-//===- LoopStrengthReduce.cpp - Strength Reduce GEPs in Loops -------------===//
+//===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===//
//
// The LLVM Compiler Infrastructure
//
//===----------------------------------------------------------------------===//
//
// This pass performs a strength reduction on array references inside loops that
-// have as one or more of their components the loop induction variable. This is
-// accomplished by creating a new Value to hold the initial value of the array
-// access for the first iteration, and then creating a new GEP instruction in
-// the loop to increment the value by the appropriate amount.
+// have as one or more of their components the loop induction variable.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
-#include "llvm/Support/CFG.h"
-#include "llvm/Support/GetElementPtrTypeIterator.h"
+#include "llvm/Transforms/Utils/AddrModeMatcher.h"
#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/CFG.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Compiler.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/ValueHandle.h"
#include "llvm/Target/TargetLowering.h"
#include <algorithm>
-#include <set>
using namespace llvm;
-STATISTIC(NumReduced , "Number of GEPs strength reduced");
+STATISTIC(NumReduced , "Number of IV uses 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");
+STATISTIC(NumImmSunk, "Number of common expr immediates sunk into uses");
+
+static cl::opt<bool> EnableFullLSRMode("enable-full-lsr",
+ cl::init(false),
+ cl::Hidden);
namespace {
SCEVHandle Stride;
SCEVHandle Base;
PHINode *PHI;
- Value *IncV;
- IVExpr(const SCEVHandle &stride, const SCEVHandle &base, PHINode *phi,
- Value *incv)
- : Stride(stride), Base(base), PHI(phi), IncV(incv) {}
+ IVExpr(const SCEVHandle &stride, const SCEVHandle &base, PHINode *phi)
+ : Stride(stride), Base(base), PHI(phi) {}
};
/// IVsOfOneStride - This structure keeps track of all IV expression inserted
struct VISIBILITY_HIDDEN IVsOfOneStride {
std::vector<IVExpr> IVs;
- void addIV(const SCEVHandle &Stride, const SCEVHandle &Base, PHINode *PHI,
- Value *IncV) {
- IVs.push_back(IVExpr(Stride, Base, PHI, IncV));
+ void addIV(const SCEVHandle &Stride, const SCEVHandle &Base, PHINode *PHI) {
+ IVs.push_back(IVExpr(Stride, Base, PHI));
}
};
LoopInfo *LI;
DominatorTree *DT;
ScalarEvolution *SE;
- const TargetData *TD;
- const Type *UIntPtrTy;
bool Changed;
/// IVUsesByStride - Keep track of all uses of induction variables that we
/// dependent on random ordering of pointers in the process.
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.
- 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.
- SetVector<Instruction*> DeadInsts;
+ SmallVector<Instruction*, 16> DeadInsts;
/// TLI - Keep a pointer of a TargetLowering to consult for determining
/// transformation profitability.
AU.addRequiredID(LoopSimplifyID);
AU.addRequired<LoopInfo>();
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:
+
+ private:
bool AddUsersIfInteresting(Instruction *I, Loop *L,
SmallPtrSet<Instruction*,16> &Processed);
- SCEVHandle GetExpressionSCEV(Instruction *E);
ICmpInst *ChangeCompareStride(Loop *L, ICmpInst *Cond,
IVStrideUse* &CondUse,
const SCEVHandle* &CondStride);
bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
const SCEVHandle *&CondStride);
bool RequiresTypeConversion(const Type *Ty, const Type *NewTy);
- unsigned CheckForIVReuse(bool, bool, const SCEVHandle&,
+ SCEVHandle CheckForIVReuse(bool, bool, bool, const SCEVHandle&,
IVExpr&, const Type*,
const std::vector<BasedUser>& UsersToProcess);
bool ValidStride(bool, int64_t,
IVUsersOfOneStride &Uses,
Loop *L,
bool &AllUsesAreAddresses,
+ bool &AllUsesAreOutsideLoop,
std::vector<BasedUser> &UsersToProcess);
+ bool ShouldUseFullStrengthReductionMode(
+ const std::vector<BasedUser> &UsersToProcess,
+ const Loop *L,
+ bool AllUsesAreAddresses,
+ SCEVHandle Stride);
+ void PrepareToStrengthReduceFully(
+ std::vector<BasedUser> &UsersToProcess,
+ SCEVHandle Stride,
+ SCEVHandle CommonExprs,
+ const Loop *L,
+ SCEVExpander &PreheaderRewriter);
+ void PrepareToStrengthReduceFromSmallerStride(
+ std::vector<BasedUser> &UsersToProcess,
+ Value *CommonBaseV,
+ const IVExpr &ReuseIV,
+ Instruction *PreInsertPt);
+ void PrepareToStrengthReduceWithNewPhi(
+ std::vector<BasedUser> &UsersToProcess,
+ SCEVHandle Stride,
+ SCEVHandle CommonExprs,
+ Value *CommonBaseV,
+ const Loop *L,
+ SCEVExpander &PreheaderRewriter);
void StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
IVUsersOfOneStride &Uses,
- Loop *L, bool isOnlyStride);
- void DeleteTriviallyDeadInstructions(SetVector<Instruction*> &Insts);
+ Loop *L);
+ void DeleteTriviallyDeadInstructions();
};
}
static RegisterPass<LoopStrengthReduce>
X("loop-reduce", "Loop Strength Reduction");
-LoopPass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
+Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
return new LoopStrengthReduce(TLI);
}
-/// getCastedVersionOf - Return the specified value casted to uintptr_t. This
-/// assumes that the Value* V is of integer or pointer type only.
-///
-Value *LoopStrengthReduce::getCastedVersionOf(Instruction::CastOps opcode,
- Value *V) {
- if (V->getType() == UIntPtrTy) return V;
- if (Constant *CB = dyn_cast<Constant>(V))
- return ConstantExpr::getCast(opcode, CB, UIntPtrTy);
-
- Value *&New = CastedPointers[V];
- if (New) return New;
-
- New = SCEVExpander::InsertCastOfTo(opcode, V, UIntPtrTy);
- DeadInsts.insert(cast<Instruction>(New));
- return New;
-}
-
-
/// DeleteTriviallyDeadInstructions - If any of the instructions is the
/// specified set are trivially dead, delete them and see if this makes any of
/// their operands subsequently dead.
-void LoopStrengthReduce::
-DeleteTriviallyDeadInstructions(SetVector<Instruction*> &Insts) {
- while (!Insts.empty()) {
- 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;
- }
- }
+void LoopStrengthReduce::DeleteTriviallyDeadInstructions() {
+ if (DeadInsts.empty()) return;
+
+ // Sort the deadinsts list so that we can trivially eliminate duplicates as we
+ // go. The code below never adds a non-dead instruction to the worklist, but
+ // callers may not be so careful.
+ array_pod_sort(DeadInsts.begin(), DeadInsts.end());
+
+ // Drop duplicate instructions and those with uses.
+ for (unsigned i = 0, e = DeadInsts.size()-1; i < e; ++i) {
+ Instruction *I = DeadInsts[i];
+ if (!I->use_empty()) DeadInsts[i] = 0;
+ while (i != e && DeadInsts[i+1] == I)
+ DeadInsts[++i] = 0;
+ }
+
+ while (!DeadInsts.empty()) {
+ Instruction *I = DeadInsts.back();
+ DeadInsts.pop_back();
+
+ if (I == 0 || !isInstructionTriviallyDead(I))
+ continue;
+
+ SE->deleteValueFromRecords(I);
- if (isInstructionTriviallyDead(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();
- Changed = true;
+ for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) {
+ if (Instruction *U = dyn_cast<Instruction>(*OI)) {
+ *OI = 0;
+ if (U->use_empty())
+ DeadInsts.push_back(U);
+ }
}
+
+ I->eraseFromParent();
+ Changed = true;
}
}
-
-/// GetExpressionSCEV - Compute and return the SCEV for the specified
-/// instruction.
-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)));
- SE->setSCEV(BCI, R);
- return R;
+/// containsAddRecFromDifferentLoop - Determine whether expression S involves a
+/// subexpression that is an AddRec from a loop other than L. An outer loop
+/// of L is OK, but not an inner loop nor a disjoint loop.
+static bool containsAddRecFromDifferentLoop(SCEVHandle S, Loop *L) {
+ // This is very common, put it first.
+ if (isa<SCEVConstant>(S))
+ return false;
+ if (const SCEVCommutativeExpr *AE = dyn_cast<SCEVCommutativeExpr>(S)) {
+ for (unsigned int i=0; i< AE->getNumOperands(); i++)
+ if (containsAddRecFromDifferentLoop(AE->getOperand(i), L))
+ return true;
+ return false;
}
-
- // Scalar Evolutions doesn't know how to compute SCEV's for GEP instructions.
- // If this is a GEP that SE doesn't know about, compute it now and insert it.
- // If this is not a GEP, or if we have already done this computation, just let
- // SE figure it out.
- GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Exp);
- if (!GEP || SE->hasSCEV(GEP))
- return SE->getSCEV(Exp);
-
- // Analyze all of the subscripts of this getelementptr instruction, looking
- // 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 = SE->getUnknown(
- getCastedVersionOf(Instruction::PtrToInt, GEP->getOperand(0)));
-
- gep_type_iterator GTI = gep_type_begin(GEP);
-
- 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>(*i)->getZExtValue();
- uint64_t Offset = SL->getElementOffset(Idx);
- GEPVal = SE->getAddExpr(GEPVal,
- SE->getIntegerSCEV(Offset, UIntPtrTy));
- } else {
- unsigned GEPOpiBits =
- (*i)->getType()->getPrimitiveSizeInBits();
- unsigned IntPtrBits = UIntPtrTy->getPrimitiveSizeInBits();
- Instruction::CastOps opcode = (GEPOpiBits < IntPtrBits ?
- Instruction::SExt : (GEPOpiBits > IntPtrBits ? Instruction::Trunc :
- Instruction::BitCast));
- Value *OpVal = getCastedVersionOf(opcode, *i);
- SCEVHandle Idx = SE->getSCEV(OpVal);
-
- uint64_t TypeSize = TD->getABITypeSize(GTI.getIndexedType());
- if (TypeSize != 1)
- Idx = SE->getMulExpr(Idx,
- SE->getConstant(ConstantInt::get(UIntPtrTy,
- TypeSize)));
- GEPVal = SE->getAddExpr(GEPVal, Idx);
+ if (const SCEVAddRecExpr *AE = dyn_cast<SCEVAddRecExpr>(S)) {
+ if (const Loop *newLoop = AE->getLoop()) {
+ if (newLoop == L)
+ return false;
+ // if newLoop is an outer loop of L, this is OK.
+ if (!LoopInfoBase<BasicBlock>::isNotAlreadyContainedIn(L, newLoop))
+ return false;
}
+ return true;
}
-
- SE->setSCEV(GEP, GEPVal);
- return GEPVal;
+ if (const SCEVUDivExpr *DE = dyn_cast<SCEVUDivExpr>(S))
+ return containsAddRecFromDifferentLoop(DE->getLHS(), L) ||
+ containsAddRecFromDifferentLoop(DE->getRHS(), L);
+#if 0
+ // SCEVSDivExpr has been backed out temporarily, but will be back; we'll
+ // need this when it is.
+ if (const SCEVSDivExpr *DE = dyn_cast<SCEVSDivExpr>(S))
+ return containsAddRecFromDifferentLoop(DE->getLHS(), L) ||
+ containsAddRecFromDifferentLoop(DE->getRHS(), L);
+#endif
+ if (const SCEVCastExpr *CE = dyn_cast<SCEVCastExpr>(S))
+ return containsAddRecFromDifferentLoop(CE->getOperand(), L);
+ return false;
}
/// getSCEVStartAndStride - Compute the start and stride of this expression,
/// returning false if the expression is not a start/stride pair, or true if it
/// is. The stride must be a loop invariant expression, but the start may be
-/// a mix of loop invariant and loop variant expressions.
+/// a mix of loop invariant and loop variant expressions. The start cannot,
+/// however, contain an AddRec from a different loop, unless that loop is an
+/// outer loop of the current loop.
static bool getSCEVStartAndStride(const SCEVHandle &SH, Loop *L,
SCEVHandle &Start, SCEVHandle &Stride,
- ScalarEvolution *SE) {
+ ScalarEvolution *SE, DominatorTree *DT) {
SCEVHandle TheAddRec = Start; // Initialize to zero.
// If the outer level is an AddExpr, the operands are all start values except
// for a nested AddRecExpr.
- if (SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(SH)) {
+ if (const SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(SH)) {
for (unsigned i = 0, e = AE->getNumOperands(); i != e; ++i)
- if (SCEVAddRecExpr *AddRec =
+ if (const SCEVAddRecExpr *AddRec =
dyn_cast<SCEVAddRecExpr>(AE->getOperand(i))) {
if (AddRec->getLoop() == L)
TheAddRec = SE->getAddExpr(AddRec, TheAddRec);
return false; // not analyzable.
}
- SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(TheAddRec);
+ const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(TheAddRec);
if (!AddRec || AddRec->getLoop() != L) return false;
// FIXME: Generalize to non-affine IV's.
if (!AddRec->isAffine()) return false;
+ // If Start contains an SCEVAddRecExpr from a different loop, other than an
+ // outer loop of the current loop, reject it. SCEV has no concept of
+ // operating on more than one loop at a time so don't confuse it with such
+ // expressions.
+ if (containsAddRecFromDifferentLoop(AddRec->getOperand(0), L))
+ return false;
+
Start = SE->getAddExpr(Start, AddRec->getOperand(0));
- if (!isa<SCEVConstant>(AddRec->getOperand(1)))
+ if (!isa<SCEVConstant>(AddRec->getOperand(1))) {
+ // If stride is an instruction, make sure it dominates the loop preheader.
+ // Otherwise we could end up with a use before def situation.
+ BasicBlock *Preheader = L->getLoopPreheader();
+ if (!AddRec->getOperand(1)->dominates(Preheader, DT))
+ return false;
+
DOUT << "[" << L->getHeader()->getName()
<< "] Variable stride: " << *AddRec << "\n";
+ }
Stride = AddRec->getOperand(1);
return true;
/// should use the post-inc value).
static bool IVUseShouldUsePostIncValue(Instruction *User, Instruction *IV,
Loop *L, DominatorTree *DT, Pass *P,
- SetVector<Instruction*> &DeadInsts){
+ SmallVectorImpl<Instruction*> &DeadInsts){
// If the user is in the loop, use the preinc value.
if (L->contains(User->getParent())) return false;
}
// Okay, all uses of IV by PN are in predecessor blocks that really are
- // dominated by the latch block. Split the critical edges and use the
- // 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, 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);
-
+ // dominated by the latch block. Use the post-incremented value.
return true;
}
-
+/// isAddressUse - 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;
+}
+
+/// getAccessType - Return the type of the memory being accessed.
+static const Type *getAccessType(const Instruction *Inst) {
+ const Type *UseTy = Inst->getType();
+ if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
+ UseTy = SI->getOperand(0)->getType();
+ else if (const 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::x86_sse_storeu_ps:
+ case Intrinsic::x86_sse2_storeu_pd:
+ case Intrinsic::x86_sse2_storeu_dq:
+ case Intrinsic::x86_sse2_storel_dq:
+ UseTy = II->getOperand(1)->getType();
+ break;
+ }
+ }
+ return UseTy;
+}
/// AddUsersIfInteresting - Inspect the specified instruction. If it is a
/// reducible SCEV, recursively add its users to the IVUsesByStride set and
/// return true. Otherwise, return false.
bool LoopStrengthReduce::AddUsersIfInteresting(Instruction *I, Loop *L,
SmallPtrSet<Instruction*,16> &Processed) {
- if (!I->getType()->isInteger() && !isa<PointerType>(I->getType()))
+ if (!SE->isSCEVable(I->getType()))
return false; // Void and FP expressions cannot be reduced.
+
+ // LSR is not APInt clean, do not touch integers bigger than 64-bits.
+ if (SE->getTypeSizeInBits(I->getType()) > 64)
+ return false;
+
if (!Processed.insert(I))
return true; // Instruction already handled.
// Get the symbolic expression for this instruction.
- SCEVHandle ISE = GetExpressionSCEV(I);
+ SCEVHandle ISE = SE->getSCEV(I);
if (isa<SCEVCouldNotCompute>(ISE)) return false;
// Get the start and stride for this expression.
SCEVHandle Start = SE->getIntegerSCEV(0, ISE->getType());
SCEVHandle Stride = Start;
- if (!getSCEVStartAndStride(ISE, L, Start, Stride, SE))
+ if (!getSCEVStartAndStride(ISE, L, Start, Stride, SE, DT))
return false; // Non-reducible symbolic expression, bail out.
std::vector<Instruction *> IUsers;
if (isa<PHINode>(User) && Processed.count(User))
continue;
- // If this is an instruction defined in a nested loop, or outside this loop,
- // don't recurse into it.
+ // Descend recursively, but not into PHI nodes outside the current loop.
+ // It's important to see the entire expression outside the loop to get
+ // choices that depend on addressing mode use right, although we won't
+ // consider references ouside the loop in all cases.
+ // If User is already in Processed, we don't want to recurse into it again,
+ // but do want to record a second reference in the same instruction.
bool AddUserToIVUsers = false;
if (LI->getLoopFor(User->getParent()) != L) {
- DOUT << "FOUND USER in other loop: " << *User
- << " OF SCEV: " << *ISE << "\n";
- AddUserToIVUsers = true;
- } else if (!AddUsersIfInteresting(User, L, Processed)) {
+ if (isa<PHINode>(User) || Processed.count(User) ||
+ !AddUsersIfInteresting(User, L, Processed)) {
+ DOUT << "FOUND USER in other loop: " << *User
+ << " OF SCEV: " << *ISE << "\n";
+ AddUserToIVUsers = true;
+ }
+ } else if (Processed.count(User) ||
+ !AddUsersIfInteresting(User, L, Processed)) {
DOUT << "FOUND USER: " << *User
<< " OF SCEV: " << *ISE << "\n";
AddUserToIVUsers = true;
if (AddUserToIVUsers) {
IVUsersOfOneStride &StrideUses = IVUsesByStride[Stride];
- if (StrideUses.Users.empty()) // First occurance of this stride?
+ if (StrideUses.Users.empty()) // First occurrence of this stride?
StrideOrder.push_back(Stride);
// Okay, we found a user that we cannot reduce. Analyze the instruction
/// Imm - The immediate value that should be added to the base immediately
/// before Inst, because it will be folded into the imm field of the
- /// instruction.
+ /// instruction. This is also sometimes used for loop-variant values that
+ /// must be added inside the loop.
SCEVHandle Imm;
- /// EmittedBase - The actual value* to use for the base value of this
- /// operation. This is null if we should just use zero so far.
- Value *EmittedBase;
+ /// Phi - The induction variable that performs the striding that
+ /// should be used for this user.
+ PHINode *Phi;
// isUseOfPostIncrementedValue - True if this should use the
// post-incremented version of this IV, not the preincremented version.
BasedUser(IVStrideUse &IVSU, ScalarEvolution *se)
: SE(se), Base(IVSU.Offset), Inst(IVSU.User),
OperandValToReplace(IVSU.OperandValToReplace),
- Imm(SE->getIntegerSCEV(0, Base->getType())), EmittedBase(0),
+ Imm(SE->getIntegerSCEV(0, Base->getType())),
isUseOfPostIncrementedValue(IVSU.isUseOfPostIncrementedValue) {}
// Once we rewrite the code to insert the new IVs we want, update the
void RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
Instruction *InsertPt,
SCEVExpander &Rewriter, Loop *L, Pass *P,
- SetVector<Instruction*> &DeadInsts);
+ SmallVectorImpl<Instruction*> &DeadInsts);
Value *InsertCodeForBaseAtPosition(const SCEVHandle &NewBase,
+ const Type *Ty,
SCEVExpander &Rewriter,
Instruction *IP, Loop *L);
void dump() const;
void BasedUser::dump() const {
cerr << " Base=" << *Base;
cerr << " Imm=" << *Imm;
- if (EmittedBase)
- cerr << " EB=" << *EmittedBase;
-
cerr << " Inst: " << *Inst;
}
Value *BasedUser::InsertCodeForBaseAtPosition(const SCEVHandle &NewBase,
+ const Type *Ty,
SCEVExpander &Rewriter,
Instruction *IP, Loop *L) {
// Figure out where we *really* want to insert this code. In particular, if
// If InsertLoop is not L, and InsertLoop is nested inside of L, figure out
// the preheader of the outer-most loop where NewBase is not loop invariant.
- while (InsertLoop && NewBase->isLoopInvariant(InsertLoop)) {
- BaseInsertPt = InsertLoop->getLoopPreheader()->getTerminator();
- InsertLoop = InsertLoop->getParentLoop();
- }
+ if (L->contains(IP->getParent()))
+ while (InsertLoop && NewBase->isLoopInvariant(InsertLoop)) {
+ BaseInsertPt = InsertLoop->getLoopPreheader()->getTerminator();
+ InsertLoop = InsertLoop->getParentLoop();
+ }
+ Value *Base = Rewriter.expandCodeFor(NewBase, Ty, BaseInsertPt);
+
// If there is no immediate value, skip the next part.
if (Imm->isZero())
- return Rewriter.expandCodeFor(NewBase, BaseInsertPt);
-
- Value *Base = Rewriter.expandCodeFor(NewBase, BaseInsertPt);
+ return Base;
// If we are inserting the base and imm values in the same block, make sure to
// adjust the IP position if insertion reused a result.
// Always emit the immediate (if non-zero) into the same block as the user.
SCEVHandle NewValSCEV = SE->getAddExpr(SE->getUnknown(Base), Imm);
- return Rewriter.expandCodeFor(NewValSCEV, IP);
-
+ return Rewriter.expandCodeFor(NewValSCEV, Ty, IP);
}
void BasedUser::RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
Instruction *NewBasePt,
SCEVExpander &Rewriter, Loop *L, Pass *P,
- SetVector<Instruction*> &DeadInsts) {
+ SmallVectorImpl<Instruction*> &DeadInsts){
if (!isa<PHINode>(Inst)) {
// By default, insert code at the user instruction.
BasicBlock::iterator InsertPt = Inst;
// cases (e.g. use of a post-incremented induction variable) the NewBase
// value will be pinned to live somewhere after the original computation.
// In this case, we have to back off.
- if (!isUseOfPostIncrementedValue) {
+ //
+ // If this is a use outside the loop (which means after, since it is based
+ // on a loop indvar) we use the post-incremented value, so that we don't
+ // artificially make the preinc value live out the bottom of the loop.
+ if (!isUseOfPostIncrementedValue && L->contains(Inst->getParent())) {
if (NewBasePt && isa<PHINode>(OperandValToReplace)) {
InsertPt = NewBasePt;
++InsertPt;
while (isa<PHINode>(InsertPt)) ++InsertPt;
}
}
- Value *NewVal = InsertCodeForBaseAtPosition(NewBase, Rewriter, InsertPt, L);
- // Adjust the type back to match the Inst. Note that we can't use InsertPt
- // here because the SCEVExpander may have inserted the instructions after
- // that point, in its efforts to avoid inserting redundant expressions.
- if (isa<PointerType>(OperandValToReplace->getType())) {
- NewVal = SCEVExpander::InsertCastOfTo(Instruction::IntToPtr,
- NewVal,
- OperandValToReplace->getType());
- }
+ Value *NewVal = InsertCodeForBaseAtPosition(NewBase,
+ OperandValToReplace->getType(),
+ Rewriter, InsertPt, L);
// Replace the use of the operand Value with the new Phi we just created.
Inst->replaceUsesOfWith(OperandValToReplace, NewVal);
- DOUT << " CHANGED: IMM =" << *Imm;
- DOUT << " \tNEWBASE =" << *NewBase;
- DOUT << " \tInst = " << *Inst;
+
+ DOUT << " Replacing with ";
+ DEBUG(WriteAsOperand(*DOUT, NewVal, /*PrintType=*/false));
+ DOUT << ", which has value " << *NewBase << " plus IMM " << *Imm << "\n";
return;
}
-
+
// PHI nodes are more complex. We have to insert one copy of the NewBase+Imm
// expression into each operand block that uses it. Note that PHI nodes can
// have multiple entries for the same predecessor. We use a map to make sure
PHINode *PN = cast<PHINode>(Inst);
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
if (PN->getIncomingValue(i) == OperandValToReplace) {
- // If this is a critical edge, split the edge so that we do not insert the
- // code on all predecessor/successor paths. We do this unless this is the
- // canonical backedge for this loop, as this can make some inserted code
- // be in an illegal position.
- BasicBlock *PHIPred = PN->getIncomingBlock(i);
- if (e != 1 && PHIPred->getTerminator()->getNumSuccessors() > 1 &&
- (PN->getParent() != L->getHeader() || !L->contains(PHIPred))) {
-
- // First step, split the critical edge.
- 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
- // move the block to be immediately before the PHI block, not
- // immediately after PredTI.
- if (L->contains(PHIPred) && !L->contains(PN->getParent())) {
- BasicBlock *NewBB = PN->getIncomingBlock(i);
- NewBB->moveBefore(PN->getParent());
+ // If the original expression is outside the loop, put the replacement
+ // code in the same place as the original expression,
+ // which need not be an immediate predecessor of this PHI. This way we
+ // need only one copy of it even if it is referenced multiple times in
+ // the PHI. We don't do this when the original expression is inside the
+ // loop because multiple copies sometimes do useful sinking of code in
+ // that case(?).
+ Instruction *OldLoc = dyn_cast<Instruction>(OperandValToReplace);
+ if (L->contains(OldLoc->getParent())) {
+ // If this is a critical edge, split the edge so that we do not insert
+ // the code on all predecessor/successor paths. We do this unless this
+ // is the canonical backedge for this loop, as this can make some
+ // inserted code be in an illegal position.
+ BasicBlock *PHIPred = PN->getIncomingBlock(i);
+ if (e != 1 && PHIPred->getTerminator()->getNumSuccessors() > 1 &&
+ (PN->getParent() != L->getHeader() || !L->contains(PHIPred))) {
+
+ // First step, split the critical edge.
+ 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
+ // move the block to be immediately before the PHI block, not
+ // immediately after PredTI.
+ if (L->contains(PHIPred) && !L->contains(PN->getParent())) {
+ BasicBlock *NewBB = PN->getIncomingBlock(i);
+ NewBB->moveBefore(PN->getParent());
+ }
+
+ // Splitting the edge can reduce the number of PHI entries we have.
+ e = PN->getNumIncomingValues();
}
-
- // Splitting the edge can reduce the number of PHI entries we have.
- e = PN->getNumIncomingValues();
}
-
Value *&Code = InsertedCode[PN->getIncomingBlock(i)];
if (!Code) {
// Insert the code into the end of the predecessor block.
- 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.
- if (isa<PointerType>(PN->getType())) {
- Code = SCEVExpander::InsertCastOfTo(Instruction::IntToPtr,
- Code,
- PN->getType());
- }
+ Instruction *InsertPt = (L->contains(OldLoc->getParent())) ?
+ PN->getIncomingBlock(i)->getTerminator() :
+ OldLoc->getParent()->getTerminator();
+ Code = InsertCodeForBaseAtPosition(NewBase, PN->getType(),
+ Rewriter, InsertPt, L);
+
+ DOUT << " Changing PHI use to ";
+ DEBUG(WriteAsOperand(*DOUT, Code, /*PrintType=*/false));
+ DOUT << ", which has value " << *NewBase << " plus IMM " << *Imm << "\n";
}
-
+
// Replace the use of the operand Value with the new Phi we just created.
PN->setIncomingValue(i, Code);
Rewriter.clear();
}
// PHI node might have become a constant value after SplitCriticalEdge.
- DeadInsts.insert(Inst);
-
- DOUT << " CHANGED: IMM =" << *Imm << " Inst = " << *Inst;
+ DeadInsts.push_back(Inst);
}
-/// isTargetConstant - Return true if the following can be referenced by the
-/// immediate field of a target instruction.
-static bool isTargetConstant(const SCEVHandle &V, const Type *UseTy,
- const TargetLowering *TLI) {
- if (SCEVConstant *SC = dyn_cast<SCEVConstant>(V)) {
+/// fitsInAddressMode - Return true if V can be subsumed within an addressing
+/// mode, and does not need to be put in a register first.
+static bool fitsInAddressMode(const SCEVHandle &V, const Type *UseTy,
+ const TargetLowering *TLI, bool HasBaseReg) {
+ if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(V)) {
int64_t VC = SC->getValue()->getSExtValue();
if (TLI) {
TargetLowering::AddrMode AM;
AM.BaseOffs = VC;
+ AM.HasBaseReg = HasBaseReg;
return TLI->isLegalAddressingMode(AM, UseTy);
} else {
// Defaults to PPC. PPC allows a sign-extended 16-bit immediate field.
}
}
- if (SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V))
- if (ConstantExpr *CE = dyn_cast<ConstantExpr>(SU->getValue()))
- if (TLI && CE->getOpcode() == Instruction::PtrToInt) {
- Constant *Op0 = CE->getOperand(0);
- if (GlobalValue *GV = dyn_cast<GlobalValue>(Op0)) {
- TargetLowering::AddrMode AM;
- AM.BaseGV = GV;
- return TLI->isLegalAddressingMode(AM, UseTy);
- }
+ if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V))
+ if (GlobalValue *GV = dyn_cast<GlobalValue>(SU->getValue())) {
+ if (TLI) {
+ TargetLowering::AddrMode AM;
+ AM.BaseGV = GV;
+ AM.HasBaseReg = HasBaseReg;
+ return TLI->isLegalAddressingMode(AM, UseTy);
+ } else {
+ // Default: assume global addresses are not legal.
}
+ }
+
return false;
}
-/// MoveLoopVariantsToImediateField - Move any subexpressions from Val that are
+/// MoveLoopVariantsToImmediateField - Move any subexpressions from Val that are
/// loop varying to the Imm operand.
-static void MoveLoopVariantsToImediateField(SCEVHandle &Val, SCEVHandle &Imm,
+static void MoveLoopVariantsToImmediateField(SCEVHandle &Val, SCEVHandle &Imm,
Loop *L, ScalarEvolution *SE) {
if (Val->isLoopInvariant(L)) return; // Nothing to do.
- if (SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
+ if (const SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
std::vector<SCEVHandle> NewOps;
NewOps.reserve(SAE->getNumOperands());
Val = SE->getIntegerSCEV(0, Val->getType());
else
Val = SE->getAddExpr(NewOps);
- } else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
+ } else if (const 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, SE);
+ MoveLoopVariantsToImmediateField(Start, Imm, L, SE);
std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
Ops[0] = Start;
/// that can fit into the immediate field of instructions in the target.
/// Accumulate these immediate values into the Imm value.
static void MoveImmediateValues(const TargetLowering *TLI,
- Instruction *User,
+ const Type *UseTy,
SCEVHandle &Val, SCEVHandle &Imm,
bool isAddress, Loop *L,
ScalarEvolution *SE) {
- const Type *UseTy = User->getType();
- if (StoreInst *SI = dyn_cast<StoreInst>(User))
- UseTy = SI->getOperand(0)->getType();
-
- if (SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
+ if (const SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
std::vector<SCEVHandle> NewOps;
NewOps.reserve(SAE->getNumOperands());
for (unsigned i = 0; i != SAE->getNumOperands(); ++i) {
SCEVHandle NewOp = SAE->getOperand(i);
- MoveImmediateValues(TLI, User, NewOp, Imm, isAddress, L, SE);
+ MoveImmediateValues(TLI, UseTy, NewOp, Imm, isAddress, L, SE);
if (!NewOp->isLoopInvariant(L)) {
// If this is a loop-variant expression, it must stay in the immediate
else
Val = SE->getAddExpr(NewOps);
return;
- } else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
+ } else if (const 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, SE);
+ MoveImmediateValues(TLI, UseTy, Start, Imm, isAddress, L, SE);
if (Start != SARE->getStart()) {
std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
Val = SE->getAddRecExpr(Ops, SARE->getLoop());
}
return;
- } else if (SCEVMulExpr *SME = dyn_cast<SCEVMulExpr>(Val)) {
+ } else if (const SCEVMulExpr *SME = dyn_cast<SCEVMulExpr>(Val)) {
// Transform "8 * (4 + v)" -> "32 + 8*V" if "32" fits in the immed field.
- if (isAddress && isTargetConstant(SME->getOperand(0), UseTy, TLI) &&
+ if (isAddress && fitsInAddressMode(SME->getOperand(0), UseTy, TLI, false) &&
SME->getNumOperands() == 2 && SME->isLoopInvariant(L)) {
SCEVHandle SubImm = SE->getIntegerSCEV(0, Val->getType());
SCEVHandle NewOp = SME->getOperand(1);
- MoveImmediateValues(TLI, User, NewOp, SubImm, isAddress, L, SE);
+ MoveImmediateValues(TLI, UseTy, NewOp, SubImm, isAddress, L, SE);
// If we extracted something out of the subexpressions, see if we can
// simplify this!
// Scale SubImm up by "8". If the result is a target constant, we are
// good.
SubImm = SE->getMulExpr(SubImm, SME->getOperand(0));
- if (isTargetConstant(SubImm, UseTy, TLI)) {
+ if (fitsInAddressMode(SubImm, UseTy, TLI, false)) {
// Accumulate the immediate.
Imm = SE->getAddExpr(Imm, SubImm);
// Loop-variant expressions must stay in the immediate field of the
// expression.
- if ((isAddress && isTargetConstant(Val, UseTy, TLI)) ||
+ if ((isAddress && fitsInAddressMode(Val, UseTy, TLI, false)) ||
!Val->isLoopInvariant(L)) {
Imm = SE->getAddExpr(Imm, Val);
Val = SE->getIntegerSCEV(0, Val->getType());
// Otherwise, no immediates to move.
}
+static void MoveImmediateValues(const TargetLowering *TLI,
+ Instruction *User,
+ SCEVHandle &Val, SCEVHandle &Imm,
+ bool isAddress, Loop *L,
+ ScalarEvolution *SE) {
+ const Type *UseTy = getAccessType(User);
+ MoveImmediateValues(TLI, UseTy, Val, Imm, isAddress, L, SE);
+}
/// SeparateSubExprs - Decompose Expr into all of the subexpressions that are
/// added together. This is used to reassociate common addition subexprs
static void SeparateSubExprs(std::vector<SCEVHandle> &SubExprs,
SCEVHandle Expr,
ScalarEvolution *SE) {
- if (SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(Expr)) {
+ if (const SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(Expr)) {
for (unsigned j = 0, e = AE->getNumOperands(); j != e; ++j)
SeparateSubExprs(SubExprs, AE->getOperand(j), SE);
- } else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Expr)) {
+ } else if (const SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Expr)) {
SCEVHandle Zero = SE->getIntegerSCEV(0, Expr->getType());
if (SARE->getOperand(0) == Zero) {
SubExprs.push_back(Expr);
}
}
-
-/// RemoveCommonExpressionsFromUseBases - Look through all of the uses in Bases,
-/// removing any common subexpressions from it. Anything truly common is
-/// 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.
+// This is logically local to the following function, but C++ says we have
+// to make it file scope.
+struct SubExprUseData { unsigned Count; bool notAllUsesAreFree; };
+
+/// RemoveCommonExpressionsFromUseBases - Look through all of the Bases of all
+/// the Uses, removing any common subexpressions, except that if all such
+/// subexpressions can be folded into an addressing mode for all uses inside
+/// the loop (this case is referred to as "free" in comments herein) we do
+/// not remove anything. This looks for things like (a+b+c) and
+/// (a+c+d) and computes the common (a+c) subexpression. The common expression
+/// is *removed* from the Bases and returned.
static SCEVHandle
RemoveCommonExpressionsFromUseBases(std::vector<BasedUser> &Uses,
- ScalarEvolution *SE) {
+ ScalarEvolution *SE, Loop *L,
+ const TargetLowering *TLI) {
unsigned NumUses = Uses.size();
- // Only one use? Use its base, regardless of what it is!
+ // Only one use? This is a very common case, so we handle it specially and
+ // cheaply.
SCEVHandle Zero = SE->getIntegerSCEV(0, Uses[0].Base->getType());
SCEVHandle Result = Zero;
+ SCEVHandle FreeResult = Zero;
if (NumUses == 1) {
- std::swap(Result, Uses[0].Base);
+ // If the use is inside the loop, use its base, regardless of what it is:
+ // it is clearly shared across all the IV's. If the use is outside the loop
+ // (which means after it) we don't want to factor anything *into* the loop,
+ // so just use 0 as the base.
+ if (L->contains(Uses[0].Inst->getParent()))
+ std::swap(Result, Uses[0].Base);
return Result;
}
// To find common subexpressions, count how many of Uses use each expression.
// If any subexpressions are used Uses.size() times, they are common.
- std::map<SCEVHandle, unsigned> SubExpressionUseCounts;
+ // Also track whether all uses of each expression can be moved into an
+ // an addressing mode "for free"; such expressions are left within the loop.
+ // struct SubExprUseData { unsigned Count; bool notAllUsesAreFree; };
+ std::map<SCEVHandle, SubExprUseData> SubExpressionUseData;
// UniqueSubExprs - Keep track of all of the subexpressions we see in the
// order we see them.
std::vector<SCEVHandle> UniqueSubExprs;
std::vector<SCEVHandle> SubExprs;
+ unsigned NumUsesInsideLoop = 0;
for (unsigned i = 0; i != NumUses; ++i) {
+ // If the user is outside the loop, just ignore it for base computation.
+ // Since the user is outside the loop, it must be *after* the loop (if it
+ // were before, it could not be based on the loop IV). We don't want users
+ // after the loop to affect base computation of values *inside* the loop,
+ // because we can always add their offsets to the result IV after the loop
+ // is done, ensuring we get good code inside the loop.
+ if (!L->contains(Uses[i].Inst->getParent()))
+ continue;
+ NumUsesInsideLoop++;
+
// If the base is zero (which is common), return zero now, there are no
// CSEs we can find.
if (Uses[i].Base == Zero) return Zero;
+ // If this use is as an address we may be able to put CSEs in the addressing
+ // mode rather than hoisting them.
+ bool isAddrUse = isAddressUse(Uses[i].Inst, Uses[i].OperandValToReplace);
+ // We may need the UseTy below, but only when isAddrUse, so compute it
+ // only in that case.
+ const Type *UseTy = 0;
+ if (isAddrUse)
+ UseTy = getAccessType(Uses[i].Inst);
+
// Split the expression into subexprs.
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)
+ // Add one to SubExpressionUseData.Count for each subexpr present, and
+ // if the subexpr is not a valid immediate within an addressing mode use,
+ // set SubExpressionUseData.notAllUsesAreFree. We definitely want to
+ // hoist these out of the loop (if they are common to all uses).
+ for (unsigned j = 0, e = SubExprs.size(); j != e; ++j) {
+ if (++SubExpressionUseData[SubExprs[j]].Count == 1)
UniqueSubExprs.push_back(SubExprs[j]);
+ if (!isAddrUse || !fitsInAddressMode(SubExprs[j], UseTy, TLI, false))
+ SubExpressionUseData[SubExprs[j]].notAllUsesAreFree = true;
+ }
SubExprs.clear();
}
// Now that we know how many times each is used, build Result. Iterate over
// UniqueSubexprs so that we have a stable ordering.
for (unsigned i = 0, e = UniqueSubExprs.size(); i != e; ++i) {
- std::map<SCEVHandle, unsigned>::iterator I =
- SubExpressionUseCounts.find(UniqueSubExprs[i]);
- assert(I != SubExpressionUseCounts.end() && "Entry not found?");
- if (I->second == NumUses) { // Found CSE!
- Result = SE->getAddExpr(Result, I->first);
- } else {
- // Remove non-cse's from SubExpressionUseCounts.
- SubExpressionUseCounts.erase(I);
+ std::map<SCEVHandle, SubExprUseData>::iterator I =
+ SubExpressionUseData.find(UniqueSubExprs[i]);
+ assert(I != SubExpressionUseData.end() && "Entry not found?");
+ if (I->second.Count == NumUsesInsideLoop) { // Found CSE!
+ if (I->second.notAllUsesAreFree)
+ Result = SE->getAddExpr(Result, I->first);
+ else
+ FreeResult = SE->getAddExpr(FreeResult, I->first);
+ } else
+ // Remove non-cse's from SubExpressionUseData.
+ SubExpressionUseData.erase(I);
+ }
+
+ if (FreeResult != Zero) {
+ // We have some subexpressions that can be subsumed into addressing
+ // modes in every use inside the loop. However, it's possible that
+ // there are so many of them that the combined FreeResult cannot
+ // be subsumed, or that the target cannot handle both a FreeResult
+ // and a Result in the same instruction (for example because it would
+ // require too many registers). Check this.
+ for (unsigned i=0; i<NumUses; ++i) {
+ if (!L->contains(Uses[i].Inst->getParent()))
+ continue;
+ // We know this is an addressing mode use; if there are any uses that
+ // are not, FreeResult would be Zero.
+ const Type *UseTy = getAccessType(Uses[i].Inst);
+ if (!fitsInAddressMode(FreeResult, UseTy, TLI, Result!=Zero)) {
+ // FIXME: could split up FreeResult into pieces here, some hoisted
+ // and some not. There is no obvious advantage to this.
+ Result = SE->getAddExpr(Result, FreeResult);
+ FreeResult = Zero;
+ break;
+ }
}
}
-
+
// If we found no CSE's, return now.
if (Result == Zero) return Result;
+ // If we still have a FreeResult, remove its subexpressions from
+ // SubExpressionUseData. This means they will remain in the use Bases.
+ if (FreeResult != Zero) {
+ SeparateSubExprs(SubExprs, FreeResult, SE);
+ for (unsigned j = 0, e = SubExprs.size(); j != e; ++j) {
+ std::map<SCEVHandle, SubExprUseData>::iterator I =
+ SubExpressionUseData.find(SubExprs[j]);
+ SubExpressionUseData.erase(I);
+ }
+ SubExprs.clear();
+ }
+
// Otherwise, remove all of the CSE's we found from each of the base values.
for (unsigned i = 0; i != NumUses; ++i) {
+ // Uses outside the loop don't necessarily include the common base, but
+ // the final IV value coming into those uses does. Instead of trying to
+ // remove the pieces of the common base, which might not be there,
+ // subtract off the base to compensate for this.
+ if (!L->contains(Uses[i].Inst->getParent())) {
+ Uses[i].Base = SE->getMinusSCEV(Uses[i].Base, Result);
+ continue;
+ }
+
// Split the expression into subexprs.
SeparateSubExprs(SubExprs, Uses[i].Base, SE);
// Remove any common subexpressions.
for (unsigned j = 0, e = SubExprs.size(); j != e; ++j)
- if (SubExpressionUseCounts.count(SubExprs[j])) {
+ if (SubExpressionUseData.count(SubExprs[j])) {
SubExprs.erase(SubExprs.begin()+j);
--j; --e;
}
- // Finally, the non-shared expressions together.
+ // Finally, add the non-shared expressions together.
if (SubExprs.empty())
Uses[i].Base = Zero;
else
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;
- if (StoreInst *SI = dyn_cast<StoreInst>(UsersToProcess[i].Inst))
- AccessTy = SI->getOperand(0)->getType();
- else if (LoadInst *LI = dyn_cast<LoadInst>(UsersToProcess[i].Inst))
- AccessTy = LI->getType();
+ if (isAddressUse(UsersToProcess[i].Inst,
+ UsersToProcess[i].OperandValToReplace))
+ AccessTy = getAccessType(UsersToProcess[i].Inst);
else if (isa<PHINode>(UsersToProcess[i].Inst))
continue;
TargetLowering::AddrMode AM;
- if (SCEVConstant *SC = dyn_cast<SCEVConstant>(UsersToProcess[i].Imm))
+ if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(UsersToProcess[i].Imm))
AM.BaseOffs = SC->getValue()->getSExtValue();
AM.HasBaseReg = HasBaseReg || !UsersToProcess[i].Base->isZero();
AM.Scale = Scale;
return true;
}
-/// RequiresTypeConversion - Returns true if converting Ty to NewTy is not
+/// RequiresTypeConversion - Returns true if converting Ty1 to Ty2 is not
/// a nop.
bool LoopStrengthReduce::RequiresTypeConversion(const Type *Ty1,
const Type *Ty2) {
if (Ty1 == Ty2)
return false;
+ Ty1 = SE->getEffectiveSCEVType(Ty1);
+ Ty2 = SE->getEffectiveSCEVType(Ty2);
+ if (Ty1 == Ty2)
+ return false;
+ if (Ty1->canLosslesslyBitCastTo(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)));
+ return true;
}
/// 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 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,
+/// reuse is possible. Factors can be negative on same targets, e.g. ARM.
+///
+/// If all uses are outside the loop, we don't require that all multiplies
+/// be folded into the addressing mode, nor even that the factor be constant;
+/// a multiply (executed once) outside the loop is better than another IV
+/// within. Well, usually.
+SCEVHandle LoopStrengthReduce::CheckForIVReuse(bool HasBaseReg,
bool AllUsesAreAddresses,
+ bool AllUsesAreOutsideLoop,
const SCEVHandle &Stride,
IVExpr &IV, const Type *Ty,
const std::vector<BasedUser>& UsersToProcess) {
- if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Stride)) {
+ if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Stride)) {
int64_t SInt = SC->getValue()->getSExtValue();
for (unsigned NewStride = 0, e = StrideOrder.size(); NewStride != e;
++NewStride) {
std::map<SCEVHandle, IVsOfOneStride>::iterator SI =
IVsByStride.find(StrideOrder[NewStride]);
- if (SI == IVsByStride.end())
+ if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first))
continue;
int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
if (SI->first != Stride &&
if (II->Base->isZero() &&
!RequiresTypeConversion(II->Base->getType(), Ty)) {
IV = *II;
- return Scale;
+ return SE->getIntegerSCEV(Scale, Stride->getType());
}
}
+ } else if (AllUsesAreOutsideLoop) {
+ // Accept nonconstant strides here; it is really really right to substitute
+ // an existing IV if we can.
+ for (unsigned NewStride = 0, e = StrideOrder.size(); NewStride != e;
+ ++NewStride) {
+ std::map<SCEVHandle, IVsOfOneStride>::iterator SI =
+ IVsByStride.find(StrideOrder[NewStride]);
+ if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first))
+ continue;
+ int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
+ if (SI->first != Stride && SSInt != 1)
+ continue;
+ for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
+ IE = SI->second.IVs.end(); II != IE; ++II)
+ // Accept nonzero base here.
+ // Only reuse previous IV if it would not require a type conversion.
+ if (!RequiresTypeConversion(II->Base->getType(), Ty)) {
+ IV = *II;
+ return Stride;
+ }
+ }
+ // Special case, old IV is -1*x and this one is x. Can treat this one as
+ // -1*old.
+ 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;
+ if (const SCEVMulExpr *ME = dyn_cast<SCEVMulExpr>(SI->first))
+ if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(ME->getOperand(0)))
+ if (Stride == ME->getOperand(1) &&
+ SC->getValue()->getSExtValue() == -1LL)
+ for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
+ IE = SI->second.IVs.end(); II != IE; ++II)
+ // Accept nonzero base here.
+ // Only reuse previous IV if it would not require type conversion.
+ if (!RequiresTypeConversion(II->Base->getType(), Ty)) {
+ IV = *II;
+ return SE->getIntegerSCEV(-1LL, Stride->getType());
+ }
+ }
}
- return 0;
+ return SE->getIntegerSCEV(0, Stride->getType());
}
/// PartitionByIsUseOfPostIncrementedValue - Simple boolean predicate that
/// 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);
+ const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Expr);
if (!Mul) return false;
// If there is a constant factor, it will be first.
- SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
+ const SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
if (!SC) return false;
// Return true if the value is negative, this matches things like (-42 * V).
return SC->getValue()->getValue().isNegative();
}
-/// 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
IVUsersOfOneStride &Uses,
Loop *L,
bool &AllUsesAreAddresses,
+ bool &AllUsesAreOutsideLoop,
std::vector<BasedUser> &UsersToProcess) {
UsersToProcess.reserve(Uses.Users.size());
for (unsigned i = 0, e = Uses.Users.size(); i != e; ++i) {
UsersToProcess.push_back(BasedUser(Uses.Users[i], SE));
- // Move any loop invariant operands from the offset field to the immediate
+ // Move any loop variant 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,
+ MoveLoopVariantsToImmediateField(UsersToProcess.back().Base,
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, SE);
+ RemoveCommonExpressionsFromUseBases(UsersToProcess, SE, L, TLI);
// 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;
+ bool HasAddress = false;
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
UsersToProcess[i].Base =
SE->getIntegerSCEV(0, UsersToProcess[i].Base->getType());
} else {
-
+ // Not all uses are outside the loop.
+ AllUsesAreOutsideLoop = false;
+
// Addressing modes can be folded into loads and stores. Be careful that
// the store is through the expression, not of the expression though.
bool isPHI = false;
++NumPHI;
}
+ if (isAddress)
+ HasAddress = true;
+
// If this use isn't an address, then not all uses are addresses.
if (!isAddress && !isPHI)
AllUsesAreAddresses = false;
}
}
- // If one of the use if a PHI node and all other uses are addresses, still
+ // If one of the use is 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;
+
+ // There are no in-loop address uses.
+ if (AllUsesAreAddresses && (!HasAddress && !AllUsesAreOutsideLoop))
+ AllUsesAreAddresses = false;
return CommonExprs;
}
+/// ShouldUseFullStrengthReductionMode - Test whether full strength-reduction
+/// is valid and profitable for the given set of users of a stride. In
+/// full strength-reduction mode, all addresses at the current stride are
+/// strength-reduced all the way down to pointer arithmetic.
+///
+bool LoopStrengthReduce::ShouldUseFullStrengthReductionMode(
+ const std::vector<BasedUser> &UsersToProcess,
+ const Loop *L,
+ bool AllUsesAreAddresses,
+ SCEVHandle Stride) {
+ if (!EnableFullLSRMode)
+ return false;
+
+ // The heuristics below aim to avoid increasing register pressure, but
+ // fully strength-reducing all the addresses increases the number of
+ // add instructions, so don't do this when optimizing for size.
+ // TODO: If the loop is large, the savings due to simpler addresses
+ // may oughtweight the costs of the extra increment instructions.
+ if (L->getHeader()->getParent()->hasFnAttr(Attribute::OptimizeForSize))
+ return false;
+
+ // TODO: For now, don't do full strength reduction if there could
+ // potentially be greater-stride multiples of the current stride
+ // which could reuse the current stride IV.
+ if (StrideOrder.back() != Stride)
+ return false;
+
+ // Iterate through the uses to find conditions that automatically rule out
+ // full-lsr mode.
+ for (unsigned i = 0, e = UsersToProcess.size(); i != e; ) {
+ const SCEV *Base = UsersToProcess[i].Base;
+ const SCEV *Imm = UsersToProcess[i].Imm;
+ // If any users have a loop-variant component, they can't be fully
+ // strength-reduced.
+ if (Imm && !Imm->isLoopInvariant(L))
+ return false;
+ // If there are to users with the same base and the difference between
+ // the two Imm values can't be folded into the address, full
+ // strength reduction would increase register pressure.
+ do {
+ const SCEV *CurImm = UsersToProcess[i].Imm;
+ if ((CurImm || Imm) && CurImm != Imm) {
+ if (!CurImm) CurImm = SE->getIntegerSCEV(0, Stride->getType());
+ if (!Imm) Imm = SE->getIntegerSCEV(0, Stride->getType());
+ const Instruction *Inst = UsersToProcess[i].Inst;
+ const Type *UseTy = getAccessType(Inst);
+ SCEVHandle Diff = SE->getMinusSCEV(UsersToProcess[i].Imm, Imm);
+ if (!Diff->isZero() &&
+ (!AllUsesAreAddresses ||
+ !fitsInAddressMode(Diff, UseTy, TLI, /*HasBaseReg=*/true)))
+ return false;
+ }
+ } while (++i != e && Base == UsersToProcess[i].Base);
+ }
+
+ // If there's exactly one user in this stride, fully strength-reducing it
+ // won't increase register pressure. If it's starting from a non-zero base,
+ // it'll be simpler this way.
+ if (UsersToProcess.size() == 1 && !UsersToProcess[0].Base->isZero())
+ return true;
+
+ // Otherwise, if there are any users in this stride that don't require
+ // a register for their base, full strength-reduction will increase
+ // register pressure.
+ for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
+ if (UsersToProcess[i].Base->isZero())
+ return false;
+
+ // Otherwise, go for it.
+ return true;
+}
+
+/// InsertAffinePhi Create and insert a PHI node for an induction variable
+/// with the specified start and step values in the specified loop.
+///
+/// If NegateStride is true, the stride should be negated by using a
+/// subtract instead of an add.
+///
+/// Return the created phi node.
+///
+static PHINode *InsertAffinePhi(SCEVHandle Start, SCEVHandle Step,
+ const Loop *L,
+ SCEVExpander &Rewriter) {
+ assert(Start->isLoopInvariant(L) && "New PHI start is not loop invariant!");
+ assert(Step->isLoopInvariant(L) && "New PHI stride is not loop invariant!");
+
+ BasicBlock *Header = L->getHeader();
+ BasicBlock *Preheader = L->getLoopPreheader();
+ BasicBlock *LatchBlock = L->getLoopLatch();
+ const Type *Ty = Start->getType();
+ Ty = Rewriter.SE.getEffectiveSCEVType(Ty);
+
+ PHINode *PN = PHINode::Create(Ty, "lsr.iv", Header->begin());
+ PN->addIncoming(Rewriter.expandCodeFor(Start, Ty, Preheader->getTerminator()),
+ Preheader);
+
+ // If the stride is negative, insert a sub instead of an add for the
+ // increment.
+ bool isNegative = isNonConstantNegative(Step);
+ SCEVHandle IncAmount = Step;
+ if (isNegative)
+ IncAmount = Rewriter.SE.getNegativeSCEV(Step);
+
+ // Insert an add instruction right before the terminator corresponding
+ // to the back-edge.
+ Value *StepV = Rewriter.expandCodeFor(IncAmount, Ty,
+ Preheader->getTerminator());
+ Instruction *IncV;
+ if (isNegative) {
+ IncV = BinaryOperator::CreateSub(PN, StepV, "lsr.iv.next",
+ LatchBlock->getTerminator());
+ } else {
+ IncV = BinaryOperator::CreateAdd(PN, StepV, "lsr.iv.next",
+ LatchBlock->getTerminator());
+ }
+ if (!isa<ConstantInt>(StepV)) ++NumVariable;
+
+ PN->addIncoming(IncV, LatchBlock);
+
+ ++NumInserted;
+ return PN;
+}
+
+static void SortUsersToProcess(std::vector<BasedUser> &UsersToProcess) {
+ // We want to emit code for users inside the loop first. To do this, we
+ // rearrange BasedUser so that the entries at the end have
+ // isUseOfPostIncrementedValue = false, because we pop off the end of the
+ // vector (so we handle them first).
+ std::partition(UsersToProcess.begin(), UsersToProcess.end(),
+ PartitionByIsUseOfPostIncrementedValue);
+
+ // Sort this by base, so that things with the same base are handled
+ // together. By partitioning first and stable-sorting later, we are
+ // guaranteed that within each base we will pop off users from within the
+ // loop before users outside of the loop with a particular base.
+ //
+ // We would like to use stable_sort here, but we can't. The problem is that
+ // SCEVHandle's don't have a deterministic ordering w.r.t to each other, so
+ // we don't have anything to do a '<' comparison on. Because we think the
+ // number of uses is small, do a horrible bubble sort which just relies on
+ // ==.
+ for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
+ // Get a base value.
+ SCEVHandle Base = UsersToProcess[i].Base;
+
+ // Compact everything with this base to be consecutive with this one.
+ for (unsigned j = i+1; j != e; ++j) {
+ if (UsersToProcess[j].Base == Base) {
+ std::swap(UsersToProcess[i+1], UsersToProcess[j]);
+ ++i;
+ }
+ }
+ }
+}
+
+/// PrepareToStrengthReduceFully - Prepare to fully strength-reduce
+/// UsersToProcess, meaning lowering addresses all the way down to direct
+/// pointer arithmetic.
+///
+void
+LoopStrengthReduce::PrepareToStrengthReduceFully(
+ std::vector<BasedUser> &UsersToProcess,
+ SCEVHandle Stride,
+ SCEVHandle CommonExprs,
+ const Loop *L,
+ SCEVExpander &PreheaderRewriter) {
+ DOUT << " Fully reducing all users\n";
+
+ // Rewrite the UsersToProcess records, creating a separate PHI for each
+ // unique Base value.
+ for (unsigned i = 0, e = UsersToProcess.size(); i != e; ) {
+ // TODO: The uses are grouped by base, but not sorted. We arbitrarily
+ // pick the first Imm value here to start with, and adjust it for the
+ // other uses.
+ SCEVHandle Imm = UsersToProcess[i].Imm;
+ SCEVHandle Base = UsersToProcess[i].Base;
+ SCEVHandle Start = SE->getAddExpr(CommonExprs, Base, Imm);
+ PHINode *Phi = InsertAffinePhi(Start, Stride, L,
+ PreheaderRewriter);
+ // Loop over all the users with the same base.
+ do {
+ UsersToProcess[i].Base = SE->getIntegerSCEV(0, Stride->getType());
+ UsersToProcess[i].Imm = SE->getMinusSCEV(UsersToProcess[i].Imm, Imm);
+ UsersToProcess[i].Phi = Phi;
+ assert(UsersToProcess[i].Imm->isLoopInvariant(L) &&
+ "ShouldUseFullStrengthReductionMode should reject this!");
+ } while (++i != e && Base == UsersToProcess[i].Base);
+ }
+}
+
+/// PrepareToStrengthReduceWithNewPhi - Insert a new induction variable for the
+/// given users to share.
+///
+void
+LoopStrengthReduce::PrepareToStrengthReduceWithNewPhi(
+ std::vector<BasedUser> &UsersToProcess,
+ SCEVHandle Stride,
+ SCEVHandle CommonExprs,
+ Value *CommonBaseV,
+ const Loop *L,
+ SCEVExpander &PreheaderRewriter) {
+ DOUT << " Inserting new PHI:\n";
+
+ PHINode *Phi = InsertAffinePhi(SE->getUnknown(CommonBaseV),
+ Stride, L,
+ PreheaderRewriter);
+
+ // Remember this in case a later stride is multiple of this.
+ IVsByStride[Stride].addIV(Stride, CommonExprs, Phi);
+
+ // All the users will share this new IV.
+ for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
+ UsersToProcess[i].Phi = Phi;
+
+ DOUT << " IV=";
+ DEBUG(WriteAsOperand(*DOUT, Phi, /*PrintType=*/false));
+ DOUT << "\n";
+}
+
+/// PrepareToStrengthReduceWithNewPhi - Prepare for the given users to reuse
+/// an induction variable with a stride that is a factor of the current
+/// induction variable.
+///
+void
+LoopStrengthReduce::PrepareToStrengthReduceFromSmallerStride(
+ std::vector<BasedUser> &UsersToProcess,
+ Value *CommonBaseV,
+ const IVExpr &ReuseIV,
+ Instruction *PreInsertPt) {
+ DOUT << " Rewriting in terms of existing IV of STRIDE " << *ReuseIV.Stride
+ << " and BASE " << *ReuseIV.Base << "\n";
+
+ // All the users will share the reused IV.
+ for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
+ UsersToProcess[i].Phi = ReuseIV.PHI;
+
+ Constant *C = dyn_cast<Constant>(CommonBaseV);
+ if (C &&
+ (!C->isNullValue() &&
+ !fitsInAddressMode(SE->getUnknown(CommonBaseV), CommonBaseV->getType(),
+ TLI, false)))
+ // 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(),
+ "commonbase", PreInsertPt);
+}
+
+static bool IsImmFoldedIntoAddrMode(GlobalValue *GV, int64_t Offset,
+ const Type *AccessTy,
+ std::vector<BasedUser> &UsersToProcess,
+ const TargetLowering *TLI) {
+ SmallVector<Instruction*, 16> AddrModeInsts;
+ for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
+ if (UsersToProcess[i].isUseOfPostIncrementedValue)
+ continue;
+ ExtAddrMode AddrMode =
+ AddressingModeMatcher::Match(UsersToProcess[i].OperandValToReplace,
+ AccessTy, UsersToProcess[i].Inst,
+ AddrModeInsts, *TLI);
+ if (GV && GV != AddrMode.BaseGV)
+ return false;
+ if (Offset && !AddrMode.BaseOffs)
+ // FIXME: How to accurate check it's immediate offset is folded.
+ return false;
+ AddrModeInsts.clear();
+ }
+ return true;
+}
+
/// 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).
+/// may not be the only stride.
void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
IVUsersOfOneStride &Uses,
- Loop *L,
- bool isOnlyStride) {
+ Loop *L) {
// If all the users are moved to another stride, then there is nothing to do.
if (Uses.Users.empty())
return;
// smaller-stride IV.
bool AllUsesAreAddresses = true;
+ // Keep track if every use of a single stride is outside the loop. If so,
+ // we want to be more aggressive about reusing a smaller-stride IV; a
+ // multiply outside the loop is better than another IV inside. Well, usually.
+ bool AllUsesAreOutsideLoop = 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
// have the full access expression to rewrite the use.
std::vector<BasedUser> UsersToProcess;
SCEVHandle CommonExprs = CollectIVUsers(Stride, Uses, L, AllUsesAreAddresses,
+ AllUsesAreOutsideLoop,
UsersToProcess);
+ // Sort the UsersToProcess array so that users with common bases are
+ // next to each other.
+ SortUsersToProcess(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(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";
- NewPHI = ReuseIV.PHI;
- IncV = ReuseIV.IncV;
+ const Type *ReplacedTy = CommonExprs->getType();
+
+ // If all uses are addresses, consider sinking the immediate part of the
+ // common expression back into uses if they can fit in the immediate fields.
+ if (TLI && HaveCommonExprs && AllUsesAreAddresses) {
+ SCEVHandle NewCommon = CommonExprs;
+ SCEVHandle Imm = SE->getIntegerSCEV(0, ReplacedTy);
+ MoveImmediateValues(TLI, Type::VoidTy, NewCommon, Imm, true, L, SE);
+ if (!Imm->isZero()) {
+ bool DoSink = true;
+
+ // If the immediate part of the common expression is a GV, check if it's
+ // possible to fold it into the target addressing mode.
+ GlobalValue *GV = 0;
+ if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(Imm))
+ GV = dyn_cast<GlobalValue>(SU->getValue());
+ int64_t Offset = 0;
+ if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Imm))
+ Offset = SC->getValue()->getSExtValue();
+ if (GV || Offset)
+ // Pass VoidTy as the AccessTy to be conservative, because
+ // there could be multiple access types among all the uses.
+ DoSink = IsImmFoldedIntoAddrMode(GV, Offset, Type::VoidTy,
+ UsersToProcess, TLI);
+
+ if (DoSink) {
+ DOUT << " Sinking " << *Imm << " back down into uses\n";
+ for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
+ UsersToProcess[i].Imm = SE->getAddExpr(UsersToProcess[i].Imm, Imm);
+ CommonExprs = NewCommon;
+ HaveCommonExprs = !CommonExprs->isZero();
+ ++NumImmSunk;
+ }
+ }
}
- const Type *ReplacedTy = CommonExprs->getType();
-
// Now that we know what we need to do, insert the PHI node itself.
//
- DOUT << "INSERTING IV of TYPE " << *ReplacedTy << " of STRIDE "
- << *Stride << " and BASE " << *CommonExprs << ": ";
+ DOUT << "LSR: Examining IVs of TYPE " << *ReplacedTy << " of STRIDE "
+ << *Stride << ":\n"
+ << " Common base: " << *CommonExprs << "\n";
SCEVExpander Rewriter(*SE, *LI);
SCEVExpander PreheaderRewriter(*SE, *LI);
-
+
BasicBlock *Preheader = L->getLoopPreheader();
Instruction *PreInsertPt = Preheader->getTerminator();
- Instruction *PhiInsertBefore = L->getHeader()->begin();
-
BasicBlock *LatchBlock = L->getLoopLatch();
+ Value *CommonBaseV = Constant::getNullValue(ReplacedTy);
- // Emit the initial base value into the loop preheader.
- Value *CommonBaseV
- = PreheaderRewriter.expandCodeFor(CommonExprs, PreInsertPt);
-
- if (RewriteFactor == 0) {
- // Create a new Phi for this base, and stick it in the loop header.
- NewPHI = PHINode::Create(ReplacedTy, "iv.", PhiInsertBefore);
- ++NumInserted;
-
- // Add common base to the new Phi node.
- NewPHI->addIncoming(CommonBaseV, Preheader);
-
- // If the stride is negative, insert a sub instead of an add for the
- // increment.
- bool isNegative = isNonConstantNegative(Stride);
- SCEVHandle IncAmount = Stride;
- if (isNegative)
- IncAmount = SE->getNegativeSCEV(Stride);
-
- // Insert the stride into the preheader.
- Value *StrideV = PreheaderRewriter.expandCodeFor(IncAmount, PreInsertPt);
- if (!isa<ConstantInt>(StrideV)) ++NumVariable;
-
- // Emit the increment of the base value before the terminator of the loop
- // latch block, and add it to the Phi node.
- SCEVHandle IncExp = SE->getUnknown(StrideV);
- if (isNegative)
- IncExp = SE->getNegativeSCEV(IncExp);
- IncExp = SE->getAddExpr(SE->getUnknown(NewPHI), IncExp);
-
- IncV = Rewriter.expandCodeFor(IncExp, LatchBlock->getTerminator());
- IncV->setName(NewPHI->getName()+".inc");
- NewPHI->addIncoming(IncV, LatchBlock);
-
- // Remember this in case a later stride is multiple of this.
- IVsByStride[Stride].addIV(Stride, CommonExprs, NewPHI, IncV);
-
- DOUT << " IV=%" << NewPHI->getNameStr() << " INC=%" << IncV->getNameStr();
+ SCEVHandle RewriteFactor = SE->getIntegerSCEV(0, ReplacedTy);
+ IVExpr ReuseIV(SE->getIntegerSCEV(0, Type::Int32Ty),
+ SE->getIntegerSCEV(0, Type::Int32Ty),
+ 0);
+
+ /// Choose a strength-reduction strategy and prepare for it by creating
+ /// the necessary PHIs and adjusting the bookkeeping.
+ if (ShouldUseFullStrengthReductionMode(UsersToProcess, L,
+ AllUsesAreAddresses, Stride)) {
+ PrepareToStrengthReduceFully(UsersToProcess, Stride, CommonExprs, L,
+ PreheaderRewriter);
} else {
- Constant *C = dyn_cast<Constant>(CommonBaseV);
- if (!C ||
- (!C->isNullValue() &&
- !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(),
- "commonbase", PreInsertPt);
- }
- DOUT << "\n";
-
- // We want to emit code for users inside the loop first. To do this, we
- // rearrange BasedUser so that the entries at the end have
- // isUseOfPostIncrementedValue = false, because we pop off the end of the
- // vector (so we handle them first).
- std::partition(UsersToProcess.begin(), UsersToProcess.end(),
- PartitionByIsUseOfPostIncrementedValue);
-
- // Sort this by base, so that things with the same base are handled
- // together. By partitioning first and stable-sorting later, we are
- // guaranteed that within each base we will pop off users from within the
- // loop before users outside of the loop with a particular base.
- //
- // We would like to use stable_sort here, but we can't. The problem is that
- // SCEVHandle's don't have a deterministic ordering w.r.t to each other, so
- // we don't have anything to do a '<' comparison on. Because we think the
- // number of uses is small, do a horrible bubble sort which just relies on
- // ==.
- for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
- // Get a base value.
- SCEVHandle Base = UsersToProcess[i].Base;
-
- // 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]);
- ++i;
- }
- }
+ // Emit the initial base value into the loop preheader.
+ CommonBaseV = PreheaderRewriter.expandCodeFor(CommonExprs, ReplacedTy,
+ PreInsertPt);
+
+ // 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.
+ RewriteFactor = CheckForIVReuse(HaveCommonExprs, AllUsesAreAddresses,
+ AllUsesAreOutsideLoop,
+ Stride, ReuseIV, ReplacedTy,
+ UsersToProcess);
+ if (isa<SCEVConstant>(RewriteFactor) &&
+ cast<SCEVConstant>(RewriteFactor)->isZero())
+ PrepareToStrengthReduceWithNewPhi(UsersToProcess, Stride, CommonExprs,
+ CommonBaseV, L, PreheaderRewriter);
+ else
+ PrepareToStrengthReduceFromSmallerStride(UsersToProcess, CommonBaseV,
+ ReuseIV, PreInsertPt);
}
- // Process all the users now. This outer loop handles all bases, the inner
+ // Process all the users now, replacing their strided uses with
+ // strength-reduced forms. This outer loop handles all bases, the inner
// loop handles all users of a particular base.
while (!UsersToProcess.empty()) {
SCEVHandle Base = UsersToProcess.back().Base;
+ Instruction *Inst = UsersToProcess.back().Inst;
// Emit the code for Base into the preheader.
- Value *BaseV = PreheaderRewriter.expandCodeFor(Base, PreInsertPt);
-
- DOUT << " INSERTING code for BASE = " << *Base << ":";
- if (BaseV->hasName())
- DOUT << " Result value name = %" << BaseV->getNameStr();
- DOUT << "\n";
-
- // If BaseV is a constant other than 0, make sure that it gets inserted into
- // the preheader, instead of being forward substituted into the uses. We do
- // this by forcing a BitCast (noop cast) to be inserted into the preheader
- // in this case.
- if (Constant *C = dyn_cast<Constant>(BaseV)) {
- if (!C->isNullValue() && !isTargetConstant(Base, ReplacedTy, TLI)) {
+ Value *BaseV = 0;
+ if (!Base->isZero()) {
+ BaseV = PreheaderRewriter.expandCodeFor(Base, Base->getType(),
+ PreInsertPt);
+
+ DOUT << " INSERTING code for BASE = " << *Base << ":";
+ if (BaseV->hasName())
+ DOUT << " Result value name = %" << BaseV->getNameStr();
+ DOUT << "\n";
+
+ // If BaseV is a non-zero constant, make sure that it gets inserted into
+ // the preheader, instead of being forward substituted into the uses. We
+ // do this by forcing a BitCast (noop cast) to be inserted into the
+ // preheader in this case.
+ if (!fitsInAddressMode(Base, getAccessType(Inst), TLI, false)) {
// 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",
// FIXME: Use emitted users to emit other users.
BasedUser &User = UsersToProcess.back();
+ DOUT << " Examining use ";
+ DEBUG(WriteAsOperand(*DOUT, UsersToProcess.back().OperandValToReplace,
+ /*PrintType=*/false));
+ DOUT << " in Inst: " << *(User.Inst);
+
// If this instruction wants to use the post-incremented value, move it
// after the post-inc and use its value instead of the PHI.
- Value *RewriteOp = NewPHI;
+ Value *RewriteOp = User.Phi;
if (User.isUseOfPostIncrementedValue) {
- RewriteOp = IncV;
+ RewriteOp = User.Phi->getIncomingValueForBlock(LatchBlock);
// If this user is in the loop, make sure it is the last thing in the
// loop to ensure it is dominated by the increment.
if (L->contains(User.Inst->getParent()))
User.Inst->moveBefore(LatchBlock->getTerminator());
}
- if (RewriteOp->getType() != ReplacedTy) {
- Instruction::CastOps opcode = Instruction::Trunc;
- if (ReplacedTy->getPrimitiveSizeInBits() ==
- RewriteOp->getType()->getPrimitiveSizeInBits())
- opcode = Instruction::BitCast;
- RewriteOp = SCEVExpander::InsertCastOfTo(opcode, RewriteOp, ReplacedTy);
- }
SCEVHandle RewriteExpr = SE->getUnknown(RewriteOp);
- // If we had to insert new instrutions for RewriteOp, we have to
+ if (SE->getTypeSizeInBits(RewriteOp->getType()) !=
+ SE->getTypeSizeInBits(ReplacedTy)) {
+ assert(SE->getTypeSizeInBits(RewriteOp->getType()) >
+ SE->getTypeSizeInBits(ReplacedTy) &&
+ "Unexpected widening cast!");
+ RewriteExpr = SE->getTruncateExpr(RewriteExpr, ReplacedTy);
+ }
+
+ // If we had to insert new instructions 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
// PHI node, we can use the later point to expand the final
// RewriteExpr.
Instruction *NewBasePt = dyn_cast<Instruction>(RewriteOp);
- if (RewriteOp == NewPHI) NewBasePt = 0;
+ if (RewriteOp == User.Phi) NewBasePt = 0;
// Clear the SCEVExpander's expression map so that we are guaranteed
// to have the code emitted where we expect it.
Rewriter.clear();
// 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 = SE->getMulExpr(SE->getIntegerSCEV(RewriteFactor,
- RewriteExpr->getType()),
+ // factor to take advantage of the addressing mode scale component.
+ if (!RewriteFactor->isZero()) {
+ // If we're reusing an IV with a nonzero base (currently this happens
+ // only when all reuses are outside the loop) subtract that base here.
+ // The base has been used to initialize the PHI node but we don't want
+ // it here.
+ if (!ReuseIV.Base->isZero()) {
+ SCEVHandle typedBase = ReuseIV.Base;
+ if (SE->getTypeSizeInBits(RewriteExpr->getType()) !=
+ SE->getTypeSizeInBits(ReuseIV.Base->getType())) {
+ // It's possible the original IV is a larger type than the new IV,
+ // in which case we have to truncate the Base. We checked in
+ // RequiresTypeConversion that this is valid.
+ assert(SE->getTypeSizeInBits(RewriteExpr->getType()) <
+ SE->getTypeSizeInBits(ReuseIV.Base->getType()) &&
+ "Unexpected lengthening conversion!");
+ typedBase = SE->getTruncateExpr(ReuseIV.Base,
+ RewriteExpr->getType());
+ }
+ RewriteExpr = SE->getMinusSCEV(RewriteExpr, typedBase);
+ }
+
+ // Multiply old variable, with base removed, by new scale factor.
+ RewriteExpr = SE->getMulExpr(RewriteFactor,
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 = SE->getAddExpr(RewriteExpr,
- SE->getUnknown(CommonBaseV));
+ // When this use is outside the loop, we earlier subtracted the
+ // common base, and are adding it back here. Use the same expression
+ // as before, rather than CommonBaseV, so DAGCombiner will zap it.
+ if (!CommonExprs->isZero()) {
+ if (L->contains(User.Inst->getParent()))
+ RewriteExpr = SE->getAddExpr(RewriteExpr,
+ SE->getUnknown(CommonBaseV));
+ else
+ RewriteExpr = SE->getAddExpr(RewriteExpr, CommonExprs);
+ }
}
// 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())
+ if (BaseV)
// Add BaseV to the PHI value if needed.
RewriteExpr = SE->getAddExpr(RewriteExpr, SE->getUnknown(BaseV));
Rewriter, L, this,
DeadInsts);
- // Mark old value we replaced as possibly dead, so that it is elminated
+ // Mark old value we replaced as possibly dead, so that it is eliminated
// if we just replaced the last use of that value.
- DeadInsts.insert(cast<Instruction>(User.OperandValToReplace));
+ DeadInsts.push_back(cast<Instruction>(User.OperandValToReplace));
UsersToProcess.pop_back();
++NumReduced;
// e.g.
// 4, -1, X, 1, 2 ==> 1, -1, 2, 4, X
struct StrideCompare {
+ const ScalarEvolution *SE;
+ explicit StrideCompare(const ScalarEvolution *se) : SE(se) {}
+
bool operator()(const SCEVHandle &LHS, const SCEVHandle &RHS) {
- SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS);
- SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS);
+ const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS);
+ const 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
+ if (ALV == ARV) {
+ if (LV != RV)
+ return LV > RV;
+ } else {
return ALV < ARV;
+ }
+
+ // If it's the same value but different type, sort by bit width so
+ // that we emit larger induction variables before smaller
+ // ones, letting the smaller be re-written in terms of larger ones.
+ return SE->getTypeSizeInBits(RHS->getType()) <
+ SE->getTypeSizeInBits(LHS->getType());
}
- return (LHSC && !RHSC);
+ return LHSC && !RHSC;
}
};
}
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();
+ unsigned BitWidth = SE->getTypeSizeInBits((*CondStride)->getType());
uint64_t SignBit = 1ULL << (BitWidth-1);
- const Type *CmpTy = C->getType();
+ const Type *CmpTy = Cond->getOperand(0)->getType();
const Type *NewCmpTy = NULL;
- unsigned TyBits = CmpTy->getPrimitiveSizeInBits();
+ unsigned TyBits = SE->getTypeSizeInBits(CmpTy);
unsigned NewTyBits = 0;
- int64_t NewCmpVal = CmpVal;
SCEVHandle *NewStride = NULL;
- Value *NewIncV = NULL;
+ Value *NewCmpLHS = NULL;
+ Value *NewCmpRHS = NULL;
int64_t Scale = 1;
+ SCEVHandle NewOffset = SE->getIntegerSCEV(0, CmpTy);
- // Check stride constant and the comparision constant signs to detect
- // overflow.
- if ((CmpVal & SignBit) != (CmpSSInt & SignBit))
- return Cond;
+ if (ConstantInt *C = dyn_cast<ConstantInt>(Cond->getOperand(1))) {
+ int64_t CmpVal = C->getValue().getSExtValue();
- // 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;
+ // Check stride constant and the comparision constant signs to detect
+ // overflow.
+ if ((CmpVal & SignBit) != (CmpSSInt & SignBit))
+ return Cond;
- Scale = SSInt / CmpSSInt;
- NewCmpVal = CmpVal * Scale;
- APInt Mul = APInt(BitWidth, NewCmpVal);
- // Check for overflow.
- if (Mul.getSExtValue() != NewCmpVal) {
- NewCmpVal = CmpVal;
- continue;
- }
+ // Look for a suitable stride / iv as replacement.
+ 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 (SSInt == CmpSSInt ||
+ abs(SSInt) < abs(CmpSSInt) ||
+ (SSInt % CmpSSInt) != 0)
+ continue;
- // Watch out for overflow.
- if (ICmpInst::isSignedPredicate(Predicate) &&
- (CmpVal & SignBit) != (NewCmpVal & SignBit))
- NewCmpVal = CmpVal;
+ Scale = SSInt / CmpSSInt;
+ int64_t NewCmpVal = CmpVal * Scale;
+ APInt Mul = APInt(BitWidth, NewCmpVal);
+ // Check for overflow.
+ if (Mul.getSExtValue() != NewCmpVal)
+ continue;
+
+ // Watch out for overflow.
+ if (ICmpInst::isSignedPredicate(Predicate) &&
+ (CmpVal & SignBit) != (NewCmpVal & SignBit))
+ continue;
- if (NewCmpVal != CmpVal) {
+ if (NewCmpVal == CmpVal)
+ continue;
// Pick the best iv to use trying to avoid a cast.
- NewIncV = NULL;
+ NewCmpLHS = 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)
+ NewCmpLHS = UI->OperandValToReplace;
+ if (NewCmpLHS->getType() == CmpTy)
break;
}
- if (!NewIncV) {
- NewCmpVal = CmpVal;
+ if (!NewCmpLHS)
continue;
- }
- NewCmpTy = NewIncV->getType();
- NewTyBits = isa<PointerType>(NewCmpTy)
- ? UIntPtrTy->getPrimitiveSizeInBits()
- : NewCmpTy->getPrimitiveSizeInBits();
+ NewCmpTy = NewCmpLHS->getType();
+ NewTyBits = SE->getTypeSizeInBits(NewCmpTy);
+ const Type *NewCmpIntTy = IntegerType::get(NewTyBits);
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;
+ unsigned Bits = NewTyBits;
+ if (ICmpInst::isSignedPredicate(Predicate))
+ --Bits;
+ uint64_t Mask = (1ULL << Bits) - 1;
+ if (((uint64_t)NewCmpVal & Mask) != (uint64_t)NewCmpVal)
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;
+ if (NewTyBits != TyBits && !isa<SCEVConstant>(CondUse->Offset))
continue;
- }
bool AllUsesAreAddresses = true;
+ bool AllUsesAreOutsideLoop = true;
std::vector<BasedUser> UsersToProcess;
SCEVHandle CommonExprs = CollectIVUsers(SI->first, SI->second, L,
AllUsesAreAddresses,
+ AllUsesAreOutsideLoop,
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
+ // stride of the compare instruction.
if (AllUsesAreAddresses &&
- ValidStride(!CommonExprs->isZero(), Scale, UsersToProcess)) {
- NewCmpVal = CmpVal;
+ ValidStride(!CommonExprs->isZero(), Scale, UsersToProcess))
continue;
- }
// If scale is negative, use swapped predicate unless it's testing
// for equality.
Predicate = ICmpInst::getSwappedPredicate(Predicate);
NewStride = &StrideOrder[i];
+ if (!isa<PointerType>(NewCmpTy))
+ NewCmpRHS = ConstantInt::get(NewCmpTy, NewCmpVal);
+ else {
+ ConstantInt *CI = ConstantInt::get(NewCmpIntTy, NewCmpVal);
+ NewCmpRHS = ConstantExpr::getIntToPtr(CI, NewCmpTy);
+ }
+ NewOffset = TyBits == NewTyBits
+ ? SE->getMulExpr(CondUse->Offset,
+ SE->getConstant(ConstantInt::get(CmpTy, Scale)))
+ : SE->getConstant(ConstantInt::get(NewCmpIntTy,
+ cast<SCEVConstant>(CondUse->Offset)->getValue()->getSExtValue()*Scale));
break;
}
}
if (!Cond->hasOneUse()) {
for (BasicBlock::iterator I = Cond, E = Cond->getParent()->end();
I != E; ++I)
- if (I == NewIncV)
+ if (I == NewCmpLHS)
return Cond;
}
- if (NewCmpVal != CmpVal) {
+ if (NewCmpRHS) {
// 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,
+ Cond = new ICmpInst(Predicate, NewCmpLHS, NewCmpRHS,
L->getHeader()->getName() + ".termcond",
OldCond);
// Remove the old compare instruction. The old indvar is probably dead too.
- DeadInsts.insert(cast<Instruction>(CondUse->OperandValToReplace));
+ DeadInsts.push_back(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);
+ IVUsesByStride[*NewStride].addUser(NewOffset, Cond, NewCmpLHS);
CondUse = &IVUsesByStride[*NewStride].Users.back();
CondStride = NewStride;
++NumEliminated;
+ Changed = true;
}
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))
+ SCEVHandle BackedgeTakenCount = SE->getBackedgeTakenCount(L);
+ if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
return Cond;
- SCEVHandle One = SE->getIntegerSCEV(1, IterationCount->getType());
+ SCEVHandle One = SE->getIntegerSCEV(1, BackedgeTakenCount->getType());
- // Adjust for an annoying getIterationCount quirk.
- IterationCount = SE->getAddExpr(IterationCount, One);
+ // Add one to the backedge-taken count to get the trip count.
+ SCEVHandle IterationCount = SE->getAddExpr(BackedgeTakenCount, One);
// Check for a max calculation that matches the pattern.
SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(IterationCount);
// Check the relevant induction variable for conformance to
// the pattern.
SCEVHandle IV = SE->getSCEV(Cond->getOperand(0));
- SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
+ const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
if (!AR || !AR->isAffine() ||
AR->getStart() != One ||
AR->getStepRecurrence(*SE) != One)
return Cond;
+ assert(AR->getLoop() == L &&
+ "Loop condition operand is an addrec in a different loop!");
+
// Check the right operand of the select, and remember it, as it will
// be used in the new comparison instruction.
Value *NewRHS = 0;
/// inside the loop then try to eliminate the cast opeation.
void LoopStrengthReduce::OptimizeShadowIV(Loop *L) {
- SCEVHandle IterationCount = SE->getIterationCount(L);
- if (isa<SCEVCouldNotCompute>(IterationCount))
+ SCEVHandle BackedgeTakenCount = SE->getBackedgeTakenCount(L);
+ if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
return;
for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e;
const Type *SrcTy = PH->getType();
int Mantissa = DestTy->getFPMantissaWidth();
if (Mantissa == -1) continue;
- if ((int)TD->getTypeSizeInBits(SrcTy) > Mantissa)
+ if ((int)SE->getTypeSizeInBits(SrcTy) > Mantissa)
continue;
unsigned Entry, Latch;
LI = &getAnalysis<LoopInfo>();
DT = &getAnalysis<DominatorTree>();
SE = &getAnalysis<ScalarEvolution>();
- TD = &getAnalysis<TargetData>();
- UIntPtrTy = TD->getIntPtrType();
Changed = false;
- // Find all uses of induction variables in this loop, and catagorize
+ // Find all uses of induction variables in this loop, and categorize
// 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.
SmallPtrSet<Instruction*,16> Processed; // Don't reprocess instructions.
AddUsersIfInteresting(I, L, Processed);
if (!IVUsesByStride.empty()) {
+#ifndef NDEBUG
+ DOUT << "\nLSR on \"" << L->getHeader()->getParent()->getNameStart()
+ << "\" ";
+ DEBUG(L->dump());
+#endif
+
+ // Sort the StrideOrder so we process larger strides first.
+ std::stable_sort(StrideOrder.begin(), StrideOrder.end(), StrideCompare(SE));
+
// 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
// 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;
-
-#ifndef NDEBUG
- DOUT << "\nLSR on ";
- DEBUG(L->dump());
-#endif
-
// 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
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);
+ StrengthReduceStridedIVUsers(SI->first, SI->second, L);
}
}
// 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();
- 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()) {
- SmallPtrSet<PHINode *, 2> 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;
- }
- }
+ if (!DeadInsts.empty())
+ DeleteTriviallyDeadInstructions();
+
+ // At this point, it is worth checking to see if any recurrence PHIs are also
+ // dead, so that we can remove them as well. To keep ScalarEvolution
+ // current, use a ValueDeletionListener class.
+ struct LSRListener : public ValueDeletionListener {
+ ScalarEvolution &SE;
+ explicit LSRListener(ScalarEvolution &se) : SE(se) {}
+
+ virtual void ValueWillBeDeleted(Value *V) {
+ SE.deleteValueFromRecords(V);
}
- DeleteTriviallyDeadInstructions(DeadInsts);
- }
+ } VDL(*SE);
+ DeleteDeadPHIs(L->getHeader(), &VDL);
+
return Changed;
}
projects / oota-llvm.git / blobdiff