"computations were sunk");
STATISTIC(NumExtsMoved, "Number of [s|z]ext instructions combined with loads");
STATISTIC(NumExtUses, "Number of uses of [s|z]ext instructions optimized");
+STATISTIC(NumAndsAdded,
+ "Number of and mask instructions added to form ext loads");
+STATISTIC(NumAndUses, "Number of uses of and mask instructions optimized");
STATISTIC(NumRetsDup, "Number of return instructions duplicated");
STATISTIC(NumDbgValueMoved, "Number of debug value instructions moved");
STATISTIC(NumSelectsExpanded, "Number of selects turned into branches");
bool optimizeCallInst(CallInst *CI, bool& ModifiedDT);
bool moveExtToFormExtLoad(Instruction *&I);
bool optimizeExtUses(Instruction *I);
+ bool optimizeLoadExt(LoadInst *I);
bool optimizeSelectInst(SelectInst *SI);
bool optimizeShuffleVectorInst(ShuffleVectorInst *SI);
+ bool optimizeSwitchInst(SwitchInst *CI);
bool optimizeExtractElementInst(Instruction *Inst);
bool dupRetToEnableTailCallOpts(BasicBlock *BB);
bool placeDbgValues(Function &F);
if (!OptSize && TLI && TLI->isSlowDivBypassed()) {
const DenseMap<unsigned int, unsigned int> &BypassWidths =
TLI->getBypassSlowDivWidths();
- for (Function::iterator I = F.begin(); I != F.end(); I++)
- EverMadeChange |= bypassSlowDivision(F, I, BypassWidths);
+ BasicBlock* BB = &*F.begin();
+ while (BB != nullptr) {
+ // bypassSlowDivision may create new BBs, but we don't want to reapply the
+ // optimization to those blocks.
+ BasicBlock* Next = BB->getNextNode();
+ EverMadeChange |= bypassSlowDivision(BB, BypassWidths);
+ BB = Next;
+ }
}
// Eliminate blocks that contain only PHI nodes and an
// Computes a map of base pointer relocation instructions to corresponding
// derived pointer relocation instructions given a vector of all relocate calls
static void computeBaseDerivedRelocateMap(
- const SmallVectorImpl<User *> &AllRelocateCalls,
- DenseMap<IntrinsicInst *, SmallVector<IntrinsicInst *, 2>> &
- RelocateInstMap) {
+ const SmallVectorImpl<GCRelocateInst *> &AllRelocateCalls,
+ DenseMap<GCRelocateInst *, SmallVector<GCRelocateInst *, 2>>
+ &RelocateInstMap) {
// Collect information in two maps: one primarily for locating the base object
// while filling the second map; the second map is the final structure holding
// a mapping between Base and corresponding Derived relocate calls
- DenseMap<std::pair<unsigned, unsigned>, IntrinsicInst *> RelocateIdxMap;
- for (auto &U : AllRelocateCalls) {
- GCRelocateOperands ThisRelocate(U);
- IntrinsicInst *I = cast<IntrinsicInst>(U);
- auto K = std::make_pair(ThisRelocate.getBasePtrIndex(),
- ThisRelocate.getDerivedPtrIndex());
- RelocateIdxMap.insert(std::make_pair(K, I));
+ DenseMap<std::pair<unsigned, unsigned>, GCRelocateInst *> RelocateIdxMap;
+ for (auto *ThisRelocate : AllRelocateCalls) {
+ auto K = std::make_pair(ThisRelocate->getBasePtrIndex(),
+ ThisRelocate->getDerivedPtrIndex());
+ RelocateIdxMap.insert(std::make_pair(K, ThisRelocate));
}
for (auto &Item : RelocateIdxMap) {
std::pair<unsigned, unsigned> Key = Item.first;
// Base relocation: nothing to insert
continue;
- IntrinsicInst *I = Item.second;
+ GCRelocateInst *I = Item.second;
auto BaseKey = std::make_pair(Key.first, Key.first);
// We're iterating over RelocateIdxMap so we cannot modify it.
// Takes a RelocatedBase (base pointer relocation instruction) and Targets to
// replace, computes a replacement, and affects it.
static bool
-simplifyRelocatesOffABase(IntrinsicInst *RelocatedBase,
- const SmallVectorImpl<IntrinsicInst *> &Targets) {
+simplifyRelocatesOffABase(GCRelocateInst *RelocatedBase,
+ const SmallVectorImpl<GCRelocateInst *> &Targets) {
bool MadeChange = false;
- for (auto &ToReplace : Targets) {
- GCRelocateOperands MasterRelocate(RelocatedBase);
- GCRelocateOperands ThisRelocate(ToReplace);
-
- assert(ThisRelocate.getBasePtrIndex() == MasterRelocate.getBasePtrIndex() &&
+ for (GCRelocateInst *ToReplace : Targets) {
+ assert(ToReplace->getBasePtrIndex() == RelocatedBase->getBasePtrIndex() &&
"Not relocating a derived object of the original base object");
- if (ThisRelocate.getBasePtrIndex() == ThisRelocate.getDerivedPtrIndex()) {
+ if (ToReplace->getBasePtrIndex() == ToReplace->getDerivedPtrIndex()) {
// A duplicate relocate call. TODO: coalesce duplicates.
continue;
}
- Value *Base = ThisRelocate.getBasePtr();
- auto Derived = dyn_cast<GetElementPtrInst>(ThisRelocate.getDerivedPtr());
+ if (RelocatedBase->getParent() != ToReplace->getParent()) {
+ // Base and derived relocates are in different basic blocks.
+ // In this case transform is only valid when base dominates derived
+ // relocate. However it would be too expensive to check dominance
+ // for each such relocate, so we skip the whole transformation.
+ continue;
+ }
+
+ Value *Base = ToReplace->getBasePtr();
+ auto Derived = dyn_cast<GetElementPtrInst>(ToReplace->getDerivedPtr());
if (!Derived || Derived->getPointerOperand() != Base)
continue;
// In this case, we can not find the bitcast any more. So we insert a new bitcast
// no matter there is already one or not. In this way, we can handle all cases, and
// the extra bitcast should be optimized away in later passes.
- Instruction *ActualRelocatedBase = RelocatedBase;
+ Value *ActualRelocatedBase = RelocatedBase;
if (RelocatedBase->getType() != Base->getType()) {
ActualRelocatedBase =
- cast<Instruction>(Builder.CreateBitCast(RelocatedBase, Base->getType()));
+ Builder.CreateBitCast(RelocatedBase, Base->getType());
}
Value *Replacement = Builder.CreateGEP(
Derived->getSourceElementType(), ActualRelocatedBase, makeArrayRef(OffsetV));
- Instruction *ReplacementInst = cast<Instruction>(Replacement);
Replacement->takeName(ToReplace);
// If the newly generated derived pointer's type does not match the original derived
// pointer's type, cast the new derived pointer to match it. Same reasoning as above.
- Instruction *ActualReplacement = ReplacementInst;
- if (ReplacementInst->getType() != ToReplace->getType()) {
+ Value *ActualReplacement = Replacement;
+ if (Replacement->getType() != ToReplace->getType()) {
ActualReplacement =
- cast<Instruction>(Builder.CreateBitCast(ReplacementInst, ToReplace->getType()));
+ Builder.CreateBitCast(Replacement, ToReplace->getType());
}
ToReplace->replaceAllUsesWith(ActualReplacement);
ToReplace->eraseFromParent();
// %val = load %ptr'
bool CodeGenPrepare::simplifyOffsetableRelocate(Instruction &I) {
bool MadeChange = false;
- SmallVector<User *, 2> AllRelocateCalls;
+ SmallVector<GCRelocateInst *, 2> AllRelocateCalls;
for (auto *U : I.users())
- if (isGCRelocate(dyn_cast<Instruction>(U)))
+ if (GCRelocateInst *Relocate = dyn_cast<GCRelocateInst>(U))
// Collect all the relocate calls associated with a statepoint
- AllRelocateCalls.push_back(U);
+ AllRelocateCalls.push_back(Relocate);
// We need atleast one base pointer relocation + one derived pointer
// relocation to mangle
// RelocateInstMap is a mapping from the base relocate instruction to the
// corresponding derived relocate instructions
- DenseMap<IntrinsicInst *, SmallVector<IntrinsicInst *, 2>> RelocateInstMap;
+ DenseMap<GCRelocateInst *, SmallVector<GCRelocateInst *, 2>> RelocateInstMap;
computeBaseDerivedRelocateMap(AllRelocateCalls, RelocateInstMap);
if (RelocateInstMap.empty())
return false;
// Preincrement use iterator so we don't invalidate it.
++UI;
+ // If the block selected to receive the cast is an EH pad that does not
+ // allow non-PHI instructions before the terminator, we can't sink the
+ // cast.
+ if (UserBB->getTerminator()->isEHPad())
+ continue;
+
// If this user is in the same block as the cast, don't change the cast.
if (UserBB == DefBB) continue;
assert(*AddI->user_begin() == CI && "expected!");
#endif
- Module *M = CI->getParent()->getParent()->getParent();
+ Module *M = CI->getModule();
Value *F = Intrinsic::getDeclaration(M, Intrinsic::uadd_with_overflow, Ty);
auto *InsertPt = AddI->hasOneUse() ? CI : AddI;
CI->eraseFromParent();
}
+/// If counting leading or trailing zeros is an expensive operation and a zero
+/// input is defined, add a check for zero to avoid calling the intrinsic.
+///
+/// We want to transform:
+/// %z = call i64 @llvm.cttz.i64(i64 %A, i1 false)
+///
+/// into:
+/// entry:
+/// %cmpz = icmp eq i64 %A, 0
+/// br i1 %cmpz, label %cond.end, label %cond.false
+/// cond.false:
+/// %z = call i64 @llvm.cttz.i64(i64 %A, i1 true)
+/// br label %cond.end
+/// cond.end:
+/// %ctz = phi i64 [ 64, %entry ], [ %z, %cond.false ]
+///
+/// If the transform is performed, return true and set ModifiedDT to true.
+static bool despeculateCountZeros(IntrinsicInst *CountZeros,
+ const TargetLowering *TLI,
+ const DataLayout *DL,
+ bool &ModifiedDT) {
+ if (!TLI || !DL)
+ return false;
+
+ // If a zero input is undefined, it doesn't make sense to despeculate that.
+ if (match(CountZeros->getOperand(1), m_One()))
+ return false;
+
+ // If it's cheap to speculate, there's nothing to do.
+ auto IntrinsicID = CountZeros->getIntrinsicID();
+ if ((IntrinsicID == Intrinsic::cttz && TLI->isCheapToSpeculateCttz()) ||
+ (IntrinsicID == Intrinsic::ctlz && TLI->isCheapToSpeculateCtlz()))
+ return false;
+
+ // Only handle legal scalar cases. Anything else requires too much work.
+ Type *Ty = CountZeros->getType();
+ unsigned SizeInBits = Ty->getPrimitiveSizeInBits();
+ if (Ty->isVectorTy() || SizeInBits > DL->getLargestLegalIntTypeSize())
+ return false;
+
+ // The intrinsic will be sunk behind a compare against zero and branch.
+ BasicBlock *StartBlock = CountZeros->getParent();
+ BasicBlock *CallBlock = StartBlock->splitBasicBlock(CountZeros, "cond.false");
+
+ // Create another block after the count zero intrinsic. A PHI will be added
+ // in this block to select the result of the intrinsic or the bit-width
+ // constant if the input to the intrinsic is zero.
+ BasicBlock::iterator SplitPt = ++(BasicBlock::iterator(CountZeros));
+ BasicBlock *EndBlock = CallBlock->splitBasicBlock(SplitPt, "cond.end");
+
+ // Set up a builder to create a compare, conditional branch, and PHI.
+ IRBuilder<> Builder(CountZeros->getContext());
+ Builder.SetInsertPoint(StartBlock->getTerminator());
+ Builder.SetCurrentDebugLocation(CountZeros->getDebugLoc());
+
+ // Replace the unconditional branch that was created by the first split with
+ // a compare against zero and a conditional branch.
+ Value *Zero = Constant::getNullValue(Ty);
+ Value *Cmp = Builder.CreateICmpEQ(CountZeros->getOperand(0), Zero, "cmpz");
+ Builder.CreateCondBr(Cmp, EndBlock, CallBlock);
+ StartBlock->getTerminator()->eraseFromParent();
+
+ // Create a PHI in the end block to select either the output of the intrinsic
+ // or the bit width of the operand.
+ Builder.SetInsertPoint(&EndBlock->front());
+ PHINode *PN = Builder.CreatePHI(Ty, 2, "ctz");
+ CountZeros->replaceAllUsesWith(PN);
+ Value *BitWidth = Builder.getInt(APInt(SizeInBits, SizeInBits));
+ PN->addIncoming(BitWidth, StartBlock);
+ PN->addIncoming(CountZeros, CallBlock);
+
+ // We are explicitly handling the zero case, so we can set the intrinsic's
+ // undefined zero argument to 'true'. This will also prevent reprocessing the
+ // intrinsic; we only despeculate when a zero input is defined.
+ CountZeros->setArgOperand(1, Builder.getTrue());
+ ModifiedDT = true;
+ return true;
+}
+
bool CodeGenPrepare::optimizeCallInst(CallInst *CI, bool& ModifiedDT) {
BasicBlock *BB = CI->getParent();
II->replaceAllUsesWith(II->getArgOperand(0));
II->eraseFromParent();
return true;
+
+ case Intrinsic::cttz:
+ case Intrinsic::ctlz:
+ // If counting zeros is expensive, try to avoid it.
+ return despeculateCountZeros(II, TLI, DL, ModifiedDT);
}
if (TLI) {
return MadeChange;
}
+// Find loads whose uses only use some of the loaded value's bits. Add an "and"
+// just after the load if the target can fold this into one extload instruction,
+// with the hope of eliminating some of the other later "and" instructions using
+// the loaded value. "and"s that are made trivially redundant by the insertion
+// of the new "and" are removed by this function, while others (e.g. those whose
+// path from the load goes through a phi) are left for isel to potentially
+// remove.
+//
+// For example:
+//
+// b0:
+// x = load i32
+// ...
+// b1:
+// y = and x, 0xff
+// z = use y
+//
+// becomes:
+//
+// b0:
+// x = load i32
+// x' = and x, 0xff
+// ...
+// b1:
+// z = use x'
+//
+// whereas:
+//
+// b0:
+// x1 = load i32
+// ...
+// b1:
+// x2 = load i32
+// ...
+// b2:
+// x = phi x1, x2
+// y = and x, 0xff
+//
+// becomes (after a call to optimizeLoadExt for each load):
+//
+// b0:
+// x1 = load i32
+// x1' = and x1, 0xff
+// ...
+// b1:
+// x2 = load i32
+// x2' = and x2, 0xff
+// ...
+// b2:
+// x = phi x1', x2'
+// y = and x, 0xff
+//
+
+bool CodeGenPrepare::optimizeLoadExt(LoadInst *Load) {
+
+ if (!Load->isSimple() ||
+ !(Load->getType()->isIntegerTy() || Load->getType()->isPointerTy()))
+ return false;
+
+ // Skip loads we've already transformed or have no reason to transform.
+ if (Load->hasOneUse()) {
+ User *LoadUser = *Load->user_begin();
+ if (cast<Instruction>(LoadUser)->getParent() == Load->getParent() &&
+ !dyn_cast<PHINode>(LoadUser))
+ return false;
+ }
+
+ // Look at all uses of Load, looking through phis, to determine how many bits
+ // of the loaded value are needed.
+ SmallVector<Instruction *, 8> WorkList;
+ SmallPtrSet<Instruction *, 16> Visited;
+ SmallVector<Instruction *, 8> AndsToMaybeRemove;
+ for (auto *U : Load->users())
+ WorkList.push_back(cast<Instruction>(U));
+
+ EVT LoadResultVT = TLI->getValueType(*DL, Load->getType());
+ unsigned BitWidth = LoadResultVT.getSizeInBits();
+ APInt DemandBits(BitWidth, 0);
+ APInt WidestAndBits(BitWidth, 0);
+
+ while (!WorkList.empty()) {
+ Instruction *I = WorkList.back();
+ WorkList.pop_back();
+
+ // Break use-def graph loops.
+ if (!Visited.insert(I).second)
+ continue;
+
+ // For a PHI node, push all of its users.
+ if (auto *Phi = dyn_cast<PHINode>(I)) {
+ for (auto *U : Phi->users())
+ WorkList.push_back(cast<Instruction>(U));
+ continue;
+ }
+
+ switch (I->getOpcode()) {
+ case llvm::Instruction::And: {
+ auto *AndC = dyn_cast<ConstantInt>(I->getOperand(1));
+ if (!AndC)
+ return false;
+ APInt AndBits = AndC->getValue();
+ DemandBits |= AndBits;
+ // Keep track of the widest and mask we see.
+ if (AndBits.ugt(WidestAndBits))
+ WidestAndBits = AndBits;
+ if (AndBits == WidestAndBits && I->getOperand(0) == Load)
+ AndsToMaybeRemove.push_back(I);
+ break;
+ }
+
+ case llvm::Instruction::Shl: {
+ auto *ShlC = dyn_cast<ConstantInt>(I->getOperand(1));
+ if (!ShlC)
+ return false;
+ uint64_t ShiftAmt = ShlC->getLimitedValue(BitWidth - 1);
+ auto ShlDemandBits = APInt::getAllOnesValue(BitWidth).lshr(ShiftAmt);
+ DemandBits |= ShlDemandBits;
+ break;
+ }
+
+ case llvm::Instruction::Trunc: {
+ EVT TruncVT = TLI->getValueType(*DL, I->getType());
+ unsigned TruncBitWidth = TruncVT.getSizeInBits();
+ auto TruncBits = APInt::getAllOnesValue(TruncBitWidth).zext(BitWidth);
+ DemandBits |= TruncBits;
+ break;
+ }
+
+ default:
+ return false;
+ }
+ }
+
+ uint32_t ActiveBits = DemandBits.getActiveBits();
+ // Avoid hoisting (and (load x) 1) since it is unlikely to be folded by the
+ // target even if isLoadExtLegal says an i1 EXTLOAD is valid. For example,
+ // for the AArch64 target isLoadExtLegal(ZEXTLOAD, i32, i1) returns true, but
+ // (and (load x) 1) is not matched as a single instruction, rather as a LDR
+ // followed by an AND.
+ // TODO: Look into removing this restriction by fixing backends to either
+ // return false for isLoadExtLegal for i1 or have them select this pattern to
+ // a single instruction.
+ //
+ // Also avoid hoisting if we didn't see any ands with the exact DemandBits
+ // mask, since these are the only ands that will be removed by isel.
+ if (ActiveBits <= 1 || !APIntOps::isMask(ActiveBits, DemandBits) ||
+ WidestAndBits != DemandBits)
+ return false;
+
+ LLVMContext &Ctx = Load->getType()->getContext();
+ Type *TruncTy = Type::getIntNTy(Ctx, ActiveBits);
+ EVT TruncVT = TLI->getValueType(*DL, TruncTy);
+
+ // Reject cases that won't be matched as extloads.
+ if (!LoadResultVT.bitsGT(TruncVT) || !TruncVT.isRound() ||
+ !TLI->isLoadExtLegal(ISD::ZEXTLOAD, LoadResultVT, TruncVT))
+ return false;
+
+ IRBuilder<> Builder(Load->getNextNode());
+ auto *NewAnd = dyn_cast<Instruction>(
+ Builder.CreateAnd(Load, ConstantInt::get(Ctx, DemandBits)));
+
+ // Replace all uses of load with new and (except for the use of load in the
+ // new and itself).
+ Load->replaceAllUsesWith(NewAnd);
+ NewAnd->setOperand(0, Load);
+
+ // Remove any and instructions that are now redundant.
+ for (auto *And : AndsToMaybeRemove)
+ // Check that the and mask is the same as the one we decided to put on the
+ // new and.
+ if (cast<ConstantInt>(And->getOperand(1))->getValue() == DemandBits) {
+ And->replaceAllUsesWith(NewAnd);
+ if (&*CurInstIterator == And)
+ CurInstIterator = std::next(And->getIterator());
+ And->eraseFromParent();
+ ++NumAndUses;
+ }
+
+ ++NumAndsAdded;
+ return true;
+}
+
/// Check if V (an operand of a select instruction) is an expensive instruction
/// that is only used once.
static bool sinkSelectOperand(const TargetTransformInfo *TTI, Value *V) {
return MadeChange;
}
+bool CodeGenPrepare::optimizeSwitchInst(SwitchInst *SI) {
+ if (!TLI || !DL)
+ return false;
+
+ Value *Cond = SI->getCondition();
+ Type *OldType = Cond->getType();
+ LLVMContext &Context = Cond->getContext();
+ MVT RegType = TLI->getRegisterType(Context, TLI->getValueType(*DL, OldType));
+ unsigned RegWidth = RegType.getSizeInBits();
+
+ if (RegWidth <= cast<IntegerType>(OldType)->getBitWidth())
+ return false;
+
+ // If the register width is greater than the type width, expand the condition
+ // of the switch instruction and each case constant to the width of the
+ // register. By widening the type of the switch condition, subsequent
+ // comparisons (for case comparisons) will not need to be extended to the
+ // preferred register width, so we will potentially eliminate N-1 extends,
+ // where N is the number of cases in the switch.
+ auto *NewType = Type::getIntNTy(Context, RegWidth);
+
+ // Zero-extend the switch condition and case constants unless the switch
+ // condition is a function argument that is already being sign-extended.
+ // In that case, we can avoid an unnecessary mask/extension by sign-extending
+ // everything instead.
+ Instruction::CastOps ExtType = Instruction::ZExt;
+ if (auto *Arg = dyn_cast<Argument>(Cond))
+ if (Arg->hasSExtAttr())
+ ExtType = Instruction::SExt;
+
+ auto *ExtInst = CastInst::Create(ExtType, Cond, NewType);
+ ExtInst->insertBefore(SI);
+ SI->setCondition(ExtInst);
+ for (SwitchInst::CaseIt Case : SI->cases()) {
+ APInt NarrowConst = Case.getCaseValue()->getValue();
+ APInt WideConst = (ExtType == Instruction::ZExt) ?
+ NarrowConst.zext(RegWidth) : NarrowConst.sext(RegWidth);
+ Case.setValue(ConstantInt::get(Context, WideConst));
+ }
+
+ return true;
+}
+
namespace {
/// \brief Helper class to promote a scalar operation to a vector one.
/// This class is used to move downward extractelement transition.
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
stripInvariantGroupMetadata(*LI);
if (TLI) {
+ bool Modified = optimizeLoadExt(LI);
unsigned AS = LI->getPointerAddressSpace();
- return optimizeMemoryInst(I, I->getOperand(0), LI->getType(), AS);
+ Modified |= optimizeMemoryInst(I, I->getOperand(0), LI->getType(), AS);
+ return Modified;
}
return false;
}
if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(I))
return optimizeShuffleVectorInst(SVI);
+ if (auto *Switch = dyn_cast<SwitchInst>(I))
+ return optimizeSwitchInst(Switch);
+
if (isa<ExtractElementInst>(I))
return optimizeExtractElementInst(I);
Instruction *VI = dyn_cast_or_null<Instruction>(DVI->getValue());
if (VI && VI != PrevNonDbgInst && !VI->isTerminator()) {
+ // If VI is a phi in a block with an EHPad terminator, we can't insert
+ // after it.
+ if (isa<PHINode>(VI) && VI->getParent()->getTerminator()->isEHPad())
+ continue;
DEBUG(dbgs() << "Moving Debug Value before :\n" << *DVI << ' ' << *VI);
DVI->removeFromParent();
if (isa<PHINode>(VI))
projects / oota-llvm.git / blobdiff