-//===- LoopStrengthReduce.cpp - Strength Reduce GEPs in Loops -------------===//
+//===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===//
//
// The LLVM Compiler Infrastructure
//
-// This file was developed by Nate Begeman and is distributed under the
-// University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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/Transforms/Scalar.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/Type.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Analysis/Dominators.h"
#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/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(NumInserted, "Number of PHIs inserted");
-STATISTIC(NumVariable, "Number of PHIs with variable strides");
+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 {
/// IVStrideUse - Keep track of one use of a strided induction variable, where
/// the stride is stored externally. The Offset member keeps track of the
- /// offset from the IV, User is the actual user of the operand, and 'Operand'
- /// is the operand # of the User that is the use.
+ /// offset from the IV, User is the actual user of the operand, and
+ /// 'OperandValToReplace' is the operand of the User that is the use.
struct VISIBILITY_HIDDEN IVStrideUse {
SCEVHandle Offset;
Instruction *User;
SCEVHandle Stride;
SCEVHandle Base;
PHINode *PHI;
- Value *IncV;
-
- IVExpr()
- : Stride(SCEVUnknown::getIntegerSCEV(0, Type::Int32Ty)),
- Base (SCEVUnknown::getIntegerSCEV(0, Type::Int32Ty)) {}
- IVExpr(const SCEVHandle &stride, const SCEVHandle &base, PHINode *phi,
- Value *incv)
- : Stride(stride), Base(base), PHI(phi), IncV(incv) {}
+
+ 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));
}
};
class VISIBILITY_HIDDEN LoopStrengthReduce : public LoopPass {
LoopInfo *LI;
- ETForest *EF;
+ DominatorTree *DT;
ScalarEvolution *SE;
- const TargetData *TD;
- const Type *UIntPtrTy;
bool Changed;
/// IVUsesByStride - Keep track of all uses of induction variables that we
/// StrideOrder - An ordering of the keys in IVUsesByStride that is stable:
/// We use this to iterate over the IVUsesByStride collection without being
/// dependent on random ordering of pointers in the process.
- std::vector<SCEVHandle> StrideOrder;
-
- /// CastedValues - As we need to cast values to uintptr_t, this keeps track
- /// of the casted version of each value. This is accessed by
- /// getCastedVersionOf.
- std::map<Value*, Value*> CastedPointers;
+ SmallVector<SCEVHandle, 16> StrideOrder;
/// DeadInsts - Keep track of instructions we may have made dead, so that
/// we can remove them after we are done working.
- std::set<Instruction*> DeadInsts;
+ SmallVector<Instruction*, 16> DeadInsts;
/// TLI - Keep a pointer of a TargetLowering to consult for determining
/// transformation profitability.
const TargetLowering *TLI;
public:
- LoopStrengthReduce(const TargetLowering *tli = NULL)
- : TLI(tli) {
+ static char ID; // Pass ID, replacement for typeid
+ explicit LoopStrengthReduce(const TargetLowering *tli = NULL) :
+ LoopPass(&ID), TLI(tli) {
}
bool runOnLoop(Loop *L, LPPassManager &LPM);
// many analyses if they are around.
AU.addPreservedID(LoopSimplifyID);
AU.addPreserved<LoopInfo>();
- AU.addPreserved<DominatorSet>();
- AU.addPreserved<ETForest>();
- AU.addPreserved<ImmediateDominators>();
AU.addPreserved<DominanceFrontier>();
AU.addPreserved<DominatorTree>();
AU.addRequiredID(LoopSimplifyID);
AU.addRequired<LoopInfo>();
- AU.addRequired<ETForest>();
- AU.addRequired<TargetData>();
+ AU.addRequired<DominatorTree>();
AU.addRequired<ScalarEvolution>();
+ AU.addPreserved<ScalarEvolution>();
}
-
- /// getCastedVersionOf - Return the specified value casted to uintptr_t.
- ///
- Value *getCastedVersionOf(Instruction::CastOps opcode, Value *V);
-private:
- bool AddUsersIfInteresting(Instruction *I, Loop *L,
- std::set<Instruction*> &Processed);
- SCEVHandle GetExpressionSCEV(Instruction *E, Loop *L);
+ private:
+ bool AddUsersIfInteresting(Instruction *I, Loop *L,
+ SmallPtrSet<Instruction*,16> &Processed);
+ ICmpInst *ChangeCompareStride(Loop *L, ICmpInst *Cond,
+ IVStrideUse* &CondUse,
+ const SCEVHandle* &CondStride);
void OptimizeIndvars(Loop *L);
- bool FindIVForUser(ICmpInst *Cond, IVStrideUse *&CondUse,
- const SCEVHandle *&CondStride);
- unsigned CheckForIVReuse(const SCEVHandle&, IVExpr&, const Type*,
- const std::vector<BasedUser>& UsersToProcess);
+ /// OptimizeShadowIV - If IV is used in a int-to-float cast
+ /// inside the loop then try to eliminate the cast opeation.
+ void OptimizeShadowIV(Loop *L);
- bool ValidStride(int64_t, const std::vector<BasedUser>& UsersToProcess);
+ /// OptimizeSMax - Rewrite the loop's terminating condition
+ /// if it uses an smax computation.
+ ICmpInst *OptimizeSMax(Loop *L, ICmpInst *Cond,
+ IVStrideUse* &CondUse);
+ bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
+ const SCEVHandle *&CondStride);
+ bool RequiresTypeConversion(const Type *Ty, const Type *NewTy);
+ SCEVHandle CheckForIVReuse(bool, bool, bool, const SCEVHandle&,
+ IVExpr&, const Type*,
+ const std::vector<BasedUser>& UsersToProcess);
+ bool ValidStride(bool, int64_t,
+ const std::vector<BasedUser>& UsersToProcess);
+ SCEVHandle CollectIVUsers(const SCEVHandle &Stride,
+ IVUsersOfOneStride &Uses,
+ Loop *L,
+ bool &AllUsesAreAddresses,
+ 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(std::set<Instruction*> &Insts);
+ Loop *L);
+ void DeleteTriviallyDeadInstructions();
};
- RegisterPass<LoopStrengthReduce> X("loop-reduce", "Loop Strength Reduction");
}
-LoopPass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
- return new LoopStrengthReduce(TLI);
-}
+char LoopStrengthReduce::ID = 0;
+static RegisterPass<LoopStrengthReduce>
+X("loop-reduce", "Loop Strength Reduction");
-/// 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;
+Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
+ return new LoopStrengthReduce(TLI);
}
-
/// 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(std::set<Instruction*> &Insts) {
- while (!Insts.empty()) {
- Instruction *I = *Insts.begin();
- Insts.erase(Insts.begin());
- if (isInstructionTriviallyDead(I)) {
- for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
- if (Instruction *U = dyn_cast<Instruction>(I->getOperand(i)))
- Insts.insert(U);
- SE->deleteInstructionFromRecords(I);
- I->eraseFromParent();
- Changed = true;
- }
- }
-}
-
-
-/// GetExpressionSCEV - Compute and return the SCEV for the specified
-/// instruction.
-SCEVHandle LoopStrengthReduce::GetExpressionSCEV(Instruction *Exp, Loop *L) {
- // Pointer to pointer bitcast instructions return the same value as their
- // operand.
- if (BitCastInst *BCI = dyn_cast<BitCastInst>(Exp)) {
- if (SE->hasSCEV(BCI) || !isa<Instruction>(BCI->getOperand(0)))
- return SE->getSCEV(BCI);
- SCEVHandle R = GetExpressionSCEV(cast<Instruction>(BCI->getOperand(0)), L);
- SE->setSCEV(BCI, R);
- return R;
+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;
}
-
- // 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);
+
+ while (!DeadInsts.empty()) {
+ Instruction *I = DeadInsts.back();
+ DeadInsts.pop_back();
- // Analyze all of the subscripts of this getelementptr instruction, looking
- // for uses that are determined by the trip count of L. First, skip all
- // operands the are not dependent on the IV.
+ if (I == 0 || !isInstructionTriviallyDead(I))
+ continue;
- // Build up the base expression. Insert an LLVM cast of the pointer to
- // uintptr_t first.
- SCEVHandle GEPVal = SCEVUnknown::get(
- getCastedVersionOf(Instruction::PtrToInt, GEP->getOperand(0)));
+ SE->deleteValueFromRecords(I);
- gep_type_iterator GTI = gep_type_begin(GEP);
-
- for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i, ++GTI) {
- // If this is a use of a recurrence that we can analyze, and it comes before
- // Op does in the GEP operand list, we will handle this when we process this
- // operand.
- if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
- const StructLayout *SL = TD->getStructLayout(STy);
- unsigned Idx = cast<ConstantInt>(GEP->getOperand(i))->getZExtValue();
- uint64_t Offset = SL->getElementOffset(Idx);
- GEPVal = SCEVAddExpr::get(GEPVal,
- SCEVUnknown::getIntegerSCEV(Offset, UIntPtrTy));
- } else {
- unsigned GEPOpiBits =
- GEP->getOperand(i)->getType()->getPrimitiveSizeInBits();
- unsigned IntPtrBits = UIntPtrTy->getPrimitiveSizeInBits();
- Instruction::CastOps opcode = (GEPOpiBits < IntPtrBits ?
- Instruction::SExt : (GEPOpiBits > IntPtrBits ? Instruction::Trunc :
- Instruction::BitCast));
- Value *OpVal = getCastedVersionOf(opcode, GEP->getOperand(i));
- SCEVHandle Idx = SE->getSCEV(OpVal);
-
- uint64_t TypeSize = TD->getTypeSize(GTI.getIndexedType());
- if (TypeSize != 1)
- Idx = SCEVMulExpr::get(Idx,
- SCEVConstant::get(ConstantInt::get(UIntPtrTy,
- TypeSize)));
- GEPVal = SCEVAddExpr::get(GEPVal, Idx);
+ 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;
}
+}
- SE->setSCEV(GEP, GEPVal);
- return GEPVal;
+/// 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;
+ }
+ 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;
+ }
+ 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) {
+ SCEVHandle &Start, SCEVHandle &Stride,
+ 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 = SCEVAddExpr::get(AddRec, TheAddRec);
+ TheAddRec = SE->getAddExpr(AddRec, TheAddRec);
else
return false; // Nested IV of some sort?
} else {
- Start = SCEVAddExpr::get(Start, AE->getOperand(i));
+ Start = SE->getAddExpr(Start, AE->getOperand(i));
}
} else if (isa<SCEVAddRecExpr>(SH)) {
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;
- Start = SCEVAddExpr::get(Start, AddRec->getOperand(0));
+ // 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;
/// the loop, resulting in reg-reg copies (if we use the pre-inc value when we
/// should use the post-inc value).
static bool IVUseShouldUsePostIncValue(Instruction *User, Instruction *IV,
- Loop *L, ETForest *EF, Pass *P) {
+ Loop *L, DominatorTree *DT, Pass *P,
+ SmallVectorImpl<Instruction*> &DeadInsts){
// If the user is in the loop, use the preinc value.
if (L->contains(User->getParent())) return false;
// Ok, the user is outside of the loop. If it is dominated by the latch
// block, use the post-inc value.
- if (EF->dominates(LatchBlock, User->getParent()))
+ if (DT->dominates(LatchBlock, User->getParent()))
return true;
// There is one case we have to be careful of: PHI nodes. These little guys
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingValue(i) == IV) {
++NumUses;
- if (!EF->dominates(LatchBlock, PN->getIncomingBlock(i)))
+ if (!DT->dominates(LatchBlock, PN->getIncomingBlock(i)))
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,
- true);
- // Splitting the critical edge can reduce the number of entries in this
- // PHI.
- e = PN->getNumIncomingValues();
- if (--NumUses == 0) break;
- }
-
+ // 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,
- std::set<Instruction*> &Processed) {
- if (!I->getType()->isInteger() && !isa<PointerType>(I->getType()))
- return false; // Void and FP expressions cannot be reduced.
- if (!Processed.insert(I).second)
+ SmallPtrSet<Instruction*,16> &Processed) {
+ 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, L);
+ SCEVHandle ISE = SE->getSCEV(I);
if (isa<SCEVCouldNotCompute>(ISE)) return false;
// Get the start and stride for this expression.
- SCEVHandle Start = SCEVUnknown::getIntegerSCEV(0, ISE->getType());
+ SCEVHandle Start = SE->getIntegerSCEV(0, ISE->getType());
SCEVHandle Stride = Start;
- if (!getSCEVStartAndStride(ISE, L, Start, Stride))
+ if (!getSCEVStartAndStride(ISE, L, Start, Stride, SE, DT))
return false; // Non-reducible symbolic expression, bail out.
- for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;) {
- Instruction *User = cast<Instruction>(*UI);
+ std::vector<Instruction *> IUsers;
+ // Collect all I uses now because IVUseShouldUsePostIncValue may
+ // invalidate use_iterator.
+ for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E; ++UI)
+ IUsers.push_back(cast<Instruction>(*UI));
+
+ for (unsigned iused_index = 0, iused_size = IUsers.size();
+ iused_index != iused_size; ++iused_index) {
- // Increment iterator now because IVUseShouldUsePostIncValue may remove
- // User from the list of I users.
- ++UI;
+ Instruction *User = IUsers[iused_index];
// Do not infinitely recurse on PHI nodes.
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
// and decide what to do with it. If we are a use inside of the loop, use
// the value before incrementation, otherwise use it after incrementation.
- if (IVUseShouldUsePostIncValue(User, I, L, EF, this)) {
+ if (IVUseShouldUsePostIncValue(User, I, L, DT, this, DeadInsts)) {
// The value used will be incremented by the stride more than we are
// expecting, so subtract this off.
- SCEVHandle NewStart = SCEV::getMinusSCEV(Start, Stride);
+ SCEVHandle NewStart = SE->getMinusSCEV(Start, Stride);
StrideUses.addUser(NewStart, User, I);
StrideUses.Users.back().isUseOfPostIncrementedValue = true;
DOUT << " USING POSTINC SCEV, START=" << *NewStart<< "\n";
/// BasedUser - For a particular base value, keep information about how we've
/// partitioned the expression so far.
struct BasedUser {
+ /// SE - The current ScalarEvolution object.
+ ScalarEvolution *SE;
+
/// Base - The Base value for the PHI node that needs to be inserted for
/// this use. As the use is processed, information gets moved from this
/// field to the Imm field (below). BasedUser values are sorted by this
/// 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.
// the loop.
bool isUseOfPostIncrementedValue;
- BasedUser(IVStrideUse &IVSU)
- : Base(IVSU.Offset), Inst(IVSU.User),
+ BasedUser(IVStrideUse &IVSU, ScalarEvolution *se)
+ : SE(se), Base(IVSU.Offset), Inst(IVSU.User),
OperandValToReplace(IVSU.OperandValToReplace),
- Imm(SCEVUnknown::getIntegerSCEV(0, Base->getType())), EmittedBase(0),
+ Imm(SE->getIntegerSCEV(0, Base->getType())),
isUseOfPostIncrementedValue(IVSU.isUseOfPostIncrementedValue) {}
// Once we rewrite the code to insert the new IVs we want, update the
// operands of Inst to use the new expression 'NewBase', with 'Imm' added
// to it.
void RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
- SCEVExpander &Rewriter, Loop *L,
- Pass *P);
+ Instruction *InsertPt,
+ SCEVExpander &Rewriter, Loop *L, Pass *P,
+ 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 (SCEVConstant *SC = dyn_cast<SCEVConstant>(Imm))
- if (SC->getValue()->isZero())
- return Rewriter.expandCodeFor(NewBase, BaseInsertPt,
- OperandValToReplace->getType());
+ if (Imm->isZero())
+ return Base;
- Value *Base = Rewriter.expandCodeFor(NewBase, BaseInsertPt);
+ // 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.
+ if (IP == BaseInsertPt)
+ IP = Rewriter.getInsertionPoint();
// Always emit the immediate (if non-zero) into the same block as the user.
- SCEVHandle NewValSCEV = SCEVAddExpr::get(SCEVUnknown::get(Base), Imm);
- return Rewriter.expandCodeFor(NewValSCEV, IP,
- OperandValToReplace->getType());
+ SCEVHandle NewValSCEV = SE->getAddExpr(SE->getUnknown(Base), Imm);
+ return Rewriter.expandCodeFor(NewValSCEV, Ty, IP);
}
// Once we rewrite the code to insert the new IVs we want, update the
// operands of Inst to use the new expression 'NewBase', with 'Imm' added
-// to it.
+// to it. NewBasePt is the last instruction which contributes to the
+// value of NewBase in the case that it's a diffferent instruction from
+// the PHI that NewBase is computed from, or null otherwise.
+//
void BasedUser::RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
- SCEVExpander &Rewriter,
- Loop *L, Pass *P) {
+ Instruction *NewBasePt,
+ SCEVExpander &Rewriter, Loop *L, Pass *P,
+ SmallVectorImpl<Instruction*> &DeadInsts){
if (!isa<PHINode>(Inst)) {
- Value *NewVal = InsertCodeForBaseAtPosition(NewBase, Rewriter, Inst, L);
+ // By default, insert code at the user instruction.
+ BasicBlock::iterator InsertPt = Inst;
+
+ // However, if the Operand is itself an instruction, the (potentially
+ // complex) inserted code may be shared by many users. Because of this, we
+ // want to emit code for the computation of the operand right before its old
+ // computation. This is usually safe, because we obviously used to use the
+ // computation when it was computed in its current block. However, in some
+ // 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 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;
+ } else if (Instruction *OpInst
+ = dyn_cast<Instruction>(OperandValToReplace)) {
+ InsertPt = OpInst;
+ while (isa<PHINode>(InsertPt)) ++InsertPt;
+ }
+ }
+ 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 << " Inst = " << *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
// that a PHI node only has a single Value* for each predecessor (which also
// prevents us from inserting duplicate code in some blocks).
- std::map<BasicBlock*, Value*> InsertedCode;
+ DenseMap<BasicBlock*, Value*> InsertedCode;
PHINode *PN = cast<PHINode>(Inst);
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
if (PN->getIncomingValue(i) == OperandValToReplace) {
- // 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, true);
-
- // 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);
+ 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();
}
}
- DOUT << " CHANGED: IMM =" << *Imm << " Inst = " << *Inst;
+
+ // PHI node might have become a constant value after SplitCriticalEdge.
+ 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)
- return TLI->isLegalAddressImmediate(VC, UseTy);
- else
+ 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.
return (VC > -(1 << 16) && VC < (1 << 16)-1);
+ }
}
- if (SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V))
- if (ConstantExpr *CE = dyn_cast<ConstantExpr>(SU->getValue()))
- if (CE->getOpcode() == Instruction::PtrToInt) {
- Constant *Op0 = CE->getOperand(0);
- if (isa<GlobalValue>(Op0) && TLI &&
- TLI->isLegalAddressImmediate(cast<GlobalValue>(Op0)))
- return true;
+ 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,
- Loop *L) {
+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());
if (!SAE->getOperand(i)->isLoopInvariant(L)) {
// If this is a loop-variant expression, it must stay in the immediate
// field of the expression.
- Imm = SCEVAddExpr::get(Imm, SAE->getOperand(i));
+ Imm = SE->getAddExpr(Imm, SAE->getOperand(i));
} else {
NewOps.push_back(SAE->getOperand(i));
}
if (NewOps.empty())
- Val = SCEVUnknown::getIntegerSCEV(0, Val->getType());
+ Val = SE->getIntegerSCEV(0, Val->getType());
else
- Val = SCEVAddExpr::get(NewOps);
- } else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
+ Val = SE->getAddExpr(NewOps);
+ } 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);
+ MoveLoopVariantsToImmediateField(Start, Imm, L, SE);
std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
Ops[0] = Start;
- Val = SCEVAddRecExpr::get(Ops, SARE->getLoop());
+ Val = SE->getAddRecExpr(Ops, SARE->getLoop());
} else {
// Otherwise, all of Val is variant, move the whole thing over.
- Imm = SCEVAddExpr::get(Imm, Val);
- Val = SCEVUnknown::getIntegerSCEV(0, Val->getType());
+ Imm = SE->getAddExpr(Imm, Val);
+ Val = SE->getIntegerSCEV(0, Val->getType());
}
}
/// 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) {
- const Type *UseTy = User->getType();
- if (StoreInst *SI = dyn_cast<StoreInst>(User))
- UseTy = SI->getOperand(0)->getType();
-
- if (SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
+ bool isAddress, Loop *L,
+ ScalarEvolution *SE) {
+ 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);
+ 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
// field of the expression.
- Imm = SCEVAddExpr::get(Imm, NewOp);
+ Imm = SE->getAddExpr(Imm, NewOp);
} else {
NewOps.push_back(NewOp);
}
}
if (NewOps.empty())
- Val = SCEVUnknown::getIntegerSCEV(0, Val->getType());
+ Val = SE->getIntegerSCEV(0, Val->getType());
else
- Val = SCEVAddExpr::get(NewOps);
+ Val = SE->getAddExpr(NewOps);
return;
- } else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
+ } 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);
+ MoveImmediateValues(TLI, UseTy, Start, Imm, isAddress, L, SE);
if (Start != SARE->getStart()) {
std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
Ops[0] = Start;
- Val = SCEVAddRecExpr::get(Ops, SARE->getLoop());
+ Val = SE->getAddRecExpr(Ops, SARE->getLoop());
}
return;
- } else if (SCEVMulExpr *SME = dyn_cast<SCEVMulExpr>(Val)) {
+ } 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 = SCEVUnknown::getIntegerSCEV(0, Val->getType());
+ SCEVHandle SubImm = SE->getIntegerSCEV(0, Val->getType());
SCEVHandle NewOp = SME->getOperand(1);
- MoveImmediateValues(TLI, User, NewOp, SubImm, isAddress, L);
+ MoveImmediateValues(TLI, UseTy, NewOp, SubImm, isAddress, L, SE);
// If we extracted something out of the subexpressions, see if we can
// simplify this!
if (NewOp != SME->getOperand(1)) {
// Scale SubImm up by "8". If the result is a target constant, we are
// good.
- SubImm = SCEVMulExpr::get(SubImm, SME->getOperand(0));
- if (isTargetConstant(SubImm, UseTy, TLI)) {
+ SubImm = SE->getMulExpr(SubImm, SME->getOperand(0));
+ if (fitsInAddressMode(SubImm, UseTy, TLI, false)) {
// Accumulate the immediate.
- Imm = SCEVAddExpr::get(Imm, SubImm);
+ Imm = SE->getAddExpr(Imm, SubImm);
// Update what is left of 'Val'.
- Val = SCEVMulExpr::get(SME->getOperand(0), NewOp);
+ Val = SE->getMulExpr(SME->getOperand(0), NewOp);
return;
}
}
// 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 = SCEVAddExpr::get(Imm, Val);
- Val = SCEVUnknown::getIntegerSCEV(0, Val->getType());
+ Imm = SE->getAddExpr(Imm, Val);
+ Val = SE->getIntegerSCEV(0, Val->getType());
return;
}
// 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
/// together for maximal sharing when rewriting bases.
static void SeparateSubExprs(std::vector<SCEVHandle> &SubExprs,
- SCEVHandle Expr) {
- if (SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(Expr)) {
+ SCEVHandle Expr,
+ ScalarEvolution *SE) {
+ if (const SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(Expr)) {
for (unsigned j = 0, e = AE->getNumOperands(); j != e; ++j)
- SeparateSubExprs(SubExprs, AE->getOperand(j));
- } else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Expr)) {
- SCEVHandle Zero = SCEVUnknown::getIntegerSCEV(0, Expr->getType());
+ SeparateSubExprs(SubExprs, AE->getOperand(j), SE);
+ } 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);
} else {
// Compute the addrec with zero as its base.
std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
Ops[0] = Zero; // Start with zero base.
- SubExprs.push_back(SCEVAddRecExpr::get(Ops, SARE->getLoop()));
+ SubExprs.push_back(SE->getAddRecExpr(Ops, SARE->getLoop()));
- SeparateSubExprs(SubExprs, SARE->getOperand(0));
+ SeparateSubExprs(SubExprs, SARE->getOperand(0), SE);
}
- } else if (!isa<SCEVConstant>(Expr) ||
- !cast<SCEVConstant>(Expr)->getValue()->isZero()) {
+ } else if (!Expr->isZero()) {
// Do not add zero.
SubExprs.push_back(Expr);
}
}
-
-/// 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) {
+RemoveCommonExpressionsFromUseBases(std::vector<BasedUser> &Uses,
+ ScalarEvolution *SE, Loop *L,
+ const TargetLowering *TLI) {
unsigned NumUses = Uses.size();
- // Only one use? Use its base, regardless of what it is!
- SCEVHandle Zero = SCEVUnknown::getIntegerSCEV(0, Uses[0].Base->getType());
+ // 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);
- // Add one to SubExpressionUseCounts for each subexpr present.
- for (unsigned j = 0, e = SubExprs.size(); j != e; ++j)
- if (++SubExpressionUseCounts[SubExprs[j]] == 1)
+ SeparateSubExprs(SubExprs, Uses[i].Base, SE);
+ // 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 = SCEVAddExpr::get(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);
+ 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
- Uses[i].Base = SCEVAddExpr::get(SubExprs);
+ Uses[i].Base = SE->getAddExpr(SubExprs);
SubExprs.clear();
}
return Result;
}
-/// isZero - returns true if the scalar evolution expression is zero.
-///
-static bool isZero(SCEVHandle &V) {
- if (SCEVConstant *SC = dyn_cast<SCEVConstant>(V))
- return SC->getValue()->isZero();
- return false;
-}
-
/// ValidStride - Check whether the given Scale is valid for all loads and
-/// stores in UsersToProcess. Pulled into a function to avoid disturbing the
-/// sensibilities of those who dislike goto's.
+/// stores in UsersToProcess.
///
-bool LoopStrengthReduce::ValidStride(int64_t Scale,
+bool LoopStrengthReduce::ValidStride(bool HasBaseReg,
+ int64_t Scale,
const std::vector<BasedUser>& UsersToProcess) {
- int64_t Imm;
+ if (!TLI)
+ return true;
+
for (unsigned i=0, e = UsersToProcess.size(); i!=e; ++i) {
- if (SCEVConstant *SC = dyn_cast<SCEVConstant>(UsersToProcess[i].Imm))
- Imm = SC->getValue()->getSExtValue();
- else
- Imm = 0;
-
// 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;
- if (!TLI->isLegalAddressScaleAndImm(Scale, Imm, AccessTy))
+ TargetLowering::AddrMode AM;
+ 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;
+
+ // If load[imm+r*scale] is illegal, bail out.
+ if (!TLI->isLegalAddressingMode(AM, AccessTy))
return false;
}
return true;
}
+/// 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 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. This allows the users of this stride to be rewritten
-/// as prev iv * factor. It returns 0 if no reuse is possible.
-unsigned LoopStrengthReduce::CheckForIVReuse(const SCEVHandle &Stride,
+/// mode scale component and optional base reg. This allows the users of
+/// this stride to be rewritten as prev iv * factor. It returns 0 if no
+/// reuse is possible. 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 (!TLI) return 0;
-
- if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Stride)) {
+ if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Stride)) {
int64_t SInt = SC->getValue()->getSExtValue();
- if (SInt == 1) return 0;
-
- for (std::map<SCEVHandle, IVsOfOneStride>::iterator SI= IVsByStride.begin(),
- SE = IVsByStride.end(); SI != SE; ++SI) {
+ for (unsigned NewStride = 0, e = StrideOrder.size(); NewStride != e;
+ ++NewStride) {
+ std::map<SCEVHandle, IVsOfOneStride>::iterator SI =
+ IVsByStride.find(StrideOrder[NewStride]);
+ if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first))
+ continue;
int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
- if (SInt != -SSInt &&
+ if (SI->first != Stride &&
(unsigned(abs(SInt)) < SSInt || (SInt % SSInt) != 0))
continue;
int64_t Scale = SInt / SSInt;
// Check that this stride is valid for all the types used for loads and
// stores; if it can be used for some and not others, we might as well use
// the original stride everywhere, since we have to create the IV for it
- // anyway.
- if (ValidStride(Scale, UsersToProcess))
+ // anyway. If the scale is 1, then we don't need to worry about folding
+ // multiplications.
+ if (Scale == 1 ||
+ (AllUsesAreAddresses &&
+ ValidStride(HasBaseReg, Scale, UsersToProcess)))
for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
IE = SI->second.IVs.end(); II != IE; ++II)
// FIXME: Only handle base == 0 for now.
// Only reuse previous IV if it would not require a type conversion.
- if (isZero(II->Base) && II->Base->getType() == Ty) {
+ if (II->Base->isZero() &&
+ !RequiresTypeConversion(II->Base->getType(), Ty)) {
IV = *II;
- return Scale;
+ return 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
return Val.isUseOfPostIncrementedValue;
}
-/// StrengthReduceStridedIVUsers - Strength reduce all of the users of a single
-/// stride of IV. All of the users may have different starting values, and this
-/// may not be the only stride (we know it is if isOnlyStride is true).
-void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
- IVUsersOfOneStride &Uses,
- Loop *L,
- bool isOnlyStride) {
- // Transform our list of users and offsets to a bit more complex table. In
- // this new vector, each 'BasedUser' contains 'Base' the base of the
- // strided accessas well as the old information from Uses. We progressively
- // move information from the Base field to the Imm field, until we eventually
- // have the full access expression to rewrite the use.
- std::vector<BasedUser> UsersToProcess;
+/// isNonConstantNegative - Return true if the specified scev is negated, but
+/// not a constant.
+static bool isNonConstantNegative(const SCEVHandle &Expr) {
+ const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Expr);
+ if (!Mul) return false;
+
+ // If there is a constant factor, it will be first.
+ 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();
+}
+
+// CollectIVUsers - Transform our list of users and offsets to a bit more
+// complex table. In this new vector, each 'BasedUser' contains 'Base', the base
+// of the strided accesses, as well as the old information from Uses. We
+// progressively move information from the Base field to the Imm field, until
+// we eventually have the full access expression to rewrite the use.
+SCEVHandle LoopStrengthReduce::CollectIVUsers(const SCEVHandle &Stride,
+ IVUsersOfOneStride &Uses,
+ Loop *L,
+ bool &AllUsesAreAddresses,
+ 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(Uses.Users[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,
- UsersToProcess.back().Imm, L);
+ 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);
-
+ 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
// the immediate field to allow as much factoring as possible.
if (!L->contains(UsersToProcess[i].Inst->getParent())) {
- UsersToProcess[i].Imm = SCEVAddExpr::get(UsersToProcess[i].Imm,
- UsersToProcess[i].Base);
+ UsersToProcess[i].Imm = SE->getAddExpr(UsersToProcess[i].Imm,
+ UsersToProcess[i].Base);
UsersToProcess[i].Base =
- SCEVUnknown::getIntegerSCEV(0, UsersToProcess[i].Base->getType());
+ SE->getIntegerSCEV(0, UsersToProcess[i].Base->getType());
} else {
-
+ // 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 isAddress = isa<LoadInst>(UsersToProcess[i].Inst);
- if (StoreInst *SI = dyn_cast<StoreInst>(UsersToProcess[i].Inst))
- if (SI->getOperand(1) == UsersToProcess[i].OperandValToReplace)
- isAddress = true;
+ bool isPHI = false;
+ bool isAddress = isAddressUse(UsersToProcess[i].Inst,
+ UsersToProcess[i].OperandValToReplace);
+ if (isa<PHINode>(UsersToProcess[i].Inst)) {
+ isPHI = true;
+ ++NumPHI;
+ }
+
+ if (isAddress)
+ HasAddress = true;
+
+ // If this use isn't an address, then not all uses are addresses.
+ if (!isAddress && !isPHI)
+ AllUsesAreAddresses = false;
MoveImmediateValues(TLI, UsersToProcess[i].Inst, UsersToProcess[i].Base,
- UsersToProcess[i].Imm, isAddress, L);
+ UsersToProcess[i].Imm, isAddress, L, SE);
}
}
- // Check if it is possible to reuse a IV with stride that is factor of this
- // stride. And the multiple is a number that can be encoded in the scale
- // field of the target addressing mode. And we will have a valid
- // instruction after this substition, including the immediate field, if any.
- PHINode *NewPHI = NULL;
- Value *IncV = NULL;
- IVExpr ReuseIV;
- unsigned RewriteFactor = CheckForIVReuse(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;
- }
+ // 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;
- 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 << " :\n";
+ return CommonExprs;
+}
- 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();
+/// 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;
- // Emit the initial base value into the loop preheader.
- Value *CommonBaseV
- = PreheaderRewriter.expandCodeFor(CommonExprs, PreInsertPt,
- ReplacedTy);
+ // 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;
- if (RewriteFactor == 0) {
- // Create a new Phi for this base, and stick it in the loop header.
- NewPHI = new PHINode(ReplacedTy, "iv.", PhiInsertBefore);
- ++NumInserted;
-
- // Add common base to the new Phi node.
- NewPHI->addIncoming(CommonBaseV, Preheader);
-
- // Insert the stride into the preheader.
- Value *StrideV = PreheaderRewriter.expandCodeFor(Stride, PreInsertPt,
- ReplacedTy);
- 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 = SCEVAddExpr::get(SCEVUnknown::get(NewPHI),
- SCEVUnknown::get(StrideV));
-
- IncV = Rewriter.expandCodeFor(IncExp, LatchBlock->getTerminator(),
- ReplacedTy);
- IncV->setName(NewPHI->getName()+".inc");
- NewPHI->addIncoming(IncV, LatchBlock);
+ // Otherwise, go for it.
+ return true;
+}
- // Remember this in case a later stride is multiple of this.
- IVsByStride[Stride].addIV(Stride, CommonExprs, NewPHI, IncV);
+/// 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 {
- Constant *C = dyn_cast<Constant>(CommonBaseV);
- if (!C ||
- (!C->isNullValue() &&
- !isTargetConstant(SCEVUnknown::get(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);
+ 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
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 consequetive with this one.
+
+ // 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]);
}
}
}
+}
- // Process all the users now. This outer loop handles all bases, the inner
+/// 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.
+void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
+ IVUsersOfOneStride &Uses,
+ Loop *L) {
+ // If all the users are moved to another stride, then there is nothing to do.
+ if (Uses.Users.empty())
+ return;
+
+ // Keep track if every use in UsersToProcess is an address. If they all are,
+ // we may be able to rewrite the entire collection of them in terms of a
+ // smaller-stride IV.
+ bool AllUsesAreAddresses = true;
+
+ // 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
+ // move information from the Base field to the Imm field, until we eventually
+ // have the full access expression to rewrite the use.
+ std::vector<BasedUser> UsersToProcess;
+ SCEVHandle CommonExprs = CollectIVUsers(Stride, Uses, L, AllUsesAreAddresses,
+ 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();
+ 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;
+ }
+ }
+ }
+
+ // Now that we know what we need to do, insert the PHI node itself.
+ //
+ 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();
+ BasicBlock *LatchBlock = L->getLoopLatch();
+
+ Value *CommonBaseV = Constant::getNullValue(ReplacedTy);
+
+ 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 {
+ // 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, 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;
- DOUT << " INSERTING code for BASE = " << *Base << ":\n";
-
// Emit the code for Base into the preheader.
- Value *BaseV = PreheaderRewriter.expandCodeFor(Base, PreInsertPt,
- ReplacedTy);
-
- // 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",
- PreInsertPt);
+ PreInsertPt);
}
}
// 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 (SE->getTypeSizeInBits(RewriteOp->getType()) !=
+ SE->getTypeSizeInBits(ReplacedTy)) {
+ assert(SE->getTypeSizeInBits(RewriteOp->getType()) >
+ SE->getTypeSizeInBits(ReplacedTy) &&
+ "Unexpected widening cast!");
+ RewriteExpr = SE->getTruncateExpr(RewriteExpr, ReplacedTy);
}
- SCEVHandle RewriteExpr = SCEVUnknown::get(RewriteOp);
+ // 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
+ // instruction was inserted so that if we're replacing a different
+ // PHI node, we can use the later point to expand the final
+ // RewriteExpr.
+ Instruction *NewBasePt = dyn_cast<Instruction>(RewriteOp);
+ if (RewriteOp == 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 =
- SCEVMulExpr::get(SCEVUnknown::getIntegerSCEV(RewriteFactor,
- RewriteExpr->getType()),
- RewriteExpr);
+ // 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 = SCEVAddExpr::get(RewriteExpr,
- SCEVUnknown::get(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 = SCEVAddExpr::get(RewriteExpr, SCEVUnknown::get(BaseV));
+ RewriteExpr = SE->getAddExpr(RewriteExpr, SE->getUnknown(BaseV));
- User.RewriteInstructionToUseNewBase(RewriteExpr, Rewriter, L, this);
+ User.RewriteInstructionToUseNewBase(RewriteExpr, NewBasePt,
+ Rewriter, L, this,
+ DeadInsts);
- // Mark old value we replaced as possibly dead, so that it is elminated
+ // 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;
// different starting values, into different PHIs.
}
-/// FindIVForUser - If Cond has an operand that is an expression of an IV,
+/// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
/// set the IV user and stride information and return true, otherwise return
/// false.
-bool LoopStrengthReduce::FindIVForUser(ICmpInst *Cond, IVStrideUse *&CondUse,
+bool LoopStrengthReduce::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
const SCEVHandle *&CondStride) {
for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e && !CondUse;
++Stride) {
return false;
}
+namespace {
+ // Constant strides come first which in turns are sorted by their absolute
+ // values. If absolute values are the same, then positive strides comes first.
+ // e.g.
+ // 4, -1, X, 1, 2 ==> 1, -1, 2, 4, X
+ struct StrideCompare {
+ const ScalarEvolution *SE;
+ explicit StrideCompare(const ScalarEvolution *se) : SE(se) {}
+
+ bool operator()(const SCEVHandle &LHS, const SCEVHandle &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) {
+ 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;
+ }
+ };
+}
+
+/// ChangeCompareStride - If a loop termination compare instruction is the
+/// only use of its stride, and the compaison is against a constant value,
+/// try eliminate the stride by moving the compare instruction to another
+/// stride and change its constant operand accordingly. e.g.
+///
+/// loop:
+/// ...
+/// v1 = v1 + 3
+/// v2 = v2 + 1
+/// if (v2 < 10) goto loop
+/// =>
+/// loop:
+/// ...
+/// v1 = v1 + 3
+/// if (v1 < 30) goto loop
+ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
+ IVStrideUse* &CondUse,
+ const SCEVHandle* &CondStride) {
+ if (StrideOrder.size() < 2 ||
+ IVUsesByStride[*CondStride].Users.size() != 1)
+ return Cond;
+ const SCEVConstant *SC = dyn_cast<SCEVConstant>(*CondStride);
+ if (!SC) return Cond;
+
+ ICmpInst::Predicate Predicate = Cond->getPredicate();
+ int64_t CmpSSInt = SC->getValue()->getSExtValue();
+ unsigned BitWidth = SE->getTypeSizeInBits((*CondStride)->getType());
+ uint64_t SignBit = 1ULL << (BitWidth-1);
+ const Type *CmpTy = Cond->getOperand(0)->getType();
+ const Type *NewCmpTy = NULL;
+ unsigned TyBits = SE->getTypeSizeInBits(CmpTy);
+ unsigned NewTyBits = 0;
+ SCEVHandle *NewStride = NULL;
+ Value *NewCmpLHS = NULL;
+ Value *NewCmpRHS = NULL;
+ int64_t Scale = 1;
+ SCEVHandle NewOffset = SE->getIntegerSCEV(0, CmpTy);
+
+ if (ConstantInt *C = dyn_cast<ConstantInt>(Cond->getOperand(1))) {
+ int64_t CmpVal = C->getValue().getSExtValue();
+
+ // Check stride constant and the comparision constant signs to detect
+ // overflow.
+ if ((CmpVal & SignBit) != (CmpSSInt & SignBit))
+ return Cond;
+
+ // Look for a suitable stride / iv as replacement.
+ 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;
+
+ 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)
+ continue;
+ // Pick the best iv to use trying to avoid a cast.
+ NewCmpLHS = NULL;
+ for (std::vector<IVStrideUse>::iterator UI = SI->second.Users.begin(),
+ E = SI->second.Users.end(); UI != E; ++UI) {
+ NewCmpLHS = UI->OperandValToReplace;
+ if (NewCmpLHS->getType() == CmpTy)
+ break;
+ }
+ if (!NewCmpLHS)
+ continue;
+
+ 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.
+ 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))
+ 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))
+ continue;
+
+ // If scale is negative, use swapped predicate unless it's testing
+ // for equality.
+ if (Scale < 0 && !Cond->isEquality())
+ Predicate = ICmpInst::getSwappedPredicate(Predicate);
+
+ NewStride = &StrideOrder[i];
+ 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;
+ }
+ }
+
+ // Forgo this transformation if it the increment happens to be
+ // unfortunately positioned after the condition, and the condition
+ // has multiple uses which prevent it from being moved immediately
+ // before the branch. See
+ // test/Transforms/LoopStrengthReduce/change-compare-stride-trickiness-*.ll
+ // for an example of this situation.
+ if (!Cond->hasOneUse()) {
+ for (BasicBlock::iterator I = Cond, E = Cond->getParent()->end();
+ I != E; ++I)
+ if (I == NewCmpLHS)
+ return Cond;
+ }
+
+ if (NewCmpRHS) {
+ // Create a new compare instruction using new stride / iv.
+ ICmpInst *OldCond = Cond;
+ // Insert new compare instruction.
+ Cond = new ICmpInst(Predicate, NewCmpLHS, NewCmpRHS,
+ L->getHeader()->getName() + ".termcond",
+ OldCond);
+
+ // Remove the old compare instruction. The old indvar is probably dead too.
+ DeadInsts.push_back(cast<Instruction>(CondUse->OperandValToReplace));
+ SE->deleteValueFromRecords(OldCond);
+ OldCond->replaceAllUsesWith(Cond);
+ OldCond->eraseFromParent();
+
+ IVUsesByStride[*CondStride].Users.pop_back();
+ IVUsesByStride[*NewStride].addUser(NewOffset, Cond, NewCmpLHS);
+ CondUse = &IVUsesByStride[*NewStride].Users.back();
+ CondStride = NewStride;
+ ++NumEliminated;
+ Changed = true;
+ }
+
+ return Cond;
+}
+
+/// OptimizeSMax - Rewrite the loop's terminating condition if it uses
+/// an smax computation.
+///
+/// This is a narrow solution to a specific, but acute, problem. For loops
+/// like this:
+///
+/// i = 0;
+/// do {
+/// p[i] = 0.0;
+/// } while (++i < n);
+///
+/// where the comparison is signed, the trip count isn't just 'n', because
+/// 'n' could be negative. And unfortunately this can come up even for loops
+/// where the user didn't use a C do-while loop. For example, seemingly
+/// well-behaved top-test loops will commonly be lowered like this:
+//
+/// if (n > 0) {
+/// i = 0;
+/// do {
+/// p[i] = 0.0;
+/// } while (++i < n);
+/// }
+///
+/// and then it's possible for subsequent optimization to obscure the if
+/// test in such a way that indvars can't find it.
+///
+/// When indvars can't find the if test in loops like this, it creates a
+/// signed-max expression, which allows it to give the loop a canonical
+/// induction variable:
+///
+/// i = 0;
+/// smax = n < 1 ? 1 : n;
+/// do {
+/// p[i] = 0.0;
+/// } while (++i != smax);
+///
+/// Canonical induction variables are necessary because the loop passes
+/// are designed around them. The most obvious example of this is the
+/// LoopInfo analysis, which doesn't remember trip count values. It
+/// expects to be able to rediscover the trip count each time it is
+/// needed, and it does this using a simple analyis that only succeeds if
+/// the loop has a canonical induction variable.
+///
+/// However, when it comes time to generate code, the maximum operation
+/// can be quite costly, especially if it's inside of an outer loop.
+///
+/// This function solves this problem by detecting this type of loop and
+/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
+/// the instructions for the maximum computation.
+///
+ICmpInst *LoopStrengthReduce::OptimizeSMax(Loop *L, ICmpInst *Cond,
+ IVStrideUse* &CondUse) {
+ // Check that the loop matches the pattern we're looking for.
+ if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
+ Cond->getPredicate() != CmpInst::ICMP_NE)
+ return Cond;
+
+ SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
+ if (!Sel || !Sel->hasOneUse()) return Cond;
+
+ SCEVHandle BackedgeTakenCount = SE->getBackedgeTakenCount(L);
+ if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
+ return Cond;
+ SCEVHandle One = SE->getIntegerSCEV(1, BackedgeTakenCount->getType());
+
+ // 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);
+ if (!SMax || SMax != SE->getSCEV(Sel)) return Cond;
+
+ SCEVHandle SMaxLHS = SMax->getOperand(0);
+ SCEVHandle SMaxRHS = SMax->getOperand(1);
+ if (!SMaxLHS || SMaxLHS != One) return Cond;
+
+ // Check the relevant induction variable for conformance to
+ // the pattern.
+ SCEVHandle IV = SE->getSCEV(Cond->getOperand(0));
+ 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;
+ if (SE->getSCEV(Sel->getOperand(1)) == SMaxRHS)
+ NewRHS = Sel->getOperand(1);
+ else if (SE->getSCEV(Sel->getOperand(2)) == SMaxRHS)
+ NewRHS = Sel->getOperand(2);
+ if (!NewRHS) return Cond;
+
+ // Ok, everything looks ok to change the condition into an SLT or SGE and
+ // delete the max calculation.
+ ICmpInst *NewCond =
+ new ICmpInst(Cond->getPredicate() == CmpInst::ICMP_NE ?
+ CmpInst::ICMP_SLT :
+ CmpInst::ICMP_SGE,
+ Cond->getOperand(0), NewRHS, "scmp", Cond);
+
+ // Delete the max calculation instructions.
+ SE->deleteValueFromRecords(Cond);
+ Cond->replaceAllUsesWith(NewCond);
+ Cond->eraseFromParent();
+ Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
+ SE->deleteValueFromRecords(Sel);
+ Sel->eraseFromParent();
+ if (Cmp->use_empty()) {
+ SE->deleteValueFromRecords(Cmp);
+ Cmp->eraseFromParent();
+ }
+ CondUse->User = NewCond;
+ return NewCond;
+}
+
+/// OptimizeShadowIV - If IV is used in a int-to-float cast
+/// inside the loop then try to eliminate the cast opeation.
+void LoopStrengthReduce::OptimizeShadowIV(Loop *L) {
+
+ SCEVHandle BackedgeTakenCount = SE->getBackedgeTakenCount(L);
+ if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
+ return;
+
+ for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e;
+ ++Stride) {
+ std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
+ IVUsesByStride.find(StrideOrder[Stride]);
+ assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
+ if (!isa<SCEVConstant>(SI->first))
+ continue;
+
+ for (std::vector<IVStrideUse>::iterator UI = SI->second.Users.begin(),
+ E = SI->second.Users.end(); UI != E; /* empty */) {
+ std::vector<IVStrideUse>::iterator CandidateUI = UI;
+ ++UI;
+ Instruction *ShadowUse = CandidateUI->User;
+ const Type *DestTy = NULL;
+
+ /* If shadow use is a int->float cast then insert a second IV
+ to eliminate this cast.
+
+ for (unsigned i = 0; i < n; ++i)
+ foo((double)i);
+
+ is transformed into
+
+ double d = 0.0;
+ for (unsigned i = 0; i < n; ++i, ++d)
+ foo(d);
+ */
+ if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->User))
+ DestTy = UCast->getDestTy();
+ else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->User))
+ DestTy = SCast->getDestTy();
+ if (!DestTy) continue;
+
+ if (TLI) {
+ /* If target does not support DestTy natively then do not apply
+ this transformation. */
+ MVT DVT = TLI->getValueType(DestTy);
+ if (!TLI->isTypeLegal(DVT)) continue;
+ }
+
+ PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
+ if (!PH) continue;
+ if (PH->getNumIncomingValues() != 2) continue;
+
+ const Type *SrcTy = PH->getType();
+ int Mantissa = DestTy->getFPMantissaWidth();
+ if (Mantissa == -1) continue;
+ if ((int)SE->getTypeSizeInBits(SrcTy) > Mantissa)
+ continue;
+
+ unsigned Entry, Latch;
+ if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
+ Entry = 0;
+ Latch = 1;
+ } else {
+ Entry = 1;
+ Latch = 0;
+ }
+
+ ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
+ if (!Init) continue;
+ ConstantFP *NewInit = ConstantFP::get(DestTy, Init->getZExtValue());
+
+ BinaryOperator *Incr =
+ dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
+ if (!Incr) continue;
+ if (Incr->getOpcode() != Instruction::Add
+ && Incr->getOpcode() != Instruction::Sub)
+ continue;
+
+ /* Initialize new IV, double d = 0.0 in above example. */
+ ConstantInt *C = NULL;
+ if (Incr->getOperand(0) == PH)
+ C = dyn_cast<ConstantInt>(Incr->getOperand(1));
+ else if (Incr->getOperand(1) == PH)
+ C = dyn_cast<ConstantInt>(Incr->getOperand(0));
+ else
+ continue;
+
+ if (!C) continue;
+
+ /* Add new PHINode. */
+ PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH);
+
+ /* create new increment. '++d' in above example. */
+ ConstantFP *CFP = ConstantFP::get(DestTy, C->getZExtValue());
+ BinaryOperator *NewIncr =
+ BinaryOperator::Create(Incr->getOpcode(),
+ NewPH, CFP, "IV.S.next.", Incr);
+
+ NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
+ NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
+
+ /* Remove cast operation */
+ SE->deleteValueFromRecords(ShadowUse);
+ ShadowUse->replaceAllUsesWith(NewPH);
+ ShadowUse->eraseFromParent();
+ SI->second.Users.erase(CandidateUI);
+ NumShadow++;
+ break;
+ }
+ }
+}
+
// OptimizeIndvars - Now that IVUsesByStride is set up with all of the indvar
// uses in the loop, look to see if we can eliminate some, in favor of using
// common indvars for the different uses.
void LoopStrengthReduce::OptimizeIndvars(Loop *L) {
// TODO: implement optzns here.
+ OptimizeShadowIV(L);
+
// Finally, get the terminating condition for the loop if possible. If we
// can, we want to change it to use a post-incremented version of its
// induction variable, to allow coalescing the live ranges for the IV into
IVStrideUse *CondUse = 0;
const SCEVHandle *CondStride = 0;
- if (!FindIVForUser(Cond, CondUse, CondStride))
+ if (!FindIVUserForCond(Cond, CondUse, CondStride))
return; // setcc doesn't use the IV.
-
+
+ // If the trip count is computed in terms of an smax (due to ScalarEvolution
+ // being unable to find a sufficient guard, for example), change the loop
+ // comparison to use SLT instead of NE.
+ Cond = OptimizeSMax(L, Cond, CondUse);
+
+ // If possible, change stride and operands of the compare instruction to
+ // eliminate one stride.
+ Cond = ChangeCompareStride(L, Cond, CondUse, CondStride);
// It's possible for the setcc instruction to be anywhere in the loop, and
// possible for it to have multiple users. If it is not immediately before
// If we get to here, we know that we can transform the setcc instruction to
// use the post-incremented version of the IV, allowing us to coalesce the
// live ranges for the IV correctly.
- CondUse->Offset = SCEV::getMinusSCEV(CondUse->Offset, *CondStride);
+ CondUse->Offset = SE->getMinusSCEV(CondUse->Offset, *CondStride);
CondUse->isUseOfPostIncrementedValue = true;
-}
-
-namespace {
- // Constant strides come first which in turns are sorted by their absolute
- // values. If absolute values are the same, then positive strides comes first.
- // e.g.
- // 4, -1, X, 1, 2 ==> 1, -1, 2, 4, X
- struct StrideCompare {
- bool operator()(const SCEVHandle &LHS, const SCEVHandle &RHS) {
- SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS);
- SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS);
- if (LHSC && RHSC) {
- int64_t LV = LHSC->getValue()->getSExtValue();
- int64_t RV = RHSC->getValue()->getSExtValue();
- uint64_t ALV = (LV < 0) ? -LV : LV;
- uint64_t ARV = (RV < 0) ? -RV : RV;
- if (ALV == ARV)
- return LV > RV;
- else
- return ALV < ARV;
- }
- return (LHSC && !RHSC);
- }
- };
+ Changed = true;
}
bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
LI = &getAnalysis<LoopInfo>();
- EF = &getAnalysis<ETForest>();
+ 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.
- std::set<Instruction*> Processed; // Don't reprocess instructions.
+ SmallPtrSet<Instruction*,16> Processed; // Don't reprocess instructions.
for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I)
AddUsersIfInteresting(I, L, Processed);
- // If we have nothing to do, return.
- if (IVUsesByStride.empty()) return false;
-
- // Optimize induction variables. Some indvar uses can be transformed to use
- // strides that will be needed for other purposes. A common example of this
- // is the exit test for the loop, which can often be rewritten to use the
- // computation of some other indvar to decide when to terminate the loop.
- OptimizeIndvars(L);
-
-
- // FIXME: We can widen subreg IV's here for RISC targets. e.g. instead of
- // doing computation in byte values, promote to 32-bit values if safe.
-
- // FIXME: Attempt to reuse values across multiple IV's. In particular, we
- // could have something like "for(i) { foo(i*8); bar(i*16) }", which should be
- // codegened as "for (j = 0;; j+=8) { foo(j); bar(j+j); }" on X86/PPC. Need
- // to be careful that IV's are all the same type. Only works for intptr_t
- // indvars.
-
- // If we only have one stride, we can more aggressively eliminate some things.
- bool HasOneStride = IVUsesByStride.size() == 1;
-
+ if (!IVUsesByStride.empty()) {
#ifndef NDEBUG
- DOUT << "\nLSR on ";
- DEBUG(L->dump());
+ DOUT << "\nLSR on \"" << L->getHeader()->getParent()->getNameStart()
+ << "\" ";
+ DEBUG(L->dump());
#endif
- // IVsByStride keeps IVs for one particular loop.
- IVsByStride.clear();
-
- // Sort the StrideOrder so we process larger strides first.
- std::stable_sort(StrideOrder.begin(), StrideOrder.end(), StrideCompare());
-
- // Note: this processes each stride/type pair individually. All users passed
- // into StrengthReduceStridedIVUsers have the same type AND stride. Also,
- // node that we iterate over IVUsesByStride indirectly by using StrideOrder.
- // This extra layer of indirection makes the ordering of strides deterministic
- // - not dependent on map order.
- for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e; ++Stride) {
- std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
- IVUsesByStride.find(StrideOrder[Stride]);
- assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
- StrengthReduceStridedIVUsers(SI->first, SI->second, L, HasOneStride);
- }
-
- // Clean up after ourselves
- if (!DeadInsts.empty()) {
- DeleteTriviallyDeadInstructions(DeadInsts);
-
- BasicBlock::iterator I = L->getHeader()->begin();
- PHINode *PN;
- while ((PN = dyn_cast<PHINode>(I))) {
- ++I; // Preincrement iterator to avoid invalidating it when deleting PN.
-
- // At this point, we know that we have killed one or more GEP
- // instructions. It is worth checking to see if the cann indvar is also
- // dead, so that we can remove it as well. The requirements for the cann
- // indvar to be considered dead are:
- // 1. the cann indvar has one use
- // 2. the use is an add instruction
- // 3. the add has one use
- // 4. the add is used by the cann indvar
- // If all four cases above are true, then we can remove both the add and
- // the cann indvar.
- // FIXME: this needs to eliminate an induction variable even if it's being
- // compared against some value to decide loop termination.
- if (PN->hasOneUse()) {
- Instruction *BO = dyn_cast<Instruction>(*PN->use_begin());
- if (BO && (isa<BinaryOperator>(BO) || isa<CmpInst>(BO))) {
- if (BO->hasOneUse() && PN == *(BO->use_begin())) {
- DeadInsts.insert(BO);
- // Break the cycle, then delete the PHI.
- PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
- SE->deleteInstructionFromRecords(PN);
- PN->eraseFromParent();
- }
- }
- }
+ // 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
+ // computation of some other indvar to decide when to terminate the loop.
+ OptimizeIndvars(L);
+
+ // FIXME: We can widen subreg IV's here for RISC targets. e.g. instead of
+ // doing computation in byte values, promote to 32-bit values if safe.
+
+ // FIXME: Attempt to reuse values across multiple IV's. In particular, we
+ // could have something like "for(i) { foo(i*8); bar(i*16) }", which should
+ // be codegened as "for (j = 0;; j+=8) { foo(j); bar(j+j); }" on X86/PPC.
+ // Need to be careful that IV's are all the same type. Only works for
+ // intptr_t indvars.
+
+ // IVsByStride keeps IVs for one particular loop.
+ assert(IVsByStride.empty() && "Stale entries in IVsByStride?");
+
+ // Note: this processes each stride/type pair individually. All users
+ // passed into StrengthReduceStridedIVUsers have the same type AND stride.
+ // Also, note that we iterate over IVUsesByStride indirectly by using
+ // StrideOrder. This extra layer of indirection makes the ordering of
+ // strides deterministic - not dependent on map order.
+ for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e; ++Stride) {
+ std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
+ IVUsesByStride.find(StrideOrder[Stride]);
+ assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
+ StrengthReduceStridedIVUsers(SI->first, SI->second, L);
}
- DeleteTriviallyDeadInstructions(DeadInsts);
}
- CastedPointers.clear();
+ // We're done analyzing this loop; release all the state we built up for it.
IVUsesByStride.clear();
+ IVsByStride.clear();
StrideOrder.clear();
- return false;
+
+ // Clean up after ourselves
+ 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);
+ }
+ } VDL(*SE);
+ DeleteDeadPHIs(L->getHeader(), &VDL);
+
+ return Changed;
}
projects / oota-llvm.git / blobdiff