinsic::x86_sse2_storel_dq:
+ if (II->getOperand(1) == OperandVal)
+ isAddress = true;
+ break;
+ }
+ }
+ return isAddress;
+}
+
+// CollectIVUsers - Transform our list of users and offsets to a bit more
+// complex table. In this new vector, each 'BasedUser' contains 'Base', the base
+// of the strided accesses, as well as the old information from Uses. We
+// progressively move information from the Base field to the Imm field, until
+// we eventually have the full access expression to rewrite the use.
+SCEVHandle LoopStrengthReduce::CollectIVUsers(const SCEVHandle &Stride,
+ IVUsersOfOneStride &Uses,
+ Loop *L,
+ bool &AllUsesAreAddresses,
+ std::vector<BasedUser> &UsersToProcess) {
UsersToProcess.reserve(Uses.Users.size());
for (unsigned i = 0, e = Uses.Users.size(); i != e; ++i) {
- UsersToProcess.push_back(Uses.Users[i]);
+ UsersToProcess.push_back(BasedUser(Uses.Users[i], SE));
// Move any loop invariant operands from the offset field to the immediate
// field of the use, so that we don't try to use something before it is
// computed.
MoveLoopVariantsToImediateField(UsersToProcess.back().Base,
- UsersToProcess.back().Imm, L);
+ UsersToProcess.back().Imm, L, SE);
assert(UsersToProcess.back().Base->isLoopInvariant(L) &&
"Base value is not loop invariant!");
}
// "A+B"), emit it to the preheader, then remove the expression from the
// UsersToProcess base values.
SCEVHandle CommonExprs =
- RemoveCommonExpressionsFromUseBases(UsersToProcess);
-
+ RemoveCommonExpressionsFromUseBases(UsersToProcess, SE);
+
// Next, figure out what we can represent in the immediate fields of
// instructions. If we can represent anything there, move it to the imm
// fields of the BasedUsers. We do this so that it increases the commonality
// of the remaining uses.
+ unsigned NumPHI = 0;
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
// If the user is not in the current loop, this means it is using the exit
// value of the IV. Do not put anything in the base, make sure it's all in
// the immediate field to allow as much factoring as possible.
if (!L->contains(UsersToProcess[i].Inst->getParent())) {
- UsersToProcess[i].Imm = SCEVAddExpr::get(UsersToProcess[i].Imm,
- UsersToProcess[i].Base);
+ UsersToProcess[i].Imm = SE->getAddExpr(UsersToProcess[i].Imm,
+ UsersToProcess[i].Base);
UsersToProcess[i].Base =
- SCEVUnknown::getIntegerSCEV(0, UsersToProcess[i].Base->getType());
+ SE->getIntegerSCEV(0, UsersToProcess[i].Base->getType());
} else {
// Addressing modes can be folded into loads and stores. Be careful that
// the store is through the expression, not of the expression though.
- bool isAddress = isa<LoadInst>(UsersToProcess[i].Inst);
- if (StoreInst *SI = dyn_cast<StoreInst>(UsersToProcess[i].Inst)) {
- if (SI->getOperand(1) == UsersToProcess[i].OperandValToReplace)
- isAddress = true;
- } else if (IntrinsicInst *II =
- dyn_cast<IntrinsicInst>(UsersToProcess[i].Inst)) {
- // Addressing modes can also be folded into prefetches.
- if (II->getIntrinsicID() == Intrinsic::prefetch &&
- II->getOperand(1) == UsersToProcess[i].OperandValToReplace)
- isAddress = true;
+ bool isPHI = false;
+ bool isAddress = isAddressUse(UsersToProcess[i].Inst,
+ UsersToProcess[i].OperandValToReplace);
+ if (isa<PHINode>(UsersToProcess[i].Inst)) {
+ isPHI = true;
+ ++NumPHI;
}
+
+ // If this use isn't an address, then not all uses are addresses.
+ if (!isAddress && !isPHI)
+ AllUsesAreAddresses = false;
MoveImmediateValues(TLI, UsersToProcess[i].Inst, UsersToProcess[i].Base,
- UsersToProcess[i].Imm, isAddress, L);
+ UsersToProcess[i].Imm, isAddress, L, SE);
}
}
- // Check if it is possible to reuse a IV with stride that is factor of this
- // stride. And the multiple is a number that can be encoded in the scale
- // field of the target addressing mode. And we will have a valid
- // instruction after this substition, including the immediate field, if any.
+ // If one of the use if a PHI node and all other uses are addresses, still
+ // allow iv reuse. Essentially we are trading one constant multiplication
+ // for one fewer iv.
+ if (NumPHI > 1)
+ AllUsesAreAddresses = false;
+
+ return CommonExprs;
+}
+
+/// StrengthReduceStridedIVUsers - Strength reduce all of the users of a single
+/// stride of IV. All of the users may have different starting values, and this
+/// may not be the only stride (we know it is if isOnlyStride is true).
+void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
+ IVUsersOfOneStride &Uses,
+ Loop *L,
+ bool isOnlyStride) {
+ // If all the users are moved to another stride, then there is nothing to do.
+ if (Uses.Users.empty())
+ return;
+
+ // Keep track if every use in UsersToProcess is an address. If they all are,
+ // we may be able to rewrite the entire collection of them in terms of a
+ // smaller-stride IV.
+ bool AllUsesAreAddresses = true;
+
+ // Transform our list of users and offsets to a bit more complex table. In
+ // this new vector, each 'BasedUser' contains 'Base' the base of the
+ // strided accessas well as the old information from Uses. We progressively
+ // move information from the Base field to the Imm field, until we eventually
+ // have the full access expression to rewrite the use.
+ std::vector<BasedUser> UsersToProcess;
+ SCEVHandle CommonExprs = CollectIVUsers(Stride, Uses, L, AllUsesAreAddresses,
+ UsersToProcess);
+
+ // If we managed to find some expressions in common, we'll need to carry
+ // their value in a register and add it in for each use. This will take up
+ // a register operand, which potentially restricts what stride values are
+ // valid.
+ bool HaveCommonExprs = !CommonExprs->isZero();
+
+ // If all uses are addresses, check if it is possible to reuse an IV with a
+ // stride that is a factor of this stride. And that the multiple is a number
+ // that can be encoded in the scale field of the target addressing mode. And
+ // that we will have a valid instruction after this substition, including the
+ // immediate field, if any.
PHINode *NewPHI = NULL;
Value *IncV = NULL;
- IVExpr ReuseIV;
- unsigned RewriteFactor = CheckForIVReuse(Stride, ReuseIV,
- CommonExprs->getType(),
- UsersToProcess);
+ IVExpr ReuseIV(SE->getIntegerSCEV(0, Type::Int32Ty),
+ SE->getIntegerSCEV(0, Type::Int32Ty),
+ 0, 0);
+ unsigned RewriteFactor = 0;
+ RewriteFactor = CheckForIVReuse(HaveCommonExprs, AllUsesAreAddresses,
+ Stride, ReuseIV, CommonExprs->getType(),
+ UsersToProcess);
if (RewriteFactor != 0) {
DOUT << "BASED ON IV of STRIDE " << *ReuseIV.Stride
<< " and BASE " << *ReuseIV.Base << " :\n";
if (RewriteFactor == 0) {
// Create a new Phi for this base, and stick it in the loop header.
- NewPHI = new PHINode(ReplacedTy, "iv.", PhiInsertBefore);
+ NewPHI = PHINode::Create(ReplacedTy, "iv.", PhiInsertBefore);
++NumInserted;
// Add common base to the new Phi node.
bool isNegative = isNonConstantNegative(Stride);
SCEVHandle IncAmount = Stride;
if (isNegative)
- IncAmount = SCEV::getNegativeSCEV(Stride);
+ IncAmount = SE->getNegativeSCEV(Stride);
// Insert the stride into the preheader.
Value *StrideV = PreheaderRewriter.expandCodeFor(IncAmount, PreInsertPt);
// Emit the increment of the base value before the terminator of the loop
// latch block, and add it to the Phi node.
- SCEVHandle IncExp = SCEVUnknown::get(StrideV);
+ SCEVHandle IncExp = SE->getUnknown(StrideV);
if (isNegative)
- IncExp = SCEV::getNegativeSCEV(IncExp);
- IncExp = SCEVAddExpr::get(SCEVUnknown::get(NewPHI), IncExp);
+ IncExp = SE->getNegativeSCEV(IncExp);
+ IncExp = SE->getAddExpr(SE->getUnknown(NewPHI), IncExp);
IncV = Rewriter.expandCodeFor(IncExp, LatchBlock->getTerminator());
IncV->setName(NewPHI->getName()+".inc");
Constant *C = dyn_cast<Constant>(CommonBaseV);
if (!C ||
(!C->isNullValue() &&
- !isTargetConstant(SCEVUnknown::get(CommonBaseV), ReplacedTy, TLI)))
+ !isTargetConstant(SE->getUnknown(CommonBaseV), ReplacedTy, TLI)))
// We want the common base emitted into the preheader! This is just
// using cast as a copy so BitCast (no-op cast) is appropriate
CommonBaseV = new BitCastInst(CommonBaseV, CommonBaseV->getType(),
// Get a base value.
SCEVHandle Base = UsersToProcess[i].Base;
- // Compact everything with this base to be consequetive with this one.
+ // Compact everything with this base to be consequtive with this one.
for (unsigned j = i+1; j != e; ++j) {
if (UsersToProcess[j].Base == Base) {
std::swap(UsersToProcess[i+1], UsersToProcess[j]);
// We want this constant emitted into the preheader! This is just
// using cast as a copy so BitCast (no-op cast) is appropriate
BaseV = new BitCastInst(BaseV, BaseV->getType(), "preheaderinsert",
- PreInsertPt);
+ PreInsertPt);
}
}
RewriteOp = SCEVExpander::InsertCastOfTo(opcode, RewriteOp, ReplacedTy);
}
- SCEVHandle RewriteExpr = SCEVUnknown::get(RewriteOp);
+ SCEVHandle RewriteExpr = SE->getUnknown(RewriteOp);
+
+ // If we had to insert new instrutions for RewriteOp, we have to
+ // consider that they may not have been able to end up immediately
+ // next to RewriteOp, because non-PHI instructions may never precede
+ // PHI instructions in a block. In this case, remember where the last
+ // instruction was inserted so that if we're replacing a different
+ // PHI node, we can use the later point to expand the final
+ // RewriteExpr.
+ Instruction *NewBasePt = dyn_cast<Instruction>(RewriteOp);
+ if (RewriteOp == NewPHI) NewBasePt = 0;
// Clear the SCEVExpander's expression map so that we are guaranteed
// to have the code emitted where we expect it.
// If we are reusing the iv, then it must be multiplied by a constant
// factor take advantage of addressing mode scale component.
if (RewriteFactor != 0) {
- RewriteExpr =
- SCEVMulExpr::get(SCEVUnknown::getIntegerSCEV(RewriteFactor,
- RewriteExpr->getType()),
- RewriteExpr);
+ RewriteExpr = SE->getMulExpr(SE->getIntegerSCEV(RewriteFactor,
+ RewriteExpr->getType()),
+ RewriteExpr);
// The common base is emitted in the loop preheader. But since we
// are reusing an IV, it has not been used to initialize the PHI node.
// Add it to the expression used to rewrite the uses.
if (!isa<ConstantInt>(CommonBaseV) ||
!cast<ConstantInt>(CommonBaseV)->isZero())
- RewriteExpr = SCEVAddExpr::get(RewriteExpr,
- SCEVUnknown::get(CommonBaseV));
+ RewriteExpr = SE->getAddExpr(RewriteExpr,
+ SE->getUnknown(CommonBaseV));
}
// Now that we know what we need to do, insert code before User for the
// immediate and any loop-variant expressions.
if (!isa<ConstantInt>(BaseV) || !cast<ConstantInt>(BaseV)->isZero())
// Add BaseV to the PHI value if needed.
- RewriteExpr = SCEVAddExpr::get(RewriteExpr, SCEVUnknown::get(BaseV));
+ RewriteExpr = SE->getAddExpr(RewriteExpr, SE->getUnknown(BaseV));
- User.RewriteInstructionToUseNewBase(RewriteExpr, Rewriter, L, this);
+ User.RewriteInstructionToUseNewBase(RewriteExpr, NewBasePt,
+ Rewriter, L, this,
+ DeadInsts);
// Mark old value we replaced as possibly dead, so that it is elminated
// if we just replaced the last use of that value.
// different starting values, into different PHIs.
}
-/// FindIVForUser - If Cond has an operand that is an expression of an IV,
+/// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
/// set the IV user and stride information and return true, otherwise return
/// false.
-bool LoopStrengthReduce::FindIVForUser(ICmpInst *Cond, IVStrideUse *&CondUse,
+bool LoopStrengthReduce::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
const SCEVHandle *&CondStride) {
for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e && !CondUse;
++Stride) {
return false;
}
+namespace {
+ // Constant strides come first which in turns are sorted by their absolute
+ // values. If absolute values are the same, then positive strides comes first.
+ // e.g.
+ // 4, -1, X, 1, 2 ==> 1, -1, 2, 4, X
+ struct StrideCompare {
+ bool operator()(const SCEVHandle &LHS, const SCEVHandle &RHS) {
+ SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS);
+ SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS);
+ if (LHSC && RHSC) {
+ int64_t LV = LHSC->getValue()->getSExtValue();
+ int64_t RV = RHSC->getValue()->getSExtValue();
+ uint64_t ALV = (LV < 0) ? -LV : LV;
+ uint64_t ARV = (RV < 0) ? -RV : RV;
+ if (ALV == ARV)
+ return LV > RV;
+ else
+ return ALV < ARV;
+ }
+ return (LHSC && !RHSC);
+ }
+ };
+}
+
+/// ChangeCompareStride - If a loop termination compare instruction is the
+/// only use of its stride, and the compaison is against a constant value,
+/// try eliminate the stride by moving the compare instruction to another
+/// stride and change its constant operand accordingly. e.g.
+///
+/// loop:
+/// ...
+/// v1 = v1 + 3
+/// v2 = v2 + 1
+/// if (v2 < 10) goto loop
+/// =>
+/// loop:
+/// ...
+/// v1 = v1 + 3
+/// if (v1 < 30) goto loop
+ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
+ IVStrideUse* &CondUse,
+ const SCEVHandle* &CondStride) {
+ if (StrideOrder.size() < 2 ||
+ IVUsesByStride[*CondStride].Users.size() != 1)
+ return Cond;
+ const SCEVConstant *SC = dyn_cast<SCEVConstant>(*CondStride);
+ if (!SC) return Cond;
+ ConstantInt *C = dyn_cast<ConstantInt>(Cond->getOperand(1));
+ if (!C) return Cond;
+
+ ICmpInst::Predicate Predicate = Cond->getPredicate();
+ int64_t CmpSSInt = SC->getValue()->getSExtValue();
+ int64_t CmpVal = C->getValue().getSExtValue();
+ unsigned BitWidth = C->getValue().getBitWidth();
+ uint64_t SignBit = 1ULL << (BitWidth-1);
+ const Type *CmpTy = C->getType();
+ const Type *NewCmpTy = NULL;
+ unsigned TyBits = CmpTy->getPrimitiveSizeInBits();
+ unsigned NewTyBits = 0;
+ int64_t NewCmpVal = CmpVal;
+ SCEVHandle *NewStride = NULL;
+ Value *NewIncV = NULL;
+ int64_t Scale = 1;
+
+ // Check stride constant and the comparision constant signs to detect
+ // overflow.
+ if ((CmpVal & SignBit) != (CmpSSInt & SignBit))
+ return Cond;
+
+ // Look for a suitable stride / iv as replacement.
+ std::stable_sort(StrideOrder.begin(), StrideOrder.end(), StrideCompare());
+ for (unsigned i = 0, e = StrideOrder.size(); i != e; ++i) {
+ std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
+ IVUsesByStride.find(StrideOrder[i]);
+ if (!isa<SCEVConstant>(SI->first))
+ continue;
+ int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
+ if (abs(SSInt) <= abs(CmpSSInt) || (SSInt % CmpSSInt) != 0)
+ continue;
+
+ Scale = SSInt / CmpSSInt;
+ NewCmpVal = CmpVal * Scale;
+ APInt Mul = APInt(BitWidth, NewCmpVal);
+ // Check for overflow.
+ if (Mul.getSExtValue() != NewCmpVal) {
+ NewCmpVal = CmpVal;
+ continue;
+ }
+
+ // Watch out for overflow.
+ if (ICmpInst::isSignedPredicate(Predicate) &&
+ (CmpVal & SignBit) != (NewCmpVal & SignBit))
+ NewCmpVal = CmpVal;
+
+ if (NewCmpVal != CmpVal) {
+ // Pick the best iv to use trying to avoid a cast.
+ NewIncV = NULL;
+ for (std::vector<IVStrideUse>::iterator UI = SI->second.Users.begin(),
+ E = SI->second.Users.end(); UI != E; ++UI) {
+ NewIncV = UI->OperandValToReplace;
+ if (NewIncV->getType() == CmpTy)
+ break;
+ }
+ if (!NewIncV) {
+ NewCmpVal = CmpVal;
+ continue;
+ }
+
+ NewCmpTy = NewIncV->getType();
+ NewTyBits = isa<PointerType>(NewCmpTy)
+ ? UIntPtrTy->getPrimitiveSizeInBits()
+ : NewCmpTy->getPrimitiveSizeInBits();
+ if (RequiresTypeConversion(NewCmpTy, CmpTy)) {
+ // Check if it is possible to rewrite it using
+ // an iv / stride of a smaller integer type.
+ bool TruncOk = false;
+ if (NewCmpTy->isInteger()) {
+ unsigned Bits = NewTyBits;
+ if (ICmpInst::isSignedPredicate(Predicate))
+ --Bits;
+ uint64_t Mask = (1ULL << Bits) - 1;
+ if (((uint64_t)NewCmpVal & Mask) == (uint64_t)NewCmpVal)
+ TruncOk = true;
+ }
+ if (!TruncOk) {
+ NewCmpVal = CmpVal;
+ continue;
+ }
+ }
+
+ // Don't rewrite if use offset is non-constant and the new type is
+ // of a different type.
+ // FIXME: too conservative?
+ if (NewTyBits != TyBits && !isa<SCEVConstant>(CondUse->Offset)) {
+ NewCmpVal = CmpVal;
+ continue;
+ }
+
+ bool AllUsesAreAddresses = true;
+ std::vector<BasedUser> UsersToProcess;
+ SCEVHandle CommonExprs = CollectIVUsers(SI->first, SI->second, L,
+ AllUsesAreAddresses,
+ UsersToProcess);
+ // Avoid rewriting the compare instruction with an iv of new stride
+ // if it's likely the new stride uses will be rewritten using the
+ if (AllUsesAreAddresses &&
+ ValidStride(!CommonExprs->isZero(), Scale, UsersToProcess)) {
+ NewCmpVal = CmpVal;
+ continue;
+ }
+
+ // If scale is negative, use swapped predicate unless it's testing
+ // for equality.
+ if (Scale < 0 && !Cond->isEquality())
+ Predicate = ICmpInst::getSwappedPredicate(Predicate);
+
+ NewStride = &StrideOrder[i];
+ break;
+ }
+ }
+
+ // Forgo this transformation if it the increment happens to be
+ // unfortunately positioned after the condition, and the condition
+ // has multiple uses which prevent it from being moved immediately
+ // before the branch. See
+ // test/Transforms/LoopStrengthReduce/change-compare-stride-trickiness-*.ll
+ // for an example of this situation.
+ if (!Cond->hasOneUse()) {
+ for (BasicBlock::iterator I = Cond, E = Cond->getParent()->end();
+ I != E; ++I)
+ if (I == NewIncV)
+ return Cond;
+ }
+
+ if (NewCmpVal != CmpVal) {
+ // Create a new compare instruction using new stride / iv.
+ ICmpInst *OldCond = Cond;
+ Value *RHS;
+ if (!isa<PointerType>(NewCmpTy))
+ RHS = ConstantInt::get(NewCmpTy, NewCmpVal);
+ else {
+ RHS = ConstantInt::get(UIntPtrTy, NewCmpVal);
+ RHS = SCEVExpander::InsertCastOfTo(Instruction::IntToPtr, RHS, NewCmpTy);
+ }
+ // Insert new compare instruction.
+ Cond = new ICmpInst(Predicate, NewIncV, RHS,
+ L->getHeader()->getName() + ".termcond",
+ OldCond);
+
+ // Remove the old compare instruction. The old indvar is probably dead too.
+ DeadInsts.insert(cast<Instruction>(CondUse->OperandValToReplace));
+ SE->deleteValueFromRecords(OldCond);
+ OldCond->replaceAllUsesWith(Cond);
+ OldCond->eraseFromParent();
+
+ IVUsesByStride[*CondStride].Users.pop_back();
+ SCEVHandle NewOffset = TyBits == NewTyBits
+ ? SE->getMulExpr(CondUse->Offset,
+ SE->getConstant(ConstantInt::get(CmpTy, Scale)))
+ : SE->getConstant(ConstantInt::get(NewCmpTy,
+ cast<SCEVConstant>(CondUse->Offset)->getValue()->getSExtValue()*Scale));
+ IVUsesByStride[*NewStride].addUser(NewOffset, Cond, NewIncV);
+ CondUse = &IVUsesByStride[*NewStride].Users.back();
+ CondStride = NewStride;
+ ++NumEliminated;
+ }
+
+ return Cond;
+}
+
+/// OptimizeSMax - Rewrite the loop's terminating condition if it uses
+/// an smax computation.
+///
+/// This is a narrow solution to a specific, but acute, problem. For loops
+/// like this:
+///
+/// i = 0;
+/// do {
+/// p[i] = 0.0;
+/// } while (++i < n);
+///
+/// where the comparison is signed, the trip count isn't just 'n', because
+/// 'n' could be negative. And unfortunately this can come up even for loops
+/// where the user didn't use a C do-while loop. For example, seemingly
+/// well-behaved top-test loops will commonly be lowered like this:
+//
+/// if (n > 0) {
+/// i = 0;
+/// do {
+/// p[i] = 0.0;
+/// } while (++i < n);
+/// }
+///
+/// and then it's possible for subsequent optimization to obscure the if
+/// test in such a way that indvars can't find it.
+///
+/// When indvars can't find the if test in loops like this, it creates a
+/// signed-max expression, which allows it to give the loop a canonical
+/// induction variable:
+///
+/// i = 0;
+/// smax = n < 1 ? 1 : n;
+/// do {
+/// p[i] = 0.0;
+/// } while (++i != smax);
+///
+/// Canonical induction variables are necessary because the loop passes
+/// are designed around them. The most obvious example of this is the
+/// LoopInfo analysis, which doesn't remember trip count values. It
+/// expects to be able to rediscover the trip count each time it is
+/// needed, and it does this using a simple analyis that only succeeds if
+/// the loop has a canonical induction variable.
+///
+/// However, when it comes time to generate code, the maximum operation
+/// can be quite costly, especially if it's inside of an outer loop.
+///
+/// This function solves this problem by detecting this type of loop and
+/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
+/// the instructions for the maximum computation.
+///
+ICmpInst *LoopStrengthReduce::OptimizeSMax(Loop *L, ICmpInst *Cond,
+ IVStrideUse* &CondUse) {
+ // Check that the loop matches the pattern we're looking for.
+ if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
+ Cond->getPredicate() != CmpInst::ICMP_NE)
+ return Cond;
+
+ SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
+ if (!Sel || !Sel->hasOneUse()) return Cond;
+
+ SCEVHandle IterationCount = SE->getIterationCount(L);
+ if (isa<SCEVCouldNotCompute>(IterationCount))
+ return Cond;
+ SCEVHandle One = SE->getIntegerSCEV(1, IterationCount->getType());
+
+ // Adjust for an annoying getIterationCount quirk.
+ IterationCount = SE->getAddExpr(IterationCount, One);
+
+ // Check for a max calculation that matches the pattern.
+ SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(IterationCount);
+ if (!SMax || SMax != SE->getSCEV(Sel)) return Cond;
+
+ SCEVHandle SMaxLHS = SMax->getOperand(0);
+ SCEVHandle SMaxRHS = SMax->getOperand(1);
+ if (!SMaxLHS || SMaxLHS != One) return Cond;
+
+ // Check the relevant induction variable for conformance to
+ // the pattern.
+ SCEVHandle IV = SE->getSCEV(Cond->getOperand(0));
+ SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
+ if (!AR || !AR->isAffine() ||
+ AR->getStart() != One ||
+ AR->getStepRecurrence(*SE) != One)
+ return Cond;
+
+ // Check the right operand of the select, and remember it, as it will
+ // be used in the new comparison instruction.
+ Value *NewRHS = 0;
+ if (SE->getSCEV(Sel->getOperand(1)) == SMaxRHS)
+ NewRHS = Sel->getOperand(1);
+ else if (SE->getSCEV(Sel->getOperand(2)) == SMaxRHS)
+ NewRHS = Sel->getOperand(2);
+ if (!NewRHS) return Cond;
+
+ // Ok, everything looks ok to change the condition into an SLT or SGE and
+ // delete the max calculation.
+ ICmpInst *NewCond =
+ new ICmpInst(Cond->getPredicate() == CmpInst::ICMP_NE ?
+ CmpInst::ICMP_SLT :
+ CmpInst::ICMP_SGE,
+ Cond->getOperand(0), NewRHS, "scmp", Cond);
+
+ // Delete the max calculation instructions.
+ SE->deleteValueFromRecords(Cond);
+ Cond->replaceAllUsesWith(NewCond);
+ Cond->eraseFromParent();
+ Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
+ SE->deleteValueFromRecords(Sel);
+ Sel->eraseFromParent();
+ if (Cmp->use_empty()) {
+ SE->deleteValueFromRecords(Cmp);
+ Cmp->eraseFromParent();
+ }
+ CondUse->User = NewCond;
+ return NewCond;
+}
+
+/// OptimizeShadowIV - If IV is used in a int-to-float cast
+/// inside the loop then try to eliminate the cast opeation.
+void LoopStrengthReduce::OptimizeShadowIV(Loop *L) {
+
+ SCEVHandle IterationCount = SE->getIterationCount(L);
+ if (isa<SCEVCouldNotCompute>(IterationCount))
+ return;
+
+ for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e;
+ ++Stride) {
+ std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
+ IVUsesByStride.find(StrideOrder[Stride]);
+ assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
+ if (!isa<SCEVConstant>(SI->first))
+ continue;
+
+ for (std::vector<IVStrideUse>::iterator UI = SI->second.Users.begin(),
+ E = SI->second.Users.end(); UI != E; /* empty */) {
+ std::vector<IVStrideUse>::iterator CandidateUI = UI;
+ ++UI;
+ Instruction *ShadowUse = CandidateUI->User;
+ const Type *DestTy = NULL;
+
+ /* If shadow use is a int->float cast then insert a second IV
+ to eliminate this cast.
+
+ for (unsigned i = 0; i < n; ++i)
+ foo((double)i);
+
+ is transformed into
+
+ double d = 0.0;
+ for (unsigned i = 0; i < n; ++i, ++d)
+ foo(d);
+ */
+ if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->User))
+ DestTy = UCast->getDestTy();
+ else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->User))
+ DestTy = SCast->getDestTy();
+ if (!DestTy) continue;
+
+ if (TLI) {
+ /* If target does not support DestTy natively then do not apply
+ this transformation. */
+ MVT DVT = TLI->getValueType(DestTy);
+ if (!TLI->isTypeLegal(DVT)) continue;
+ }
+
+ PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
+ if (!PH) continue;
+ if (PH->getNumIncomingValues() != 2) continue;
+
+ const Type *SrcTy = PH->getType();
+ int Mantissa = DestTy->getFPMantissaWidth();
+ if (Mantissa == -1) continue;
+ if ((int)TD->getTypeSizeInBits(SrcTy) > Mantissa)
+ continue;
+
+ unsigned Entry, Latch;
+ if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
+ Entry = 0;
+ Latch = 1;
+ } else {
+ Entry = 1;
+ Latch = 0;
+ }
+
+ ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
+ if (!Init) continue;
+ ConstantFP *NewInit = ConstantFP::get(DestTy, Init->getZExtValue());
+
+ BinaryOperator *Incr =
+ dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
+ if (!Incr) continue;
+ if (Incr->getOpcode() != Instruction::Add
+ && Incr->getOpcode() != Instruction::Sub)
+ continue;
+
+ /* Initialize new IV, double d = 0.0 in above example. */
+ ConstantInt *C = NULL;
+ if (Incr->getOperand(0) == PH)
+ C = dyn_cast<ConstantInt>(Incr->getOperand(1));
+ else if (Incr->getOperand(1) == PH)
+ C = dyn_cast<ConstantInt>(Incr->getOperand(0));
+ else
+ continue;
+
+ if (!C) continue;
+
+ /* Add new PHINode. */
+ PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH);
+
+ /* create new increment. '++d' in above example. */
+ ConstantFP *CFP = ConstantFP::get(DestTy, C->getZExtValue());
+ BinaryOperator *NewIncr =
+ BinaryOperator::Create(Incr->getOpcode(),
+ NewPH, CFP, "IV.S.next.", Incr);
+
+ NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
+ NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
+
+ /* Remove cast operation */
+ SE->deleteValueFromRecords(ShadowUse);
+ ShadowUse->replaceAllUsesWith(NewPH);
+ ShadowUse->eraseFromParent();
+ SI->second.Users.erase(CandidateUI);
+ NumShadow++;
+ break;
+ }
+ }
+}
+
// OptimizeIndvars - Now that IVUsesByStride is set up with all of the indvar
// uses in the loop, look to see if we can eliminate some, in favor of using
// common indvars for the different uses.
void LoopStrengthReduce::OptimizeIndvars(Loop *L) {
// TODO: implement optzns here.
+ OptimizeShadowIV(L);
+
// Finally, get the terminating condition for the loop if possible. If we
// can, we want to change it to use a post-incremented version of its
// induction variable, to allow coalescing the live ranges for the IV into
IVStrideUse *CondUse = 0;
const SCEVHandle *CondStride = 0;
- if (!FindIVForUser(Cond, CondUse, CondStride))
+ if (!FindIVUserForCond(Cond, CondUse, CondStride))
return; // setcc doesn't use the IV.
-
+
+ // If the trip count is computed in terms of an smax (due to ScalarEvolution
+ // being unable to find a sufficient guard, for example), change the loop
+ // comparison to use SLT instead of NE.
+ Cond = OptimizeSMax(L, Cond, CondUse);
+
+ // If possible, change stride and operands of the compare instruction to
+ // eliminate one stride.
+ Cond = ChangeCompareStride(L, Cond, CondUse, CondStride);
// It's possible for the setcc instruction to be anywhere in the loop, and
// possible for it to have multiple users. If it is not immediately before
// If we get to here, we know that we can transform the setcc instruction to
// use the post-incremented version of the IV, allowing us to coalesce the
// live ranges for the IV correctly.
- CondUse->Offset = SCEV::getMinusSCEV(CondUse->Offset, *CondStride);
+ CondUse->Offset = SE->getMinusSCEV(CondUse->Offset, *CondStride);
CondUse->isUseOfPostIncrementedValue = true;
-}
-
-namespace {
- // Constant strides come first which in turns are sorted by their absolute
- // values. If absolute values are the same, then positive strides comes first.
- // e.g.
- // 4, -1, X, 1, 2 ==> 1, -1, 2, 4, X
- struct StrideCompare {
- bool operator()(const SCEVHandle &LHS, const SCEVHandle &RHS) {
- SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS);
- SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS);
- if (LHSC && RHSC) {
- int64_t LV = LHSC->getValue()->getSExtValue();
- int64_t RV = RHSC->getValue()->getSExtValue();
- uint64_t ALV = (LV < 0) ? -LV : LV;
- uint64_t ARV = (RV < 0) ? -RV : RV;
- if (ALV == ARV)
- return LV > RV;
- else
- return ALV < ARV;
- }
- return (LHSC && !RHSC);
- }
- };
+ Changed = true;
}
bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
SE = &getAnalysis<ScalarEvolution>();
TD = &getAnalysis<TargetData>();
UIntPtrTy = TD->getIntPtrType();
+ Changed = false;
// Find all uses of induction variables in this loop, and catagorize
// them by stride. Start by finding all of the PHI nodes in the header for
// this loop. If they are induction variables, inspect their uses.
- std::set<Instruction*> Processed; // Don't reprocess instructions.
+ SmallPtrSet<Instruction*,16> Processed; // Don't reprocess instructions.
for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I)
AddUsersIfInteresting(I, L, Processed);
- // If we have nothing to do, return.
- if (IVUsesByStride.empty()) return false;
+ if (!IVUsesByStride.empty()) {
+ // Optimize induction variables. Some indvar uses can be transformed to use
+ // strides that will be needed for other purposes. A common example of this
+ // is the exit test for the loop, which can often be rewritten to use the
+ // computation of some other indvar to decide when to terminate the loop.
+ OptimizeIndvars(L);
- // Optimize induction variables. Some indvar uses can be transformed to use
- // strides that will be needed for other purposes. A common example of this
- // is the exit test for the loop, which can often be rewritten to use the
- // computation of some other indvar to decide when to terminate the loop.
- OptimizeIndvars(L);
+ // FIXME: We can widen subreg IV's here for RISC targets. e.g. instead of
+ // doing computation in byte values, promote to 32-bit values if safe.
+ // FIXME: Attempt to reuse values across multiple IV's. In particular, we
+ // could have something like "for(i) { foo(i*8); bar(i*16) }", which should
+ // be codegened as "for (j = 0;; j+=8) { foo(j); bar(j+j); }" on X86/PPC.
+ // Need to be careful that IV's are all the same type. Only works for
+ // intptr_t indvars.
- // FIXME: We can widen subreg IV's here for RISC targets. e.g. instead of
- // doing computation in byte values, promote to 32-bit values if safe.
-
- // FIXME: Attempt to reuse values across multiple IV's. In particular, we
- // could have something like "for(i) { foo(i*8); bar(i*16) }", which should be
- // codegened as "for (j = 0;; j+=8) { foo(j); bar(j+j); }" on X86/PPC. Need
- // to be careful that IV's are all the same type. Only works for intptr_t
- // indvars.
-
- // If we only have one stride, we can more aggressively eliminate some things.
- bool HasOneStride = IVUsesByStride.size() == 1;
+ // If we only have one stride, we can more aggressively eliminate some
+ // things.
+ bool HasOneStride = IVUsesByStride.size() == 1;
#ifndef NDEBUG
- DOUT << "\nLSR on ";
- DEBUG(L->dump());
+ DOUT << "\nLSR on ";
+ DEBUG(L->dump());
#endif
- // IVsByStride keeps IVs for one particular loop.
- IVsByStride.clear();
-
- // Sort the StrideOrder so we process larger strides first.
- std::stable_sort(StrideOrder.begin(), StrideOrder.end(), StrideCompare());
-
- // Note: this processes each stride/type pair individually. All users passed
- // into StrengthReduceStridedIVUsers have the same type AND stride. Also,
- // node that we iterate over IVUsesByStride indirectly by using StrideOrder.
- // This extra layer of indirection makes the ordering of strides deterministic
- // - not dependent on map order.
- for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e; ++Stride) {
- std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
- IVUsesByStride.find(StrideOrder[Stride]);
- assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
- StrengthReduceStridedIVUsers(SI->first, SI->second, L, HasOneStride);
+ // IVsByStride keeps IVs for one particular loop.
+ assert(IVsByStride.empty() && "Stale entries in IVsByStride?");
+
+ // Sort the StrideOrder so we process larger strides first.
+ std::stable_sort(StrideOrder.begin(), StrideOrder.end(), StrideCompare());
+
+ // Note: this processes each stride/type pair individually. All users
+ // passed into StrengthReduceStridedIVUsers have the same type AND stride.
+ // Also, note that we iterate over IVUsesByStride indirectly by using
+ // StrideOrder. This extra layer of indirection makes the ordering of
+ // strides deterministic - not dependent on map order.
+ for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e; ++Stride) {
+ std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
+ IVUsesByStride.find(StrideOrder[Stride]);
+ assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
+ StrengthReduceStridedIVUsers(SI->first, SI->second, L, HasOneStride);
+ }
}
+ // We're done analyzing this loop; release all the state we built up for it.
+ CastedPointers.clear();
+ IVUsesByStride.clear();
+ IVsByStride.clear();
+ StrideOrder.clear();
+
// Clean up after ourselves
if (!DeadInsts.empty()) {
DeleteTriviallyDeadInstructions(DeadInsts);
BasicBlock::iterator I = L->getHeader()->begin();
- PHINode *PN;
- while ((PN = dyn_cast<PHINode>(I))) {
- ++I; // Preincrement iterator to avoid invalidating it when deleting PN.
-
- // At this point, we know that we have killed one or more GEP
- // instructions. It is worth checking to see if the cann indvar is also
- // dead, so that we can remove it as well. The requirements for the cann
- // indvar to be considered dead are:
- // 1. the cann indvar has one use
- // 2. the use is an add instruction
- // 3. the add has one use
- // 4. the add is used by the cann indvar
- // If all four cases above are true, then we can remove both the add and
- // the cann indvar.
+ while (PHINode *PN = dyn_cast<PHINode>(I++)) {
+ // At this point, we know that we have killed one or more IV users.
+ // It is worth checking to see if the cann indvar is also
+ // dead, so that we can remove it as well.
+ //
+ // We can remove a PHI if it is on a cycle in the def-use graph
+ // where each node in the cycle has degree one, i.e. only one use,
+ // and is an instruction with no side effects.
+ //
// FIXME: this needs to eliminate an induction variable even if it's being
// compared against some value to decide loop termination.
- if (PN->hasOneUse()) {
- Instruction *BO = dyn_cast<Instruction>(*PN->use_begin());
- if (BO && (isa<BinaryOperator>(BO) || isa<CmpInst>(BO))) {
- if (BO->hasOneUse() && PN == *(BO->use_begin())) {
- DeadInsts.insert(BO);
- // Break the cycle, then delete the PHI.
- PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
- SE->deleteValueFromRecords(PN);
- PN->eraseFromParent();
- }
+ if (!PN->hasOneUse())
+ continue;
+
+ SmallPtrSet<PHINode *, 4> PHIs;
+ for (Instruction *J = dyn_cast<Instruction>(*PN->use_begin());
+ J && J->hasOneUse() && !J->mayWriteToMemory();
+ J = dyn_cast<Instruction>(*J->use_begin())) {
+ // If we find the original PHI, we've discovered a cycle.
+ if (J == PN) {
+ // Break the cycle and mark the PHI for deletion.
+ SE->deleteValueFromRecords(PN);
+ PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
+ DeadInsts.insert(PN);
+ Changed = true;
+ break;
}
+ // If we find a PHI more than once, we're on a cycle that
+ // won't prove fruitful.
+ if (isa<PHINode>(J) && !PHIs.insert(cast<PHINode>(J)))
+ break;
}
}
DeleteTriviallyDeadInstructions(DeadInsts);
}
-
- CastedPointers.clear();
- IVUsesByStride.clear();
- StrideOrder.clear();
- return false;
+ return Changed;
}