//===----------------------------------------------------------------------===//
#include "llvm/Analysis/ScalarEvolutionExpander.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/LLVMContext.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/LLVMContext.h"
#include "llvm/Support/Debug.h"
-#include "llvm/Target/TargetData.h"
-#include "llvm/ADT/STLExtras.h"
using namespace llvm;
Value *SCEVExpander::ReuseOrCreateCast(Value *V, Type *Ty,
Instruction::CastOps Op,
BasicBlock::iterator IP) {
+ // This function must be called with the builder having a valid insertion
+ // point. It doesn't need to be the actual IP where the uses of the returned
+ // cast will be added, but it must dominate such IP.
+ // We use this precondition to produce a cast that will dominate all its
+ // uses. In particular, this is crucial for the case where the builder's
+ // insertion point *is* the point where we were asked to put the cast.
+ // Since we don't know the builder's insertion point is actually
+ // where the uses will be added (only that it dominates it), we are
+ // not allowed to move it.
+ BasicBlock::iterator BIP = Builder.GetInsertPoint();
+
+ Instruction *Ret = nullptr;
+
// Check to see if there is already a cast!
- for (Value::use_iterator UI = V->use_begin(), E = V->use_end();
- UI != E; ++UI) {
- User *U = *UI;
+ for (User *U : V->users())
if (U->getType() == Ty)
if (CastInst *CI = dyn_cast<CastInst>(U))
if (CI->getOpcode() == Op) {
- // If the cast isn't where we want it, fix it.
- if (BasicBlock::iterator(CI) != IP) {
+ // If the cast isn't where we want it, create a new cast at IP.
+ // Likewise, do not reuse a cast at BIP because it must dominate
+ // instructions that might be inserted before BIP.
+ if (BasicBlock::iterator(CI) != IP || BIP == IP) {
// Create a new cast, and leave the old cast in place in case
// it is being used as an insert point. Clear its operand
// so that it doesn't hold anything live.
- Instruction *NewCI = CastInst::Create(Op, V, Ty, "", IP);
- NewCI->takeName(CI);
- CI->replaceAllUsesWith(NewCI);
+ Ret = CastInst::Create(Op, V, Ty, "", IP);
+ Ret->takeName(CI);
+ CI->replaceAllUsesWith(Ret);
CI->setOperand(0, UndefValue::get(V->getType()));
- rememberInstruction(NewCI);
- return NewCI;
+ break;
}
- rememberInstruction(CI);
- return CI;
+ Ret = CI;
+ break;
}
- }
// Create a new cast.
- Instruction *I = CastInst::Create(Op, V, Ty, V->getName(), IP);
- rememberInstruction(I);
- return I;
+ if (!Ret)
+ Ret = CastInst::Create(Op, V, Ty, V->getName(), IP);
+
+ // We assert at the end of the function since IP might point to an
+ // instruction with different dominance properties than a cast
+ // (an invoke for example) and not dominate BIP (but the cast does).
+ assert(SE.DT->dominates(Ret, BIP));
+
+ rememberInstruction(Ret);
+ return Ret;
}
/// InsertNoopCastOfTo - Insert a cast of V to the specified type,
"InsertNoopCastOfTo cannot change sizes!");
// Short-circuit unnecessary bitcasts.
- if (Op == Instruction::BitCast && V->getType() == Ty)
- return V;
-
+ if (Op == Instruction::BitCast) {
+ if (V->getType() == Ty)
+ return V;
+ if (CastInst *CI = dyn_cast<CastInst>(V)) {
+ if (CI->getOperand(0)->getType() == Ty)
+ return CI->getOperand(0);
+ }
+ }
// Short-circuit unnecessary inttoptr<->ptrtoint casts.
if ((Op == Instruction::PtrToInt || Op == Instruction::IntToPtr) &&
SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(V->getType())) {
BasicBlock::iterator IP = I; ++IP;
if (InvokeInst *II = dyn_cast<InvokeInst>(I))
IP = II->getNormalDest()->begin();
- while (isa<PHINode>(IP) || isa<DbgInfoIntrinsic>(IP) ||
- isa<LandingPadInst>(IP))
+ while (isa<PHINode>(IP) || isa<LandingPadInst>(IP))
++IP;
return ReuseOrCreateCast(I, Ty, Op, IP);
}
}
// Save the original insertion point so we can restore it when we're done.
- BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
- BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
+ DebugLoc Loc = Builder.GetInsertPoint()->getDebugLoc();
+ BuilderType::InsertPointGuard Guard(Builder);
// Move the insertion point out of as many loops as we can.
while (const Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock())) {
// If we haven't found this binop, insert it.
Instruction *BO = cast<Instruction>(Builder.CreateBinOp(Opcode, LHS, RHS));
- BO->setDebugLoc(SaveInsertPt->getDebugLoc());
+ BO->setDebugLoc(Loc);
rememberInstruction(BO);
- // Restore the original insert point.
- if (SaveInsertBB)
- restoreInsertPoint(SaveInsertBB, SaveInsertPt);
-
return BO;
}
const SCEV *&Remainder,
const SCEV *Factor,
ScalarEvolution &SE,
- const TargetData *TD) {
+ const DataLayout *DL) {
// Everything is divisible by one.
if (Factor->isOne())
return true;
// In a Mul, check if there is a constant operand which is a multiple
// of the given factor.
if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
- if (TD) {
- // With TargetData, the size is known. Check if there is a constant
+ if (DL) {
+ // With DataLayout, the size is known. Check if there is a constant
// operand which is a multiple of the given factor. If so, we can
// factor it.
const SCEVConstant *FC = cast<SCEVConstant>(Factor);
return true;
}
} else {
- // Without TargetData, check if Factor can be factored out of any of the
+ // Without DataLayout, check if Factor can be factored out of any of the
// Mul's operands. If so, we can just remove it.
for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
const SCEV *SOp = M->getOperand(i);
const SCEV *Remainder = SE.getConstant(SOp->getType(), 0);
- if (FactorOutConstant(SOp, Remainder, Factor, SE, TD) &&
+ if (FactorOutConstant(SOp, Remainder, Factor, SE, DL) &&
Remainder->isZero()) {
SmallVector<const SCEV *, 4> NewMulOps(M->op_begin(), M->op_end());
NewMulOps[i] = SOp;
if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
const SCEV *Step = A->getStepRecurrence(SE);
const SCEV *StepRem = SE.getConstant(Step->getType(), 0);
- if (!FactorOutConstant(Step, StepRem, Factor, SE, TD))
+ if (!FactorOutConstant(Step, StepRem, Factor, SE, DL))
return false;
if (!StepRem->isZero())
return false;
const SCEV *Start = A->getStart();
- if (!FactorOutConstant(Start, Remainder, Factor, SE, TD))
+ if (!FactorOutConstant(Start, Remainder, Factor, SE, DL))
return false;
- // FIXME: can use A->getNoWrapFlags(FlagNW)
- S = SE.getAddRecExpr(Start, Step, A->getLoop(), SCEV::FlagAnyWrap);
+ S = SE.getAddRecExpr(Start, Step, A->getLoop(),
+ A->getNoWrapFlags(SCEV::FlagNW));
return true;
}
AddRecs.push_back(SE.getAddRecExpr(Zero,
A->getStepRecurrence(SE),
A->getLoop(),
- // FIXME: A->getNoWrapFlags(FlagNW)
- SCEV::FlagAnyWrap));
+ A->getNoWrapFlags(SCEV::FlagNW)));
if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Start)) {
Ops[i] = Zero;
Ops.append(Add->op_begin(), Add->op_end());
// without the other.
SplitAddRecs(Ops, Ty, SE);
+ Type *IntPtrTy = SE.DL
+ ? SE.DL->getIntPtrType(PTy)
+ : Type::getInt64Ty(PTy->getContext());
+
// Descend down the pointer's type and attempt to convert the other
// operands into GEP indices, at each level. The first index in a GEP
// indexes into the array implied by the pointer operand; the rest of
// array indexing.
SmallVector<const SCEV *, 8> ScaledOps;
if (ElTy->isSized()) {
- const SCEV *ElSize = SE.getSizeOfExpr(ElTy);
+ const SCEV *ElSize = SE.getSizeOfExpr(IntPtrTy, ElTy);
if (!ElSize->isZero()) {
SmallVector<const SCEV *, 8> NewOps;
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
const SCEV *Op = Ops[i];
const SCEV *Remainder = SE.getConstant(Ty, 0);
- if (FactorOutConstant(Op, Remainder, ElSize, SE, SE.TD)) {
+ if (FactorOutConstant(Op, Remainder, ElSize, SE, SE.DL)) {
// Op now has ElSize factored out.
ScaledOps.push_back(Op);
if (!Remainder->isZero())
bool FoundFieldNo = false;
// An empty struct has no fields.
if (STy->getNumElements() == 0) break;
- if (SE.TD) {
- // With TargetData, field offsets are known. See if a constant offset
+ if (SE.DL) {
+ // With DataLayout, field offsets are known. See if a constant offset
// falls within any of the struct fields.
if (Ops.empty()) break;
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[0]))
if (SE.getTypeSizeInBits(C->getType()) <= 64) {
- const StructLayout &SL = *SE.TD->getStructLayout(STy);
+ const StructLayout &SL = *SE.DL->getStructLayout(STy);
uint64_t FullOffset = C->getValue()->getZExtValue();
if (FullOffset < SL.getSizeInBytes()) {
unsigned ElIdx = SL.getElementContainingOffset(FullOffset);
}
}
} else {
- // Without TargetData, just check for an offsetof expression of the
+ // Without DataLayout, just check for an offsetof expression of the
// appropriate struct type.
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Ops[i])) {
V = InsertNoopCastOfTo(V,
Type::getInt8PtrTy(Ty->getContext(), PTy->getAddressSpace()));
+ assert(!isa<Instruction>(V) ||
+ SE.DT->dominates(cast<Instruction>(V), Builder.GetInsertPoint()));
+
// Expand the operands for a plain byte offset.
Value *Idx = expandCodeFor(SE.getAddExpr(Ops), Ty);
}
// Save the original insertion point so we can restore it when we're done.
- BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
- BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
+ BuilderType::InsertPointGuard Guard(Builder);
// Move the insertion point out of as many loops as we can.
while (const Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock())) {
Value *GEP = Builder.CreateGEP(V, Idx, "uglygep");
rememberInstruction(GEP);
- // Restore the original insert point.
- if (SaveInsertBB)
- restoreInsertPoint(SaveInsertBB, SaveInsertPt);
-
return GEP;
}
// Save the original insertion point so we can restore it when we're done.
- BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
- BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
+ BuilderType::InsertPoint SaveInsertPt = Builder.saveIP();
// Move the insertion point out of as many loops as we can.
while (const Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock())) {
rememberInstruction(GEP);
// Restore the original insert point.
- if (SaveInsertBB)
- restoreInsertPoint(SaveInsertBB, SaveInsertPt);
+ Builder.restoreIP(SaveInsertPt);
return expand(SE.getAddExpr(Ops));
}
-/// isNonConstantNegative - Return true if the specified scev is negated, but
-/// not a constant.
-static bool isNonConstantNegative(const SCEV *F) {
- const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(F);
- 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();
-}
-
/// PickMostRelevantLoop - Given two loops pick the one that's most relevant for
/// SCEV expansion. If they are nested, this is the most nested. If they are
/// neighboring, pick the later.
const Loop *SCEVExpander::getRelevantLoop(const SCEV *S) {
// Test whether we've already computed the most relevant loop for this SCEV.
std::pair<DenseMap<const SCEV *, const Loop *>::iterator, bool> Pair =
- RelevantLoops.insert(std::make_pair(S, static_cast<const Loop *>(0)));
+ RelevantLoops.insert(std::make_pair(S, nullptr));
if (!Pair.second)
return Pair.first->second;
if (isa<SCEVConstant>(S))
// A constant has no relevant loops.
- return 0;
+ return nullptr;
if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
if (const Instruction *I = dyn_cast<Instruction>(U->getValue()))
return Pair.first->second = SE.LI->getLoopFor(I->getParent());
// A non-instruction has no relevant loops.
- return 0;
+ return nullptr;
}
if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S)) {
- const Loop *L = 0;
+ const Loop *L = nullptr;
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
L = AR->getLoop();
for (SCEVNAryExpr::op_iterator I = N->op_begin(), E = N->op_end();
return RelevantLoops[D] = Result;
}
llvm_unreachable("Unexpected SCEV type!");
- return 0;
}
namespace {
// If one operand is a non-constant negative and the other is not,
// put the non-constant negative on the right so that a sub can
// be used instead of a negate and add.
- if (isNonConstantNegative(LHS.second)) {
- if (!isNonConstantNegative(RHS.second))
+ if (LHS.second->isNonConstantNegative()) {
+ if (!RHS.second->isNonConstantNegative())
return false;
- } else if (isNonConstantNegative(RHS.second))
+ } else if (RHS.second->isNonConstantNegative())
return true;
// Otherwise they are equivalent according to this comparison.
// Emit instructions to add all the operands. Hoist as much as possible
// out of loops, and form meaningful getelementptrs where possible.
- Value *Sum = 0;
+ Value *Sum = nullptr;
for (SmallVectorImpl<std::pair<const Loop *, const SCEV *> >::iterator
I = OpsAndLoops.begin(), E = OpsAndLoops.end(); I != E; ) {
const Loop *CurLoop = I->first;
for (++I; I != E && I->first == CurLoop; ++I)
NewOps.push_back(I->second);
Sum = expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, expand(Op));
- } else if (isNonConstantNegative(Op)) {
+ } else if (Op->isNonConstantNegative()) {
// Instead of doing a negate and add, just do a subtract.
Value *W = expandCodeFor(SE.getNegativeSCEV(Op), Ty);
Sum = InsertNoopCastOfTo(Sum, Ty);
// Emit instructions to mul all the operands. Hoist as much as possible
// out of loops.
- Value *Prod = 0;
+ Value *Prod = nullptr;
for (SmallVectorImpl<std::pair<const Loop *, const SCEV *> >::iterator
I = OpsAndLoops.begin(), E = OpsAndLoops.end(); I != E; ) {
const SCEV *Op = I->second;
SE.getAddRecExpr(SE.getConstant(A->getType(), 0),
A->getStepRecurrence(SE),
A->getLoop(),
- // FIXME: A->getNoWrapFlags(FlagNW)
- SCEV::FlagAnyWrap));
+ A->getNoWrapFlags(SCEV::FlagNW)));
}
if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(Base)) {
Base = A->getOperand(A->getNumOperands()-1);
return isNormalAddRecExprPHI(PN, IncV, L);
}
-/// Determine if this cyclic phi is in a form that would have been generated by
-/// LSR. We don't care if the phi was actually expanded in this pass, as long
-/// as it is in a low-cost form, for example, no implied multiplication. This
-/// should match any patterns generated by getAddRecExprPHILiterally and
-/// expandAddtoGEP.
-bool SCEVExpander::isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV,
- const Loop *L, Type *ExpandTy) {
+/// getIVIncOperand returns an induction variable increment's induction
+/// variable operand.
+///
+/// If allowScale is set, any type of GEP is allowed as long as the nonIV
+/// operands dominate InsertPos.
+///
+/// If allowScale is not set, ensure that a GEP increment conforms to one of the
+/// simple patterns generated by getAddRecExprPHILiterally and
+/// expandAddtoGEP. If the pattern isn't recognized, return NULL.
+Instruction *SCEVExpander::getIVIncOperand(Instruction *IncV,
+ Instruction *InsertPos,
+ bool allowScale) {
+ if (IncV == InsertPos)
+ return nullptr;
+
switch (IncV->getOpcode()) {
+ default:
+ return nullptr;
// Check for a simple Add/Sub or GEP of a loop invariant step.
case Instruction::Add:
- case Instruction::Sub:
- return IncV->getOperand(0) == PN
- && L->isLoopInvariant(IncV->getOperand(1));
+ case Instruction::Sub: {
+ Instruction *OInst = dyn_cast<Instruction>(IncV->getOperand(1));
+ if (!OInst || SE.DT->dominates(OInst, InsertPos))
+ return dyn_cast<Instruction>(IncV->getOperand(0));
+ return nullptr;
+ }
case Instruction::BitCast:
- IncV = dyn_cast<GetElementPtrInst>(IncV->getOperand(0));
- if (!IncV)
- return false;
- // fall-thru to GEP handling
- case Instruction::GetElementPtr: {
- // This must be a pointer addition of constants (pretty) or some number of
- // address-size elements (ugly).
+ return dyn_cast<Instruction>(IncV->getOperand(0));
+ case Instruction::GetElementPtr:
for (Instruction::op_iterator I = IncV->op_begin()+1, E = IncV->op_end();
I != E; ++I) {
if (isa<Constant>(*I))
continue;
- // ugly geps have 2 operands.
- // i1* is used by the expander to represent an address-size element.
+ if (Instruction *OInst = dyn_cast<Instruction>(*I)) {
+ if (!SE.DT->dominates(OInst, InsertPos))
+ return nullptr;
+ }
+ if (allowScale) {
+ // allow any kind of GEP as long as it can be hoisted.
+ continue;
+ }
+ // This must be a pointer addition of constants (pretty), which is already
+ // handled, or some number of address-size elements (ugly). Ugly geps
+ // have 2 operands. i1* is used by the expander to represent an
+ // address-size element.
if (IncV->getNumOperands() != 2)
- return false;
- unsigned AS = cast<PointerType>(ExpandTy)->getAddressSpace();
+ return nullptr;
+ unsigned AS = cast<PointerType>(IncV->getType())->getAddressSpace();
if (IncV->getType() != Type::getInt1PtrTy(SE.getContext(), AS)
&& IncV->getType() != Type::getInt8PtrTy(SE.getContext(), AS))
- return false;
+ return nullptr;
break;
}
- IncV = dyn_cast<Instruction>(IncV->getOperand(0));
- if (IncV && IncV->getOpcode() == Instruction::BitCast)
- IncV = dyn_cast<Instruction>(IncV->getOperand(0));
- return IncV == PN;
+ return dyn_cast<Instruction>(IncV->getOperand(0));
}
- default:
+}
+
+/// hoistStep - Attempt to hoist a simple IV increment above InsertPos to make
+/// it available to other uses in this loop. Recursively hoist any operands,
+/// until we reach a value that dominates InsertPos.
+bool SCEVExpander::hoistIVInc(Instruction *IncV, Instruction *InsertPos) {
+ if (SE.DT->dominates(IncV, InsertPos))
+ return true;
+
+ // InsertPos must itself dominate IncV so that IncV's new position satisfies
+ // its existing users.
+ if (isa<PHINode>(InsertPos)
+ || !SE.DT->dominates(InsertPos->getParent(), IncV->getParent()))
+ return false;
+
+ // Check that the chain of IV operands leading back to Phi can be hoisted.
+ SmallVector<Instruction*, 4> IVIncs;
+ for(;;) {
+ Instruction *Oper = getIVIncOperand(IncV, InsertPos, /*allowScale*/true);
+ if (!Oper)
+ return false;
+ // IncV is safe to hoist.
+ IVIncs.push_back(IncV);
+ IncV = Oper;
+ if (SE.DT->dominates(IncV, InsertPos))
+ break;
+ }
+ for (SmallVectorImpl<Instruction*>::reverse_iterator I = IVIncs.rbegin(),
+ E = IVIncs.rend(); I != E; ++I) {
+ (*I)->moveBefore(InsertPos);
+ }
+ return true;
+}
+
+/// Determine if this cyclic phi is in a form that would have been generated by
+/// LSR. We don't care if the phi was actually expanded in this pass, as long
+/// as it is in a low-cost form, for example, no implied multiplication. This
+/// should match any patterns generated by getAddRecExprPHILiterally and
+/// expandAddtoGEP.
+bool SCEVExpander::isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV,
+ const Loop *L) {
+ for(Instruction *IVOper = IncV;
+ (IVOper = getIVIncOperand(IVOper, L->getLoopPreheader()->getTerminator(),
+ /*allowScale=*/false));) {
+ if (IVOper == PN)
+ return true;
+ }
+ return false;
+}
+
+/// expandIVInc - Expand an IV increment at Builder's current InsertPos.
+/// Typically this is the LatchBlock terminator or IVIncInsertPos, but we may
+/// need to materialize IV increments elsewhere to handle difficult situations.
+Value *SCEVExpander::expandIVInc(PHINode *PN, Value *StepV, const Loop *L,
+ Type *ExpandTy, Type *IntTy,
+ bool useSubtract) {
+ Value *IncV;
+ // If the PHI is a pointer, use a GEP, otherwise use an add or sub.
+ if (ExpandTy->isPointerTy()) {
+ PointerType *GEPPtrTy = cast<PointerType>(ExpandTy);
+ // If the step isn't constant, don't use an implicitly scaled GEP, because
+ // that would require a multiply inside the loop.
+ if (!isa<ConstantInt>(StepV))
+ GEPPtrTy = PointerType::get(Type::getInt1Ty(SE.getContext()),
+ GEPPtrTy->getAddressSpace());
+ const SCEV *const StepArray[1] = { SE.getSCEV(StepV) };
+ IncV = expandAddToGEP(StepArray, StepArray+1, GEPPtrTy, IntTy, PN);
+ if (IncV->getType() != PN->getType()) {
+ IncV = Builder.CreateBitCast(IncV, PN->getType());
+ rememberInstruction(IncV);
+ }
+ } else {
+ IncV = useSubtract ?
+ Builder.CreateSub(PN, StepV, Twine(IVName) + ".iv.next") :
+ Builder.CreateAdd(PN, StepV, Twine(IVName) + ".iv.next");
+ rememberInstruction(IncV);
+ }
+ return IncV;
+}
+
+/// \brief Hoist the addrec instruction chain rooted in the loop phi above the
+/// position. This routine assumes that this is possible (has been checked).
+static void hoistBeforePos(DominatorTree *DT, Instruction *InstToHoist,
+ Instruction *Pos, PHINode *LoopPhi) {
+ do {
+ if (DT->dominates(InstToHoist, Pos))
+ break;
+ // Make sure the increment is where we want it. But don't move it
+ // down past a potential existing post-inc user.
+ InstToHoist->moveBefore(Pos);
+ Pos = InstToHoist;
+ InstToHoist = cast<Instruction>(InstToHoist->getOperand(0));
+ } while (InstToHoist != LoopPhi);
+}
+
+/// \brief Check whether we can cheaply express the requested SCEV in terms of
+/// the available PHI SCEV by truncation and/or invertion of the step.
+static bool canBeCheaplyTransformed(ScalarEvolution &SE,
+ const SCEVAddRecExpr *Phi,
+ const SCEVAddRecExpr *Requested,
+ bool &InvertStep) {
+ Type *PhiTy = SE.getEffectiveSCEVType(Phi->getType());
+ Type *RequestedTy = SE.getEffectiveSCEVType(Requested->getType());
+
+ if (RequestedTy->getIntegerBitWidth() > PhiTy->getIntegerBitWidth())
+ return false;
+
+ // Try truncate it if necessary.
+ Phi = dyn_cast<SCEVAddRecExpr>(SE.getTruncateOrNoop(Phi, RequestedTy));
+ if (!Phi)
return false;
+
+ // Check whether truncation will help.
+ if (Phi == Requested) {
+ InvertStep = false;
+ return true;
+ }
+
+ // Check whether inverting will help: {R,+,-1} == R - {0,+,1}.
+ if (SE.getAddExpr(Requested->getStart(),
+ SE.getNegativeSCEV(Requested)) == Phi) {
+ InvertStep = true;
+ return true;
}
+
+ return false;
}
/// getAddRecExprPHILiterally - Helper for expandAddRecExprLiterally. Expand
SCEVExpander::getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
const Loop *L,
Type *ExpandTy,
- Type *IntTy) {
+ Type *IntTy,
+ Type *&TruncTy,
+ bool &InvertStep) {
assert((!IVIncInsertLoop||IVIncInsertPos) && "Uninitialized insert position");
// Reuse a previously-inserted PHI, if present.
BasicBlock *LatchBlock = L->getLoopLatch();
if (LatchBlock) {
+ PHINode *AddRecPhiMatch = nullptr;
+ Instruction *IncV = nullptr;
+ TruncTy = nullptr;
+ InvertStep = false;
+
+ // Only try partially matching scevs that need truncation and/or
+ // step-inversion if we know this loop is outside the current loop.
+ bool TryNonMatchingSCEV = IVIncInsertLoop &&
+ SE.DT->properlyDominates(LatchBlock, IVIncInsertLoop->getHeader());
+
for (BasicBlock::iterator I = L->getHeader()->begin();
PHINode *PN = dyn_cast<PHINode>(I); ++I) {
- if (!SE.isSCEVable(PN->getType()) ||
- (SE.getEffectiveSCEVType(PN->getType()) !=
- SE.getEffectiveSCEVType(Normalized->getType())) ||
- SE.getSCEV(PN) != Normalized)
+ if (!SE.isSCEVable(PN->getType()))
continue;
- Instruction *IncV =
- cast<Instruction>(PN->getIncomingValueForBlock(LatchBlock));
+ const SCEVAddRecExpr *PhiSCEV = dyn_cast<SCEVAddRecExpr>(SE.getSCEV(PN));
+ if (!PhiSCEV)
+ continue;
+ bool IsMatchingSCEV = PhiSCEV == Normalized;
+ // We only handle truncation and inversion of phi recurrences for the
+ // expanded expression if the expanded expression's loop dominates the
+ // loop we insert to. Check now, so we can bail out early.
+ if (!IsMatchingSCEV && !TryNonMatchingSCEV)
+ continue;
+
+ Instruction *TempIncV =
+ cast<Instruction>(PN->getIncomingValueForBlock(LatchBlock));
+
+ // Check whether we can reuse this PHI node.
if (LSRMode) {
- if (!isExpandedAddRecExprPHI(PN, IncV, L, ExpandTy))
+ if (!isExpandedAddRecExprPHI(PN, TempIncV, L))
continue;
- }
- else {
- if (!isNormalAddRecExprPHI(PN, IncV, L))
+ if (L == IVIncInsertLoop && !hoistIVInc(TempIncV, IVIncInsertPos))
+ continue;
+ } else {
+ if (!isNormalAddRecExprPHI(PN, TempIncV, L))
continue;
}
+
+ // Stop if we have found an exact match SCEV.
+ if (IsMatchingSCEV) {
+ IncV = TempIncV;
+ TruncTy = nullptr;
+ InvertStep = false;
+ AddRecPhiMatch = PN;
+ break;
+ }
+
+ // Try whether the phi can be translated into the requested form
+ // (truncated and/or offset by a constant).
+ if ((!TruncTy || InvertStep) &&
+ canBeCheaplyTransformed(SE, PhiSCEV, Normalized, InvertStep)) {
+ // Record the phi node. But don't stop we might find an exact match
+ // later.
+ AddRecPhiMatch = PN;
+ IncV = TempIncV;
+ TruncTy = SE.getEffectiveSCEVType(Normalized->getType());
+ }
+ }
+
+ if (AddRecPhiMatch) {
+ // Potentially, move the increment. We have made sure in
+ // isExpandedAddRecExprPHI or hoistIVInc that this is possible.
+ if (L == IVIncInsertLoop)
+ hoistBeforePos(SE.DT, IncV, IVIncInsertPos, AddRecPhiMatch);
+
// Ok, the add recurrence looks usable.
// Remember this PHI, even in post-inc mode.
- InsertedValues.insert(PN);
+ InsertedValues.insert(AddRecPhiMatch);
// Remember the increment.
rememberInstruction(IncV);
- if (L == IVIncInsertLoop)
- do {
- if (SE.DT->dominates(IncV, IVIncInsertPos))
- break;
- // Make sure the increment is where we want it. But don't move it
- // down past a potential existing post-inc user.
- IncV->moveBefore(IVIncInsertPos);
- IVIncInsertPos = IncV;
- IncV = cast<Instruction>(IncV->getOperand(0));
- } while (IncV != PN);
- return PN;
+ return AddRecPhiMatch;
}
}
// Save the original insertion point so we can restore it when we're done.
- BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
- BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
+ BuilderType::InsertPointGuard Guard(Builder);
+
+ // Another AddRec may need to be recursively expanded below. For example, if
+ // this AddRec is quadratic, the StepV may itself be an AddRec in this
+ // loop. Remove this loop from the PostIncLoops set before expanding such
+ // AddRecs. Otherwise, we cannot find a valid position for the step
+ // (i.e. StepV can never dominate its loop header). Ideally, we could do
+ // SavedIncLoops.swap(PostIncLoops), but we generally have a single element,
+ // so it's not worth implementing SmallPtrSet::swap.
+ PostIncLoopSet SavedPostIncLoops = PostIncLoops;
+ PostIncLoops.clear();
// Expand code for the start value.
Value *StartV = expandCodeFor(Normalized->getStart(), ExpandTy,
SE.DT->properlyDominates(cast<Instruction>(StartV)->getParent(),
L->getHeader()));
- // Expand code for the step value. Insert instructions right before the
- // terminator corresponding to the back-edge. Do this before creating the PHI
- // so that PHI reuse code doesn't see an incomplete PHI. If the stride is
- // negative, insert a sub instead of an add for the increment (unless it's a
- // constant, because subtracts of constants are canonicalized to adds).
+ // Expand code for the step value. Do this before creating the PHI so that PHI
+ // reuse code doesn't see an incomplete PHI.
const SCEV *Step = Normalized->getStepRecurrence(SE);
- bool isPointer = ExpandTy->isPointerTy();
- bool isNegative = !isPointer && isNonConstantNegative(Step);
- if (isNegative)
+ // If the stride is negative, insert a sub instead of an add for the increment
+ // (unless it's a constant, because subtracts of constants are canonicalized
+ // to adds).
+ bool useSubtract = !ExpandTy->isPointerTy() && Step->isNonConstantNegative();
+ if (useSubtract)
Step = SE.getNegativeSCEV(Step);
+ // Expand the step somewhere that dominates the loop header.
Value *StepV = expandCodeFor(Step, IntTy, L->getHeader()->begin());
// Create the PHI.
continue;
}
- // Create a step value and add it to the PHI. If IVIncInsertLoop is
- // non-null and equal to the addrec's loop, insert the instructions
- // at IVIncInsertPos.
+ // Create a step value and add it to the PHI.
+ // If IVIncInsertLoop is non-null and equal to the addrec's loop, insert the
+ // instructions at IVIncInsertPos.
Instruction *InsertPos = L == IVIncInsertLoop ?
IVIncInsertPos : Pred->getTerminator();
Builder.SetInsertPoint(InsertPos);
- Value *IncV;
- // If the PHI is a pointer, use a GEP, otherwise use an add or sub.
- if (isPointer) {
- PointerType *GEPPtrTy = cast<PointerType>(ExpandTy);
- // If the step isn't constant, don't use an implicitly scaled GEP, because
- // that would require a multiply inside the loop.
- if (!isa<ConstantInt>(StepV))
- GEPPtrTy = PointerType::get(Type::getInt1Ty(SE.getContext()),
- GEPPtrTy->getAddressSpace());
- const SCEV *const StepArray[1] = { SE.getSCEV(StepV) };
- IncV = expandAddToGEP(StepArray, StepArray+1, GEPPtrTy, IntTy, PN);
- if (IncV->getType() != PN->getType()) {
- IncV = Builder.CreateBitCast(IncV, PN->getType());
- rememberInstruction(IncV);
- }
- } else {
- IncV = isNegative ?
- Builder.CreateSub(PN, StepV, Twine(IVName) + ".iv.next") :
- Builder.CreateAdd(PN, StepV, Twine(IVName) + ".iv.next");
- rememberInstruction(IncV);
+ Value *IncV = expandIVInc(PN, StepV, L, ExpandTy, IntTy, useSubtract);
+ if (isa<OverflowingBinaryOperator>(IncV)) {
+ if (Normalized->getNoWrapFlags(SCEV::FlagNUW))
+ cast<BinaryOperator>(IncV)->setHasNoUnsignedWrap();
+ if (Normalized->getNoWrapFlags(SCEV::FlagNSW))
+ cast<BinaryOperator>(IncV)->setHasNoSignedWrap();
}
PN->addIncoming(IncV, Pred);
}
- // Restore the original insert point.
- if (SaveInsertBB)
- restoreInsertPoint(SaveInsertBB, SaveInsertPt);
+ // After expanding subexpressions, restore the PostIncLoops set so the caller
+ // can ensure that IVIncrement dominates the current uses.
+ PostIncLoops = SavedPostIncLoops;
// Remember this PHI, even in post-inc mode.
InsertedValues.insert(PN);
PostIncLoopSet Loops;
Loops.insert(L);
Normalized =
- cast<SCEVAddRecExpr>(TransformForPostIncUse(Normalize, S, 0, 0,
- Loops, SE, *SE.DT));
+ cast<SCEVAddRecExpr>(TransformForPostIncUse(Normalize, S, nullptr,
+ nullptr, Loops, SE, *SE.DT));
}
// Strip off any non-loop-dominating component from the addrec start.
const SCEV *Start = Normalized->getStart();
- const SCEV *PostLoopOffset = 0;
+ const SCEV *PostLoopOffset = nullptr;
if (!SE.properlyDominates(Start, L->getHeader())) {
PostLoopOffset = Start;
Start = SE.getConstant(Normalized->getType(), 0);
Normalized = cast<SCEVAddRecExpr>(
SE.getAddRecExpr(Start, Normalized->getStepRecurrence(SE),
Normalized->getLoop(),
- // FIXME: Normalized->getNoWrapFlags(FlagNW)
- SCEV::FlagAnyWrap));
+ Normalized->getNoWrapFlags(SCEV::FlagNW)));
}
// Strip off any non-loop-dominating component from the addrec step.
const SCEV *Step = Normalized->getStepRecurrence(SE);
- const SCEV *PostLoopScale = 0;
+ const SCEV *PostLoopScale = nullptr;
if (!SE.dominates(Step, L->getHeader())) {
PostLoopScale = Step;
Step = SE.getConstant(Normalized->getType(), 1);
Normalized =
- cast<SCEVAddRecExpr>(SE.getAddRecExpr(Start, Step,
- Normalized->getLoop(),
- // FIXME: Normalized
- // ->getNoWrapFlags(FlagNW)
- SCEV::FlagAnyWrap));
+ cast<SCEVAddRecExpr>(SE.getAddRecExpr(
+ Start, Step, Normalized->getLoop(),
+ Normalized->getNoWrapFlags(SCEV::FlagNW)));
}
// Expand the core addrec. If we need post-loop scaling, force it to
// expand to an integer type to avoid the need for additional casting.
Type *ExpandTy = PostLoopScale ? IntTy : STy;
- PHINode *PN = getAddRecExprPHILiterally(Normalized, L, ExpandTy, IntTy);
+ // In some cases, we decide to reuse an existing phi node but need to truncate
+ // it and/or invert the step.
+ Type *TruncTy = nullptr;
+ bool InvertStep = false;
+ PHINode *PN = getAddRecExprPHILiterally(Normalized, L, ExpandTy, IntTy,
+ TruncTy, InvertStep);
// Accommodate post-inc mode, if necessary.
Value *Result;
BasicBlock *LatchBlock = L->getLoopLatch();
assert(LatchBlock && "PostInc mode requires a unique loop latch!");
Result = PN->getIncomingValueForBlock(LatchBlock);
+
+ // For an expansion to use the postinc form, the client must call
+ // expandCodeFor with an InsertPoint that is either outside the PostIncLoop
+ // or dominated by IVIncInsertPos.
+ if (isa<Instruction>(Result)
+ && !SE.DT->dominates(cast<Instruction>(Result),
+ Builder.GetInsertPoint())) {
+ // The induction variable's postinc expansion does not dominate this use.
+ // IVUsers tries to prevent this case, so it is rare. However, it can
+ // happen when an IVUser outside the loop is not dominated by the latch
+ // block. Adjusting IVIncInsertPos before expansion begins cannot handle
+ // all cases. Consider a phi outide whose operand is replaced during
+ // expansion with the value of the postinc user. Without fundamentally
+ // changing the way postinc users are tracked, the only remedy is
+ // inserting an extra IV increment. StepV might fold into PostLoopOffset,
+ // but hopefully expandCodeFor handles that.
+ bool useSubtract =
+ !ExpandTy->isPointerTy() && Step->isNonConstantNegative();
+ if (useSubtract)
+ Step = SE.getNegativeSCEV(Step);
+ Value *StepV;
+ {
+ // Expand the step somewhere that dominates the loop header.
+ BuilderType::InsertPointGuard Guard(Builder);
+ StepV = expandCodeFor(Step, IntTy, L->getHeader()->begin());
+ }
+ Result = expandIVInc(PN, StepV, L, ExpandTy, IntTy, useSubtract);
+ }
+ }
+
+ // We have decided to reuse an induction variable of a dominating loop. Apply
+ // truncation and/or invertion of the step.
+ if (TruncTy) {
+ Type *ResTy = Result->getType();
+ // Normalize the result type.
+ if (ResTy != SE.getEffectiveSCEVType(ResTy))
+ Result = InsertNoopCastOfTo(Result, SE.getEffectiveSCEVType(ResTy));
+ // Truncate the result.
+ if (TruncTy != Result->getType()) {
+ Result = Builder.CreateTrunc(Result, TruncTy);
+ rememberInstruction(Result);
+ }
+ // Invert the result.
+ if (InvertStep) {
+ Result = Builder.CreateSub(expandCodeFor(Normalized->getStart(), TruncTy),
+ Result);
+ rememberInstruction(Result);
+ }
}
// Re-apply any non-loop-dominating scale.
if (PostLoopScale) {
+ assert(S->isAffine() && "Can't linearly scale non-affine recurrences.");
Result = InsertNoopCastOfTo(Result, IntTy);
Result = Builder.CreateMul(Result,
expandCodeFor(PostLoopScale, IntTy));
const Loop *L = S->getLoop();
// First check for an existing canonical IV in a suitable type.
- PHINode *CanonicalIV = 0;
+ PHINode *CanonicalIV = nullptr;
if (PHINode *PN = L->getCanonicalInductionVariable())
if (SE.getTypeSizeInBits(PN->getType()) >= SE.getTypeSizeInBits(Ty))
CanonicalIV = PN;
for (unsigned i = 0, e = S->getNumOperands(); i != e; ++i)
NewOps[i] = SE.getAnyExtendExpr(S->op_begin()[i], CanonicalIV->getType());
Value *V = expand(SE.getAddRecExpr(NewOps, S->getLoop(),
- // FIXME: S->getNoWrapFlags(FlagNW)
- SCEV::FlagAnyWrap));
- BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
- BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
+ S->getNoWrapFlags(SCEV::FlagNW)));
BasicBlock::iterator NewInsertPt =
- llvm::next(BasicBlock::iterator(cast<Instruction>(V)));
+ std::next(BasicBlock::iterator(cast<Instruction>(V)));
+ BuilderType::InsertPointGuard Guard(Builder);
while (isa<PHINode>(NewInsertPt) || isa<DbgInfoIntrinsic>(NewInsertPt) ||
isa<LandingPadInst>(NewInsertPt))
++NewInsertPt;
- V = expandCodeFor(SE.getTruncateExpr(SE.getUnknown(V), Ty), 0,
+ V = expandCodeFor(SE.getTruncateExpr(SE.getUnknown(V), Ty), nullptr,
NewInsertPt);
- restoreInsertPoint(SaveInsertBB, SaveInsertPt);
return V;
}
if (!S->getStart()->isZero()) {
SmallVector<const SCEV *, 4> NewOps(S->op_begin(), S->op_end());
NewOps[0] = SE.getConstant(Ty, 0);
- // FIXME: can use S->getNoWrapFlags()
- const SCEV *Rest = SE.getAddRecExpr(NewOps, L, SCEV::FlagAnyWrap);
+ const SCEV *Rest = SE.getAddRecExpr(NewOps, L,
+ S->getNoWrapFlags(SCEV::FlagNW));
// Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
// comments on expandAddToGEP for details.
Header->begin());
rememberInstruction(CanonicalIV);
+ SmallSet<BasicBlock *, 4> PredSeen;
Constant *One = ConstantInt::get(Ty, 1);
for (pred_iterator HPI = HPB; HPI != HPE; ++HPI) {
BasicBlock *HP = *HPI;
+ if (!PredSeen.insert(HP).second) {
+ // There must be an incoming value for each predecessor, even the
+ // duplicates!
+ CanonicalIV->addIncoming(CanonicalIV->getIncomingValueForBlock(HP), HP);
+ continue;
+ }
+
if (L->contains(HP)) {
// Insert a unit add instruction right before the terminator
// corresponding to the back-edge.
}
Value *SCEVExpander::expandCodeFor(const SCEV *SH, Type *Ty,
- Instruction *I) {
- BasicBlock::iterator IP = I;
- while (isInsertedInstruction(IP) || isa<DbgInfoIntrinsic>(IP))
- ++IP;
+ Instruction *IP) {
Builder.SetInsertPoint(IP->getParent(), IP);
return expandCodeFor(SH, Ty);
}
if (!L) break;
if (BasicBlock *Preheader = L->getLoopPreheader())
InsertPt = Preheader->getTerminator();
+ else {
+ // LSR sets the insertion point for AddRec start/step values to the
+ // block start to simplify value reuse, even though it's an invalid
+ // position. SCEVExpander must correct for this in all cases.
+ InsertPt = L->getHeader()->getFirstInsertionPt();
+ }
} else {
// If the SCEV is computable at this level, insert it into the header
// after the PHIs (and after any other instructions that we've inserted
// there) so that it is guaranteed to dominate any user inside the loop.
if (L && SE.hasComputableLoopEvolution(S, L) && !PostIncLoops.count(L))
InsertPt = L->getHeader()->getFirstInsertionPt();
- while (isInsertedInstruction(InsertPt) || isa<DbgInfoIntrinsic>(InsertPt))
- InsertPt = llvm::next(BasicBlock::iterator(InsertPt));
+ while (InsertPt != Builder.GetInsertPoint()
+ && (isInsertedInstruction(InsertPt)
+ || isa<DbgInfoIntrinsic>(InsertPt))) {
+ InsertPt = std::next(BasicBlock::iterator(InsertPt));
+ }
break;
}
// Check to see if we already expanded this here.
- std::map<std::pair<const SCEV *, Instruction *>,
- AssertingVH<Value> >::iterator I =
- InsertedExpressions.find(std::make_pair(S, InsertPt));
+ std::map<std::pair<const SCEV *, Instruction *>, TrackingVH<Value> >::iterator
+ I = InsertedExpressions.find(std::make_pair(S, InsertPt));
if (I != InsertedExpressions.end())
return I->second;
- BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
- BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
+ BuilderType::InsertPointGuard Guard(Builder);
Builder.SetInsertPoint(InsertPt->getParent(), InsertPt);
// Expand the expression into instructions.
Value *V = visit(S);
// Remember the expanded value for this SCEV at this location.
- if (PostIncLoops.empty())
- InsertedExpressions[std::make_pair(S, InsertPt)] = V;
-
- restoreInsertPoint(SaveInsertBB, SaveInsertPt);
+ //
+ // This is independent of PostIncLoops. The mapped value simply materializes
+ // the expression at this insertion point. If the mapped value happened to be
+ // a postinc expansion, it could be reused by a non-postinc user, but only if
+ // its insertion point was already at the head of the loop.
+ InsertedExpressions[std::make_pair(S, InsertPt)] = V;
return V;
}
InsertedPostIncValues.insert(I);
else
InsertedValues.insert(I);
-
- // If we just claimed an existing instruction and that instruction had
- // been the insert point, adjust the insert point forward so that
- // subsequently inserted code will be dominated.
- if (Builder.GetInsertPoint() == I) {
- BasicBlock::iterator It = cast<Instruction>(I);
- do { ++It; } while (isInsertedInstruction(It) ||
- isa<DbgInfoIntrinsic>(It));
- Builder.SetInsertPoint(Builder.GetInsertBlock(), It);
- }
-}
-
-void SCEVExpander::restoreInsertPoint(BasicBlock *BB, BasicBlock::iterator I) {
- // If we acquired more instructions since the old insert point was saved,
- // advance past them.
- while (isInsertedInstruction(I) || isa<DbgInfoIntrinsic>(I)) ++I;
-
- Builder.SetInsertPoint(BB, I);
}
/// getOrInsertCanonicalInductionVariable - This method returns the
SE.getConstant(Ty, 1), L, SCEV::FlagAnyWrap);
// Emit code for it.
- BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
- BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
- PHINode *V = cast<PHINode>(expandCodeFor(H, 0, L->getHeader()->begin()));
- if (SaveInsertBB)
- restoreInsertPoint(SaveInsertBB, SaveInsertPt);
+ BuilderType::InsertPointGuard Guard(Builder);
+ PHINode *V = cast<PHINode>(expandCodeFor(H, nullptr,
+ L->getHeader()->begin()));
return V;
}
+
+/// replaceCongruentIVs - Check for congruent phis in this loop header and
+/// replace them with their most canonical representative. Return the number of
+/// phis eliminated.
+///
+/// This does not depend on any SCEVExpander state but should be used in
+/// the same context that SCEVExpander is used.
+unsigned SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
+ SmallVectorImpl<WeakVH> &DeadInsts,
+ const TargetTransformInfo *TTI) {
+ // Find integer phis in order of increasing width.
+ SmallVector<PHINode*, 8> Phis;
+ for (BasicBlock::iterator I = L->getHeader()->begin();
+ PHINode *Phi = dyn_cast<PHINode>(I); ++I) {
+ Phis.push_back(Phi);
+ }
+ if (TTI)
+ std::sort(Phis.begin(), Phis.end(), [](Value *LHS, Value *RHS) {
+ // Put pointers at the back and make sure pointer < pointer = false.
+ if (!LHS->getType()->isIntegerTy() || !RHS->getType()->isIntegerTy())
+ return RHS->getType()->isIntegerTy() && !LHS->getType()->isIntegerTy();
+ return RHS->getType()->getPrimitiveSizeInBits() <
+ LHS->getType()->getPrimitiveSizeInBits();
+ });
+
+ unsigned NumElim = 0;
+ DenseMap<const SCEV *, PHINode *> ExprToIVMap;
+ // Process phis from wide to narrow. Mapping wide phis to the their truncation
+ // so narrow phis can reuse them.
+ for (SmallVectorImpl<PHINode*>::const_iterator PIter = Phis.begin(),
+ PEnd = Phis.end(); PIter != PEnd; ++PIter) {
+ PHINode *Phi = *PIter;
+
+ // Fold constant phis. They may be congruent to other constant phis and
+ // would confuse the logic below that expects proper IVs.
+ if (Value *V = SimplifyInstruction(Phi, SE.DL, SE.TLI, SE.DT, SE.AT)) {
+ Phi->replaceAllUsesWith(V);
+ DeadInsts.push_back(Phi);
+ ++NumElim;
+ DEBUG_WITH_TYPE(DebugType, dbgs()
+ << "INDVARS: Eliminated constant iv: " << *Phi << '\n');
+ continue;
+ }
+
+ if (!SE.isSCEVable(Phi->getType()))
+ continue;
+
+ PHINode *&OrigPhiRef = ExprToIVMap[SE.getSCEV(Phi)];
+ if (!OrigPhiRef) {
+ OrigPhiRef = Phi;
+ if (Phi->getType()->isIntegerTy() && TTI
+ && TTI->isTruncateFree(Phi->getType(), Phis.back()->getType())) {
+ // This phi can be freely truncated to the narrowest phi type. Map the
+ // truncated expression to it so it will be reused for narrow types.
+ const SCEV *TruncExpr =
+ SE.getTruncateExpr(SE.getSCEV(Phi), Phis.back()->getType());
+ ExprToIVMap[TruncExpr] = Phi;
+ }
+ continue;
+ }
+
+ // Replacing a pointer phi with an integer phi or vice-versa doesn't make
+ // sense.
+ if (OrigPhiRef->getType()->isPointerTy() != Phi->getType()->isPointerTy())
+ continue;
+
+ if (BasicBlock *LatchBlock = L->getLoopLatch()) {
+ Instruction *OrigInc =
+ cast<Instruction>(OrigPhiRef->getIncomingValueForBlock(LatchBlock));
+ Instruction *IsomorphicInc =
+ cast<Instruction>(Phi->getIncomingValueForBlock(LatchBlock));
+
+ // If this phi has the same width but is more canonical, replace the
+ // original with it. As part of the "more canonical" determination,
+ // respect a prior decision to use an IV chain.
+ if (OrigPhiRef->getType() == Phi->getType()
+ && !(ChainedPhis.count(Phi)
+ || isExpandedAddRecExprPHI(OrigPhiRef, OrigInc, L))
+ && (ChainedPhis.count(Phi)
+ || isExpandedAddRecExprPHI(Phi, IsomorphicInc, L))) {
+ std::swap(OrigPhiRef, Phi);
+ std::swap(OrigInc, IsomorphicInc);
+ }
+ // Replacing the congruent phi is sufficient because acyclic redundancy
+ // elimination, CSE/GVN, should handle the rest. However, once SCEV proves
+ // that a phi is congruent, it's often the head of an IV user cycle that
+ // is isomorphic with the original phi. It's worth eagerly cleaning up the
+ // common case of a single IV increment so that DeleteDeadPHIs can remove
+ // cycles that had postinc uses.
+ const SCEV *TruncExpr = SE.getTruncateOrNoop(SE.getSCEV(OrigInc),
+ IsomorphicInc->getType());
+ if (OrigInc != IsomorphicInc
+ && TruncExpr == SE.getSCEV(IsomorphicInc)
+ && ((isa<PHINode>(OrigInc) && isa<PHINode>(IsomorphicInc))
+ || hoistIVInc(OrigInc, IsomorphicInc))) {
+ DEBUG_WITH_TYPE(DebugType, dbgs()
+ << "INDVARS: Eliminated congruent iv.inc: "
+ << *IsomorphicInc << '\n');
+ Value *NewInc = OrigInc;
+ if (OrigInc->getType() != IsomorphicInc->getType()) {
+ Instruction *IP = isa<PHINode>(OrigInc)
+ ? (Instruction*)L->getHeader()->getFirstInsertionPt()
+ : OrigInc->getNextNode();
+ IRBuilder<> Builder(IP);
+ Builder.SetCurrentDebugLocation(IsomorphicInc->getDebugLoc());
+ NewInc = Builder.
+ CreateTruncOrBitCast(OrigInc, IsomorphicInc->getType(), IVName);
+ }
+ IsomorphicInc->replaceAllUsesWith(NewInc);
+ DeadInsts.push_back(IsomorphicInc);
+ }
+ }
+ DEBUG_WITH_TYPE(DebugType, dbgs()
+ << "INDVARS: Eliminated congruent iv: " << *Phi << '\n');
+ ++NumElim;
+ Value *NewIV = OrigPhiRef;
+ if (OrigPhiRef->getType() != Phi->getType()) {
+ IRBuilder<> Builder(L->getHeader()->getFirstInsertionPt());
+ Builder.SetCurrentDebugLocation(Phi->getDebugLoc());
+ NewIV = Builder.CreateTruncOrBitCast(OrigPhiRef, Phi->getType(), IVName);
+ }
+ Phi->replaceAllUsesWith(NewIV);
+ DeadInsts.push_back(Phi);
+ }
+ return NumElim;
+}
+
+namespace {
+// Search for a SCEV subexpression that is not safe to expand. Any expression
+// that may expand to a !isSafeToSpeculativelyExecute value is unsafe, namely
+// UDiv expressions. We don't know if the UDiv is derived from an IR divide
+// instruction, but the important thing is that we prove the denominator is
+// nonzero before expansion.
+//
+// IVUsers already checks that IV-derived expressions are safe. So this check is
+// only needed when the expression includes some subexpression that is not IV
+// derived.
+//
+// Currently, we only allow division by a nonzero constant here. If this is
+// inadequate, we could easily allow division by SCEVUnknown by using
+// ValueTracking to check isKnownNonZero().
+//
+// We cannot generally expand recurrences unless the step dominates the loop
+// header. The expander handles the special case of affine recurrences by
+// scaling the recurrence outside the loop, but this technique isn't generally
+// applicable. Expanding a nested recurrence outside a loop requires computing
+// binomial coefficients. This could be done, but the recurrence has to be in a
+// perfectly reduced form, which can't be guaranteed.
+struct SCEVFindUnsafe {
+ ScalarEvolution &SE;
+ bool IsUnsafe;
+
+ SCEVFindUnsafe(ScalarEvolution &se): SE(se), IsUnsafe(false) {}
+
+ bool follow(const SCEV *S) {
+ if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
+ const SCEVConstant *SC = dyn_cast<SCEVConstant>(D->getRHS());
+ if (!SC || SC->getValue()->isZero()) {
+ IsUnsafe = true;
+ return false;
+ }
+ }
+ if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
+ const SCEV *Step = AR->getStepRecurrence(SE);
+ if (!AR->isAffine() && !SE.dominates(Step, AR->getLoop()->getHeader())) {
+ IsUnsafe = true;
+ return false;
+ }
+ }
+ return true;
+ }
+ bool isDone() const { return IsUnsafe; }
+};
+}
+
+namespace llvm {
+bool isSafeToExpand(const SCEV *S, ScalarEvolution &SE) {
+ SCEVFindUnsafe Search(SE);
+ visitAll(S, Search);
+ return !Search.IsUnsafe;
+}
+}
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